**This article addresses the science associated with DHA supplements, not fish oil capsules. DHA is a component of fish oil, but fish oil contains other components as well, and is addressed in another article on this site**
We live in a supplement-obsessed culture. Otherwise healthy men and women take multivitamins as “insurance” against nutritional deficiencies and to elicit supposed health benefits. Prenatal vitamins are no longer reserved for pregnant women; these days, women start taking them well before trying to conceive, and some non-pregnant women take them under the (erroneous) impression that they’ll promote hair and nail growth, improve complexion, and regulate hormones. We even dose our infants with supplements; formula companies try to outdo one another with their list of included “beneficial” nutrients, and even manage to sell products to breastfeeding mothers (the formula company Enfamil is the manufacturer of one of the most widely available vitamin D preparations for breastfeeding infants). We’re not just obsessed with supplements, however; we’re also obsessed with brain-building. This is why the Baby Einstein products have done so well, despite evidence that they do no good (and a statement from the American Academy of Pediatrics specifically advising against screen time for the under-two set).
DHA, docosahexaenoic acid, allows us to indulge both our supplement obsession and our brain-building obsession at the same time, so it’s no wonder DHA has started showing up everywhere. It’s packaged with prenatal vitamins, added to formula, sold in capsules for breastfeeding mothers, and put in gummy candy form for children. What is DHA, though, and do we really need it? More importantly, could it hurt us or our children?
DHA is one of the omega-3 fatty acids, where the latter are essential fatty acids. This means that the human body requires them to maintain function, but can’t synthesize them, so they must be consumed. Omega-3 fatty acids have many different roles in the human body, but can generally be said to promote normal metabolism and help counteract inflammation. DHA, in particular, is a major component of the human brain, which is why it’s said to be important to brain development (Singh). Diets too high in omega-6 fatty acids (another class of essential fatty acids) result in increased inflammation, including higher rates of cancer, asthma, and cardiovascular disease. It appears that the ideal ratio for omega-6/omega-3 consumption is 1/1, but studies suggest that ratios of 2-3/1 are nevertheless quite helpful in reducing inflammatory disease processes (Simopoulos). The typical Western diet, however, has a ratio of closer to 15-17/1.
The problem is that omega-3 fatty acids are harder to come by than omega-6 fatty acids are. Grains and grain oils, ubiquitous in the Western diet, are sources of omega-6 fatty acids. Omega-3s, however, come from only a few vegetable sources (flax, pumpkin seeds, and soybean oil, to name a few), in addition to coldwater fish and algae. The omega-3 fatty acids in vegetable sources, however, aren’t in the form of DHA or EPA (eicosapentaenoic acid), which are the omega-3s responsible for most of the important health effects. Instead, plants are sources of ALA (alpha-linolenic acid), which has to be converted into DHA and EPA. Humans aren’t efficient at this conversion, so even though flax and other plants technically contain omega-3 fatty acids, they’re not actually useful sources. The best sources of biologically active omega-3 fatty acids are fatty fish and algae. Since most Westerners don’t eat these very often, manufacturers of DHA supplements rush in to fill the dietary gaps.
However, while research strongly supports the inclusion of dietary sources of DHA (University of Maryland Medical Center has a comprehensive list of research references), there isn’t any research support for using pure DHA supplements. For instance, a non-randomized, non-placebo-controlled study (this negatively impacts study power, because the study design allows factors outside the variable being tested to impact results) showed that infants fed DHA-containing formula for the first six months of life didn’t end up any smarter (Gale et al). However, because mothers were allowed to choose whether they gave their babies DHA-containing formula or not, the researchers did see a bit of correlation between DHA formula consumption and intelligence. Subsequent analysis, however, suggested that mothers who were concerned enough about brain development to give DHA-containing formula were also more intelligent themselves, better educated, and were more likely to engage with their children in brain development-promoting ways, which the researchers felt explained the difference.
While research doesn’t currently support using DHA supplements, however, neither does there appear to be research that indicates DHA supplements do harm. There’s been some suggestion that cultures that eat larger quantities of DHA have higher incidence of stroke, but it seems that this may be due more to the potential for mercury contamination in coldwater fatty fish than to the DHA itself (Wennberg et al). Several studies suggest increased intake of omega-3 fatty acid decreases risk of stroke when mercury contamination is removed as a confounding factor (see, for instance, Bouzan et al, He et al).
While a number of noted childcare and healthcare experts with large Internet presences (including Dr. Michael Roizen) recommend giving DHA supplements to pregnant women, breastfeeding women, and children, it’s worth bearing in mind that these experts aren’t free from conflict of interest. For instance, Dr. Roizen is a scientific consultant for Martek, a supplement manufacturer that makes several DHA supplements.
Science Bottom Line:* There isn’t sufficient evidence to support using a DHA supplement. Since some dietary supplements (even those once thought beneficial or safe) can turn out to be harmful, it’s probably best to steer clear of unproven supplements like DHA. There is ample evidence to support consuming DHA-containing fish, however. The Environmental Protection Agency provides information about safe seafood consumption and reducing the risk of mercury intake. For those who are interested in making seafood decisions that support sustainable fishing practices in addition to minimizing risk of mercury and toxin exposure, the Monterey Bay Aquarium provides excellent resources.
Do you use DHA or other supplements?
American Academy of Pediatrics Babies and Television. Accessed 17 Oct 2011.
AskDrSears.com DHA Supplements. Accessed 17 Oct 2011.
Bouzan et al. A quantitative analysis of fish consumption and stroke risk. Am J Prev Med. 2005 Nov;29(4):347-52.
Gale et al. Breastfeeding, the use of docosahexaenoic acid-fortified formulas in infancy and neuropsychological function in childhood. Arch Dis Child. 2010 Mar;95(3):174-9. Epub 2010 Feb 4.
He et al. Fish consumption and incidence of stroke: a meta-analysis of cohort studies. Stroke. 2004 Jul;35(7):1538-42. Epub 2004 May 20.
Simopoulos, A. The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomed Pharmacother. 2002 Oct;56(8):365-79.
Singh, M. Essential fatty acids, DHA and human brain. Indian J Pediatr. 2005 Mar;72(3):239-42.
University of Maryland Medical Center Omega-3 Fatty Acids. Accessed 17 Oct 2011.
Wennberg et al. Fish intake, mercury, long-chain n-3 polyunsaturated fatty acids and risk of stroke in northern Sweden. Br J Nutr. 2007 Nov;98(5):1038-45. Epub 2007 May 31.