What are the types of omega-3 fatty acids?
There are several types of Omega-3 fatty acids by the three that are most involved in human nutrition are a-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). ALA is the Omega-3 mostly found in plant sources while EPA and DHA are more prevalent in animal sources such as fish, eggs, and meat. Oily fish such as salmon, trout, and herring have the highest amounts of EFA and contain 10 to 100 times more DHA than plant-based omega-3 sources such as dark leafy greens, whole grains, seeds, and nuts.
Importance of omega-3 fatty acids
We, as humans, are unable to synthesize omega-3 fatty acids and must obtain them through diet. We eat foods containing ALA, the shorter-chain omega-3 fatty acid, and then convert it into long-chain omega-3 fatty acids, EPA and DHA. DHA is arguably the most important Omega-3 fatty acid and plays a large role in inflammation reduction and disease prevention.
DHA plays a role in cognitive function and enhances learning and memory. It is abundant in wild salmon and is found in other fish as well as flaxseed, and walnuts. In addition to the brain, where DHA makes up 40% of its polyunsaturated fatty acids, DHA makes up 60% of polyunsaturated fatty acids found in the retina of the eye. DHA levels are very high in breast milk and studies have shown that infants develop better vision when fed breast milk over baby formula that lacks this essential fatty acid.
Several paleo experts are convinced that vegans can not get enough DHA even though there are several plant sources that contain high levels of omega-3s. This is because the omega-3 found in plants is predominantly ALA, which is biologically inactive until it is converted into EPA or DHA. So the question becomes, how effective is the body in converting ALA to EPA and DHA?
Studies of healthy men show that only 8% of dietary ALA was converted to EPA and 0-4% was converted to DHA. In healthy young women, these numbers increase to 21% in the conversion to EPA and 9% to DHA. It is believed that this difference is due to the effects of estrogen which is generally higher in women. (1) (2)
Because vegans rely on the metabolism of ALA to obtain EPA and DHA, many nutritionists will recommend a DHA supplement in addition to a diet high in plant-based omega-3s. Seaweed is one of the only plant sources of DHA and EPA, but because the fat content of this plant is low, so is the fatty acid concentration.
On the other side of the argument, people claim that even though vegans consume significantly less DHA and EPA than fish eaters, their bodies simply respond by increasing the conversion of ALA to DHA and EPA. In fact, there are studies to back up this claim.
A glance at the research
One recent study looked at the dietary intake and status of polyunsaturated fatty acids in fish-eating and non-fish-eating meat eaters, vegetarians, and vegans (3). Because fish is a major source of EPA and DHA, researchers wanted to compare blood levels of those who are getting these omega-3 types directly and those who must obtain them from plant-derived ALA. The study involved 14,422 men and women aged 39 to 78 and blood fatty acid levels were measured in 4902 of the individuals.
Results showed that although the omega-3 intake in non-fish eaters was between 57 and 80% lower compared to fish-eaters, the difference in blood levels did not reflect this difference. In fish-eaters, the average EPA level was 64.7 micromoles per liter while the non-fish eating groups had average levels ranging from 50 to 57 micromoles per liter. The DHA levels showed similar trends. Fish-eaters had average DHA levels of 271 and the other three groups had average levels that ranged from 223.5 to 286.4. This study shows that vegans can indeed maintain adequate levels of EPA and DHA; they simply convert more ALA to EPA and DHA.
Vegans can definitely utilize the omega-3 fatty acids found in plants. Though the average conversion of ALA to EPA and DHA might be low, it likely increases in vegans. The body is extremely smart and wants to keep you nourished and healthy, so it doesn’t come as a surprise that it would figure out a way to make sure it is getting the omega-3s that it needs.