Think you're eating healthy? You may be missing this heart-protecting nutrient

Most adults think they eat healthily. They eat vegetables, they had oats for breakfast, they save fast food for special occasions. But a new study from Tufts University, published in the Journal of the American Heart Association, finds that a large share of these volunteers fall short on the nutrient with the strongest evidence for heart protection: omega-3 fatty acids. Science Daily reports that the researchers identify a simple fix: fish, leafy greens and walnuts, not complicated supplements.

The study enrolled 5,842 US adults who had rated their diet as healthy in the previous six months and reported regular intake of fruit, vegetables and whole grains. Researchers measured the erythrocyte omega-3 index in their blood — the most reliable biomarker of long-term omega-3 intake.

The finding is striking. Sixty-eight per cent of participants had an omega-3 index below the 8% threshold recommended by cardiologists for cardiovascular protection. A subset of 23% scored below 4%, the level Harvard School of Public Health research links to a clear increase in sudden cardiac death risk.

Where does the deficit come from? The Tufts team identifies three drivers. First, low fish intake: only 19% of participants reported eating fatty fish (salmon, sardines, mackerel, herring) twice a week — the American Heart Association's recommendation. Second, inadequate plant-based omega-3 sources (flax, walnuts, chia). Third, high omega-6 intake: the refined vegetable oils common in US diets complicate the body's omega-3 conversion.

A clarification is important. Omega-3 fatty acids come in three main forms. EPA and DHA, found mostly in fatty fish, are the long-chain versions; ALA, found in plant sources, is the short-chain version. EPA and DHA carry the strongest evidence on heart rhythm, vessel function and inflammation; ALA is only converted in modest amounts to EPA and DHA in the body.

Where does the heart-protection evidence come from? Large meta-analyses cited by the Tufts team find that adults with the highest EPA and DHA intake had an 18% lower rate of death from myocardial infarction and a 35% lower rate of sudden cardiac death over an eight-year follow-up. The American Heart Association recommends 1 g/day of EPA+DHA for people with coronary heart disease and two servings of fatty fish a week for everyone else.

Lead author Dr Aleksandra Markova says people who consider themselves healthy eaters often miss the fish-intake gap. "They tell me 'I eat vegetables, I switched to white meat, I cut out dessert'. But omega-3 sits in a different category — fish, or carefully chosen supplements, is the quick route there."

Supplements are a contested area. Evidence on high-dose fish-oil capsules for cardiovascular benefit is mixed: some large trials (REDUCE-IT) showed benefit from high-dose EPA in specific high-risk patients; others (VITAL) found no significant effect in lower-risk adults. Markova views supplements as a practical bridge for people who cannot or will not adjust their diet — but food is the first choice.

The study also touches on childhood diets. The Tufts team observed that low omega-3 intake starts in adolescence — fast-food-heavy diets contain no fish — producing a cumulative deficit over a lifetime. The US Department of Health and Human Services in its 2025 nutrition guidance recommended adding fatty fish to school meal programmes at least once a week.

The overall message: if you believe your diet is healthy, measuring your omega-3 index (a cheap, simple at-home blood test) can be informative. If it is low, the fastest fix is salmon or sardines twice a week, a handful of walnuts daily and ground flax on salads. For people at high cardiovascular risk, a doctor-supervised EPA/DHA supplement may be considered. According to the Tufts researchers, this is one of the small dietary interventions with disproportionate impact on annual cardiovascular mortality.