Vitamins and Mortality: An Interview With Jaakko Mursu

Linda Brookes, MSc; Jaakko Mursu, PhD

Disclosures

January 24, 2012

In This Article

The Interview

Medscape: How did you come to study the effects of supplementation in this population?

Dr. Mursu: The main goal of our original study was to look at different dietary patterns. The part of the study about supplementation was supposed to be a small side project, but it turned out to be bigger. Previous findings for supplement use were so dramatic[2] that we wanted to study them further. Supplement use is very common, especially in the United States, so the aim of our study was to determine whether there was any justification for their use. Even though supplements are not necessarily very expensive, if you use them for years, then there should be some justification for their use, and studies as a whole do not seem to support that view or that use.

Medscape: How did your study of supplement use tie in with the study of the dietary patterns?

Dr. Mursu: One of the ideas that we had originallywas that nutritionists tend to believe that in cases where the diet is deficient in nutrients, supplementing with multivitamins or with some other vitamin product or supplement would be beneficial or provide some additional health benefit. The next step was to investigate whether the quality of the diet affects how the supplements affect individuals, because that is the theory. Usually nutritionists, physicians, or health experts recommend supplements, or at least they feel that it would be the most logical scenario, where they could provide some benefits if the diet is not good. However, although this seemed to be a very sound theory to start with, there are hardly any studies based on it.

Medscape: Were the women in the Iowa Women's Health Study asked the reasons why they were taking vitamin and other supplements?

Dr. Mursu: That is a very good question. Actually, no, and that is one of the limitations of the study. It would have been very interesting to know that because, for example for supplemental iron, we do not know why the women in the study were using it. My feeling is that supplemental iron is most often used for a specific reason, usually for an underlying illness that causes anemia. However, we could not study this further, so that was a limitation of the study. I would like to study whether iron itself is toxic or otherwise harmful or whether it is just an indicator of underlying disease. Basically, there are 2 options for iron: It could be harmful, but we could not exclude the possibility that it could be just a marker of something else.

Medscape: In your study, the supplement users actually had a healthier lifestyle than the nonusers at baseline. So, they were unlikely to be taking supplements to make up for a deficiency in diet, but for prevention and treatment.

Dr. Mursu: That seems to be the case, and that has been noticed in other studies as well, so usually the supplement users are the ones who do not really need them. Usually, they have healthier lifestyles and they are not taking them to make up for a dietary deficiency.

In our study, among the supplement users, their diet was better, they were exercising more, they were less likely to be smokers, and they were better educated -- so, if you did not adjust for these factors, the findings would be that these supplements are beneficial. Taking these factors into account in the statistical models, then, is a crucial part of the study. I was surprised to see that, after adjustment for these factors, supplements seemed to be harmful. I remember early findings in the 1980s, when such factors were not always that carefully adjusted for or taken into account, the findings were a little more optimistic or positive. I have heard it suggested quite often that these women were sick in the first place, but that did not seem to be the case in our study.

Medscape: Was this finding that healthier women use more supplements different from other studies, then?

Dr. Mursu: No, actually it was not; it is very common. Usually the health-conscious people are the ones using supplements. The logic is a little twisted: The ones who might need them are the ones who do not even consider using them, and the ones who would need them the least are using them.

Medscape: So, you think that in this type of population, it is related to awareness of the negative effects of the menopause on, for example, cardiovascular risk?

Dr. Mursu: I think that is exactly the case. As you get older, if you know that cardiovascular disease runs in your family, then of course you try to prevent it from getting worse or from happening in the first place. I think that is one of the reasons people are using supplements.

One of the limitations of the study was that although we had some information about the health status of these women, it is still possible that some received a diagnosis at some point, and when they got sick they changed their behavior. However, when the study started, the health status for each participant was assessed extensively, and so we were able to include only women who were healthy at the start -- and our findings were the same. It is a problem that we do not have all the details of what happened during the study, so in some instances it could be a potential factor that we were not able to not address.

Medscape: Did quality of diet modify any effects of the supplements used?

Dr. Mursu: I have done the analysis and am writing the report on that, but the findings were the same. I was expecting that at least, on the basis of previous theories or hypotheses, supplements in people with a worse diet could provide some benefits, but that did not seem to be the case. So, despite the quality of the diet, the findings were the same. They rather contradict the theory that supplements would be beneficial in cases of deficient diets. We have to look at that further. In this study, even the worst diets were still good enough so that the women did not have any clinical deficiencies of nutrients or vitamins.

Medscape: This contradicts the previously widely held belief that taking vitamin and mineral supplements would be beneficial for health.

Dr. Mursu: When the Iowa Women's Health Study started in the 1980s, there was a good theory that antioxidants and supplements could be beneficial because they provide additional nutrients. However, most studies -- especially the clinical trials, which are more reliable -- have found that there is really no benefit. The majority of those studies reported no beneficial effects on risk for cardiovascular disease or cancer, and some found that some of the supplements could be harmful. So, most of our findings were in line with those of previous studies, basically providing further evidence that supplements are not very useful if you want to prevent cardiovascular disease or cancer.

Medscape: Except for the result for calcium. Most previous studies didn't support your finding of a beneficial effect of calcium on total mortality. In the main, they concluded that there is a small but significant elevated risk for cardiovascular disease associated with calcium supplementation.

Dr. Mursu: That was the only one. Calcium was very strongly associated with a healthy lifestyle, despite doing all we did, adjusting for the other factors. Two possibilities may explain this result. Calcium itself could be beneficial -- that is, it protects bones and various other functions in the human body. The other possibility, which cannot be excluded, is that calcium is just a marker. Not being able to exclude this is a limitation of a study like this, and that is the challenge. For a long time people, including experts, felt that calcium should be beneficial for bone health and that it is safe, but now even that setting has become more blurry. There have been a few meta-analyses of the effects of calcium, and now there have been some concerns about potential harmful effects regarding myocardial infarction. In some studies, it has been found to increase the risk for myocardial infarction.

Medscape: Your finding for calcium wasn't affected by whether it was used with vitamin D or not? Some studies have suggested that this combination might have a beneficial effect on mortality.[7,8,9]

Dr. Mursu: We would have liked to study whether combining calcium with vitamin D produced different findings, but in 1986, hardly anyone used that combination.

Medscape: From the hazard ratios for the supplements you studied, some of the increases in risk seemed quite small.

Dr. Mursu: Yes. We studied 15 different supplements, and out of those, 7 were associated with increased risk for mortality -- but, as you said, the risk increase was relatively small. That is one of the reasons we have tried to tone down the message that supplements are not providing any benefit. Some of the headlines in the newspapers went too far in describing the risks. There is a potential for harm, but supplements are not killing you. In most cases, the risk increase was between 6% and 10%. So, it is not a dramatic increase. And you have to remember, this is relative risk. The absolute risk takes into account how common these diseases were, and those numbers were even smaller. So for example, for a multivitamin, the relative increase in risk was 6%, but the absolute risk was 2.4%. I would put more emphasis on his number as the more reliable estimate.

Medscape: From your study, could you exclude the possibility that dietary supplements could still be beneficial?

Dr. Mursu: We cannot exclude the possibility that in some cases for some diseases, these supplements would be beneficial. The aim of our study was to take a broader look, but the main causes of mortality in this population are still cardiovascular disease and cancer. If supplements were beneficial, then you would have expected to see an effect with the simple approach that we used. They may be beneficial against some specific rare diseases, so that would not have a big impact at a population level. We cannot exclude that in some cases supplement use would be beneficial, but for the main causes of death, that does not seem to be the case.

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