What about the conversion rates of Omega 3 Fatty Acids? Does this affect vegans and vegetarians?
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Numerous chemical and biological processes in the body occur at conversion rates that support health and prevent disease and essential fatty acid conversion is no different. The conversion rate of the pre-cursor Omega 3 fatty acid, α-linolenic acid (ALA) and downstream products is limited, or “tight” with anywhere from minimal to upwards of 20% to EPA and minimal to upwards of 9% to DHA in omnivores and varies due to a number of factors including: age, gender, genes and genotype variability, composition and type of the diet, supplement usage, BMI, caffeine intake, medical conditions such as diabetes, metabolic syndrome, hypertension, or fat mal-absorption, medications like glucocorticoids (prescribed and natural), lack of vitamin and mineral cofactors like zinc, magnesium, niacin, vitamin C, saturated fat and trans-fat from processed vegetable oils).
Depending on needs or conditions, conversion rates increase such as for infants or during early reproductive years in females, or during pregnancy. However, most of the literature has framed this process as inefficient and therefore suggest preformed EPA and or DHA for those without a dietary source of EPA/DHA such as vegans/vegetarians. Few, if any researchers highlight that the other essential fatty acid pathway, Omega 6, shares a similar limited conversion rate to ends end products including Arachidonic Acid. This makes sense, as both pathways produce powerful and potent chemicals and substances. The conversion rate of Omega 6 is even less than Omega 3, thus we certainly wouldn't follow the logic of therefore need to consume or supplement with Arachidonic Acid. Nature doesn't decide which pathway (3 or 6) is considered healthy and which one is not. They are both essential and needed. Both DHA and AA play important separate roles in body functioning including brain.
The body’s processes to ensure homeostasis is well known for other nutrients. Low, does not always mean deficient. A few examples: calcium, heme-iron intake, protein intake – all usually compared to omnivores, in the past were considered to be problematic for vegans and vegetarians. Hence, taken together, I view the conversion rates are intelligently designed rather than of poor efficiency and are functioning as should be. There also may be a valid biochemical reason for lower conversion rates. For example, as omega 3 are anti-inflammatory, slow rates could be a way to ensure that body stays in balance with regard to inflammation and anti-inflammation. Could too much omega 3 suppress immune function and lead to disease? Both Omega 3 and 6 have limited conversion rates and that may be exactly how the body prefers it to be.
While vegans show lower blood or plasma EPA/DHA (but not in all studies) there isn’t sufficient research to demonstrate there is any disadvantage to lower status of these EFA’s. As Sarter (2015) mentioned as part of a vegan and omnivore study, “…at present, there is no direct evidence that raising the omega-3 (intakes) would confer additional health benefits over and above their already-protective vegan diet”. Welch, 2010 suggested while dietary intake of EPA and DHA may vary greatly between fish eaters and vegetarians and vegans, the differences in plasma levels were much smaller than what would be expected by dietary intake. As mentioned, the Adventist Health study 2 findings suggests adipose levels of EPA (as a percent of fatty acids) were similar in both vegans and non-vegans and also had stored low but sizable amounts of DHA suggesting that what is stored in the body maybe quite different than levels seen in blood samples and that the body may convert what is needed, meaning circulating EPA/DHA levels in blood cells may not be as meaningful in attempting to suggest that vegans require supplementation because their blood levels are typically lower than seen in omnivores.
Lastly, if levels are of EPA/DHA are “chronically low” in vegetarians or vegans, we would expect to see an increased in inflammatory mediated disease i.e CVD, diabetes, dementia, rheumatoid arthritis, asthma, systemic lupus erythematosus, multiple sclerosis, as well as other conditions like visual acuity, macular degeneration and dry eye syndrome. Almost all of these are not only not higher in vegans, though a recent Adventist study found an increase in dementia (while almost all other studies did not), but on the contrary, some of these show reduced risk and benefit for those following vegan or vegetarian diets.