Do Vitamins Prevent or Cause Cancer? How research can Confuse the issues

Are multivitamins worth taking?

As a kid I used to love taking multivitamins, mostly because they came in fun shapes and flavors. It also made me feel like I was doing something good for myself, like I was taking a magic tablet that would keep me healthy. In the past few years however multivitamins have gotten very mixed results in scientific studies causing some doctors to recommend that people not bother taking them. Some people have gone as far as concluding that vitamins could increase your risk of cancer based on a study where participants considered high risk for developing lung cancer were given beta-carotene in combination with Vitamin A. The dose of beta-carotene and vitamin A used in this study were much higher than what is considered biologically needed, 25,000 IU versus the recommend 3,000 IU a day for adult men and 2,310 IU for adult women. The study was cut short because the rate of cancer and mortality in the group taking beta-carotene and vitamin A was significantly higher than the control group. However all this shows is that taking extremely high doses of a vitamin in a group that is high risk for cancer may have accelerated the cancer instead of decreasing it as the researchers had expected. 

“The study was cut short because the rate of cancer and mortality…”

Another study concluded that multivitamins have no noticeable benefit in terms of preventing heart attacks in people who have already had a heart attack however the authors of the study note that the high level of withdrawal and non-adherence make it hard to draw conclusions. In fact many studies on multivitamins are fairly questionable because they do not take into account the amount of vitamins people are getting in their diets. We know that some vitamins, like vitamin A and vitamin E, are toxic at high levels so it seems only logical that if someone is getting the required daily amount of these vitamins in their diet adding more via supplements would either not be beneficial or possibly cause some harm. 

To be fair I do want to mention a pretty comprehensive study from 2015 that analyzed data from over 10,000 adults. This study took many variables into consideration and made a distinction between multi-vitamin supplements and multivitamin-mineral supplements. Their results showed that there was a correlation between long term use (at least over 3 years) of multivitamin-mineral supplements and a reduced rate of cardiovascular disease among healthy women. No benefits were seen for men at all (sorry guys) and there were no benefits for women who just took multivitamins. However even this data is not a straightforward win for vitamin supplements. As the authors note taking supplements is often a sign that a person is more health conscious and it’s possible that other healthy lifestyle choices had an impact on the reduced rate of cardiovascular disease among this group.

Realistically the people who can afford expensive multi-vitamins are not the people who likely need them. If you’re getting fresh produce in your diet and eating a decent mix of fruits and vegetables then it’s safe to say you probably don’t need multivitamins. However if you have symptoms of a vitamin or mineral deficiency then you should talk to your doctor about getting tested. There are genetic conditions that can cause some people to be prone to vitamin deficiencies so for some people a healthy diet is not enough and a supplement is a good idea. But that is not something you can diagnose yourself.

“Realistically the people who can afford expensive multi-vitamins are not the people who likely need them”

A study published in May 2019 concluded that children who have low food security also have lower micro-nutrient quality in their diets. This means children living in poverty who have restricted access to food are at higher risk of having vitamin or mineral deficiencies because they are not getting enough healthy foods in their diet. This type of research is important and should be used to help create better public policies and assistance programs for people in poverty. In addition to free lunch at school maybe a vitamin supplement could help these kids avoid preventable disease? A study from 2012 suggests that there are pro’s and con’s to children taking supplements. The study found that in children age 8 to 18 “dietary supplements added micro-nutrients to diets that would have otherwise been inadequate for magnesium, phosphorus, vitamins A, C, and E. Supplement use contributed to the potential for excess intakes of some nutrients.” This kind of information could be used to create better children’s supplements designed to help those most at risk.

Most doctors will tell you that you’re better off getting your nutrients from food versus a pill and current data seems to support that. However with 23.5 million people in the US living in a food desert (according to a 2009 study released by the department of Agriculture) where they cannot easily access healthy food a vitamin supplement might be the next best option.