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. However, adherence to healthy lifestyle, including 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.
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 du 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 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.
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.
On 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 you choose 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.
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. Consumption of omega-3 fatty acids reduces 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 with 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 also be found in most poultry, particularly chicken and turkey.
8. A Mediterranean diet is anti-inflammatory
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. 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-rade 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.
10. Magnesium reduces inflammation
Whole grain is one of our most important sources of magnesium. Other sources are green leafy vegetables, nuts, and legumes.
Magnesium consumption has been associated with low levels of inflammatory markers in post-menopausal women. In a dietary index developed by the University of South Carolina, magnesium intake was the most highly rated factor.