Category: Food

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The Year of the Fat

Estimated reading time: 9 minutes

During the first few months of this year, we’ve seen at least three strong signs suggesting that health authorities have misled the public for several decades about dietary fats. This finding is of particular interest because later this year the 2015 Dietary Guidelines for Americans will be published.

Ever since the beginning of the 1960s, “eat less fat, in particular, less saturated fat and cholesterol” has been repeatedly emphasized by medical professionals and other experts.

Food manufacturers have played along by emphasizing low-fat food varieties of all possible kinds, whether it’s dairy products or something else. Butter consumption has decreased, and cooking oils have become very popular, all according to public health advice with the aim to eliminate cholesterol and saturated fat from our dishes.

What started all this was observational data showing an association between blood cholesterol and the risk of cardiovascular disease. Many health experts assumed that by reducing cholesterol and saturated fat in our diet the epidemic of heart disease might be stopped because these interventions would lower blood cholesterol. However, this was an untested hypothesis.

Nobody knew what would happen after the first US dietary recommendations were launched in 1980 because the implications of such an advice had never been tested in a scientific study.

Today, these guidelines may be regarded as a research protocol for the biggest dietary intervention trial so far performed. The trial was designed without a control group; everybody had the same advice. There was no informed consent and the trial wasn’t performed according to defined ethical principles for medical research involving human subjects (1).

However, to be fair, the death rated from coronary heart disease has dropped dramatically in most western countries for the past 30 years. Of course, this achievement is due both to modification of risk factors and improved treatment. Data from the US and many other countries suggest that lowering of cholesterol in the population may have contributed to this benefit (2).

On the other hand, since the introduction of the dietary guidelines, rates of obesity and diabetes have risen dramatically.

In fact, questions have repeatedly been asked about the Dietary Guidelines for Americans. It has been pointed out that the guidelines were implemented despite lack of supportive evidence and in the face of contradictory evidence (3).

Recently, the Dietary Guidelines Advisory Committee published its Scientific Report (4) preparing for the upcoming 2015 edition of the Dietary Guidelines for Americans. The U.S. Department of Health and Human Services (HHS) and the U.S. Department of Agriculture (USDA) jointly publish the Dietary Guidelines every five years.

The Scientific Report reflects important changes regarding dietary fats compared with previous guidelines. At the same time, two recent scientific publications suggest that our basic assumptions on dietary fats may have been wrong from the beginning.

Dietary Cholesterol

Recommendations to reduce dietary cholesterol were initiated by the American Heart Association (AHA) in the 1960s and have been a mainstay of the USDA and other public health guidelines for many years. All this time, excess dietary cholesterol has been regarded as a public health concern.

According to the Recent Scientific Report from the Dietary Guidelines Advisory Committee (4), ”Cholesterol is not considered a nutrient of concern for overconsumption.” It is assumed that this change of direction will make it to the final guidelines that will be published later this year.

Although blood levels of cholesterol are still considered an important risk factor for cardiovascular disease, the abrupt change of direction reflects scientific data suggesting that cholesterol consumed in food appears to play a minor role in determining the blood levels of this substance.

So apparently, the guidelines have been wrong for decades. There is no reason anymore to believe that eating eggs or other food rich in cholesterol will cause heart disease.

It will be interesting to see how the AHA will approach this recent change of heart.

Saturated Fat and Heart Disease

From the beginning, dietary guidelines have underscored the importance of limiting the amount of saturated fat in our diet. This advice was based on observational data showing an association between the intake of saturated fats and death rate from heart disease.

It is well known that although observational studies may show an association between two variables, they can very rarely prove a causative relationship. Although dietary guideline committees have always been aware of this fact, they have been determined to stick with their initial approach regarding saturated fat, most likely because of their immense respect for blood levels of LDL cholesterol (5).

For decades, LDL cholesterol has been regarded as an important target when it comes to reducing the risk of heart disease. It’s often assumed the almost every measure able to lower LDL cholesterol will be beneficial.

There is some evidence linking the consumption of some types of saturated fat with raised LDL cholesterol. Accordingly, these fats will increase risk. But, using surrogate markers like LDL cholesterol to determine risk may be misleading (6).

Only randomized clinical trials can prove that the intake of saturated fats will increase the risk of heart disease. Interestingly, results from such trials were available the time of the publication of the first dietary guidelines

Last month, British investigators published a systematic review and meta-analysis of results from randomized clinical trials that were available when the first US and UK dietary guidelines were published in the late 1970s and early 1980s (7).

The authors found six dietary trials, including a total of 2.467 male participants. The intervention differed somewhat between studies but all aimed at reducing total fat and/or saturated fat consumption in the intervention group.

There were no differences in all-cause mortality and non-significant differences in mortality from heart disease, resulting from the dietary interventions. The reductions in mean serum cholesterol levels were significantly higher in the intervention groups.

So despite lowering cholesterol, interventions aimed at reducing saturated fat intake did not lower mortality nor decrease death rate from heart disease.

The authors arrived at three pretty sobering conclusions:

Government dietary fat recommendations were untested in any trial prior to being introduced

Dietary recommendations were introduced for 220 million US and 56 million UK citizens by 1983, in the absence of supporting evidence from randomized clinical trials

The present review concludes that dietary advice not merely needs review; it should not have been introduced

Macronutrient Consumption Data

In 1977 the U.S. Senate Selection Committee on Nutrition and Human Needs issued Dietary Goals for the United States, which recommends that fat consumption be reduced to 30% of energy intake, and that carbohydrate consumption be increased to account for 55-60% of energy intake (8).

The focus on the relative contribution of different macronutrients was maintained by the first Dietary Guidelines for Americans that were launched by the USDA in 1980 and have remained largely unchanged since then.

There were two reasons experts believed reducing fats and increasing carbohydrates would be beneficial. Firstly, this would lower blood cholesterol and thereby the risk of heart disease. Secondly, because one gram of fat contains more calories than one gram of carbohydrates, the intervention would reduce the risk of obesity.

A recently published U.S. paper addresses the long-term dietary consumption of the U.S. population from 1965-2011 based on NHANES (National Health and Nutrition Examination Survey) data focusing on Americans aged 18-64 (9).

The main goal of the study was to address whether Americans have been following dietary guidelines with regards to the macronutrient composition of the diet.

Cohen et al, Statistical review of U.S. macronutrient consumption data, 1965–2011 Americans have been following dietary guidelines, coincident with the rise in obesity doi:10.1016/j.nut.2015.02.007

In 1965, fat consumption comprised 44.7% of calories of adult Americans’ diets, compared with 39% for carbohydrate. By 1999, fat consumption reached a through of 32.4% while carbohydrate consumption hit its peak at 52.1%. Protein consumption remained relatively constant throughout the period.

In 1971, saturated fat comprised 13.5% of total calories. By 2011, Americans were eating 10.7% of their calories as saturated fat (a 20.5% reduction since 1971).

Per capita cholesterol consumption decreased down below 300 mg/day, from over 400 mg/day in 1971.

The study also confirms a clear shift towards more obesity during the study period.

The authors underscore that there is a strong correlation between the increase in carbohydrate share of total intake and obesity.

They also address the question whether the increased prevalence of obesity can be explained by an increase in overall calorie intake by conducting their tests over two subsamples of participants who consumed similar calories over time. They conclude “the increase in calorie consumption since 1971 is not likely to offer any significant explanation for the increase in BMI (body mass index) over the last four decades.”

The main findings of the study were

  • Americans have been adhering to federal dietary guidelines for the past 40 years
  • Fat consumption by U.S. adults has decreased from 45% to 34% between 1965 and 2011
  • Carbohydrate consumption has increased from 39% to 51% over this same period
  • There is a high correlation between the change in diet and the rise of obesity
  • The percentage of overweight adults has increased from 42% to 66% since 1971

The Bottom Line

Recently we have seen important evidence suggesting that the fear of dietary fats, in particular, the fear of saturated fats and cholesterol is not based on reliable scientific data.

This evidence adds further to the belief that we have been misinformed for decades by public authorities about dietary fat intake.

Although authors of dietary guidelines seem to have admitted that there is no reason to avoid dietary cholesterol, I’m still afraid they haven’t got it right. For example, the advice to avoid saturated fats was never based on evidence from randomized clinical trials.

It is hard to accept that public health recommendations are not based on solid scientific evidence.

A  part of the problem is that the guideline process is too complicated, and recommendations are often hard to change.

The dietary fat history is a tragic example of how easy it is to mess things up for years when you get it wrong from the beginning.

Guideline writers should acknowledge the lack of evidence for most recommendations and write shorter guidelines. They should stick to hard evidence. Who needs hundreds of pages of expert consensus? The public deserves to be guided by real science.

Finally, despite the forthcoming 2015 Dietary Guidelines for Americans, this could be the year of the fat.

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What About Saturated Fats if You Already Have Heart Disease?

Estimated reading time: 7 minutes

We’re all aware of the aggressive campaign driven by public health authorities and medical professionals to decrease blood cholesterol.

It all started more than fifty years ago when the Framingham Heart Study reported that high blood cholesterol was a major risk factor for coronary heart disease (1).  

 

Central to the dogma was the belief that lowering blood cholesterol would lower the risk of heart disease.

At the same time, it was assumed that dietary saturated fats and dietary cholesterol caused an increase in blood levels of total cholesterol as well as LDL cholesterol (the “bad” cholesterol).

So, it was a foregone conclusion that dietary saturated fats and dietary cholesterol would cause heart disease because they supposedly raised blood cholesterol.

However, recently evidence questioning a lack of a causal relationship between the intake of saturated fats and heart disease has accumulated (3). Even so, restriction of dietary saturated fats is still included in most current dietary guidelines and recommendations on cardiovascular prevention (4,5).

Although some recent studies have suggested that replacing saturated fatty acids with monounsaturated or polyunsaturated fatty acids may be beneficial, replacing saturated fats with carbohydrates may increase risk (6).

Before I go further, keep in mind that the lack of evidence for a causal relationship between the intake of saturated fats and heart disease doesn’t necessarily defy or contradict the lipid hypothesis.

Although high intake of saturated fats may raise total cholesterol and LDL cholesterol, it also tends to elevate HDL cholesterol (the “good” cholesterol).

In addition, high intake of saturated fats is associated with a higher concentration of large cholesterol-enriched LDL particles and lower concentration of small, dense LDL particles (7). The presence of small, dense LDL particles is associated with an increased risk of subsequently developing heart disease (8), and appears a strong predictor of blockage in the coronary arteries (9).

So, a lack of relationship between high intake of saturated fats and the occurrence of heart disease may indeed fit quite well with the lipid hypothesis. However, it suggests that the simplified version of this hypothesis, the one that only targets LDL cholesterol may be misleading (10).

What About Saturated Fats if You Already Have Heart Disease?

The public recommendation to restrict the intake of saturated fats has been primarily targeted at healthy people in order to reduce the risk of heart disease. However, the same advice has been given extensively to patients diagnosed with cardiovascular disease, whether it be coronary heart disease or stroke.

Very few studies have investigated the impact of saturated fat intake in patients already diagnosed with heart disease. For this reason, I became quite interested to find a scientific paper on the issue published very recently in the Journal of Nutrition (11).

The study included 2,412 patients who underwent coronary angiography because of coronary artery disease or aortic valve stenosis between 1994 and 2004 at two university hospitals in Norway (Haukeland University Hospital, Bergen and Stavanger University Hospital, Stavanger).

Information on dietary intake was obtained at baseline by an FFQ (Food Frequency Questionnaire) developed at the Department of Nutrition, University of Oslo.

The patients were divided into quartiles based on the amount of saturated fat consumed (percentage of energy consumed). In group 1, the amount of saturated fat intake was between 3.9-9.8%, in group 2 it was between 9.8-11.5%, in group 3 between 11.5-13.2 and group 4 between 13.2-28.7.

There were some quite interesting findings at baseline. For example, patients with a higher intake of saturated fats were less likely to have a history of heart attack, prior coronary artery bypass surgery or to have triple heart disease (blockages of all three main coronary arteries) at baseline.

Increased intake of saturated fatty acids corresponded to an increased intake of both total energy and total fat. Participants with the highest saturated fatty acid intake also had higher consumption of mono-and polyunsaturated fat and dietary cholesterol.

High intake of saturated fats was associated with lower consumption of total carbohydrates, dietary fibre and alcohol. Patients with higher intake of saturated fats had higher intakes of meat, cheese, butter, milk, eggs, cakes, sugar and sweets.

Interestingly, despite higher calorie consumption among those with the highest saturated fatty acid intake, body mass index (BMI) was similar in all four groups.

Patients with higher intake of saturated fats were less likely to have high blood pressure but more likely to smoke. Their blood levels of total and LDL cholesterol tended to be higher but triglycerides lower compared to those with lower intake of saturated fats. There were no significant differences in the blood levels of HDL cholesterol between the groups.

The prevalence of diabetes was similar in all four groups.

During a median follow-up of 4.8 years, a total of 292 (12%) patients experienced a coronary event (heart attack, unstable angina or coronary death), and 137 patients died from any cause.

During follow-up, most of the patients were on conventional medication such as aspirin (90%), statins (89%) and beta-blockers (78%).

There were no significant associations between the intake of saturated fatty acids and coronary events or death from any cause. In other words, patients with high intake of saturated fats did not do worse than those with lower intake of saturated fatty acids. This was true also after multivariate adjustments for possible confounding factors.

Of course, this study has several strength and limitations. For example, it is important to understand that dietary intake was estimated at baseline only. No such information was collected during follow-up. For this reason, it is not possible to account for changes in dietary habits during the study period.

However, the authors point out that the majority of patients selected for participation in the study had known coronary heart disease at baseline. Thus, it may be assumed that most patients willing to change their dietary habits towards less SFA intake had already done so before inclusion in the study.

The Bottom Line

For decades, cardiologists have advised patients with heart disease to restrict the intake of saturated fats and dietary cholesterol. Many patients still believe this to be the cornerstone of their lifestyle modification.

The main reason for avoiding saturated fats is the assumption that they adversely affect the lipid profile of our patients.

Public authorities and medical societies usually recommend restricting the intake of saturated fats to less than 10 percent of total energy consumption. In the above study, only 27% of the patients met these dietary recommendations.

The American Heart Association goes even further by recommending a dietary pattern that achieves 5% to 6% of calories from saturated fat. That means, for example, if you need about 2,000 calories a day, no more than 120 of them should come from saturated fats. That’s about 13 grams of saturated fats a day (12). That equals two slices of cheddar cheese.

Recent studies suggest that the recommendation to avoid saturated fats may have been premature and not based on solid scientific evidence.

Now, a recently published Norwegian study shows that dietary intake of saturated fatty acids was not associated with risk of future events or death among patients with established coronary artery disease.

It is important to keep in mind that most of the patients were receiving secondary prevention drug therapy including aspirin, beta blockers and statins.

Anyhow, the results of the study certainly suggest that high intake of saturated fats is not a risk factor among patients with coronary heart disease receiving modern-day treatment.

These recent scientific data don’t imply hat we should urge our patients to consume high amounts of saturated fats. They only tell us that there is no association and accordingly, restriction won’t help.

So, it’s certainly a lifeline for those who believe red meat, whole-fat milk, cheese, cream, butter and eggs can be a part of a healthy diet.

On the other hand, we must realise that scientific studies often provide contradictory results. A US study published last year suggested that greater adherence to a low carbohydrate diet high in animal sources of fat and protein was associated with higher all-cause and cardiovascular mortality following acute heart attack (13).

It appears the jury is still out…



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Five Tips on How to Prevent a Heart Attack

Cardiology is renowned for its innovative procedures and cutting edge technology. However, one of my favorite scientific papers of 2014 did not address innovative techniques, DNA sequencing or new wonder drugs. It dealt with the fact that certain lifestyle habits and the absence of abdominal obesity may prevent most heart attacks.

Toady, chronic noncommunicable diseases are one of the biggest challenges of medicine and healthcare in general. One hundred years ago doctors were busy dealing with infections; pneumonia, tuberculosis and gastroenteritis (1). Today it is heart disease, cancer, dementia, diabetes, and obesity.

The pandemic of chronic diseases seems to have started only a few decades ago. Although the underlying causes are multifactorial, modern western lifestyles are often blamed, implying that these diseases are potentially preventable.

However, the knowledge that lifestyle contributes to disease doesn’t necessarily provide an easy solution. Our lifestyle choices are easily manipulated by the external environment. We are constantly bombarded with advertisement, and the internet provides a steady flow of information that may be both overwhelming and confusing. What should we believe and who can we trust? 

Of course, every doctor should educate their patients about the relationship between lifestyle and disease. However, as Dr Bernard Lown, a great cardiologist and Nobel Peace Prize recipient once said: “Diligent prevention, unfortunately, plays second fiddle to heroic cures.”

It’s a fact that cardiologists are often more interested in the high-tech diagnostic and therapeutic aspects of their discipline than in preventive lifestyle measures. However, the 2014 paper I mentioned before certainly suggests that the latter may be much more effective when it comes to reducing the burden of heart disease in our society.

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Five Tips on How to Prevent Heart Attack

In September 2014, a paper by scientists lead by Agneta Åkesson PhD at Karolinska Institutet, Stockholm, Sweden, was published in the Journal of the American College of Cardiology (JACC), suggesting that five basic lifestyle factors may prevent approximately 80 percent of heart attacks in men (2).

But it’s not only about men because another study published 2007 by the same group of researchers observed that low-risk dietary and lifestyle behaviors may prevent 77% of heart attacks in women (3).

I’m not sure whether the medical community understands the potential impact of these findings. At least the 2014 paper didn’t to steal many news headlines.

About 600,000 people die of heart disease in the United States every year. This is approximately 25% of all deaths (3). Coronary heart disease, the most common cause of heart disease causes nearly 380,000 deaths annually.

Every year about 720,000 Americans have a heart attack (4). Of those, 515,000 are a first heart attack. Imagine if this number could be reduced by 80%, to 103.000 cases annually, with a therapy that is mostly without side effects and risks.

In 1997, the Swedish researchers sent a questionnaire that included approximately 350 items to men aged 45-79 years residing in two counties in central Sweden. A total of 48,850 men returned the questionnaire, but those with a history of cancer, coronary heart disease, self-reported hypertension and self-reported high cholesterol were excluded from this particular analysis, leaving 20,721 for the main analysis.

The men were followed for a mean of 11 years. During that period, there were 1,361 cases of a first myocardial infarction (heart attack).

The scientists studied the risk of heart attack in relation to the following five low-risk lifestyle behaviors: a healthy diet, moderate alcohol consumption, no smoking, being physically active, and having no abdominal obesity.

1. A Healthy Diet

After mutual adjustment for other elements of the low-risk profile, individuals with the highest score for a healthy diet had an 18% lower risk of heart attack than those with lower scores for the healthy diet.

A healthy diet was identified according to a Recommended Food Score developed by Kant and coworkers (5). This score emphasizes foods such as fruits, vegetables, legumes, nuts, reduced-fat dairy products, whole grains, and fish.

A non-Recommended Food Score was defined based on 21 food items including red and processed meat, fried potatoes, solid fats, full-fat cheese, white bread and refined cereals and various sweet foods.

The men with the highest Recommended Food Score were more likely to have a higher level of education and were less likely to smoke or live alone, compared to men with lower scores of recommended foods.

Interestingly, men with the highest Recommended Food Score had a mean non-Recommended Food Score of 17 while those with lower scores of recommended foods had a mean non-Recommended Food Score of 15.

Although not mentioned in the paper, this suggests that those who ate the most “healthy” food didn’t eat less of the “unhealthy” food products.

Furthermore, mean daily energy intake was 2,900 kcal among that 20 % with the highest Recommended Food Score but 2,700 among the others.

A varied diet consisting of fruits, vegetables, legumes, nuts, reduced-fat dairy products, whole grains and fish is associated with approximately 18% lower risk of having heart attack.

2. Moderate Alcohol Consumption

A low-risk alcohol group comprised men who consumed moderate amounts of alcohol (10-30 g/day). This is usually defined as no more than two drinks per day for men.

After adjustment for other low-risk profile elements, moderate alcohol consumption was associated with 11% lower risk of heart attack.

Previous studies have suggested that moderate alcohol consumption may provide cardiovascular benefits.

However, because heavy alcohol consumption is associated with a number of disease conditions and increased mortality, it is very difficult for the clinician to recommend moderate consumption of alcohol in order to reduce the risk of cardiovascular disease.

Recommending people who don’t drink to start drinking in order to achieve possible health benefits is also highly controversial.

For those who already drink, it is important to understand that the evidence suggesting that alcohol improves health only applies to light or moderate drinking and not to binge drinking or heavy drinking.

Moderate alcohol consumption is associated with 11% lower risk of heart attack

3. No Smoking

Never smokers and those who quit smoking > 20 years ago were classified as non-smokers.

Not smoking was associated with 36% lower risk of heart attack after adjustment for other low-risk profile elements.

Of course, this doesn’t come as a surprise. The evidence linking smoking to increased risk of myocardial infarction and death is incontrovertible (7). However, the results highlight the huge health benefits of not smoking.

Not smoking is associated with 36%  lower risk of heart attack 

4. Being Physically Active


Physical activity was assessed by the equestionnaire. Participants reported their level of activity at work and home and during leisure time in the year before the study started.

A low-risk physical activity behavior included both daily non-exercise physical activity (walking/bicycling) and a more vigorous weekly exercise, pre-specified according to criteria from another study (3).

After statistical adjustment, men who were physically active had a 3% lower risk of heart attack compared to those who were not physically active.

The importance of exercise for cardiovascular health has been previously documented. Fifteen years ago the Honolulu Heart Program clearly illustrated the effect of regular walking, suggesting that the risk of coronary heart disease is reduced with increases in distance walked (8).

Physical activity is associated with a 3% lower risk off heart attack 

5. Having No Abdominal Obesity

Central or visceral obesity has been found to be a strong marker of cardiovascular risk in a number of studies.

The Swedish investigators defined abdominal obesity as a waist circumference > 95 cm (38 inches).

After adjustment for other low-risk profile elements, the absence of abdominal obesity was associated with a 12% lower risk of heart attack.

The absence of abdominal obesity is associated with a 12% lower risk of heart attack

The Take-Home Message

Although the study by Åkesson and coworkers defined five separate low-risk elements associated with lower risk of heart attack, it also underscores the importance of multiple combined lifestyle habits.

A total of 1,724 (8%) men had none of the five low-risk elements present, and 166 (10%) of that group suffered heart attacks.

In contrast, 212 (1%) men had all five low-risk elements. Of those only three (1.4%) had heart attacks.

Therefore, almost 4 of 5 heart attacks may be preventable with a combined low-risk behavior.

In an accompanying editorial to the paper in the JACC (9) Darius Mozaffarian MD wrote: “In light of the breadth of previous mechanistic, physiological, observational, and clinical trial evidence on the impact of lifestyle, it is time to prioritize these most basic and fundamental behaviors to reduce the health and economic burdens of cardiometabolic diseases.”

So my message is simple:

If you eat healthily, don’t smoke, consume alcohol in moderation, regularly exercise and avoid overweight you will greatly reduce your risk of having a heart attack. These measures are more effective than any known medical therapy. Most people don’t need complex technology or a magic pill to avoid heart disease.

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“We no longer suggest avoiding saturated fats per se …”

The story of saturated fats and their proposed association with coronary heart disease is bewildering. Although it illustrates the great power of public health authorities and the food industry, it tragically exposes the frailty of governmental handling of health issues.

 

When dietary and lifestyle recommendations don’t rely on solid scientific evidence, the outcome may be disastrous. Further damage may result from the fact that as soon as contradictory evidence becomes available, authorities will tend to sweep it under the carpet. That’s human nature. You will want to defend your position for as long as you can.

Although most public health authorities still stick with their recommendations about saturated fat, recently an important clinical support resource called UpToDate changed their stands regarding the issue.

UpToDate is an evidence-based clinical decision support system authored by physicians to help clinicians make the right decisions at the point of care. It is highly respected and used by medical professionals and universities worldwide. UpToDate is probably the most trusted clinical decision support resource in the world.

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Saturated Fats and Coronary Heart Disease

For decades, doctors, dietitians and other medical professionals have recommended that we limit the intake of saturated fats in order to reduce the risk of coronary heart disease.

When it comes to dietary advice, avoiding animal and dairy fats has frequently been top of the list among the experts. Red meat, whole-fat milk, cheese, cream, butter and eggs should be avoided as much as possible.

Slowly but securely this has become ingrained into our way of thinking. Having eggs and bacon for breakfast is associated with a feeling of guilt. We can almost vision the fat plugging our arteries. So strong is the power of education.

Health officials have urged us to avoid saturated fats as much as possible, saying it should be replaced with polyunsaturated fats like that found in nuts, fish, seeds and vegetable oils.

In an article updated September 24, 2014 the recommendations of the American Heart Association are very clear:

Eating foods that contain saturated fats raises the level of cholesterol in your blood. High levels of LDL cholesterol in your blood increase your risk of heart disease and stroke.

Eating foods that contain saturated fats raises the level of cholesterol in your blood. Be aware, too, that many foods high in saturated fats can be high in calories too.

The American Heart Association recommends aiming for a dietary pattern that achieves 5% to 6% of calories from saturated fat. That means, for example, if you need about 2,000 calories a day, no more than 120 of them should come from saturated fats. That’s about 13 grams of saturated fats a day.

One of the main reasons saturated fats have a bad reputation is that they increase LDL-cholesterol, a type of cholesterol associated with risk of heart attacks.

However, the effects of saturated fats on blood lipids are much more complex than that.

For example saturated fats also increase HDL-cholesterol, the so-called good cholesterol. Furthermore, intake of saturated fats appears to increase the size of LDL-particles. In theory, this could help reduce risk.

So the association with blood lipids is hardly reason enough to advise against the intake of saturated fats. Then, what is?

During the last ten years, a substantial amount of evidence has emerged suggesting that the association between saturated fats and coronary heart disease is either very weak or may not exist at all. Nonetheless, public health authorities have stood firmly by their earlier recommendations.

Recently a large meta-analysis of observational studies found no relationship between the intake of saturated fats and coronary artery disease.

Although many experts did criticize this paper, it certainly doesn’t add any support to the conclusion that eating saturated fats is associated with increased risk.

UpToDate’s recent revision indicates their experts have taken these recent data very seriously:

Although it is known that there is a continuous graded relationship between serum cholesterol concentration and coronary heart disease (CHD), and that dietary intake of saturated fats raises total serum cholesterol, a 2014 meta-analysis of prospective observational studies found no association between intake of saturated fat and risk for CHD.

The meta-analysis also found no relationship between monounsaturated fat intake and CHD, but suggested a reduction in CHD with higher intake of omega-3 polyunsaturated fats; a benefit with omega-6 polyunsaturated fats remains uncertain.

Given these results, we no longer suggest avoiding saturated fats per se, although many foods high in saturated fats are less healthy than foods containing lower levels.

The Bottom Line

In 1977 senator George McGovern’s Select Committee on Nutrition and Human Needs published its famous report, “Dietary goals for the United States”, highlighting the importance of limiting the intake of saturated fats.

Following the publication, Doctor D.M. Hegsted, professor of nutrition at Harvard School of Public Health, who assisted in the preparation of the report said: “The question to be asked, therefore, is not why should we change our diet but why not. What are the risks associated with eating less meat, less fat, less saturated fat, less cholesterol, less sugar, less salt and more fruits, vegetables, unsaturated fat and cereal products – especially whole grain cereals? There are none that can be identified, and important benefits can be expected.”

In my opinion, these words reflect the unscientific approach of the committee.

Certainly Hegsted had developed the so-called “Hegsted equation” showing that cholesterol and saturated fats raised blood levels of LDL-cholesterol while monounsaturated fats had little effect and polyunsaturated fats appeared to lower the levels.

However, at that time there was no evidence that the effect on LDL-cholesterol was a measure of a heart healthy diet. It was only a hypothesis, yet to be tested.

Today, blaming the rising incidence of coronary heart disease 40-50 years ago on the intake of red meat, whole-fat milk, cheese, cream, butter and eggs appears naive at best.

To condemn one macronutrient and suggest it be replaced with another, without having any scientific evidence that such and intervention is helpful, would today be considered careless and irresponsible.

Sticking with the same conclusion for 40 years, despite abundant contradictory evidence is shocking and hard to understand. Hopefully, UpToDate’s recent reconsideration of the issue is a sign that the tide is turning.

Of course, there’s no reason to promote high consumption of saturated fats and surely there will often be healthier options. However, it’s time we stop telling people that avoiding saturated fats may protect them from heart disease. Why should we say such a thing if it’s not supported by evidence?

It will be interesting to see how public authorities such as the American Heart Association will react to recent scientific evidence on the proposed link between saturated fats and coronary artery disease. Will we  see a change in the forthcoming 2015 version of The Dietary Guidelines for Americans?

Will their approach be evidence-based or not? Will they accept that red meat, whole-fat milk, cheese, cream, butter and eggs can be a part of a healthy diet? Will they reconsider their recommendations like UpToDate now has officially done? Only time will tell.

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Fish Oil – Health Benefits of Omega-3 Explained

Estimated reading time: 10 minutes

Fish oil is one of the most commonly used dietary supplement.

It has been recommended by some major societies and public health authorities for cardiovascular risk modification, to treat high blood triglycerides and as a treatment following acute myocardial infarction (heart attack).

However, many questions remain unanswered. How does fish oil improve health? Is the evidence strong enough to recommend its use? Should it be recommended to everyone or only those at increased risk of heart disease? Are there any side effects? What’s the optimal daily dose? Is consuming oily fish enough or do we need additional fish oil supplement?

History

More than forty years ago, Danish scientists found that the total amount of fat in the diet of Americans, Danes and Greenland Eskimos was similar (1).

At the same time they reported that the death rate from coronary artery was much lower among the Greenland Eskimos, compared with the Americans and Danes.

While visiting Greenland and studying the diet of the native Eskimos, the Danish researchers found that their diet was indeed quite different from that in the US and Denmark.

The fat content of the native diet was largely from whale blubber, seal fat, and fish fat, all very high in omega-3 fatty acids.

The scientists attributed the low death rate from heart disease among the Eskimos to the high consumption of marine-derived omega-3 fatty acids.

Recently, a Canadian paper (2) claimed that the Danish researchers may have underestimated the incidence of coronary artery disease among the Inuits, and therefore their conclusions may not be valid. However, these early studies sparked a great amount of interest among scientists in the possible cardiovascular benefits of omega-3 fatty acids.

Since then, scientific studies have have identified two types of long chain omega-3 polyunsaturated fatty acids in fish oils as the most likely active constituents behind the positive health effects of seafood. These are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

Omega-3 Fatty Acids

The body can synthesize most fatty acids as it needs them. Therefore, it is not necessary to get them in the diet.

Some fatty acids cannot be produced by the human body. This is true for the omega-6 and omega-3 fatty acids. These fatty acids must come from food and are therefore called essential fatty acids.

Omega-3 fatty acids are polyunsaturated fatty acids with a double bond at the third carbon atom from the end of the carbon chain. There are three main types; alpha-linolenic acid (ALA), EPA and DHA. ALA is found in many vegetable oils (rapeseed, flaxseed, and soybean), seeds and nuts. EPA and DHA are typically found in fatty fish and fish oils.

Docosahexaenoic acid (DHA) is a chain of 22 carbon atoms with six double bonds (22:6)

ALA is an 18-carbon fatty acid with three double bonds (18:3). It can be elongated and desaturated in the body to EPA with 20 carbon atoms and five double bonds (20:5) and DHA with 22 carbons and six double bonds (22:6).

However, for these reactions to occur it must compete with omega-6, so only a fraction of ALA is converted to EPA and DHA.

Like other dietary fatty acids, EPA and DHA are transported in the circulation mainly as triglycerides in lipoprotein particles. These two fatty acids are incorporated into phospholipids in cell membranes throughout the body, particularly in the heart and brain. They are also stored in fat tissue as triglycerides.

The Effects of Fish Oil on Health and Cardiovascular Disease Mechanisms

The intake of marine omega-3 fatty acids may have several health benefits. For example, some studies suggest positive effects on rheumatoid arthritis (3), inflammatory bowel disease (4) and Alzheimer’s disease (5). There is also evidence suggesting that fish oil may promote hair growth (6).

Most of the research on the possible health benefits of omega-3 fatty acids has been within the field of cardiovascular medicine. Several studies have addressed the effects on cardiovascular risk factors, endothelial function, blood clotting and inflammation.

Fish Oil and Blood Lipids

High blood levels of triglycerides, LDL cholesterol (the bad cholesterol) and low levels of HDL cholesterol (the good cholesterol) are associated with increased risk of heart disease.

Intake of fish oil can lower blood levels of triglycerides by as much as 50 percent (7). Relatively high doses are needed to achieve this effect (up to 3-4 g/day).

Fish oil consumption modestly elevates blood levels of LDL cholesterol and HDL cholesterol.

Intake of omega-3 may lower the preponderance of small dense LDL-particles (8). This may account for the slightly raised LDL cholesterol. Large particles can carry more cholesterol. However, small LDL-particles have a stronger association with cardiovascular risk than large particles (9).

Fish Oil, Blood Pressure and Heart Rate

High blood pressure is a risk factor for coronary artery disease, heart failure and stroke.

Many studies have addressed the effects of fish oil on blood pressure. A meta-analysis of 36 randomized trials (10) indicated that fish oils may reduce both systolic and diastolic blood pressure, especially among elderly people with hypertension. Relatively high doses were used in most of these studies (median dose 3.7 g/d).

 

It is believed that the blood pressure lowering effects of fish oil is due to reduced vascular resistance in small arteries, probably mediated by increased production of nitric oxide. Nitric oxide is a powerful vasodilator (dilates arteries).

Studies also suggest that intake of fish oil lowers heart rate (11).

Fish Oil and Endothelial Function

The endothelium is a thin cellular layer lining the innermost part of the arteries. Endothelial cells are in direct contact with circulating blood. The endothelium plays an important role for the regulation of blood flow.

Abnormal endothelial function is often found among people with high blood pressure, diabetes and heart disease. Improving endothelial function may be important for individuals suffering from these disorders.

Several randomized studies have suggested that fish oil improves endothelial function (12).

This effect may explain some of the proposed beneficial effects of omega-3 fatty acids on cardiovascular function.

Fish Oil and Blood Clotting

During the early studies of the dietary habits and health of the Inuits it became apparent that they often suffered from nose bleeds. This is probably due to the increased bleeding time caused by ingestion of high doses of omega-3 fatty acids.

Despite the increased bleeding time, clinical studies have not shown that high doses of omega-3 fatty acids increase the rates of clinical bleeding problems (13).

Whether fish oils can reduce the risk of thrombosis (blood clotting inside blood vessels) remains to be proven.

Fish Oil and Inflammation

EPA and DHA are precursors to substances called eicosanoids. Eicosanoids are important regulators of inflammation.

Therefore, many experts believe that fish oils may help to reduce chronic low-grade inflammation.

Although some studies have not been able to show that fish oil consumption reduces blood markers of inflammation, other studies (14) have suggested that they may do so when relatively high doses are given (> 2 g/day).

Clinical Efficacy of Fish Oil

The clinical efficacy of fish oil has been intensively studied, particularly in the field of cardiovascular disease. A number of trials haves assessed the effects on coronary heart disease, arrhythmia (heart rhythm disorders) and sudden death.

Many experts believe that the positive effects of fish oil consumption on blood lipids, blood pressure, endothelial function, blood clotting and inflammation may be translated into improved clinical outcome.

There are three important questions that have to be asked about the efficacy of fish oils when it comes to cardiovascular disease. Firstly, does intake of fish oils lower the risk of healthy individuals. Secondly, does fish oil reduce risk among people at increased risk. And finally, does fish oil consumption improve outcome among these already affected by heart disease?

So, what do the studies say?

Fish Oil and Coronary Artery Disease

Observational studies on the consumption of fish and fish oils among western populations have shown conflicting results.While some studies have indicated less risk of cardiovascular disease among individuals with high consumption of fish and fish oils, others have not (15, 16).

In a large Japanese cohort, where the intake of omega-3 fatty acids was high, consumption of fish and fish oils was associated with reduced risk of coronary heart disease (17).

One systematic review and meta-analysis pooled data from 19 large prospective cohort studies and randomized trials in participants consuming either fish or fish oil supplements. The study found that consumption of marine omega-3 fatty acids was associated with lower risk of death from heart disease and sudden cardiac death (18).  The authors concluded that the benefits of fish consumption exceed the potential risks.

 

Randomized clinical trials have studied whether fish oil intake may reduce the risk of cardiovascular events. Some of these studies have indicated a positive effect while others have not.

One of the first randomized trials addressing the issue was published in 1989 (19). Two groups of more than 1000 men each who had just had a myocardial infarction (heart attack) were studied. One group was advised to ingest oily fish two times a week. The other group was not given this advice. After two years, there was a 29% reduction in life-threatening arrhythmias in the men advised to eat oily fish compared with the other group.

These initial results were later supported by the GIZZI-Prevenzione Trial (20), a large prospective randomized trial of more than 11.000 patients who had a recent myocardial infarction. Compared with placebo, 850 mg EPA+DHA significantly lowered the risk of death due to cardiovascular causes as well as death from all causes. There was a 45 % reduction in the risk of sudden death.

However, these highly positive results were not replicated in subsequently published large trials (21, 22, 23).

A meta-analysis of available randomized clinical trials published 2012 indicated that omega-3 fatty acid supplementation was not associated with a lower risk of heart attack or stroke or death from any cause, death from heart disease or sudden death (24).

The large Risk and Prevention Study, a double-blind placebo controlled trial published 2013 enrolled 13.513 patients with multiple cardiovascular risk factors or known cardiovascular disease (24). Patients were assigned 1 g/day of omega-3 fatty acids or placebo (olive oil). After a median follow–up of five years, the number of cardiovascular deaths, heart attacks and stroke was similar in both groups.

In this study, the participants received maximal medical therapy including aspirin, angiotensin-converting enzyme (ACE) inhibitors, beta-blockers and cholesterol-lowering drugs. It has been suggested that the beneficial effects of omega-3 fatty acids may be diminished in patients already receiving aggressive risk management.

Administration and Dosing

EPA and DHA are found in cold-water fish such as salmon, mackerel, halibut, sardines, tuna, and herring.

Many over-the-counter preparations of fish oil are available. There is also a prescription formula (Lovaza, Omacor) in the US.

Different fish oil formulations contain variable amounts of EPA and DHA. Thus, a 1 g capsule may contain between 200 and 950 mg of EPA and DHA. A common amount in fish oil capsules is 180 mg of EPA and 120 mg of DHA, a total of 300 mg (EPA + DHA).

It is believed that a reasonable target intake to affect cardiovascular risk is 250 to 500 mg/day of EPA + DHA. This can be achieved by 1 g/day of fish oil supplement (between 200 to 800 mg of EPA+DHA, depending on the formulation) or 1-2 servings per week of fatty fish.

Although it appears that higher doses are safe, the US FDA does not recommend ordinary daily intakes of more than 2 g EPA+DHA. However, doses of 4 g/day have been approved for the treatment of high blood triglycerides (hypertriglyceridemia).

Fish Oils and Cardiovascular Disease – The Bottom Line

Treatment with marine-derived omega-3 fatty acid for the prevention of major cardiovascular adverse outcomes is supported by a number of randomized clinical trials and refuted by others.

Therefore, it is hard to give general advice on fish oil as a tool to reduce the risk of cardiovascular events among healthy people or to improve prognosis among those already affected by cardiovascular disease.

We will have to await results from ongoing clinical trials to further clarify this issue.

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