Why don't multivitamins work better?

    Five reasons why they can disappoint.

    Multivitamins should be more effective than study results show. What’s going on?

    Some background

    In order to be healthy, you have no choice but to consume enough of each of the 13 essential vitamins (except for vitamin D, which is synthesized in sun-exposed skin). The definition of enough varies by person, but you catch my drift.

    Some of these vitamins can be produced by your gut bacteria, such as vitamin K and certain B-group vitamins, but production levels are highly variable based on your microbiome composition and age, among other factors. Don’t count on your gut bugs to save you from a nutrient-poor diet.

    The central importance of vitamins was illustrated by the legendary biochemist Bruce Ames, who came up with something called triage theory.

    It states that when your micronutrient intake is low, your body prioritizes their use for short term survival processes over long term survival processes. This could make chronic diseases more likely to develop.

    How have multivitamins done in studies?

    Imagine the cat as the multivitamin, and the box as the study.
    Or something.

    Really?? Got any examples?

    The majority of multivitamin meta-analyses haven’t found benefit, for uses ranging from cognition in cognitively healthy people to prevention of cancer and cardiovascular disease.

    This might be hard for you to believe. Vitamins have a sheen of efficacy powered by tradition and ubiquity that’s hard to look past. I didn’t know much about this until 20 years ago, when I had a doctor’s appointment and we started chatting about nutrition.

    When I told him that I was involved in a nutrition project for school, I thought I was pretty dang impressive. Big man on campus. After the appointment, I looked him up, and found that he was the primary investigator for a landmark study in which antioxidants miserably failed. If my cheeks were capable of blushing, they would have.

    Anyway, I digress …

    What could explain these findings?

    1. Baseline vitamin intake can be high enough to leave little room for benefit from supplementation. It’s tough to know exactly who to enroll in a trial — a broad cross-section of people, or mostly those who are at lower intake levels? And in real world situations, people who take multis tend to already eat more vitamin-rich diets compared to people who don’t. In other words, the people who could most benefit from multivitamins are less likely to use them.
    2. Multivitamins work for a small number of targeted uses. Maybe not everyone should take a multivitamin for general disease prevention. But multivitamins have promising randomized trial evidence for a few specific uses, such as immune health and cognitive function specifically for older adults.
    3. They might take a long, long time to provide benefits. In nutrition, a two or three-year trial is quite an accomplishment. Not many multivitamin trials go out past five years, so they might not capture all the potential benefits of extended, consistent use. That said, in 12 years of follow-up, the Physicians’ Health Study II found no benefit of multivitamins for cognitive function. It’s tough to know how other facets of health would fare in long term studies, though.
    4. There’s rarely a single magic bullet. Chronic conditions can be tough to treat. Maybe multivitamins give some people a fighting chance, but for others there might not be much that helps, save for pharmaceuticals or high-effort combination treatments, such as meditation plus a healthy diet plus good sleep hygiene — which can be tough to follow if you’re already struggling with a chronic condition!
    5. You can easily go 2 Fast 2 Furious. Have you noticed that very few multivitamins stop at 100% of a nutrient’s requirement? Nowadays, partly to compete with other brands, vitamin levels go higher and higher, often well over 1,000% of the requirement. This can result in potentially detrimental excess vitamin intake when combined with vitamins from food. While this nutrient excess doesn’t apply as much to most studies, it definitely applies to the real world impact of multivitamins.

    That wasn’t an exhaustive list of possible explanations, but I think you get the picture.

    Multivitamins are tough to study for a variety of reasons, and the results can be unexpected. These surprises also extend to smaller combinations of vitamins and lifestyle factors, such as the potentially increased mortality rates in smokers who supplemented with vitamin E and beta carotene (which is technically a provitamin, not a vitamin).

    A good rule to keep in mind: when it comes to supplementation, learn as much as you can (from Examine and other reliable sources … although we’re obviously the best 🙂), and then account for what you don’t know.

    That means you should leave some room for error. Don’t try a bunch of supplements all at once if you can help it, don’t assume all studies are 100% reflective of reality just because they’re peer reviewed, and don’t think because you’re taking “just vitamins” that they’re obviously safe. As the old saying goes, your body is your temple! And entrants to your temple need to be thoroughly screened.


    Kamal Patel
    Co-founder, Examine