10 Scientific Facts About Diet and Inflammation

Most of us realize that lifestyle plays a profound role in many of the chronic diseases of modern society.

Despite our knowledge, it seems that somewhere along the path we have gone astray.

Body weight is on the rise and people are becoming more sedentary. Obesity, the metabolic syndrome, and type-2 diabetes are becoming public health problems of pandemic proportions.

Top 10 Things You Should Know About Diet and InflammationHowever, adherence to a healthy lifestyle, including a healthy diet and regular physical exercise could turn things around and cut the burden of many modern diseases.

Many physicians still believe that a low-fat diet is the healthiest food choice, and the most effective one to reduce the risk of heart disease. This assumption is based on the diet-heart hypothesis suggesting that high consumption of fats, saturated fats, in particular, will increase blood levels of cholesterol and thereby the risk of heart disease.

However, this simplified view dismisses a huge amount of scientific data suggesting that the effects of diets on cardiovascular health are mediated through many biologic pathways other than cholesterol, including oxidative stress, low-grade inflammation, insulin sensitivity, endothelial dysfunction and blood clotting mechanisms.

Low-grade inflammation has recently emerged as a common underlying cause of many chronic diseases. Heart disease, type 2 diabetes, Alzheimer’s disease and many types of cancer have all been associated with chronic inflammation. Recently, diets that involve cleansing have become popular based on the assumption that these may rid the body of harmful chemicals and thereby reduce inflammation.

However, we should be aware that inflammation is a double-edged sword.  Inflammatory responses triggered by our immune system offer protection from many diseases, such as infections and cancer. Thus, when inflammation is appropriate, it protects us from disease. However, when inflammation is inappropriate or gets out of hand it can promote disease.

Acute inflammatory reactions are usually self-limiting and resolve rapidly. If you cut your finger and notice it turns a little red, it is probably due to inflammation. Inflammation is important for the healing process. Regulated inflammatory responses are essential to our health and wellbeing. This is totally different from chronic or low-grade inflammation. In low-grade inflammation, the immune response continues and appears uncontrolled, making inflammation a problem in itself.

Choosing a proper diet is one of the most effective lifestyle measures available to lessen the risk of disease. Recently, much has been written about food products and dietary approaches that either promote or reduce systemic inflammation. However, keep in mind that much of this is only speculation, and some is pure marketing. Despite immense research, our knowledge of the effects of different foods on inflammation is limited. More research is needed to better define and understand the relationship between diet and inflammation.

In order to know whether food products or specific diets affect inflammation in a positive or negative way, we have to be able to measure inflammation. Most commonly, blood measurements of so-called inflammatory biomarkers are used to determine whether systemic inflammation is present or not. Thus, a simple blood sample can sometimes give us an answer.

Many observational trials and clinical studies have used high-sensitivity C-reactive protein (hsCRP)  to test the relationship between nutrient intake and systemic inflammation. Other inflammatory markers such as tumor necrosis factor-alpha (TNF-alfa), Interleukin-1 (IL-1), and Interleukin-6 (IL-6) have been used as well.

Before we go further it is important to understand that it has not been proven that every food product that increases inflammatory markers will increase the risk of disease. Similarly, it has not been proven that foods that decrease inflammatory markers will always protect from disease.

Epidemiological and interventional studies have been used to assess a possible relationship between dietary patterns and inflammation. Although epidemiological studies may show a correlation between the consumption of specific food products and inflammation, they are seldom able to proof a causative relationship. On the other hand, intervention studies are usually designed to test whether a causative relationship is present or not.

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1. Obesity is Associated with Low-Grade Inflammation

Elevated blood levels of inflammatory markers are commonly found in people with type 2 diabetes or the metabolic syndrome. These two conditions are commonly associated with obesity. In general, inflammatory mediators are higher in obese than normal weight persons. However, there is a substantial overlap between non-obese and obese persons.

It has been shown that adipose (fat) tissue synthesizes and releases pro-inflammatoty cytokines. Adipose tissue is a major source of pro-inflammatory mediators which may initiate the development of chronic inflammation, insulin resistance and possibly atherosclerosis. Interestingly, adipose tissue in the chest or abdomen, often termed visceral or central obesity, results in an increased risk of diabetes and heart disease.

VOn the other hand, excess fat tissue in the lower part of the body, often termed gynoid obesity, is not associated with increased risk. Abdominal fat is associated with chronic elevation of inflammatory markers. It appears that the anatomical localization of fat tissue is of paramount importance when it comes to low-grade inflammation.

Many studies have shown that weight loss is associated with decreased concentration of inflammatory markers. However, it is sometimes difficult to tell whether this effect is due to the weight loss per se or to the nature of the diet used to induce weight loss.

Bottom line: Low-grade inflammation is associated with obesity, type 2 diabetes, and the metabolic syndrome. Abdominal obesity is much more strongly associated with inflammation, diabetes, and heart disease than fat accumulation in the lower part of the body. Losing weight will usually reduce low-grade inflammation.

2. Type of Carbs May Affect Inflammation 

Diets with a relatively high glycemic index (GI)were found to be associated with higher levels of CRP in a large group of women participating in the Harvard Women’s Health Study. The relationship between GI and inflammation has been confirmed in a few other studies, although there have been some inconsistencies between trials.

Fiber consumption was associated with less inflammation in seven studies using hsCRP as a marker of inflammation.

Although the mechanisms underlying the associations between GI and inflammation are not fully clear, some data shows that rapid changes in blood sugar levels may increase free radicals and pro-inflammatory cytokines, leading to inflammation.

In general, whole grains are associated with less inflammation than refined grains. This may be due to one or many of the active constituents of whole grain which may include dietary fiber, minerals, vitamins, and phytochemicals.

Bottom line: In order to minimize inflammation, choose complex carbohydrates rich in fiber, rather than simple refined sugars.  Whole grains are associated with less inflammation than refined grains.

3. Fruit and Vegetables Reduce Inflammation

Numerous studies indicate that the consumption of fruits and vegetables is associated with less inflammation. In the MESA study, dietary patterns including fruit and vegetables were associated with lower levels of inflammatory markers. A randomized German study found that healthy non-smoking men randomized to 8 servings of fruit and vegetables for 4 weeks had lower levels of hsCRP.

Observational studies have shown that vegetarian diets are associated with lower concentrations of inflammatory markers compared with non-vegetarian diets. This effect may be associated with less risk for heart disease.

Bottom line: Making fruits and vegetables a large part of your daily diet will reduce inflammation.

4. Trans-Fatty Acids Promote Inflammation

There is strong evidence that consumption of trans-fats increases systemic inflammation. In the Harvard Nurses Health Study, consumption of trans-fats was associated with higher levels of inflammatory biomarkers. This relationship was stronger among women who were overweight.

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5. Saturated Fats May or May Not Promote Inflammation !

There is some evidence indicating that the consumption of saturated fats may increase the levels of inflammatory biomarkers. An Indian study of adolescents and young adults found that saturated fatty acids were the single most important nutrient causing an elevation of hsCRP. However, a Swedish study of healthy elderly men and women did not find an association between levels of saturated fatty acids in cholesterol esters and hsCRP.

A study in overweight adolescents showed a positive correlation between blood levels of saturated fatty acids and inflammatory markers. Another study found such a correlation in overweight subjects but not in lean individuals. However, it is important to keep in mind that blood levels of saturated fats are not only determined by the amount of saturated fat consumed.

Research has shown that in people with metabolic syndrome, a low-carb, high-fat diet decreases blood levels of saturated fat, whereas a low-fat diet saw no decrease in blood saturates. In their book The Art and Science of Low Carbohydrate Living, Volek and Phinney propose that this paradox may occur “because keto-adapted people dramatically increase the rate their bodies burn saturated fat”.

Therefore, whether saturated fats promote inflammation appears a bit controversial. It may depend on the amount as well as the type of saturated fat.

A recent study indicated that exchanging saturated fats with polyunsaturated fatty acids (n-6) may reduce the inflammatory response to a mixed meal among overweight men.

Bottom line: There appears to be a positive correlation between blood levels of saturated fats and blood levels of inflammatory markers. Replacing saturated fats with polyunsaturated fatty acids may reduce inflammation.

6. Omega-3 Fatty Acids Are Associated With Less Inflammation

Numerous studies have shown that consumption of omega-3 fatty acids is associated with lower levels of inflammatory markers. In a Norwegian study, consumption of food products rich in omega-3, such as salmon was associated with a significant reduction in IL-6.

Studies on the consumption of omega-6 fatty acids have shown conflicting results. However, there is some evidence that high consumption of omega-6 fatty acids may reduce the protective effect of omega-3, indicating that the ratio of omega-3/omega-6 consumed may be of importance.

Western diets are deficient in omega-3 fatty acids and have excessive amounts of omega-6 fatty acids compared with the diet on which human beings evolved. A lower ratio of omega-6/omega-3 fatty acids is often considered desirable. In the Greece ATTICA study, the ratio of omega-6/omega-3 fatty acid consumption was strongly related to biomarkers of systemic inflammation.

In one study, high intake of both omega-3 and omega-6 fatty acids was associated with the lowest level of inflammation. Another study indicated that the combined intake of these fatty acids is associated with lower risk of cardiovascular disease than either type of fatty acid alone. A recent overview of randomized trials indicated that increasing the consumption of omega-6 fatty acids does not increase markers of systemic inflammation.

Despite the widely held view that consumption of omega-6 may increase inflammation, scientific studies have provided conflicting results. So, whatever you may read about omega-6 causing inflammation and the importance of omega-6/omega-3 ratio, scientifically this issue appears less clear than you might think.

Bottom line: Diet rich in omega-3 fatty acids reduces inflammation.

7. Monounsaturated Fats Reduce Inflammation

A few studies indicate that dietary consumption of monounsaturated fats, oleic acid, in particular, may reduce biomarkers of inflammation.

One of the chief sources of this acid in foods is olive oil.  Canola oil, rapeseed oil, and grapeseed oil also contain oleic acid. Many nuts and seeds contain oleic acid, and it can also be found in most poultry, particularly chicken and turkey.

8. A Mediterranean Diet Is Anti-Inflammatory

13911967_mThe term Mediterranean diet refers to a traditional dietary pattern characteristic of many parts of Greece, Southern Italy, Southern Spain and elsewhere in the Mediterranean region. It is rich in fruit, vegetables, whole grains, beans, nuts, fish and low-fat dairy products. There is usually moderate consumption of wine and the principal source of fat is olive oil.

Observational studies have generally reported low inflammatory markers associated with the Mediterranean diet. A few intervention studies have been conducted to assess the effects of this diet on low-grade inflammation, a few of them relatively large. Taken together, the results from these studies strongly suggest that a Mediterranean-type diet reduces chronic low-grade inflammation and lowers the risk of heart disease.

Bottom line: A Mediterranean diet is a good example of a diet that reduces low-grade inflammation and at the same time appears to reduce the risk of heart disease.

9. Carotenoids and Flavonoids May Reduce Inflammation

Carotenoids are a class of more than 600 naturally occurring pigments synthesized by plants, algae, and photosynthetic bacteria. These richly colored molecules are the sources of the yellow, orange, and red colors of many plants. Fruits and vegetables provide most of the carotenoids in the human diet.

Flavonoids are compounds found in fruits, vegetables, and certain beverages that have diverse beneficial biochemical and antioxidant effects.

The consumption of carotenoids and flavonoids has been associated with lower levels of inflammatory markers.

10. Magnesium Intake Is Associated with Less Inflammation

Whole grain is one of our most important sources of magnesium. Other sources are green leafy vegetables, nuts, and legumes.

Magnesium consumption is associated with low levels of inflammatory markers in post-menopausal Women.

Recent evidence from epidemiologic studies suggests that magnesium intake is inversely associated markers of inflammation. Animal studies have provided mechanistic possibilities to explain a possible link between magnesium and inflammation. However, further studies are needed in order to better understand this relationship.

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85 thoughts on “10 Scientific Facts About Diet and Inflammation”

  1. When all is said and done I suspect that the beneficial effects of the Mediterranean Diet will prove to be more from its anti-inflammatory actions than the very modest effect on blood lipids. That would help explain the 75% lesser likelihood of dying of heart disease observed in Crete compared to the US in the Seven Countries Study, at equivalent cholesterol levels, along the whole range of cholesterol levels.

    Very helpful review Axel.

  2. “The term Mediterranean diet refers to a traditional dietary pattern characteristic of many parts of Greece, Southern Italy, Southern Spain and elsewhere in the Mediterranean region. It is rich in fruit, vegetables, whole grains, beans, nuts, fish and low-fat dairy products.”

    I’m curious whether it was traditional in the Mediterranean region to reduce the fat content of dairy products before consuming them? Seems like full fat dairy is more likely. And what about meat consumption?

    My understanding is that those cuisines traditionally had ample amounts of lamb, pork, goat, and some beef. The Mediterranean diet is not known to be low fat or vegetarian, except in modern books trying to sell the Mediterranean diet. That’s not to say the traditional Mediterranean diet isn’t a good one for reducing inflammation, but you make it sound like a vegetarian and low fat diet, which it is not.

    • Janknitz. I agree with you, the Mediterranean diet is not a low fat diet. There is high consumption of monounsaturated fats and to some extent polyunsaturated ones. However, the consumption of saturated fats is relatively low.

      This is how the concept is introduced in the ATTICA study paper: “A diet rich in fruits, vegetables, legumes, whole grains, fish, nuts, and low-fat dairy products protects against the development and progression of CVD. The traditional Mediterranean diet, whose principal source of fat is olive oil, encompasses these dietary characteristics”. These are basically the same words I used when describing a Mediterranean diet.

      So, according to the commonly used definitions, the consumption of read meat is rather low. However, it´s absolutely not a vegetarian diet, and not a low fat diet either. I´apologize if i made it sound like that. It wasn´t my intention.

      • I think it’s worth adding that dairy products are mostly consumed in the form of cheese and yoghurt, that is, in fermented form. Some studies have shown that fatty cheese doesn’t e.g. raise LDL levels as compared to high fat dairy products, e.g. butter.

      • Here’s another opinion about what comprises the Mediterranean diet: https://www.westonaprice.org/traditional-diets/mediterranean-diet

        We see people like Keyes who characterized these diets in the fifties, relatively soon after WWII in countries devastated by the war and by economic depression that led up to the war years. Meat may not have been abundant at that particular time for those reasons. It does not mean that Mediterranean people traditionally ate little or no meat. And you’ll never convince me that their dairy was low fat.

        I cannot imagine native people in these Mediterranean areas avoiding fish and seafood (in the south), eggs, chicken, turkey, ducks, geese, lamb, pig, goat, and beef, not also drinking Unfermented whole fluid milk from their dairy animals,or not making or consuming butter. Perhaps the animals that populated their bucolic and pastoral scenes were for decoration???

        Maybe the ATTICA study scientists should have looked up from their precious theories and taken a look at old cookbooks or asked participants what their grandparents ate.

      • Janknitz, you’re more or less making the same mistake which I mentioned below. To quote myself:

        “There’s a slight difference there between Mediterranean diet as used in modern interventions and described in modern epidemiological data and Mediterranean diet as found on Crete in the late 1940s, but there’s no reason to get stuck with the latter when there’s evidence to indicate that the former works.”

        Of course you can bounce the questions of how much meat was consumed etc. back and forth (based on selected cook books and other non-scientific sources), but that does nothing to change the facts. Mediterranean diet as used in interventions & defined as e.g. in ATTICA has quite an extensive amount of evidence to back up the health claims. And this diet is not a high meat diet – nor that high in animal products in general.

      • No mistake. As Doc points out “The term Mediterranean diet refers to a TRADITIONAL dietary pattern characteristic of MANY parts of Greece, Southern Italy, Southern Spain and elsewhere in the Mediterranean region.

        ATTICA notwithstanding, it is the the TRADITIONAL diet I believe he was referring to, not modern and contrived interventional diets based on Food Fact Questionnaires.

        The traditional Mediterranean diet may not be “high meat”, but nor is it meatless or low fat. From the description given, it sounds like My Plate with Olives. Hardly.

      • You’ll have to ask Axel what he’s referring to exactly, but the diet proven efficient by e.g. RCT evidence (PREDIMED, Lyon Heart Study) and epidemiological evidence is precisely the “modern” version described e.g. in ATTICA.

        That’s the main point. In fact, the ONLY relevant point from the point of view of the topic (dietary solution for reducing inflammation).

  3. Axel, I mostly agree but the references in the SAFA part are a bit lacking. E.g. the Swedish study is a single cross-sectional study, a design whose problems are quite evident.

    This review

    https://www.ncbi.nlm.nih.gov/pubmed/22133051

    discusses the role of different fats as studied in epidemiological studies. SAFA seems somewhat detrimental in terms of inflammation. And it is widely used in clinical feeding studies to measure post-prandial inflammatory responses. However, it seems that the dose itself is quite important. And, of course, the context: are we talking about hyperlipidemic people or not? People with diabetes or not?

    • You´re absolutely right Mie. I have added some more substance and a few more references to the SAFA discussion.

  4. Doc,

    The Rockefeller institute ran a huge epidemiological research into Crete in 1949. Only 7% of calories came from animal sources (cheese, yogurt), very little fish was consumed. Starch provided theb bulk of the calories. Ancel Keys studied the Cretans as well as the Southern Italians thoroughly. The poor peasant in Southern Italy who were in good health had actually quite a low fat intake (~20% of calories). Keys wanted the world to understand the Mediterranean diet as lacto-ovo-vegeterian diet.

    https://ajcn.nutrition.org/content/61/6/1321S.full.pdf
    https://ajcn.nutrition.org/content/61/6/1313S.full.pdf

    In fact, the New York Times did a great article about the Ikaria island, part if the “blue zone”. The local edlerly people on the island have been raised on plant-based diet. Staple foods of the islanders include potatoes, beans, whole-grain wheat-bread and yes, the olive oil.
    https://www.nytimes.com/2012/10/28/magazine/the-island-where-people-forget-to-die.html?pagewanted=all&_r=0

    I think a better photographic illustration of the Mediterranean diet would have entailed whole-grain bread, pasta, legumes and olive oil. Not Fish! That’s the picture of the diet of the Icelanders.

    • Ok Richard. I´ve already changed the illustration of the Mediterranean diet once. Maybe I should do it again or just skip the picture altogether. There seems to be some disagreement on what the term Mediterranean diet implies.

    • There’s no need to change the working definition of the diet, as explained in Attica. No basis whatsoever to exclude fish. There’s a slight difference there between Mediterranean diet as used in modern interventions and described in modern epidemiological data and Mediterranean diet as found on Crete in the late 1940s, but there’s no reason to get stuck with the latter when there’s evidence to indicate that the former works.

      • I am not talking about excluding fish, I am talking about images that best convey the essence of the Mediterranian diet. This is about signals. We need to signal that the Mediterranian diet is a plant-based diets centering around whole-wheat products, legumes and greens.Foods of animal origin are used as condiments, they are not the staple food consumed in abundance. Do you think a picture of dead fish represents the Mediterranean diet?

      • This is quite funny. Conveying a message with an illustration is probably more important than I realized. So, I decided to remove the dead fish. Now the composition of the Mediterranean diet is left to the readers imagination.

      • Axel, I absolutely protest! The illustration you’ve added suggests that Mediterranean people ate at place with white table clothes, when the truth (see Keys / Weston A. Price / whoever) obviously is that they dined from tables with NO table clothes whatsover. This picture doesn’t represent the Mediterranean diet and should be scrapped as misleading.

        P.S. 🙂

  5. Hey Axel,

    this is what Keys reported from Italy of the 1950s (see the second link by Marion Nestle), this is from the Naples with mean fat intake accounting for 20% of the calories, the diet typically included:

    “homemade minesterone….pasta in endless variety…served with tomato sauce and sprinkle of cheese, only occasionally enriched with some bits of meat, or served with a little local seafood…a hearty dish of beans and short lenghts of macaroni…lots of bread never more than a few hours from the oven and never served with any kind of spread; great quantaties of fresh vegatables, a modest portion of meat or fish maybe twice a week…wine of the type we used to call “Dago red”…always fresh fruit for desert”.

  6. Thanks for this pretty balanced post. I had missed that Mg story, it was interesting. Best sources of Mg: whole grains, nuts, seeds, cocoa, beans (no animal foods in top).

    You did not cover dairy products. Many paleo fans claim that dairy products are proinflammatory. I guess it would be fair to state that recent meta-analysis of randomized trials showed dairy to be neutral. https://www.ncbi.nlm.nih.gov/pubmed/23446894

    About olive oil and MUFA. It seems that refined olive oil is neutral and extra virgin olive oil is anti-inflammatory. There is data from meal studies, RCTs and cohort studies to support this notion. Here’s just one example in CHD patients https://goo.gl/v9uVwP

    Axel, what’s your opinion on high SFA low carb diets and inflammatory status? There are some clinical trials which have probed into this.

  7. I have to throw in a comment about Olive Oil. Please let’s remember that although olive oil may be used extensively to cook with (and brilliantly marketed) in Mediterranean countries and now around the world, it was used for centuries primarily to fuel furnaces, as lamp-oil or for massaging/cosmetic purposes.
    Remember: The world’s best and most expensive lard also comes from Italy. https://www.discoveritalianfood.com/organic-lard.html.
    Those Cretans were sad that after the war in1949, their access to traditional meats and fats was so limited.
    The famous Roseto community in Pennysylvania maintained its traditional use of lard in cooking right through to the 1960’s before they eventually caught up with American society. Their’s just happens to be the community most spared the ravages of cardiovascular disease… until the 60’s.

  8. I’d rather see and eat a fish than a tablecloth. But, more importantly, the conversation is what I’m consuming here. Thanks!

  9. I should mention, my husband and I are trying to eat a Mediterranean diet. It’s a little tough for me since I cannot eat gluten or dairy. Really appreciate all the evidence-based input.

  10. I am considered obese, I am a good 50 lbs. overweight, I am 50 years old, have had a complete hysterectomy, and am leptin resistant. I have tried every diet known to man, including low carb, but nothing works. Before I turned 40, I didn’t have to worry about weight gain, it just didn’t happen to me. Now? If I even look at food, I gain. My dream is that they come up with an easier way to reverse my leptin resistance soon. I can’t really afford to “eat right”. We are only about to spend about $75 a week on groceries, and that doesn’t get you very far. Hamburger helper and Kraft mac n cheese make frequent appearances in my house.

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