It is estimated that there are more than 100,000 different dietary supplements on the market in North America. Some of these, like 鈥渄etox鈥� supplements are totally useless, others such as immune boosters and megadoses of antioxidants have insignificant evidence while multivitamins mostly amount to an expensive soothing of nutritional anxieties without any evidence of reducing the risk of cancer, cardiovascular disease, cognitive decline or all-cause mortality in the general population. However, there are some supplements that are supported by clinical evidence in some situations. Vitamin D for bone strength, creatine for short bursts of muscle activity, probiotics for gut health, and omega-3 fatty acids for cardiovascular health. In any discussion of supplements, it has to be mentioned that these products are very loosely regulated and do not require evidence of efficacy before being marketed. Furthermore, numerous studies have shown that the content of the product does not always conform to what is indicated on the label.
Omega-3 fatty acids merit discussion because they have been extensively studied and have shown potential for benefit in at least some clinical trials. The term 鈥渙mega-3鈥� refers to an aspect of molecular structure. Fatty acids are composed of a chain of carbon atoms with the last carbon referred to as the 鈥渙mega鈥� carbon from the Greek for 鈥渓ast.鈥� If there are multiple double bonds holding the carbons together in the chain and the first one encountered counting from the end of the chain is on the third carbon, we have an omega-3-fat. If it is on the sixth carbon, we have an omega-6 fat. Omega 3 fats are found mostly in fish, but flaxseed, chia seed and walnuts also contain some. Omega-6 fats are found mostly in seed oils.
There is evidence that increasing the intake of omega-3 fats by people who have a low intake, mostly because of lack of fish consumption, can reduce the risk of cardiovascular disease. There are several plausible mechanisms that can account for the reduced risk. The strongest evidence comes from a reduction in blood triglycerides in response to an increased intake of omega-3 fats. Triglycerides are fats that cruise around in the bloodstream and can penetrate arterial walls and promote the formation of deposits, or 鈥減laques,鈥� that can curb blood flow, or worse, burst and cause the formation of a blood clot that can result in a heart attack. However, if omega-3 fats get incorporated into the deposits they become more stable and less likely to rupture.
The risk of rupture is also increased by chronic inflammation and omega-3 fats have an anti-inflammatory effect. Furthermore, omega-3 fats also get incorporated into cells that line blood vessels, the endothelium, and improve the response to changes in blood pressure. There is also a reduced risk of ventricular arrythmias as well as a reduction in the risk of blood clot formation since omega-3 fats reduce platelet aggregation. On the downside, at a high dose, 3-4 grams a day, omega-3s slightly increase the risk of atrial fibrillation.
How does one decide if taking an omega-3 supplement is indicated? For someone who consumes no fish, a supplement of 1-1.5 grams of combined eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is likely worthwhile. But really the only way to know one鈥檚 omega-3 status is to do a blood test. Much has been made of the fact that the ratio of omega-3 to omega-6 fats has steadily dropped in the western diet, mostly due to increased consumption of processed foods loaded with omega-6 fats. This has been linked to an increased risk of cardiovascular disease. A Norwegian multi-level-marketing company, Zinzino, claims to have come up with a way to reduce the risk by improving the omega-3/omega-6 ratio with a dietary supplement made of fish oil, with the optimal dose being determined by a blood test.
The customer performs a simple finger prick and places a drop of blood on a filter paper that is then mailed to the company. The omega-3/omega-6 ratio is determined, and an appropriate dose of the supplement is suggested, which of course is available from the company. Besides the fish oils, the supplement also contains an extract of extra-virgin olive oil with the claim that its polyphenol content protects the fish oil in the supplement as well as fats in human cells from oxidation. There is no bargain here. The test costs about $170 US and the supplements run around $50 a month.
After several months on the supplement, the ratio of omega-3 to omega-6 has been shown to increase, but there are no studies to indicate that this results in a clinical benefit, that is in a reduction of adverse cardiovascular events. Zinzino marketing often implies improvements in inflammation, immunity and longevity without any evidence. Such hype is unfortunately a common feature of muti-level-marketing companies with independent distributors making unfounded claims.
A better and cheaper way to get a handle on one鈥檚 omega-3 status is a blood test, known as the 鈥渙mega-3 index.鈥� This measures the most important omega-3 fats, EPA and DHA, as a percentage of total fatty acids in red blood cell membranes and reflects an average intake over 3-4 months since that is the lifetime of red blood cells. The index has been correlated with outcome data and when omega-3 fats are less than 4% of total fatty acids, there is a higher risk of cardiovascular disease. The range of 8-12% is associated with the lowest risk. This suggests that risk is actually a function of the absolute level of EPA and DHA which this test measures. The ratio of omega-3 to omega-6 fats is not as good an indicator because this ratio can be improved not only by increasing omega-3 fats but also by reducing omega-6 fats in the diet. It is well established that reducing omega-6 fats does not improve cardiovascular outcomes.
What is the bottom line here? Forget the Zinzino ratio test and the expensive supplements. If fish intake is low, consider an inexpensive omega-3 supplement, 1-1.5 grams combined EPA and DHA a day. If you want to be scientific about it, a finger prick test to determine the omega-3 index is available from several laboratories for about $55 US. If the index comes out to less than 4%, then a supplement is probably beneficial. Is there any risk? Minimal. At high doses, 3-4 grams, there is an increased risk of atrial fibrillation but there is no reason to take such a high dose. The small anticoagulant effect attributed to fish oils may be of importance to someone already taking anticoagulant medication. There is one other concern. Fish oil supplements can result in burps that will make any cat in the neighbourhood drool.
