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DHA - Should we supplement or not?

There has been much chatter lately regarding supplementation of DHA (a long chain form of Alpha Linolenic Acid or ALA which is more commonly known as Omega 3 fatty acid) especially in plant-based diets. Many “experts” in the field are saying that we don’t get enough DHA and that even if we did; we would not be able to adequately convert it in our bodies.

Where is this concern coming from? The study cited by many “experts” who recommend DHA was a small study that included 23 omnivores, 25 vegetarians, 37 vegans, and 13 semi-omnivores. This study found that the vegans had lower DHA levels than the omnivores. But what does that really mean? Vegans also have lower cholesterol than most omnivores, so should we supplement that as well? Even before we get into these more abstract discussions, let us take a closer look at the study itself because we feel there are several problems with this study and therefore with its conclusion. For one thing, the sample was very small and the study was observational which means the conclusions made were based on watching a particular group. The problem here is there are many variables that can account for a given change and by observing them all; we can make erroneous associations and wrong conclusions. For example, if you sampled a group of women in the gym and observed their heart disease risk, you might find that women in the gym have decreased risk. But, you can also observe that women in the gym wear more sports bras. So, you could equally conclude that women that wear sports bras have a decreased risk of heart disease. The point is that the most accurate study is really a randomized controlled double blind study and to date, one has not been done assessing DHA.

The other problem with this study is that although it looked at DHA levels, it did not look at the overall health of the participants. This is important because many factors contribute to how much or how little DHA we make. As a matter of fact, many Americans don’t convert ALA to DHA efficiently because (in their poor diet) they get too little ALA to begin with (and you can’t adequately convert something you don’t have enough of), they don’t consume foods that are helpful in the conversion process (fruits and vegetables rich in magnesium, zinc, and Vitamins C, B6, and B3), they eat other foods that inhibit an effective conversion process (including saturated fats, trans fats, hydrogenated fats, alcohol, and cholesterol), and/or they get too much omega 6 that then competes with omega 3 (ALA) for the enzymes required in the conversion process. The point here is that a poor diet (vegan or not) can lead to low levels of DHA.

But, we are not interested in those people on poor diets because we know that DHA deficiency is by no means their biggest problem. In addition to DHA deficiency, they need to worry about general malnutrition, heart disease, diabetes, obesity, high blood pressure, and high cholesterol among others. These people need to supplement their entire diet, but again not with pills, rather with fruits, vegetables, legumes, whole grains, etc. So, instead we are interested in healthy people on a whole foods, low fat, oil free, plant based diet. These people have optimized their health and now we can focus on DHA levels and their effects on health. In order to conclude that these people need to supplement with DHA, you would need a study that actually looked at this healthy population, determined the average DHA level, and if low then proved that this low level actually does harm in this healthy group of people.

Our concern is that maybe high levels of DHA are actually harmful, especially if achieved with supplements. For example, one study described how excess DHA (a polyunsaturated fat) in our bodies winds up just getting turned into saturated fat, and we all know how damaging saturated fat is. Furthermore, this study showed that while the supplemental DHA oils were equivalent with respect to DHA bioavailability and accretion, they had “markedly different effects on ARA levels.” ARA or Arachidonic acid comes from omega 6 fat (linoleic acid) and is actually pro-inflammatory. The finding that different types as well as different doses of DHA oils resulted in different plasma levels of ARA, a pro-inflammatory substance (likely harmful in excess) is very concerning. At the least, it tells us that more studies need to be completed before consumption of these supplemental oils is recommended for all people, especially healthy people!

As for the DHA and fish connection, it is true that fish already do the conversion from omega 3 to DHA for us so that when we eat fish, we get those derivatives directly. But again, we need to ask ourselves at what price because, fish are also laden with cholesterol and environmental toxins like mercury and PCBs to name a few. Why would we want to risk exposure to these toxic substances when we can obtain our essential fatty acids in other, healthier ways? Keep in mind that the amount we actually need is very small. In fact, the National Academy of Sciences report says that the adequate daily intake for women is 1.1 grams and for men is 1.6 grams of ALA. 1.6 grams of ALA is in 1 tablespoon of flax seed or 1.5 cups of soybeans. In fact, ALA is found in most whole plant foods in small amounts and that is OK because we don’t need that much. So, as long as we get a majority of our calories from whole plant foods (vegetables, grains, legumes, and fruits) we will get more than enough ALA to meet our need.

In summary, when dealing with supplements, the default recommendation should be no supplement…never the opposite and DHA is no exception. Once studied, we often find problems with supplements besides just their expense…such as increased mortality (vitamin A, E, and beta carotene). Furthermore, the analysis of any recommendation to people should be done in very large groups (ideally as large as the group you are making the recommendations to...but definitely not just a study of 20-30 people) and tested over very long periods of time (ideally over billions of years of evolution or at least for as long as you plan on recommending the pill...but definitely not just a few months). In the case of DHA, the results of such studies (randomized controlled double blind) would have to conclude not only that healthy people on a low fat, oil free, plant based diet have lower levels and that these levels actually cause harm but that supplementation not only raises levels but eliminates that harm. Only after such studies have been done can we truly analyze the data and, if appropriate (based on incontrovertible evidence), make recommendations for supplementation. Until then, we are doing our patients and ourselves a disservice recommending supplements that may not only be unnecessary but potentially harmful. Even worse, fixating on supplements allows the average person to ignore the major cause of their poor health, the toxic American diet and lifestyle.

REFERENCES:

Dayong Wu, MD, PhD, Sung Nim Han, PhD, RD, et al. Effect of Concomitant Consumption of Fish Oil and Vitamin E on T Cell Mediated Function in the Elderly:

A Randomized Double-Blind Trial. Journal of the American College of Nutrition, Vol. 25, No. 4, 300–306 (2006)

Eileen E. Birchab, Sharon Garfielda, et al. Visual acuity and cognitive outcomes at 4 years of age in a double-blind, randomized trial of long-chain polyunsaturated fatty acid-supplemented infant formula. Volume 83, Issue 5, Pages 279-284 (May 2007).

Hooper L, Thompson RL, et al. Risks and benefits of omega 3 fats for mortality, cardiovascular disease, and cancer: systematic review BMJ. 2006 Apr 1;332(7544):752-60. Epub 2006 Mar 24.

Innis SM, Friesen RW. Essential n-3 fatty acids in pregnant women and early visual acuity maturation in term infants. Am J Clin Nutr. 2008 Mar;87(3):548-57.

Kornsteiner M, Singer I, Elmadfa I. Very low n-3 long-chain polyunsaturated fatty acid status in Austrian vegetarians and vegans. Ann Nutr Metab. 2008;52(1):37-47. Epub 2008 Feb 28.

Linda M. Arterburn, Harry A. Oken, et al. Bioequivalence of Docosahexaenoic Acid from Different Algal Oils in Capsules and in a DHA-Fortified Food. Lipids, Volume 42, Number 11 / November, 2007. 1011-1024.

Michelle P Judge, Ofer Harel and Carol J Lammi-Keefe. Maternal consumption of a docosahexaenoic acid–containing functional food during pregnancy: benefit for infant performance on problem-solving but not on recognition memory tasks at age 9 mo. American Journal of Clinical Nutrition, Vol. 85, No. 6, 1572-1577, June 2007

MOHSEN MEYDANI, FELICIA NATIELLO, et al. Effect of Long-Term Fish Oil Supplementation on Vitamin E Status and Lipid Peroxidation in Women. American Institute of Nutrition. Received 26 March 1990. Accepted 8 August 1990.

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OMEGA-Trial: Omega-3 fatty acids provide no additional beneﬁt for

patients with MI. American College of Cardiology’s 58th Annual Scientific Sessions

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