Can multivitamins supplement a bad diet?
Is taking a multivitamin a good idea?
Will taking one increase your lifespan, or reduce the risk of disease and death?
According to the bulk of scientific studies, multivitamins are NOT the holy grail and they can be HARMFUL.
A study, published in the Annals of Internal Medicine, examined data from about 31,000 participants. It found that adequate intake of nutrients from foods reduced the risk of death, but supplemental nutrients did not have the same effect.
In fact, excess intake of some supplemental nutrients, like calcium, increased the risk of death. Chris Kresser has written about this on his blog, the risks of calcium supplements. Men should not be supplementing with iron as the iron overload is associated with many chronic illnesses and many “multivitamins for men” contain iron!
Although multivitamins can contain valuable nutrients that can be useful for those who are deficient, they also contain a lot of vitamins and minerals that we might not need. As usual, the “more is better” approach to vitamins and minerals is not the case, high levels of certain minerals and fat-soluble vitamins can be detrimental to our health. Multivitamins do not allow us to choose which vitamins and minerals we absorb or the specific dosage we should be getting, you get what you're given.
Did you know that calcium and zinc block the absorption of iron? Why would be put these three minerals in one supplement? Did you know plant-based iron absorption is very low? What type of iron do they use in a multivitamin? Who honestly knows?
The takeaway is that we should get as many of our nutrients from food as possible. We should be nutrivores - those who hunters and gatherers their food based on nutrient-dense.
“You simply can’t supplement yourself out of a bad diet!”
So does that mean there is no place at all for supplementation? I would disagree.
Examine.com did a review of multivitamins that suggested certain populations might benefit from a multivitamin, including those who are at risk of nutritional deficiencies and are not able to change their diet (e.g. pregnant women, the elderly, and people following calorie-restricted diets).
It’s important to note that the quality of the multivitamins varies wildly. Most studies don’t assess the possible difference in effect that people taking high-quality multivitamins with high enough doses and/or the right forms of nutrients might have compared with people taking low-quality products with sub-therapeutic doses and/or the wrong forms of nutrients.
Looking beyond multivitamins, there is also a place for “selective supplementation.” This involves taking nutrients for a targeted purpose, such as:
Correcting a deficiency that is identified via lab testing
Treating a condition (e.g., taking vitamin A and zinc when you have a cold, taking magnesium for constipation, etc.)
Achieving a certain effect (e.g., taking NADH for energy, taking a nootropic for mental clarity)
Selective supplementation is not the same thing as taking a multivitamin. That’s why ridiculous headlines claiming that “supplements are useless” are a waste of print. Calling supplements useless is like saying a healthy diet is about the quantity of food (calories) and not the quality of food (nutrient density).
You cannot make an intelligent statement about “supplements” as a category. It’s simply too broad and diverse. There are supplements that are helpful, some are neutral, and some are harmful. As usual, the devil is in the details and working with a professional is always the best step.
If you are taking a supplement and you don’t know exactly why you are taking it, you possibly should not be taking it.
