ALA-DHA conversion negligible, say fatty acids experts
By Shane Starling, 25-Mar-2009
Related topics: Omega-3, Research, Nutritional lipids and oils, Cognitive and mental function, Maternal & infant health
Alpha-linolenic acid, (ALA) does not convert to docosahexaenoic acid (DHA) at levels that confer any physiological benefit, according to a summary of omega-3 research conducted by the International Society for the Study of Fatty Acids and Lipids (ISSFAL).
In a statement, the group that counts fatty acid researchers and some of the world’s biggest omega-3 suppliers including Ocean Nutrition Canada and Martek Biosciences Corporation among its members, added that bodily DHA levels were most effectively raised by consuming “pre-formed” DHA.
Both ALA and EPA (eicosapentaenoic acid), converted to DHA at negligible levels, said Tom Brenna, professor of nutritional sciences at Cornell University in Ithaca in New York state, and chair of the ISSFAL committee that drafted the statement.
“…conversion of ALA to EPA is very low, and to DHA is even less – essentially negligible,” ISSFAL stated. “These very low conversion rates mean that ALA cannot meet the body’s need for DHA.”
Not all omega-3s created equal
More broadly, Brenna, in a statement, said marine-sourced omega-3s were more potent physiologically than their plant-sourced cousins, at least in the area of brain health and infant brain health.
“Each type of omega-3 has distinct nutritional functions. Nevertheless, seafood/algal omega-3s – also known as long-chain omega-3s – are more potent than terrestrial plant sources of omega-3s and boast certain critical functions that terrestrial plant-based omega-3s simply cannot perform,” he stated.
Brenna told NutraIngredients-USA.com that this statement could be revised if plant-sourced DHA and EPA – under development by several large biotech firms – came on-stream.
“But at the moment, key sources of bioactive omega-3s are marine-based,” he said.
The ISSFAL statement then focused on DHA, noting that the brain produces very little of its own DHA and is reliant on inputs from some oily fish, DHA-fortified foods and dietary supplements.
It referenced a study, co-authored by Brenna and published in a recent edition of the journal, Prostaglandins, Leukotrienes and Essential Fatty Acids, that stated:
“With no other changes in diet, improvement of blood DHA status can be achieved with dietary supplements of preformed DHA, but not with supplementation of ALA, EPA, or other precursors.”
Martek, the world's leading DHA supplier, welcomed the group’s findings. “This statement will go a long way toward ending the confusion about the best sources of DHA," said the Maryland-based company’s medical director, Edward B Nelson, MD.
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