Supplement Safety

A new report on the safety of supplement use in older women has been released from the Iowa Women’s Health Study (1).

The study tracked women 55 to 69 years old, almost entirely white, for an average of 19 years. After adjusting for age, education, place of residence, diabetes, high blood pressure, body mass index, waist to hip ratio, hormone replacement therapy, physical activity, smoking, energy, alcohol, saturated fatty acids, whole grain products, fruits, and vegetables, they found the following:

– Multivitamins were associated with a 6% increase in mortality (1.06, 1.02-1.10).

– Iron (1.10, 1.03-1.17) and copper (1.45, 1.20-1.75) were associated with an increased risk for mortality.

– Vitamin B6 (1.10, 1.01-1.21), folic acid (1.15, 1.00-1.32), magnesium (1.08 1.01-1.15), and zinc (1.08, 1.01-1.15), were all associated with a borderline statistically significant increased risk of mortality.

– Vitamin A, beta-carotene, vitamin B complex, vitamin C, vitamin D, vitamin E, and selenium supplements were not associated with an increase in mortality.

– Calcium supplements were associated with a decreased risk of mortality (0.91, 0.88-0.94).


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There was not a lot of data on amounts, except for iron and calcium. The groups with an increased risk of mortality from iron were taking fairly hefty amounts of iron, with the biggest risks associated with 50 to > 400 mg/day! That is a lot of iron ‒ the RDA for women 51 to 70 years old is 8 mg.

The levels of calcium associated with the reduced risk of mortality were basically anything less than 1,300 mg per day.

The authors summed up their findings with, “In conclusion, in this large prospective cohort of older women, we found that most dietary supplements were unrelated to total mortality rate. However, several commonly used dietary vitamin and mineral supplements were associated with increased total mortality rate, most strongly supplemental iron; calcium showed some evidence of lower risk.”

This study is just one piece to a very large puzzle, and I would not take it to mean anything conclusive. If you look at the entire body of research, results regarding supplements have been quite mixed and this tends to make me think they do not have a strong effect on mortality one way or the other, although there is still more to be learned.

One thing I would take away from this study is that it is further evidence that people should not take iron supplements, especially more than the RDA, unless under the guidance of a physician.

As for vegans, studying supplements in terms of their ability to decrease or increase mortality in a population that does not have acute deficiencies is not the same as for people whose diets are significantly lower than the DRIs for particular nutrients. This study would not give me any reason to change my recommendations.

Reference

1. Mursu J, Robien K, Harnack LJ, Park K, Jacobs DR. Dietary Supplements and Mortality Rate in Older Women: The Iowa Women’s Health Study. Arch Intern Med. 2011;171(18):1625-1633.   |   Link

12 Responses to “Supplement Safety”

  1. Reed Says:

    might be worth explaining to your readers the difference between association and causation

  2. Jack Norris RD Says:

    Reed,

    I think you just did it with your implication that association is not causation. I don’t know if there is much more to say about it. I guess I’ll add that in the realm of nutrition and chronic disease, it takes a whole lot to prove causation.

  3. Edanator Says:

    What was the risk for women who took supplements with “only” the RDA of iron?

    Also, I have never seen multivitamins with the levels you describe, I wonder why they took such enormous amounts.

    In this study, beta-carotene was NOT associated with increased risk. Wasn’t there a study a while back that claimed the opposite? I think there are still a lot of unresolved questions regarding multivitamins.

  4. Jack Norris RD Says:

    Edanator,

    > What was the risk for women who took supplements with “only” the RDA of iron?

    The lowest category was for 0 to 50 mg of iron. That amount was tested for 4 different time periods:

    1986-2008 1.02 (.93-1.12)
    1986-1996 1.09 (.92-1.30)
    1997-2003 1.13 (.92-1.39)
    2004-2008 1.66 (1.28-2.14)

    So, for the most recent group, the increase risk reached statistical significance, but for the most part the risks did not.

    > Also, I have never seen multivitamins with the levels you describe, I wonder why they took such enormous amounts.

    They were not multi-vitamins, they were iron supplements. The multivitamins were studied separately, with the finding mentioned above that there was a slight increase in risk.

    > In this study, beta-carotene was NOT associated with increased risk. Wasn’t there a study a while back that claimed the opposite?

    Yes, there was. It was a trial of beta-carotene for smokers that increased cancer. Here is a 2011 meta-analysis of beta-carotene trials:

    http://www.ncbi.nlm.nih.gov/pubmed/21981610

  5. Jack Norris on Diabetes and Multivitamins Says:

    […] Jack Norris published a pair of important blog entries yesterday. First, the strongest evidence to date has emerged that a vegan diet is indeed protective against diabetes. Second, it’s looking like multivitamins might cause health risks. […]

  6. Supplements and Mortality | The Vegan RD Says:

    […] Study suggest that supplement use in post-menopausal women is linked to increased mortality.  Jack blogged about this research yesterday, and I want to also mention it here since I’ve had quite a few […]

  7. Brandon Becker Says:

    I currently take the Deva iron-free multivitamin each day and the VegLife 25mg iron supplement once a week. Should I stop taking the iron supplement? I regularly eat lots of iron-rich foods like dark green leafy vegetables, beans, nuts, and legumes.

  8. Brandon Becker Says:

    Also, what do you think of this supplement from the Vegan Society?:
    http://shop.vegansociety.com/product_info.php?cPath=33&products_id=288

    Here’s a picture with the label:
    http://1.bp.blogspot.com/_bnRq_zInM0I/TDMeRrhV_gI/AAAAAAAADTk/Wz2pb46gcdI/S1600-R/veg1.jpg

    Since I eat pretty healthy, I’m wondering if I should try this?

  9. Jack Norris RD Says:

    Brandon,

    I recommend that people only take iron supplements if they have been found to be deficient. Eating foods high in vitamin C with meals is a better plan for increasing iron absorption.

  10. Jack Norris RD Says:

    Brandon,

    I try to avoid giving my opinion on specific brands of supplements. My best advice is to consider your own diet, what might be lacking in it, and making up for it with only those nutrients. The data on long-term effects of multivitamins is mixed. There is some data which indicates people shouldn’t be taking folic acid unless they are possibly going to get pregnant. As you saw in the article I reviewed here, folic acid was linked to a 5% increase risk of death that was barely statistically significant, and it’s not clear how much folic acid was being taken.

    It’s really a judgment call each person has to make for themselves – it’s like asking me if 4 servings of soy or 5 servings of soy per day is best to eat. I just don’t know. I don’t mean to be snarky or to avoid answering the question but I can see benefits and risks from taking multivitamins, but probably not a large chance of either one. Personally, I don’t take a multivitamin, but it’s not because I think they are deadly, I just don’t think I need one.

  11. Edanator Says:

    Thanks for the replies!

    What about folic acid that is often added to B12-supplement? Vegans DO need to take B12, but if that B12 is also coupled with a known risk factor, what to do? I know that not taking B12 is not an option, but should we only choose the very few B12-products that do not have folic acid? What role does the folic acid play, anyway? Are the levels in B12-supplement significant and/or potentially dangerous?

  12. Jack Norris RD Says:

    Edanator,

    > but should we only choose the very few B12-products that do not have folic acid?

    The next time you purchase B12 supplements, it’s probably best to get one without folic acid (unless you might become pregnant). Finishing off your current supply of B12 that contains folic acid is unlikely to shorten your life span. You can find lots of info on what folic acid does with a Google search.

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