Chemicals and Toxins — What Is Safe?

One of the most common questions I get from SquintMom readers is along the lines of is item/substance/compound XYZ toxic? I’d like to go ahead and answer this once and for all: YES, it is.

Now let me explain what I mean, and how I can answer this very generic question in a catch-all way without specifying the item/substance/compound to which I refer. Because he said it so well that it doesn’t need rephrasing, I’ll quote the Renaissance-era botanist Philippus Aureolus Paracelsus, who said:

All substances are poisons; there is none that is not a poison. The right dose differentiates a poison from a remedy.

Phrased more generally, this is simply that any substance can be either safe or toxic; the dose (quantity) to which one is exposed is what makes the difference. I’ve mentioned in previous posts (like this one about oxybenzone in sunscreen) that the notoriously jumpy Environmental Working Group (EWG) systematically fails to recognize this particular principle; they have a tendency to vilify anything that proves toxic in any dose, under any conditions. This attitude, however well intentioned, leads us to some interesting places. Pause for a moment and check out the cautionary website Note that the highly toxic dihydrogen monoxide (DHMO) is associated with cancer (it’s found in every tumor ever identified), has serious environmental impact (it’s a major greenhouse gas and overexposure is associated with thousands upon thousands of deaths every year), and, per the website:

[DHMO’s] basis is the highly reactive hydroxyl radical, a species shown to mutate DNA, denature proteins, disrupt cell membranes, and chemically alter critical neurotransmitters.

Sounds horrid, doesn’t it? No doubt we should ban it. Except that… is a joke website, and dihydrogen monoxide is the almost never-used, formal chemical name for water.

None of the information on is false, which is what makes it both amusing and apropos to this discussion. Water does, in fact, directly result in many deaths. Not only through “overexposure” via flooding and/or drowning, but also through overconsumption. For instance, in 2007, a radio station held a contest (“Hold your wee for a Wii”), the idea of which was to drink as much water as possible without a bathroom break; the caller who drank the most would win a coveted Wii game console. Contestant Jennifer Strange won (and then lost) by consuming more than 2 gallons of water in the space of less than an hour. She died shortly thereafter of hyponatremia, a condition in which there is an insufficient concentration of sodium in the body fluids to support life (sodium is critical to cellular function, neural conduction, muscular contraction, brain function, and so forth). This is not the only incident of water toxicity on record; similar cases have resulted from fraternity hazings, bizarre diet plans, and overconsumption of water during endurance sporting events like marathons.

On the other hand, there are substances that we typically consider highly toxic that are, in the right dose, of great medicinal utility. Clostridium botulinum is a species of bacteria that produces botulinum toxin, generally considered the deadliest substance on Earth. The average 150 pound man would have a 50:50 chance of survival if exposed to merely 341 ng (that’s less than a millionth of a gram) of pure botulinum toxin. Regardless, marketed under the trade name Botox, botulinum toxin is used for cosmetic purposes (wrinkle treatment and prevention). Of perhaps greater medical importance, it’s also used to ease the painful symptoms of temporomandibular joint syndrome (TMJ) and other spasmodic disorders, and mitigate the symptoms of diabetic neuropathy (damage to peripheral nerves, often in the feet, due to diabetes).

Further complicating matters, our perception that “natural” substances are somehow safer or better for us than “artificial” substances is misinformed. A simple example is the flavoring agents found in many foods. While the common perception is that natural flavors come from the food of which they taste (strawberry flavor, for instance, comes from strawberries), nothing could be further from the truth. In reality, natural and artificial flavors are generally identical chemicals, collected or produced in different ways.* Natural almond flavor, for instance, isn’t a mixture of “natural substances” that come from almonds. Instead, it’s a chemical called benzaldehyde that is extracted from peach pits. Artificial almond flavor is also benzaldehyde, but unlike natural almond flavor, the artificial stuff is made in the lab. Funnily enough, it’s possible to get benzaldehyde made in the lab much more pure than that extracted from peach pits. Further, the stuff that comes from peach pits — the natural almond flavor, remember — contains small amounts of deadly cyanide that occurs naturally in those same peach pits (one of many reasons it’s not wise to eat the pits of stone fruit).

*Eric Schlosser’s excellent book Fast Food Nation contains a very interesting chapter on this topic, for further reading.

Where does this leave us, in trying to avoid toxins? First, as a chemist, let me just say that the word toxin is very often misused in popular sources and conversation, and the word chemical is almost always misused. “Chemicals” are not bad things that cause harm and should be avoided. Instead, they are matter; they are what makes up the physical universe. Nothing that has mass and occupies space — nothing we touch, eat, drink, breathe — is not chemical. There’s no such thing as chemical-free bread, shampoo, or paint. Water is a chemical (and — let’s not forget — a toxic one at that). With regard to toxins, the word is used too often in a vague, handwaving sense on the Interwebs. I see pop-authors (who are generally trying to sell something) write about how Product X contains “toxins,” and should therefore be avoided, or Product Y (which they’re selling) contains no toxins.* I’m not sure what these folks mean when they say “toxins” (and since they rarely name said toxins, I’m not sure they know either); after all, let’s not forget that all substances are toxic in the right dose.

*Or worse yet, Product Y (which they’re selling) is a detoxifying agent. This is ridiculous; almost all humans (with the exception of a few with significant disease) are possessed of one of the most powerful detoxifying mechanisms known to man — a liver. Livers work really well, particularly when they’re left alone to do their job.

This is not to say that we should all go about our business with no concern whatsoever for the things we touch/eat/drink/breathe; it’s simply to say that we simultaneously worry too much and worry too little about “chemicals.” To take one particular example, a few scare-articles about bisphenol A (BPA) have some of us so worried (and confused) that we’re willing to shell out extra cash for BPA-free diaper wipe containers, toys, and even a bath toy organizer. In reality, if BPA has any effect at all in doses to which we’re routinely exposed (which has not yet been established), it would require significant physical contact with the compound to absorb it. Holding, playing with, or storing one’s bath toys in a BPA-containing item would not be a problem, particularly given that while the absorption rate of BPA through human skin hasn’t been thoroughly evaluated or established, it nevertheless appears to be significantly lower than the (already modest) rate of absorption through the skin of other animals (Marquet et al). Based upon the current research, might it be worth avoiding storing food in BPA-containing plastics? Possibly. This is because food might leech BPA out of the plastic in sufficient quantities to possibly have some effect on people (because we eat the food, which gives it an easy route into the system). Is it worth it to avoid all BPA in our houses, however? Simply, no. And on that note, it particularly amuses me to watch women with painted nails shopping for BPA-free toys for their daughters (also with painted nails), given that the exposure to potentially harmful substances (like toluene) is much greater when one physically paints said chemicals on one’s body.*

*For those who are curious, I do paint my nails, because I really don’t think this is that big a deal. But it’s certainly a more significant exposure to chemicals (ew! chemicals!) than touching a rubber ducky in the tub.

So, we worry too much. But we also worry too little. In our desire for the “natural” (whatever that means), we choose the cyanide-laced flavoring agent over the one made under strict conditions and control in the lab. We go to the natural foods store and buy herbs to treat our ailments — which are essentially unregulated for either safety or efficacy, and which may interact unsafely with prescription and over-the-counter drugs or be toxic in their own right — rather than using the “unnatural chemicals” prescribed by medical professionals, despite the fact that the latter have undergone many years of pre-marketing research, followed by decades of post-marketing surveillance. We’re more willing to expose our children to the 1/330 risk of death due to the measles than the 1/3000 risk of a moderate side effect of measles vaccination (e.g. seizure with no permanent effects, mild rash), and immeasurably small risk of serious side effect. We further eschew the vaccination because, in a complete failure to understand the mechanics of human immunity, we have come to believe that “natural” immunity from disease is superior to “artificial” immunity from vaccination. When it comes to the “natural” versus the “toxic” and/or “chemical,” we’re chasing flies out of the chicken coop while the foxes sneak in.

So what do we do about it? This is difficult. We know that all substances are toxic in the right (wrong?) dose, but when it comes to many substances, we still don’t know what that dose is. Some exposures are unavoidable (by virtue of living in a city, for instance, one is going to be exposed to a certain amount of benzene from exhaust, industrial processes, etc). Some exposures are avoidable, but avoiding them reduces quality of life (no one HAS to eat foods containing coloring agents, for instance, many of which are of questionable safety, but the complete avoidance of these would make for a stoic existence, particularly for children). In most cases, when it comes to toxic chemicals (and once more, all substances are chemicals, and all chemicals are toxic when one is exposed to them…all together now…in the right dose), one must do a risk-to-benefit analysis. Some cases are relatively clear. Is codeine toxic? Yes, in the right dose. Is it worth the risk to take codeine for recreational purposes? Probably not. Is it worth the risk to take codeine after a painful surgery? Probably. Is water toxic? Yes, in the right dose. Is it worth the risk to drink water when one is thirsty? Absolutely. Is it worth the risk to drink water to win a contest? Probably not. Some cases are less so, as with the previous example of BPA. With the evidence still equivocal, financial means and convenience likely become a large part of the decision. Those of greater means or with greater willingness to be inconvenienced might buy the BPA-free rubbery ducky, the BPA-free cabinet safety locks. Others might decide to buy the BPA-free food storage, but be content with the plain old, BPA-containing bath caddy. Regardless of these personal decisions when it comes to substances of yet-unknown safety, it’s worth remembering that the media, the product manufacturers, and the fad-authors capitalize upon the lucrative combination of public confusion and fear, and that the words “chemical,” “toxic,” “artificial,” and “natural” are as powerful as they are misused and misunderstood.


Marquet et al. In vivo and ex vivo percutaneous absorption of [14C]-bisphenol A in rats: a possible extrapolation to human absorption? Arch Toxicol. 2011 Sep;85(9):1035-43. Epub 2011 Feb 2.

Are Megadoses of Vitamins Healthy and Safe?

Photo by Ragesos

Megavitamin therapy is the use of very large doses of vitamins to prevent or treat illness or some symptom thereof. While not the first major proponent of megavitamin therapy, Linus Pauling is perhaps the best known; he advocated using huge doses of vitamin C (many grams per day) to treat and prevent disease. As a chemist, I have enormous respect for Pauling. His publication record is impressive, and his work in quantum chemistry helped lay the foundation of that field. Oh, and he was part of the team that helped discover the structure of DNA, which was kind of the Holy Grail of chemistry. As much as I hold him in esteem as a chemist, however, I have to wonder what business he thought he had dabbling in nutrition and medicine; he had training in neither of those fields. In any case, there was and is no evidence to support any of Pauling’s theories regarding megadoses of vitamin C. Neither is there evidence to support use of other vitamins in megadoses. The popularity of megavitamins is a “more is better” fallacy. Here’s the science bottom line: we need vitamins in small amounts. They serve a variety of critical roles in the body, and we experience illness, disease, and loss of function in the case of deficiency. More of a vitamin than the body needs, however, does it no good. Depending upon the vitamin, it’s either excreted or builds up and becomes toxic. Let’s stick with vitamin C as an example. Among its functions, vitamin C helps maintain the immune system; you’ll become more susceptible to disease (among other symptoms) if you’re vitamin C deficient. However, taking more vitamin C than recommended (the USDA currently recommends 90 mg/day for adult men, and 75 mg/day for non-pregnant, non-lactating adult women) doesn’t “supercharge” the immune system or help it function any better than it otherwise would. Think about it like this: if you’re trying to wash your hair in the shower, you need shampoo. If you use none, your hair doesn’t get clean. If you use a teeny, tiny amount, your hair gets a little cleaner. Use more, and your hair gets cleaner…up to a point. Once you’re using sufficient shampoo (usually anywhere from a dime-size to a quarter-size dollop, depending upon how much hair you have and how dirty it was), using more won’t get your hair any cleaner. It won’t do anything at all…except go down the shower drain. The same is true of vitamin C. Consume none, and you have problems. Consume some (but less than you need), and you have less severe symptoms of deficiency. Get what you need, and you achieve normal function (where it relates to vitamin C). If you take more vitamin C than your body needs to maintain function, however, the excess is excreted and goes down the toilet (or the shower drain, I suppose, depending upon your habits). Some vitamins aren’t as forgiving. For instance, vitamin A is quite toxic in megadoses. In any case, while there’s all sorts of scientific evidence to support getting your recommended daily dose of each vitamin, there’s just no evidence for — and in many cases, there’s evidence against — using megavitamins.


What’s your vitamin strategy?



USDA Dietary Guidelines. Accessed 11 Nov 2011.


Fish Oil And Health

I wanted to follow up last week’s post on DHA supplementation with a look into the research on fish oil supplementation, since while fish oil is a common source of supplemental DHA, there are supplements that contain pure DHA (as opposed to the normal mix of fats present in fish oil). While I concluded that there isn’t scientific research to support supplementing with pure DHA, there’s a fair amount of work that supports fish oil supplementation.

Certain benefits associated with fish oil supplementation begin during pregnancy. Thorsdottir (ok, sorry for the commentary, but that is a REALLY cool name when you say it out loud!) and colleagues found that Icelandic women who consumed the lowest quantities of fatty fish had smaller babies than those who consumed larger quantities of fish. Interestingly enough, however, those who consumed the most fish (containing more than a tablespoon of fish oil daily) also had shorter babies with smaller head circumferences. These women were getting three times the recommended daily vitamin A, and twice the recommended vitamin D as a result of their very high fish intake, which the researchers speculated might have had something to do with the results (both vitamins A and D are toxic in excessive quantities). Thorsdottir and colleagues recommended moderate fish and/or fish oil consumption during pregnancy (though “moderate” to an Icelandic research team is probably not the same as “moderate” to an American, given dietary norms). Olsen and colleagues found that moderate fish oil supplementation helped prevent pre-term delivery of a singleton baby in a high-risk (earlier pre-term delivery) mother, though the fish oil didn’t prevent pre-term delivery of twins. The researchers noticed no negative effects of fish oil on either mother or infant. Fish oil supplements during pregnancy appear to extend their effects into the first six months of lactation (Dunstan et al, 2007). Polyunsaturated fatty acids (PUFAs) from fish oil clearly pass into breast milk The key PUFAs are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which typically represent a large fraction of the total fish oil in a supplement capsule. In the Dunstan study, women who took fish oil during pregnancy (but not continuing into lactation) had higher levels of DHA in breast milk at three days, six weeks, and six months postpartum. The differences between the women who were supplemented and those who were not supplemented disappeared after six months postpartum. Infants of women with higher PUFA levels in breast milk had higher PUFA status themselves, and scored higher on a variety of developmental tests (both physical and cognitive) at 2.5 years. On the other hand, a very large study by Makrides et al failed to find much benefit associated with fish oil supplementation during pregnancy; women taking fish oil did not have lower rates of postpartum depression, nor did their infants score better on developmental assessments. A commentary on that same study (Oken et al) points out that some of the observational studies suggesting PUFA intake benefits (such as the Icelandic study by Thorsdottir) are based upon intake of whole fish, rather than fish oil supplements. Whole fish could contain more biologically active PUFAs, minerals that affect PUFA action, or other unidentified compounds. Oken and colleagues also note that the Makrides study tested infant development, while other fish oil studies tested toddlers and preschoolers. They point out that tests might not be sensitive enough to detect differences in infant development, and that differences might not become apparent until the babies were older. A further commentary on the Makrides study (Suzuki) points out that there were some differences in postpartum depression levels between women supplemented with fish oil and those receiving a placebo, but that the depression score cutoff value that Makrides et al chose did not allow for detection of those differences. Suzuki suggests that fish oil supplementation may play a role in reducing cases of subclinical (or less easily detected) depression.

Continued fish oil supplementation during lactation also appears to have benefits. Supplementation appears to increase levels of IgA (a type of antibody passed from mother to baby through breast milk) (Dunstan et al, 2004). There’s also evidence that it helps to reduce the risk of allergies (see, for instance, Dunstan et al 2003, Furuhjelm et al). Direct supplementation of infants may also confer benefits; a study by Damsgaard and colleagues noted that infants supplemented with fish oil had healthier blood lipid (fat) profiles at a year of age. Since blood lipid profile is a marker for heart disease risk, this is a potentially important finding.

Developmental benefits aside, fish oil supplements have also been associated with a reduction in several inflammatory disease processes, including rheumatoid arthritis (Kremer et al), asthma (Nagakura et al), ulcerative colitis (Hawthorne et al), and cardiovascular disease (see, for instance, Nestel et al, Geleijnse et al). Many of the studies on the benefits of fish oil refer to doses in the neighborhood of 3-4 grams of fish oil (containing 1-2 grams each of EPA and DHA) a day, with the caveats that while some fish oil is better than none, higher dosages show diminishing returns (and possibly harm).

It’s worth noting that while the benefits above are all conferred by DHA-containing fish oil capsules (and while many of the benefits are directly linked to the DHA in those capsules), supplementation with fish oil isn’t the same as supplementation with pure DHA. This is because fish oil is a blend of many different fats, of which DHA and EPA are only two. Research has shown repeatedly that separating out, purifying, and supplementing with a single compound suspected to be the “active” agent in a healthful food can have unintended (and sometimes detrimental) consequences. This is, for instance, what Miller and colleagues found in their work on vitamin E, which had previously (Knekt et al) been touted as having heart disease-reducing properties. In the case of vitamin E, it’s likely that by separating out a single form (alpha-tocopherol) of a vitamin that occurs in nature as a mixture of several forms, the supplemental vitamin E could be sending an unintended biological signal. Further support for the notion that there’s more to fish than DHA lies in the observation (Oken et al) that habitual fish-eaters note more predictable fish-related benefits than those taking fish oil supplements. With regard to supplements, there are two things to keep in mind: more is not better, and purifying the active ingredient isn’t necessarily an improvement over seeking out a source of that beneficial ingredient.


Science Bottom Line:* There is a multitude of evidence to support using fish oil (or better yet, eating fatty fish regularly!) if you’re…human. And especially if you’re a human who is pregnant, nursing, growing, and/or affected by an inflammatory disease process. No research suggests that moderate fish oil supplementation is harmful, and since fish oil is typically manufactured from small fish like anchovies, there’s absolutely minimal risk of mercury contamination in commercial capsules (meaning you don’t really need to seek out algae-based capsules, and probably shouldn’t, since the research is largely on fish, as opposed to algae, oil).


What has been your experience with fish oil?



Damsgaard et al. Fish oil affects blood pressure and the plasma lipid profile in healthy Danish infants. J Nutr. 2006 Jan;136(1):94-9.

Dunstan et al. Fish oil supplementation in pregnancy modifies neonatal allergen-specific immune responses and clinical outcomes in infants at high risk of atopy: a randomized, controlled trial. J Allergy Clin Immunol. 2003 Dec;112(6):1178-84.

Dunstan et al. The effect of supplementation with fish oil during pregnancy on breast milk immunoglobulin A, soluble CD14, cytokine levels and fatty acid composition. Clin Exp Allergy. 2004 Aug;34(8):1237-42.

Dunstan et al. The Effects of Fish Oil Supplementation in Pregnancy on Breast Milk Fatty Acid Composition Over the Course of Lactation: A Randomized Controlled Trial. Pediatr Res. 2007 Dec;62(6):689-94.

Furuhjelm et al. Fish oil supplementation in pregnancy and lactation may decrease the risk of infant allergy. Acta Paediatr. 2009 Sep;98(9):1461-7. Epub 2009 Jun 1.

Geleijnse et al. Blood pressure response to fish oil supplementation: metaregression analysis of randomized trials. J Hypertens. 2002 Aug;20(8):1493-9.

Hawthorne et al. Treatment of ulcerative colitis with fish oil supplementation: a prospective 12 month randomised controlled trial. Gut. 1992 Jul;33(7):922-8.

Knekt et al. Antioxidant vitamin intake and coronary mortality in a longitudinal population study. Am J Epidemiol. 1994 Jun 15;139(12):1180-9.

Kremer et al. Effects of high-dose fish oil on rheumatoid arthritis after stopping nonsteroidal antiinflammatory drugs. Clinical and immune correlates. Arthritis Rheum. 1995 Aug;38(8):1107-14.

Makrides et al. Effect of DHA Supplementation During Pregnancy on Maternal Depression and Neurodevelopment of Young Children: A Randomized Controlled Trial. JAMA. 2010 Oct 20;304(15):1675-83.

Miller et al. Meta-Analysis: High-Dosage Vitamin E Supplementation May Increase All-Cause Mortality. Ann Intern Med. 2005 Jan 4;142(1):37-46. Epub 2004 Nov 10.

Nagakura et al. Dietary supplementation with fish oil rich in omega-3 polyunsaturated fatty acids in children with bronchial asthma Eur Respir J. 2000 Nov;16(5):861-5.

Nestel et al. Fish oil and cardiovascular disease: lipids and arterial function. Am J Clin Nutr. 2000 Jan;71(1 Suppl):228S-31S.

Oken et al. Fish, Fish Oil, and Pregnancy. JAMA. 2010 Oct 20;304(15):1717-8.

Olsen et al. Randomised clinical trials of fish oil supplementation in high risk pregnancies. Fish Oil Trials In Pregnancy (FOTIP) Team. BJOG. 2000 Mar;107(3):382-95.

Suzuki T. Maternal Depression and Child Development After Prenatal DHA Supplementation — A Reply. JAMA. 2011 Jan 26;305(4):359-60; author reply 360-1.

Thorsdottir et al. Association of fish and fish liver oil intake in pregnancy with infant size at birth among women of normal weight before pregnancy in a fishing community. Am J Epidemiol. 2004 Sep 1;160(5):460-5.

Do DHA Supplements Help Build Brains?

**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. 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.

Martek Dr. Michael Roizen Accessed 17 Oct 2011.

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.

Nursing and Vitamin D

The American Academy of Pediatrics (AAP) acknowledges that breast milk is the gold standard in infant nutrition, but nevertheless recommends supplementing all infants — formula- or breastfed — with a daily dose of 400 IU of vitamin D. Two things about this mystify me. First, the implication that human milk is universally low in vitamin D doesn’t seem plausible; after all, the human race survived for millennia without the benefit of store-bought supplements. Second, research increasingly suggests that the vitamin D intake recommendations are set quite low (for both adults and children), making the determination that 400 IU per day is appropriate for infants somewhat random.

If the 400 IU of vitamin D recommended by the AAP is low by an increasing body of research, how much vitamin D is appropriate for a breastfeeding infant? This is a little hard to say. Some studies suggest a dose several times that recommended by the AAP (Hypponen et al 2001; Pittard et al 1991). However, there’s the concern of toxicity, since it’s possible to take too much of the vitamin. Currently, the National Institutes of Health (NIH) has the tolerable upper limit set at 1000 IU for babies under 6 months of age, but even this number may be conservative, since the Hypponen study found a protective effect of vitamin D against type 1 diabetes at twice that dose. My analysis, after looking at the data, is that 400 IU of supplementation is probably a little low, but there’s limited evidence that supports going over 1000 IU.

However, it may not be necessary to supplement a nursing infant at all, under the right conditions. You don’t need to consume vitamin D; assuming you get enough sun exposure, you can make it yourself (this route is appropriate for adults and older children, but not for babies, as infants shouldn’t be exposed to direct sunlight). This is a good thing, because there aren’t a wide variety of foods that contain the vitamin. It takes a light-skinned individual only about 10-15 minutes per day to make adequate vitamin D, though sunscreen negatively impacts production. Also, lower-intensity sunlight (such as at higher latitudes) isn’t sufficient to produce the vitamin. Still, an increase in time spent indoors means that many nursing mothers today aren’t getting the sunlight our ancestors did. It’s not that human milk is universally low in vitamin D, it’s that most women simply don’t spend enough time in the sun. If you work or exercise outdoors — year-round — in Phoenix, AZ, you probably don’t need to supplement your nursing infant with vitamin D. If you live in Buffalo, NY, you probably do.

It seems intuitive that a breastfeeding mother who is receiving enough vitamin D from sun exposure and/or food should be able to pass adequate quantities of vitamin D into her milk, making supplementing unnecessary. Several studies support this, including an older study by Hollis et al, and one published more recently by Taylor et al. The Taylor study, in particular, found good results with very high vitamin D intake by nursing mothers, noting that maternal consumption of 6400 IU of vitamin D a day provided for nursing infant vitamin D needs and appeared safe for both mother and baby. This is somewhat above the 4000 IU per day set as the tolerable upper limit by the NIH, though a study by Hathcock et al notes no adverse effects up to 10,000 IU per day.

Science Bottom Line:* Evidence supports nursing mothers taking supplemental vitamin D in quantities of around 4000-6400 IU per day. There doesn’t appear to be any need to supplement a nursing infant with adequate maternal vitamin D intake.


Do you or did you supplement your nursing baby with vitamin D? Leave a comment below.



Hathcock et al. Risk assessment for vitamin D. Am J Clin Nutr. 2007 85:6–18.

Hollis et al. Vitamin D requirements during lactation: high-­‐dose maternal supplementation as therapy to prevent hypovitaminosis D for both the mother and the nursing infant. Am J Clin Nutr. 2004 Dec;80(6 Suppl):1752S-­‐8S.

Hyppönen et al. Intake of vitamin D and risk of type 1 diabetes: a birth-­‐cohort study. Lancet. 2001 358:1500–1503.

Pittard et al. How much vitamin D for neonates? Am J Dis Child. 1991 145:1147– 1149.

Taylor et al. Vitamin D Supplementation during Lactation to Support Infant and Mother. J Am Coll Nutr. 2008 Dec;27(6):690-­‐701.

*The “Science Bottom Line” at the end of each article is not intended as medical advice. It is merely my analysis of one or more papers referenced in a given post.

**”SquintMom’s Decision,” likewise, is not intended as medical advice. It’s merely what I do in my own home, based upon the results of my analysis of the information available.