Should I Take a Multivitamin?

By Ashley Reaver, MS, RD, CSSD, July 22, 2021

woman green smoothie multivitamin supplement

Dietary supplements are extremely popular, and multivitamins can seem particularly appealing for their potential to cover multiple possible nutritional issues. But do you really need supplements? Do multivitamins actually help? Should you take a multivitamin every day? Contrary to common marketing practices, we do not believe that multivitamins are a worthwhile expense, as they can be (at best) a waste of money or (at worst) cause dangerous nutrient toxicities.

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Do I need a multivitamin?

The short answer is no. If you are reading this blog, chances are that you have access to a wide variety of foods. From the same cell phone that you are reading this on, you could order a range of fruits, vegetables, grains, and proteins with the swipe of a finger. All of those foods contain the essential vitamins and minerals that your body needs to function at its best—the same you’d find in a multivitamin. 

Multivitamins typically claim to provide 100% or more of the Recommended Daily Value (%DV) of the nutrients listed on their labels. (Note: just because it’s listed on the label, doesn’t mean it’s really in the bottle! Read our blog about choosing supplements for more info on this topic.) If you are eating a variety of foods, your diet is certainly providing more than 0% of these nutrients. There’s a good chance that it’s providing the vast majority of them. 

Should I take a multivitamin every day? 

There are some people who could benefit from a multivitamin: 
  1. People who have a very limited or restrictive diet due to personal preferences, lack of availability, or medical conditions should consider a multivitamin, as they are less likely to get adequate nutrients from food alone. 
  2. Those with absorptive disorders or issues with their gastrointestinal tract may also benefit from a multivitamin. Individuals with celiacs disease or inflammatory bowel diseases may have a difficult time absorbing adequate amounts of certain nutrients due to damage to the lining of the small or large intestines. A multivitamin could provide an additional boost of nutrients to avoid deficiency.
  3. Lastly, women who are trying to conceive or are pregnant should be taking a prenatal vitamin under the care of their physician. Prenatal vitamins contain higher amounts of particular nutrients that are essential for the healthy development of a growing baby. 

Multivitamins are often thought of as “insurance policies” for individuals who fall outside of these three categories—a way to ensure that nutrition needs are being met. And while this isn't typically a dangerous approach, it's certainly not a cost-effective one. Looking more closely at the contents of a multivitamin can help you determine just how expensive (and potentially unnecessary) such an insurance policy it is.


What’s in a multivitamin?

Multivitamins usually contain a mixture of essential vitamins and minerals. "Essential" is a key term here, as essential nutrients are ones that humans either cannot produce themselves or cannot produce in high enough amounts to meet the needs of the body (fun fact: humans, bats, and very few other animals require vitamin C from their diets—most other animals can produce vitamin C themselves). So what are these essential nutrients found in a standard multivitamin and do you really need them? 


Water soluble vitamins

Water-soluble vitamins are those that are absorbed in the body with water. They include the 8 B-vitamins (thiamin, riboflavin, niacin, pantothenic acid, B6, folate, biotin, and B12) and vitamin C. These vitamins play critical roles in converting the food you eat into a form of energy that your cells can use. They also have other functions like the formation of collagen (vitamin C) and play a crucial role in the formation of the brain and spinal cord (folate). 
Multivitamins Middle of optimal zone

Deficiencies of water-soluble vitamins are incredibly rare in the developed world. Not only do most foods contain water-soluble vitamins, but many foods are fortified with them, too. Water-soluble vitamins cannot be stored in the body, so any excess water-soluble vitamin you consume is excreted. If you’ve ever wondered why your urine is bright yellow after taking a multivitamin, you can blame that on the excess riboflavin (B2), which is yellow in color (flavinis from the Latin word for yellow). Fun fact: it also glows under a black light!

Though water-soluble vitamins are not stored in tissues, constant supplementation can still result in unnecessarily high levels of these vitamins. In fact, InsideTracker dietitians have found that InsideTracker users who report taking a multivitamin often have excessively high levels of vitamin B12. While excessive intake of water-soluble vitamins is not clinically harmful, it’s simply unnecessary. 

Fat soluble vitamins

Fat-soluble vitamins require fat to be absorbed and are stored in the body’s fat tissue and liver. The fat-soluble vitamins include vitamins A, D, E, and K. Fat-soluble vitamins have a wide range of functions, from essential roles in the antioxidant defense network and cell differentiation, to regulating calcium absorption from the GI tract and influencing blood clotting. 

Unlike water-soluble vitamins, fat-soluble vitamins are stored in the body. Because of this, it is very possible to reach toxic levels of these vitamins with continuous excessive intake. And toxicity from certain vitamins, like vitamin A, have very serious side effects. Supplementing with fat-soluble vitamins therefore is not recommended unless there is an observed deficiency.

Ideally, these vitamins will instead come from foods, as the body can better regulate their absorption and the risk of toxicity is much lower. Vitamin D is unique, however—while there are some food sources of vitamin D (fortified dairy and non-dairy milks, some fish), the body typically produces vitamin D in the skin as a result of sun exposure. Vitamin D deficiency, like other fat-soluble vitamins, can easily be checked with a blood test. Based on your level, you may need to take a corresponding supplemental dosage to improve your levels. Our philosophy at InsideTracker is always "test, don’t guess," to ensure you're giving your body what it needs.


Major minerals

Multivitamins also contain the two categories of minerals. The first of the two, major minerals, are needed in large amounts of more than 100mg per day. They include calcium, phosphorus, magnesium, and potassium. These minerals also have a wide range of functions, from bone formation to fluid balance.

Similar to fat-soluble vitamins, minerals accumulate in the body and are therefore not required every day. Because of this, it is possible to take reach toxic, dangerous levels of these minerals if they are taken in too high a dose. Some groups of people, however, like post-menopausal females, may have a more difficult time reaching their needs of certain nutrients, as the recommended intake of calcium increases with to protect bone integrity and prevent osteoporosis. In these cases, targeted supplementation (read: not from a multivitamin) may be warranted.


Trace minerals

Trace minerals are required in small amounts—less than 100mg per day. Trace minerals include iron, zinc, copper, manganese, iodine, selenium, and molybdenum. Like the major minerals, the trace minerals are stored in the body, so the chance of consuming too much is a distinct possibility. 

One trace mineral in particular is often given prominence on supplement shelves: iron. Iron is the most common nutrient deficiency in the United States, largely due to the very high iron requirement in premenopausal women that many struggle to reach. Accordingly, iron supplementation is relatively common, particularly in women who do not consume sufficient iron from food sources. Men, on the other hand, do not experience iron deficiency at the same rate. Even still, iron is very often included in multivitamin supplements targeted to men. This decision by supplement companies can have detrimental effects: excess levels of iron can be harmful, as it can deposit itself in the soft tissues of the muscles, organs, brain, and joints. 

So, in general, though supplementation of trace minerals can be critically important for some groups, unnecessary supplementation of these minerals (even that from a multivitamin) can have deleterious effects.

Is it good to take a multivitamin everyday?

The best multivitamin you can take is a varied diet. As a personalized nutrition company, InsideTracker is definitely a bit biased when it comes to multivitamins. We believe in targeted approaches to nutritional deficiencies and inadequacies and always recommend avoiding taking blanket supplements that don't necessarily address your body's needs. Multivitamins will definitely include at least some vitamin and mineral content that your body does not need, and on the other hand, will not include the dosage necessary raise your levels into the optimal zone if you are experiencing a nutritional deficiency.

Many think of a multivitamin as an insurance policy—something to cover all nutritional bases. But the truth is that you likely don't need everything that's in such a supplement, making a multivitamin more comparable to wasting money on "incidentals"—items that you don't really need and didn't intend to pay for. Plus, the dosages found in multivitamins are often not even high enough to fix a deficiency if one is present. For example, the level of vitamin D that is commonly included in multivitamins is much lower than is necessary to increase your vitamin D level if it is low. 

If you aren’t sure which nutrients you should be focusing on, Test. Don’t guess. InsideTracker blood tests include a range of vitamins and minerals to assess whether your diet is meeting your needs. It includes personalized optimized zones for each marker based on your age, gender, activity level, and ethnicity, so you can tell exactly where your blood levels stand. You’ll also get recommendations for the exact dosages of supplements if your blood work shows they are required. 


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Ashley Reaver, MS, RD, CSSD
Ashley is the Lead Nutrition Scientist at InsideTracker. As a registered dietitian and educator, Ashley enjoys cooking and teaching individuals the power that food has on their health. You’ll find Ashley hiking, eating, and spending time with her family. Follow her on Instagram @lower.cholesterol.nutrition.

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