How to get omega-3 fatty acids from plant foods and the risks of eating shellfish
The eating of certain marine animals such as fish and shellfish is often recommended as a source of omega-3 fatty acids. However, there is no need to eat fish or shellfish to obtain a healthy diet. At present, there is considerable uncertainty about the exact role of these fats in human health and nutrition. Some past claims about the effects of increasing omega-3 levels have proved incorrect. Nevertheless it is clear that omega-3 fatty acids are important elements of human nutrition.
The three types of omega-3 fatty acid involved in human physiology are α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA ). Large amounts of DHA, for example, are found in the brain and in the retina. Amongst other things, EPA helps the body manufacture important, hormone-like substances called eicosanoids . EPA and DHA can be made in the body from ALA. ALA is found in a large number of foods including hemp seeds (best with the shells taken off), flax seeds, chia and walnuts. Smaller amounts are found in a wide range of other plant foods. However, the amounts of EPA and DHA made from ALA are often very small, though women of child-bearing age appear to be able to make more than adult men.1
There is not space here to go through all the research and different (often conflicting) theories about omega-3. However, there is a very simple solution for those that wish to be certain of getting enough DHA and EPA from a plant food diet. This is to get their DHA and EPA from where fish get theirs- algae. There are now numerous brands offering algae in capsule, liquid or other forms, which have been grown under safe and controlled conditions. The American Dietetic Association suggests that those who should consider taking these supplements include pregnant and lactating women. 2 At these stages in development, the young brain is growing rapidly and needs sufficient amounts of DHA and EPA to develop optimally. It is difficult to find accurate and conclusive research, however children and the elderly are also groups which might need to take algae supplements. As for adults in general, it may be possible to do without algae supplements if enough foods containing ALA are consumed , but again there is not enough knowledge at present to reach any definite conclusions. One thing is certain however, there is absolutely no need to eat marine animals in order to get sufficient DHA and EPA.
Caveat: it needs to be emphasised again that, despite the many studies carried out, there are many unanswered questions and there is not enough good quality research to make certain suggestions about which groups might need algae supplements. Always check with your health provider for the latest information.
One objection that is sometimes made is that it is unnatural to take supplements . The counter argument to this is that in a sense all human food production that does not involve hunting and gathering is unnatural. Moreover, even in these cases it is unclear exactly what our ancestors’ diet consisted of.
Disease risks from eating shellfish
There is evidence from a UN study that inhumane slaughter methods damage meat. While this study was largely done on mammals, anecdotally the inhumane slaughter of shellfish appears to have the same effect.3
Like fish, but more so, many shellfish are subject to the contamination of our seas with pollutants such as mercury.4
The ingestion of natural toxins by shellfish can cause severe illness or death if the latter are eaten.5
Another reason to beware of eating shellfish is that allergic reactions to them are common. 6 See archive page for more details.
In summary, therefore, it is more humane, safer, cheaper and easier to obtain omega-3 fatty acids from plant foods, not to mention more environmentally sustainable.
REFERENCES
1) Geppert J1, et al, 2010 (Jan), Gender-specific fatty acid profiles in platelet phosphatidyl-choline and -ethanolamine. Prostaglandins Leukot Essent Fatty Acids. 2010 Jan;82(1):51-6. doi: 10.1016/j.plefa.2009.09.002. Epub 2009 Oct 17.
2)Position of the American Dietetic Association:
Vegetarian Diets https://www.andeal.org/vault/2440/web/JADA_VEG.pdf , accessed 20.11.17
3 ) Guidelines for Humane Handling, Transport and Slaughter of Livestock, Food and Agriculture Organisation of the United Nations
4)Aranda N, 2017, Consumption of seafood and its estimated heavy metals are associated with lipid profile and oxidative lipid damage on healthy adults from a Spanish Mediterranean area, Environ Res. 2017 Jul;156:644-651. doi: 10.1016/j.envres.2017.04.037. Epub 2017 May 5.
5)Brown J. et al, 2001, Paralytic Shellfish Poisoning on the East Coast of the UK in Relation to Seasonal Density-driven Circulation, Journal of Plankton Research, Volume 23, Issue 1, 1 January 2001, Pages 105–116
6) Alonso LL, Warrington SJ., 2017, Shellfish Allergy, StatPearls Publishing.