Welcome to Straight Talk on Health. I’m your host Dr. Chet Zelasko. Straight Talk on Health is a joint production with WGVU in Grand Rapids MI. I examine the world of health. Nutrition. Exercise. Diet. Supplementation. If there’s something new, I look at the science behind them, and let you know whether it’s real or not. You can check out other things that I do on my website Drchet.com and sign up for my free emails.
A couple of months ago, the health headlines were full of warnings about multivitamins and how they might increase your risk of an early death. The published warnings even went so far that a long-time researcher even did a video to explain the study and recommend who should and should not take a MV. This response was to a study that demonstrated an increase in Hazard Ratio if a person took a multivitamin every day, compared to occasionally or never. More about the HR in a moment. On the face of it, this seemed to be a compelling study. Data were combined from three large studies that totaled over 390,000 participants. The data were taken from health and nutrition questionnaires first given more than 20 years ago, with the mean follow up time of about 21 years. The questionnaires asked about a variety of demographic data as well as health and nutrition habits; the nutrition data were the old-style FFQ form—and you know how much I love those.
What’s a HR? The National Cancer Institute defines a HR is a measure of how often a particular event happens in one group compared to how often it happens in another group, over time. In cancer research, hazard ratios are often used in clinical trials to measure survival at any point in time in a group of patients who have been given a specific treatment compared to a control group given another treatment or a placebo. In the case of this study, they were looking at those who regularly took a MV versus those that took it occasionally or not at all. A hazard ratio of 1.0 means that there is no difference in survival between the two groups. A hazard ratio of greater than one means that survival was worse in one of the groups, less than one means it was better in another
Let’s say that the HR was 1.13 with a 95% confidence interval of 1.10 to 1.17. That would mean that there was a 13% increased risk of a negative outcome happening in the experimental group compared to the control group. If the HR was below 1, such as .78 and the CI was 0.64-0.95, that would mean there was a 22% decreased risk of the event happening. Back to the study.
After analyzing the data, researchers found a 4% increase in mortality risk in those participants who took a multivitamin every day compared to those who did not. The question is should you be worried? Aside from the number of covariates they considered, there were at least two problems.
Before I go any further, if you’re concerned about taking your multivitamin, I think you can lower the concern. Is it still possible that there may be individuals who may have a unique set of genes and specific covariates that may increase the risk? Sure, it’s possible, but this study brought us no closer to finding out if that’s true. Here’s why.
The issues with the study are as follows. The problems lie not in what the researchers did; it’s in what the researchers didn’t do.
While the researchers used 13 different covariates, they didn’t break the data down by macronutrient or micronutrient. They used the Healthy Eating Index. Let’s stop right there: What is the Healthy Eating Index? According to the USDA, the HEI is a measure of diet quality used to assess how well a set of foods aligns with key recommendations and dietary patterns published in the Dietary Guidelines for Americans.
The HEI uses a scoring system to evaluate a set of foods. The scores range from 0 to 100. An ideal overall HEI score of 100 reflects that the set of foods aligns with key dietary recommendations and dietary patterns published in the Dietary Guidelines. What is the set of foods? Total fruits, whole fruits, total vegetables, greens and beans, legumes, whole grains, dairy, total protein foods, seafood and plant proteins, fatty acids. There are also three moderation components: refined grains, sodium, and added sugars
The HEI ranks the quality of the diet from 0 to 100; that’s not the same as breaking the subjects’ diets down by intake of vegetables or antioxidants. It’s possible that someone who ate more vegetables could have higher antioxidant levels, which could contribute to getting too much of a nutrient by taking a multivitamin. That’s unlikely as most MV don’t exceed the RDA, The same would be true if they also were taking a complete multivitamin-multimineral and getting too much calcium or iron. That might have given valuable information to the people most at risk if there were such a relationship.
The researchers also did not give any explanation for mechanisms through which a multivitamin could increase mortality. That’s not unusual, because they didn’t examine any nutrient factors—but still, what was the point of saying there may be an increase in mortality, but nothing more than that?
The most likely explanation is that the results happened by chance because they tested multivitamin intake only twice early in the studies. Think of what you were eating 20 years ago. Has that changed? It’s reasonable to expect that some peoples’ habits changed, just as their dietary intake may have changed. We don’t know because they couldn’t go back and do the questionnaires every year or two, or even every five years. They suggest that this was a problem due to the latency of the data, and they were correct in my opinion.
This study illustrates the problem with going back to analyze data collected decades ago: you’re limited by the data you have rather than actually planning the study from the beginning. It’s an interesting observation after chunking lots of numbers, but it’s not meaningful in the real world due to the lack of ability to do an adequate analysis of the data.
But wait, there’s more. The journal also included a commentary by a well-known physician, who is the President of the Physicians Committee for Responsible Medicine, and a couple of other physicians. This is the physician group who promote veganism for a variety of reasons but especially for improved health. To their credit, the Commentary did cite the benefits of some targeted supplements such as beta-carotene for eye health and others.
Where they go off the rails to criticize the multivitamins was by citing studies that did not demonstrate benefits and were not multivitamins. They cited the beta-carotene and lung cancer studies as causing an increase in lung cancer. They did not state that synthetic beta-carotene was used in amounts at least 5 times the normal intake in those studies. They suggest that multivitamins that contain vitamin K may reduce the efficacy of warfarin, the blood thinner. They didn’t say that foods containing vitamin K can do the same thing and that it is vitamin K2 that assists with bone growth. They also imply that iron in multivitamins may increase the total intake from supplement and food to exceed the tolerable upper level. It seems like they have ignored that there is a difference in the source of iron in those studies that associated iron intake with heart disease. Heme iron found in meat is associated with heart disease, not ferrous fumarate, the type found in vegetables. There is more but that’s enough. They selected studies that cast doubt on MV yet haven’t done the research to suggest alternative issues associated with those studies.
We do agree on one thing. Mortality may not be the best or only way to assess the use of dietary supplements. Maybe, just maybe, sometime in the future someone will ask supplement users one question that relates to why people take supplements in the first place: how do you feel since taking the supplement? I can only hope but right now, I’m all out of time. This is Dr. Chet Zelasko saying health is a choice. Choose wisely today and every day.
Reference:
JAMA Network Open. 2024;7(6):e2418729.
