Vitamin Supplements are a Waste of Money

November 17, 2019 0 By Ewald Bahringer


Welcome to Impact Factor, your weekly morsel
of commentary on a new medical study, I’m Perry Wilson. This week – how do you tell what a nephrologist
thinks of vitamins? Don’t worry, they’ll let you know. Yes nephrons like me are fond of telling people
that taking vitamins give you expensive pee, but it’s nice to see our flippant attitude
bolstered by some real science, as seen in this study appearing in the Annals of Internal
Medicine which suggests that taking vitamins has no effect on overall mortality. Researchers examined data from about 31,000
individuals who were part of the National Health And Nutrition Examination Survey often
referred to as NHANES. Participants in NHANES complete a variety
of questionnaires that capture vitamin and supplement use as well as a dietary recall
to get a sense of what they are eating. The researchers linked those responses to
overall mortality to explore whether vitamins and supplements prevent, well, death, and
if so – which ones do. Now people who take vitamins may be subject
to what is known as the healthy user effect. They are much more likely to do other healthful
things too. Just over 50% of the population was taking
at least one vitamin or supplement and there were quite a few differences between the takers
and non-takers. Those who partook of encapsulated nutrients
tended to be older, more often female, more often white, more highly educated, and were
less likely to smoke or drink alcohol. They also had a higher “healthy eating index”
meaning their regular diet was better quality as well. But the vitamin-users did have more comorbid
conditions – 12% had a history of cancer compared to just 6% of the non-users. The authors suggest that this could be due
to individuals with chronic conditions taking their health into their own hands. I think it’s also likely that once you are
taking a prescription medication, the threshold to add a pill another day is not such a high
bar to cross. After adjusting for all these differences,
the authors found… basically nothing. Out of 43 vitamins and minerals studied, only
1 – lycopene – seemed to have any protective effect. Don’t get excited ketchup lovers – due
to the multiple vitamins tested there was around a 90% chance that at least one would
pop up as a false positive. So vitamins don’t do anything. But – plot twist – food does. When the authors looked at those food diaries
they were able to tell who was getting adequate intake of 22 nutrient – like niacin, where
nearly 100% of the population has adequate intake, or fiber, where nearly 100% do NOT
have adequate intake. Two nutrients appeared to be protective in
terms of all-cause mortality – vitamin K and magnesium, but only if you got them via
food. Here’s a comparison of the food-intake benefit
of these nutrients compared to the benefit you get from supplementing these nutrients. Here’s the thing – this study doesn’t
show us that there is something magical about getting these nutrients in food compared to
in pill-form that makes them protective. None of these nutrients are likely doing anything. Sure, if you have a severe deficiency of something,
the nutrients help, but no one in this study had scurvy, or beriberi, or even rickets. If more Vitamin K is better, we should see
a signal from the supplements. That we don’t teaches us an important lesson. Dietary research that purports to link a single
nutrient to an important outcome is often hopelessly confounded by the strong relationships
between the intake of that nutrient and ALL the other things you put in your body and
do for your body. People who get more vitamin K from food live
longer not because they eat more vitamin K, but because they eat a host of things – like
green leafy vegetables – that correlate with Vitamin K. Vitamin K is just a stand-in
for a whole package of behaviors. What’s a clinician to do? Don’t encourage your patients to eat more
vitamin K or magnesium. Encourage them to eat good, nutritious foods,
and engage in all the healthful behaviors – like regular exercise – that really
drive these observed benefits.