Omega fatty acids are well known to be important for the normal functioning of our body. These fatty acids are essential for the formation of the cell membrane. They play a critical role in brain health. In addition, they are crucial for fertility, visual acuity, and optimal cardiovascular health. Omega-3 fatty acids also have an anti-inflammatory effect.
DHA is an omega-3 fatty acid. Omega fatty acids belong to a group called polyunsaturated fatty acids (PUFA). There are several kinds of omega-3 fatty acids, but for humans, three of them are considered to be essential. These are alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).
ALA is a short-chain fatty acid that cannot be made by our body and thus regarded as essential. EPA and DHA are classified as long-chain fatty acids. Our body can produce them in small quantities and a very inefficient manner. This is why one’s diet should provide enough of the essential and semi-essential omega-3 fatty acids. ALA is the only fatty acid which is present in plant-based food products.
Although EPA and DHA, both of which are particularly essential for brain health, can be produced in the body from ALA, the conversion process is not very efficient. It is believed that only ~15% of dietary ALA can be converted to EPA or DHA. ALA is present in canola oil, flaxseed oil, and in some other plant oils in sufficient quantities, whereas DHA and ALA are mainly present in seafood (various varieties of fish) and found in small amounts in other animal or poultry products.
Research has shown that although fish are rich in omega fatty acids, they are not able to produce DHA or EPA. In fact, they get omega-3 fatty acids by ingesting phytoplankton. Phytoplankton, in turn, get DHA and EPA by eating microalgae that are able to produce these fatty acids. These findings draw attention to two important facts: the importance of fish and animal products in our diet for optimal cognitive health and the importance of preserving the fragile environmental balance where everything is interconnected.
Omega-3 fatty acids are essential for the formation of phospholipids that are in turn required for cellular membranes. DHA is particularly critical for brain health, as demonstrated by its high content in the brain. Furthermore, since DHA helps to reduce the inflammatory responses, it may have a neuroprotective action.
There are lots of studies regarding the optimal intake of omega-3 and omega-6 fatty acids and their optimal ratio in one’s diet. However, the recommendations in this regard remain inconclusive. Rather than focusing on the total amount of omega fatty acids or the ratio of various fatty acids, one should focus on the overall dietary intake of EPA and DHA.
Although EPA and DHA have been accepted to be essential for wellbeing, healthy aging, and slowing down or preventing neurodegeneration, their levels are rarely assessed in clinical conditions. There is no standardized, universally accepted range, but the most widely accepted normal level is ~3–4% of all plasma phospholipids (for EPA and DHA combined).
Plasma or serum fatty acid values are not very accurate, as they may change according to the content of recent meals. For this reason, many researchers recommend checking the content of EPA and DHA inthe red blood cell membranes, as this can give the approximate average of the last 120 days. At present, for European and American populations, 3–5% of EPA and DHA in erythrocyte membranes is considered in the normal range. In the Japanese population for example, where consumption of seafood is much higher, these numbers may be much higher too.
So what are the dietary recommendations for Omega-3s?
At present, for a healthy brain, it is recommended to consume 1.6 g of omega-3s daily for males, and 1.1 g daily for females. As mentioned earlier, specific attention should be paid to the content of DHA and EPA in food items. Flaxseed oil, chia seeds, and walnuts are all rich in ALA. However, DHA and EPA are mainly present in fish, seafood, and poultry. Considering that only a small amount of ALA can be converted to DHA or EPA, it puts vegans at risk of developing a deficiency in these omega acids and thus raises the risk of neurodegenerative disorders.
To counter the deficit of DHA in plant-based products, many manufacturers have started to fortify soy beverages, juices, and milk products with DHA. Dietary supplements are another way of obtaining sufficient amounts of DHA. However, as most dietary supplements are based on fish oil or krill oil, if a person is strictly vegetarian, they can take algal oil-based supplements.
The National Health and Nutrition Examination Survey (NHANES) 2011-12 indicates that most of the population in the US are obtaining enough dietary omega-3 fatty acids. However, the majority of omega fatty acids are coming from a plant-based diet, meaning that American food is rich in ALA but deficient in EPA and DHA.
Diagnosing the omega-3 deficiency is not an easy task, as there is no lower cut-off value. Researchers don’t currently know at which level an omega fatty acid insufficiency may start causing problems. Things get complicated further by individual differences. Present scientific data are insufficient to know at what level there is a risk of neural deficits, visual impairment, or alterations in immune responses. However, some people may develop specific dermatological signs in the omega-3 deficiency, like scaling of the skin or unexplained dermatitis.
Classical omega-3 deficiency is rare in the US, but considering the importance of DHA and EPA for healthy aging and cognitive capacity, one may suppose that strict vegans, vegetarians, or those who don’t eat fish may be at higher risk when compared to those that do eat fish without supplementation.
References
Dyall, S. C. (2015). Long-chain omega-3 fatty acids and the brain: a review of the independent and shared effects of EPA, DPA and DHA. Frontiers in Aging Neuroscience, 7. doi:10.3389/fnagi.2015.00052
McNamara, R. K. (2010). DHA Deficiency and Prefrontal Cortex Neuropathology in Recurrent Affective Disorders. The Journal of Nutrition, 140(4), 864–868. doi:10.3945/jn.109.113233
Office of Dietary Supplements – Omega-3 Fatty Acids. https://ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional/
Weiser, M. J., Butt, C. M., & Mohajeri, M. H. (2016). Docosahexaenoic Acid and Cognition throughout the Lifespan. Nutrients, 8(2). doi:10.3390/nu8020099
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