Introduction

An estimated one third of adults and twenty-five percent of children in the United States (U.S.) take some form of multivitamin supplements. There are numerous brand name and generic options available at pharmacies, grocery stores, and online.   

The overall U.S. market for vitamins and mineral supplements is expected to exceed $4.8 billion annually in 2025. Demand has risen considerably since the COVID 19 pandemic, as consumers seek ways to boost immunity, improve mental wellness, manage stress, and support overall health.  

In addition, the rising popularity of fitness and health promoted through social media and the internet has led many consumers to use supplements.   

Multivitamins continue to dominate as the most widely used supplement, with 70% of supplement users confirming their use of multivitamins in the past year. (U.S. Dietary Supplements Market Size Industry Report 2023).   

Multivitamin and mineral supplements are available in tablet, capsule, gummy, liquid, or powder forms, and can be a brand name or generic. 

Are vitamin and mineral supplements necessary?

For most healthy Americans, a balanced diet provides adequate vitamins and minerals, and multivitamins are not necessary. A healthy diet of fruits, vegetables, whole grains, healthy fats, and lean proteins provides not only vitamins and minerals, but also fiber, antioxidants, and other beneficial compounds, that would not be found in a supplement.  

Vitamin and mineral deficiencies are rare today, except for iron deficiency in women, and vitamin D deficiency in many adults. Magnesium is another nutrient that has been shown to be inadequate. Most deficiencies have been addressed over the years through fortification of foods, and increased diet variety.   

For instance, most grains-breakfast cereals in particular-are now fortified (if whole grains) or enriched (if processed) to contain substantial levels of B vitamins like folate, thiamin, riboflavin, niacin, and iron. A healthy adult or child of the general population can get all nutrients through the diet without supplementation. 

What do multivitamin and mineral supplements contain

Multivitamins usually contain about 13 vitamins and at least 10 essential minerals and often provide 100% of the recommended daily allowance (RDA) of these micronutrients. Multivitamins are often formulated for use by people according to age and sex. The Food and Drug Administration (FDA) uses RDAs as a basis for setting Daily Values (DV’s), which are the nutrient reference values seen on the nutrition facts labels of multivitamin and mineral supplements. Supplements that contain mega-doses (many times the Recommended Daily Allowance) of vitamins and minerals are not recommended, as some micronutrients such as vitamins A, E, and K can interfere with medications, or become toxic over time. 

How are multivitamins absorbed:

Multivitamins, though packed with vitamins and minerals, can vary widely in terms of how well they are absorbed by an individual. Vitamin absorption is a complex process that occurs primarily in the small intestine.  

The absorption rate of vitamins can vary depending on the type of vitamins, the individual's health status, gut health, and presence of other nutrients in the body. Water soluble vitamins like vitamin C and the B vitamins are quickly absorbed; however, excess levels are not stored by the body but are excreted in the urine.  

Fat soluble vitamins A, D, E, and K are absorbed more slowly and are stored in the body’s fat tissues and liver. Because they are stored, these vitamin requirements do not need to be filled daily. 

Some vitamins are better taken on an empty stomach, while others are better taken with meals. Fat soluble vitamins require dietary fat to be properly absorbed. Certain vitamins when taken together can enhance each other’s absorption, such as vitamin C and iron and vitamin D and calcium. In addition, the form in which a vitamin is consumed can influence the absorption rate.  

Some studies suggest that liquid forms are better absorbed than tablets or capsules; however, more research is needed to determine the extent. There is no difference in bioavailability between expensive multivitamin mineral supplements and generic brands. 

Regulation of multivitamin and mineral supplements:

The FDA regulates multivitamin and mineral supplements, classifying them as dietary supplements and regulating them under the Dietary Supplement Health and Education Act of 1994 (DSHEA).  

The DSHEA provides a regulatory framework requiring manufacturers to ensure safety and proper labeling. Unlike drugs however, dietary supplements do not require approval before hitting the market. The FDA can act against unsafe or mislabeled products, including recalls or legal action. The FDA has established good manufacturing practices (GMP’s) that manufacturers must follow to ensure product quality and prevent contamination.   

There are third party organizations like NSF International and US Pharmacopeia (USP) that offer testing and certifications, but these are not mandatory. Both NSF and USP verify that the product contains the ingredients listed on the label, at the stated potency, and is free of harmful contaminants. When shopping for a multivitamin and mineral supplement, look for the NSF or USP seal of approval. 

A deeper look at vitamin D

For most people, a vitamin D supplement is recommended because it is hard to get enough through food. Some foods are fortified with vitamin D, but few have it naturally. Good dietary sources include fatty fish, fish oils, egg yolk, butter and liver. Fortified products include milk, orange juice, margarine, and breakfast cereals.   

Vitamin D production in the skin with sunlight exposure is the primary way people get vitamin D, but many have insufficient levels because they live in places where sunlight is limited or they have limited sun exposure.  

Vitamin D supplements are available in two forms: Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol).  Vitamin D3 is generally considered more effective as it tends to raise and maintain vitamin D levels in the blood for longer periods.  

While not on a regular CBC blood test panel, Vitamin D can easily be added to an order by a provider to diagnose insufficiency or deficiency.  

A deeper look at magnesium

Dietary surveys of people in the U.S. consistently show that many people consume less than the recommended amounts of magnesium. Groups most at risk include people with gastrointestinal diseases, type 2 diabetes, alcohol dependence, and older adults, either due to insufficient intake and/or reduced magnesium absorption or increased losses by the body.   

While many foods contain magnesium, consumption has decreased significantly over the past few decades with changes in dietary habits. In addition, magnesium is often removed during food processing. Foods that are high in magnesium include nuts, seeds, legumes, green leafy vegetables, whole grains, milk and yogurt. Magnesium is added to some breakfast cereals and other fortified foods.  

Magnesium is important for muscle and nerve function, bone health, and blood sugar regulation. It also is associated with lower risk of inflammation and may contribute to improved gut health.  

Magnesium deficiency has been implicated with increased risk of cardiovascular events, coronary heart disease, stroke. The recommended intake of magnesium for adults is approximately 300-400 mg per day.    

If they do not obtain this amount from foods, consumers may need to ask their healthcare provider for guidance regarding supplementation. The forms most efficiently absorbed by the body are magnesium glycinate, citrate, aspartate, lactate, and chloride. 

Groups who would benefit from a multivitamin and mineral supplement

• Pregnant women or women trying to conceive 

Folic acid supplementation is recommended to prevent neural tube defects such as spina bifida. A pregnant woman needs 600 micrograms of folic acid each day, which is difficult to get from food alone. Doctors recommend a daily prenatal vitamin with at least 400 micrograms of folic acid, at least one month before, and during the first 12 weeks of pregnancy. 

• People with specific medical conditions 

Those with conditions such as celiac disease, ulcerative colitis, Crohn’s disease, or those who have had gastric bypass surgery may have impaired nutrient absorption and require supplementation. They may need a multivitamin containing a combination of supplements, such as iron, B12, vitamin D, copper, and zinc. 

• People with osteoporosis 

These patients may need additional calcium and vitamin D. 

• People with limited diets  

Individuals following restrictive diets, vegans, or experiencing poor appetite may need to consider supplementation. Vegans should consider supplementing vitamin B12, vitamin D, iodine, selenium, and omega-3-fatty acids, as these are difficult to obtain in sufficient quantities from plant-based sources alone.  Also, iron, calcium and zinc might need supplementing. 

• People who are diagnosed with nutrient deficiencies  

If a doctor identifies a specific deficiency through testing, supplementation may be recommended to correct it. 

• Older age 

The elderly are at risk for poor food intake for various reasons: difficulty chewing and swallowing food, experiencing unpleasant taste changes caused by multiple medications, or depressed appetite. They may also have trouble absorbing vitamin B12 from food. Vitamin B12 supplementation may be recommended. 

• People on certain medications   

Some diuretics prescribed to lower blood pressure can deplete the body’s stores of magnesium, potassium, and calcium. Some medications prescribed for Parkinson’s disease can reduce absorption of B vitamins, including folate, B6 and B12. 

Health claims

Social media has become a powerful tool for marketing vitamin and mineral supplements, with many influencers posting testimonials on Instagram and Tik Tok. Claims involve wellness and immunity, benefit to skin, hair and nails, energy, eye and brain health, among others.  

It is difficult to determine whether multivitamins provide health benefits because studies often use different products. Also, many people who take multivitamins tend to have healthier diets and lifestyles, making it harder for researchers to identify the benefits from the products alone.  

The label of a dietary supplement such as multivitamins may contain three types of claims: health claim, nutrient content claim, or structure/function claim.   

Most studies have found that multivitamins have little or no effect on risk of health problems such as cancer, heart disease, osteoporosis, lung disorders, and psychiatric disorders. A specific combination of vitamins and minerals can slow down vision loss from age, such as related macular degeneration (AMD), however they do not reduce the risk of getting AMD or cataracts.  

Multivitamins may improve immunity or hair growth if deficiencies exist, however, they are not a miracle cure for lowered immunity or hair loss. Be wary of supplemental vitamin labels with promises of supporting brain health or energy or healthy skin and hair. These are general statements about vitamins used for marketing but are not specific to the supplement itself. 

Should I avoid multivitamin and mineral supplements if I take medication?

Drug interactions between multivitamins and prescription medication aren’t that common, but they do exist. The most significant interactions come from some of the active ingredients in multivitamins negatively affecting the absorption of certain drugs. In addition, many contain ingredients beyond vitamins and minerals, such as herbs, which are well-known to have numerous interactions.   

Vitamin K can counteract the effects of blood thinning medications, like warfarin. Some medications for Parkinson’s disease, like levodopa, interact with vitamin B6. Diuretic medications can interact with multivitamins, particularly those containing magnesium. And certain supplements like calcium and iron can interfere with the absorption of thyroid hormone replacement medications, like levothyroxine. If you take several medications, consult with your health care provider or pharmacist to identify any potential interactions.

Conclusion

For most of the general population, the cheapest and safest way to receive all essential nutrients is through a varied diet of fruits, vegetables, whole grains, lean proteins, and healthy fats. A healthy diet also provides fiber, antioxidants, and other beneficial compounds that a multivitamin supplement would not provide.   

Anyone in the general population looking to use a multivitamin and mineral supplement should look for one that contains only 100% of the recommended daily allowance and bears the USP or NSF seal of approval on the label. There are many expensive brand names as well as standard generic names on the market; both are effective.  

Vitamin and mineral supplements can play an important role for some groups when nutrient requirements are not met through diet alone. Those groups should receive specific guidance from their physician or a registered dietitian.  

Resources

Dietary supplements: What you need to know [Fact sheet for consumers]. (2023, January 4). National Institutes of Health, Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/DietarySupplements-Consumer/ 

Dooley, C. (2015, December 19). Revealing popular misconceptions about multivitamins. UConn Extension, Expanded Food and Nutrition Education Program. https://efnep.uconn.edu/2015/12/19/revealing-popular-misconceptions-about-multivitamins/ 

Fatima, G., Dzupina, A., Alhmadi, H. B., Magomedova, A., Siddiqui, Z., Mehdi, A., & Hadi, N. (2024, October 13). Magnesium matters: A comprehensive review of its vital role in health and diseases. Cureus, 16(10), e71392. https://doi.org/10.7759/cureus.71392 

Hui-Anderson, A. (2023, June 8). These are supplements you should avoid taking with medication. Verywell Health. https://www.verywellhealth.com/supplements-you-should-avoid-taking-with-medication-7488798 

Magnesium: Fact sheet for health professionals. (2022, June 2). National Institutes of Health, Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/ 

Multivitamin/mineral supplements [Fact sheet for consumers]. (2022, October 11). National Institutes of Health, Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/MVMS-Consumer/ 

Razzaque, M. S. (2018). Magnesium: Are we consuming enough? Nutrients, 10(12), 1863. https://doi.org/10.3390/nu10121863 

Should I take a daily multivitamin? (2023, June). The Nutrition Source, Harvard T. H. Chan School of Public Health. https://www.hsph.harvard.edu/nutritionsource/should-i-take-a-multivitamin/ 

Staiger, B. (2019, October 27). Do multivitamins have drug interactions? Verywell Health. https://www.verywellhealth.com/do-multivitamins-have-drug-interactions-1124050 

U.S. dietary supplements market size, share & trends analysis report, by ingredients, by types, by form, by end user, by distribution channel, and segment forecasts, 2025–2033. (n.d.). Grand View Research. https://www.grandviewresearch.com/industry-analysis/us-dietary-supplements-market 

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