Omega-3, 6, 7 and 9 what’s the difference?

Guest blog contributed by Claire Saunders, a student at Oxford Brookes University, currently on placement at CABI.

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Many people are not sure how omega oils feature in their diet and in what quantities they should be consuming them. Confounded by acronyms such as PUFA, ALA and DHA, it’s tempting just to eat a piece of fish and hope for the best. Considering that many of are not getting even the minimum levels in our diet that are deemed “critical” to health by the World Health Organization (WHO),  maybe we should rethink our 'laissez faire' attitude.  A 2016 systematic review  revealed that 80% of the world has low or very low blood levels of  DPA and EHA. When questioned,  a third or consumers in Germany, UK and USA were unsure how much they should be consuming.  There follows a practical guide to omega oils.

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Omega-3 fatty acids – what have we learned?

It’s well known that omega-3 fatty acids are crucial to the development of the brain. Animal studies have suggested that a specific fatty acid, docosahexaenoic acid (DHA), plays a role in the development of cognitive abilities. So will taking extra DHA as a child make you cleverer? A paper in CAB Reviews by Carol Cheatham at the University of Kansas Medical Center looks at the evidence from both animal and human studies.

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Animal studies have shown clearly that DHA deficiency affects memory and learning, and that providing extra DHA can restore these abilities to some extent. However, in humans, fewer than half the randomised clinical trials report effects on cognition from DHA.

Babies born early miss out on the final weeks of DHA they would receive from their mothers via the placenta. Studies show that providing preterm babies with DHA does improve memory and attention relative to controls. However, for babies born at term, providing extra DHA has not given the same clear outcome, with different trials giving different results.

Cheatham looks at three possible reasons. One is that the doses of DHA may not have been high enough to work. Also, the trials used a wide variety of measures of learning and memory. Looking at more specific measures of cognition could give less mixed results. Few studies have looked at the long- term impacts, and so studying children some years after taking DHA supplements in more sophisticated tests may reveal differences.

The paper,Omega-3 fatty acids and the development of cognitive abilities: a review of DHA supplementation studies, by Carol L. Cheatham appears in CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources, 2008, 3, No. 001.

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