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[text: QQs: Are multivitamins really good for you?]

Michael: From colorful pills to chewy gummies in the shape of your favorite cartoon character, there are tons of multivitamin supplements to choose from, and people spend billions of dollars every year trying to boost their health with them. But if you look on the back of the bottle lots of these supplements have more than 100%. Sometimes up to 500% or 2,000% of the recommended daily value for different vitamins inside. So, why are they so jam-packed with vitamins? And is taking all these supplements actually good for you?

Well, if you are healthy and eating a balanced diet, you should be getting all the vitamins you need. So at best, they probably aren't doing very much. At worst, they could be doing you harm. Vitamins are important compounds that our bodies need to grow and function. But we need to get them from food because we can't make them, or enough of them, ourselves. There are fat-soluble vitamins A, D, E and K which means they dissolve in lipids and B vitamins and Vitamin C are water-soluble which means they dissolve in water. And different vitamins come from different foods.

Vitamin K, for example, can come from dark green vegetables, while Vitamin C is in all kinds of citrus fruits, and your body can vitamin D after spending some time in the sun. If you're deficient in any of them, your cells and enzymes won't be able to work properly, and you could be prone to diseases. So the reason to taking multi-vitamin supplements is usually to prevent any vitamin deficiencies. Sounds reasonable. But taking supplements when you don't actually need them can cause problems. Multi-vitamins generally have more than 100% of your Recommended Dietary Allowance, or RDA.

RDA values are set by national organizations that study food and nutrition. They're basically the estimated nutrient requirements for healthy people. The same scientific committees also estimate a tolerable Upper intake Level, or UL which is the max amount of these nutrients you can take, without risking some negative health effects. Generally, the levels for water-soluble vitamins are a lot higher than for fat-soluble vitamins. Either way, when you take a multivitamin that has more than 100% of the RDA for different vitamins, your body might not be digesting and absorbing it all.

Your body tends to get rid of any excess water-soluble vitamins by peeing them out. But it stores the extra fat-soluble vitamins in your fatty tissues. The problem is megadoses of vitamins. If you consistently take the UL dose over weeks or months, especially with fat-soluble vitamins, these vitamins will keep building up in your body, and eventually cause toxicity or other health problems.

For example, Vitamin D normally helps your body absorb calcium but a lot Vitamin D could cause a buildup of calcium in your blood called Hypercalcemia or even damage your heart. So even though your body needs vitamins to survive, taking multivitamins doesn't replace the nutrients you get from a balanced diet, and can even be harmful if you overdo it. If you have some sort of health condition, or pregnant, definitely listen to your doctor and the supplements they recommend. But, usually just taking a bunch of extra multivitamins won't do much for your health.

Thanks to Patreon Patreon Richard Willis for asking this question. And thanks especially to all of our patrons on Patreon who keep these answers coming. If you'd like to submit questions to be answered, or get some videos a few days early, go to Patreon.com/SciShow. Don't forget to go to Youtube.com/Scishow and subscribe.