Fishing for a link between fat consumption and immunity


Modern changes in food production, such as the introduction of intensive farming methods, food processing and use of pesticides, herbicides and fertilizers have led to cheaper, readily available foods. The consequences of such convenience have led to an influx of food products with poor nutritional value. The substantial rise in highly processed ‘convenience’ and ‘junk’ food has taken over from home cooked meals and, more often than not, such food is being seen as the ‘norm’ and merely part of 21st century living. The long-term effects, however, are routinely and consistently being exposed as having a profound negative effect on our health.

A good diet is central to overall good health and a healthy diet that provides the right balance of carbohydrate, fat and protein can reduce the risk of developing many types of chronic disease. For many years we have been advised that eating too much fat is bad for us, with high-fat diets linked to cardiovascular disease, stroke, obesity related conditions such as metabolic syndrome and type II diabetes, and even some forms of cancer.

A very important element of the diet, however, relates to the types of fat that we eat. Saturated fats and trans fats, found in animal products and processed foods, have a negative effect on our health. In contrast, polyunsaturated fats (omega-6 and omega-3) have substantial beneficial effects on our heath because they are converted in the body to powerful hormone-like substances called ‘eicosanoids’. It is these eicosanoids that regulate physiological functions, with major roles in cardiovascular health, inflammation, immunity and mood.

Consuming a diet that is balanced in these types of fat can help to ensure that our bodies work most efficiently, right down to the cellular level. Consuming too much in the way of omega-6 fatty acids, however, can have negative consequences. Omega-6s are found in plant oils such as vegetable oil and corn oil, or non-organic meat (these animals are fed on grains rich in omega-6), and while omega-6 fats are essential for good health, if omega-3 intake is low, the omega-6 pathway shuttles down an inflammatory route and can result in the over-production of eicosanoids from a specific type of omega-6 called arachidonic acid (AA). This triggers pain processing pathways and increases the production of inflammatory products, which may lead to over-stimulation of the immune system. When, however, adequate omega-3 (which has the opposite effect of omega-6) is consumed, the omega-6 pathway is able to produce anti-inflammatory products from a fatty acid called dihomo-gamma linolenic acid (DGLA), and the production of AA products is reduced.
Indeed, the balance between omega-3 and omega-6 is vitally important for immunity and overall wellbeing, since they interact with each other in the body, affecting various physiological processes. Generally, Western diets are very high in omega-6 and low in omega-3. Increasing omega-3 fatty acids, especially one known as EPA (eicosapentaenoic acid) found in oily fish, can help reduce the production of specific cytokines and proteins, which trigger pain and inflammation and decrease the risk of cardiovascular disease, inflammatory diseases and immune diseases through preventing the incorporation of inflammatory AA.

EPA is known to reduce the incorporation of AA and therefore also the production of inflammatory products and cytokines, making it a sensible solution to increase our omega-3 intake. The easiest, most effective way to do this is to consume more fish. Unfortunately, since there is an association between fish consumption and contamination from levels of toxins such as methyl mercury, PCBs and dioxins, we are restricted in terms of the types of fish we can eat. Larger, longer living species, for example, are more likely to contain higher amounts of contaminants. Therefore, whilst eating fish may be the easiest way to increase omega-3 levels, the risk to health due to contamination levels in some fish species may outweigh the benefits. Highly concentrated and purified fish oil supplements offer a convenient and safe way of ensuring optimal levels of these important fats are met.
Omega-3 supplements rich in EPA are becoming increasingly common as a viable treatment for a variety of conditions where altered immune, inflammatory or pain pathways are present, and there has been a plethora of research investigating the role of omega-3s in managing conditions where there is an exaggerated immune response, increased inflammation and chronic pain.

There are two main omega-3 fatty acids (EPA and DHA) present within fish oil, with differing biological actions. It appears that, of the two, EPA has the strongest effect on inflammation and immunity. Given the large variation in strength and concentration between different products, not all fish oils offer the same benefits and care should be taken if deciding on using fish oils as an alternative/add-on treatment in managing symptoms of a specific condition. For example, both the concentration and ratio of EPA and DHA within fish oil appears to be important. Fish oils that are high in EPA and low in DHA (or absent in the case of Vegepa which contains exclusively EPA omega-3) have been consistently shown to be superior for treating conditions for which exaggerated immune and inflammatory responses are key players.

As such, several authors hypothesise that, in a given supplement, it is the EPA that is in excess of DHA that is the active component, the actions of which are unopposed in the body and are free to exhibit a therapeutic outcome (Martins, 2009, Sublette et al., 2011, Bloch and Qawasmi, 2011). It is likely that the absence of DHA, and therefore absence of competition between EPA and DHA for biological sites of action, may be in part responsible for the positive outcomes seen in such studies. As previously suggested, however, not all omega-6 fats are ‘bad’ for us and the addition of gamma-linolenic acid, (an anti-inflammatory omega-6 found in evening primrose oil) can further prevent AA accumulation, providing enhanced benefits to a supplementation regime through the increased production of DGLA-derived anti-inflammatory by-products (Barham et al., 2000).
It is widely acknowledged that omega-3 fatty acids play an important role in preventing the development of inflammatory diseases by directly and indirectly affecting different stages of the immune response. In addition, EPA and GLA in combination can alleviate inflammatory processes that already exist, thus highlighting the therapeutic importance of incorporating these fatty acids into the diet.

BARHAM, J. B., EDENS, M. B., FONTEH, A. N., JOHNSON, M. M., EASTER, L. & CHILTON, F. H. 2000. Addition of eicosapentaenoic acid to gamma-linolenic acid-supplemented diets prevents serum arachidonic acid accumulation in humans. The Journal of nutrition, 130, 1925-31.
BLOCH, M. H. & QAWASMI, A. 2011. Omega-3 fatty acid supplementation for the treatment of children with attention-deficit/hyperactivity disorder symptomatology: systematic review and meta-analysis. Journal of the American Academy of Child and Adolescent Psychiatry, 50, 991-1000.
MARTINS, J. G. 2009. EPA but not DHA appears to be responsible for the efficacy of omega-3 long chain polyunsaturated fatty acid supplementation in depression: evidence from a meta-analysis of randomized controlled trials. Journal of the American College of Nutrition, 28, 525-42.
SUBLETTE, M. E., ELLIS, S. P., GEANT, A. L. & MANN, J. J. 2011. Meta-analysis of the effects of eicosapentaenoic acid (EPA) in clinical trials in depression. The Journal of clinical psychiatry.

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Dr Nina Bailey

About Dr Nina Bailey

Nina is a leading expert in marine fatty acids and their role in health and disease. Nina holds a master’s degree in Clinical Nutrition and received her doctorate from Cambridge University. Nina’s main area of interest is the role of essential fatty acids in inflammatory disorders. She is a published scientist and regularly features in national health publications and has featured as a nutrition expert on several leading and regional radio stations including SKY.FM, various BBC stations and London’s Biggest Conversation. Nina regularly holds training workshops and webinars both with the public and health practitioners.