There’s a theory among evolutionary psychologists that the human brain is hard-wired to worry about not having enough. Most particularly, not enough food. It makes total sense in view of our species’ history; paleoanthropologists have found consistent evidence that our ancestors faced frequent food shortages, indicated by changes in bones that take place during growth phases.
Consequently, although the most pressing and dangerous nutritional problem across the globe is now excess rather than lack, most people are still more concerned about suffering a nutritional deficiency than they are about the visibly obvious fact that they’re eating too much – too much food, too many calories, too much fat, too much refined carbohydrate, too much animal protein.
There’s a multibillion dollar supplement industry capitalising on this ‘not-enough’ anxiety, of course, and that industry has had a pervasive and insidious effect on not only the general public, but also on health professionals. Almost everyone who has adopted a plant-based diet has faced a barrage of questions from their friends, personal trainer, mother-in-law and doctor alike – “Where will you get your protein? What about calcium and iron?” And more often than not, “Where will you get your omega-3 fats?”
Among the most frequent questions I’m asked by clients who have gone plant-based – especially those who have children or are intending to start a family – are “Do I need to take an omega-3 supplement?” and “Will my kids’ brain development suffer if they don’t take one?”
My response to this question has changed over time.
I confess to having been influenced by the ‘deficiency mentality’ during my training. Most of my nutrition lectures at naturopathic college raised the spectre of deficiency in some way, shape or form, whether it was during the foundational teaching on nutrients that detailed the functions of each vitamin and mineral, and the terrible things that happened when animals or humans were experimentally deprived of them; or the sessions on clinical nutrition which attributed virtually every human malady to a lack of some nutrient or other, with the implication that all our suffering could be resolved if we just took enough supplements of said nutrients.
Fish oil supplements were the darling of almost all my lecturers, who emphasised the importance of the long chain omega-3 fats DHA and EPA in supporting brain development and function, reducing inflammation, regulating immune activity and supporting cardiovascular health – in particular, preventing heart attacks and strokes.
As a plant-based eater myself, and as concerns mounted about rapidly depleting fish stocks, I was deeply uncomfortable about recommending fish oil supplements to my clients. But in the late 1990s, supplements of long-chain omega-3 fats that were extracted from algae – simple aquatic organisms – began to enter the market. Problem solved, I thought. Anyone who needs an omega-3 supplement for their depression, cardiovascular disease, rheumatoid arthritis or developing baby can just take an algal-derived product.
However, as the years rolled by and the outcomes of large, well-designed studies on omega-3 supplements emerged, the whole idea that anyone ‘needs’ an omega-3 supplement at all has come into serious doubt.
It started with trials of fish oil for prevention of heart attacks, which showed either no benefit or even an increased risk in those taking the supplements compared to those taking placebo. Eventually, several meta-analyses combining data from all the high-quality studies on omega-3 supplementation for cardiovascular disease – including a Cochrane Review, considered the gold standard of medical evidence – concluded that it was most likely worthless.
Then studies casting doubt on the value of omega-3 supplements for arthritis (no benefit for osteoarthritis, and uncertain benefit for rheumatoid arthritis), prevention of asthma and allergic disease – all conditions that my nutrition lecturers were convinced would respond to omega-3 supplements – emerged.
The last bastion for omega-3 supplement enthusiasts was mental health. Surely, given the important role that long chain omega-3 fats play in the development and function of our nervous systems, deficiency must play a role in mental health disorders and supplements should help with their treatment.
But now, a newly published meta-analysis on omega-3 supplementation, commissioned by the World Health Organization, has found that it offers no benefit in the prevention or treatment of depression and anxiety.
Researchers included 31 trials assessing the effects of long-chain omega-3 (DHA and/or EPA, found in fish oil and vegan omega 3 supplements), one of alpha-linolenic acid (ALA, the short-chain omega-3 fat found in flaxseed, chia, hemp and walnuts), and one of total polyunsaturated fat. In all, data from over 51 000 individuals were included.
The findings were:
- Increased DHA and/or EPA intake probably has little or no effect on risk of developing depression or anxiety symptoms.
- If you have already been diagnosed with depression, it is unlikely that taking DHA and/or EPA will reduce the severity of your symptoms or help you go into remission.
- Weak evidence indicates that increasing ALA intake by 2 grams per day may increase the risk of depression symptoms very slightly over 40 months; the number needed to harm is 1000 meaning that if 1000 people were to take this much ALA for over 3 years, one would become more depressed. Note that 1 tbsp of ground flaxseed contains 1.6 g of ALA, so only people taking flaxseed oil, which contains over 7 g of ALA per tbsp, are likely at risk of overconsumption.
It’s particularly striking that these disappointing results were consistent regardless of the dose used, the duration of the study, the nutrients replaced by the omega-3 supplements and the studies’ funding sources. The bottom line is that omega-3 supplements just don’t work for depression or anxiety.
And we shouldn’t be overly surprised. The consistent theme emerging from research on the effects of diet on mental health – and for that matter, physical health conditions too – is that it’s the dietary pattern which matters.
Adding omega-3 supplements to a diet of low nutritional quality and expecting them to improve any symptom of illness is like spraying air freshener on a garbage heap, hoping it will cancel out the stench.
We need to disentangle our minds from the ‘scarcity hangover’ of our ancestral past, recognise that that only dietary deficiency that most of us face is a deficiency of real food (fruits, vegetables, whole grains, legumes, nuts and seeds) and stop expecting supplements to save us from poor diet and lifestyle choices.
Research on comprehensive dietary interventions for depression, which aim to shift the entire dietary pattern in a healthier direction rather than myopically focusing on single nutrients – such as the SMILEs Trial – show promising results.
Combining a diet of high nutritional quality with the other foundations of Lifestyle Medicine including regular exercise, sleep hygiene and building social connections, along with effective therapy for the disordered thinking which drives both depression and anxiety, offers the only genuine prospect for overcoming mental health disorders and enhancing our well-being.
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