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Should You Take A Multivitamin? Benefits & Side Effects

By Charlie Seltzer, MD / February 20, 2016

Put simply, a multivitamin is a nutritional supplement that includes a combination of vitamins, and often minerals. Vitamins are good for you, right? So it should be a no-brainer: why not take a multivitamin.

The hitch is that there is no standard or regulatory definition for multivitamins, meaning that the composition and quality can vary significantly from product to product.

Originally designed to protect against micronutrient deficiencies resulting from inadequate dietary intake, multivitamins’ application has been broadened over time. Now not only do you have vitamins to supplement nutrient deficiencies, but products with specialized formulas which purport to meet a variety of goals, including: increasing performance, aiding in weight loss, protecting against cancer and other illnesses, and improving longevity. Can vitamins really do all that, or is it just a big marketing game?

Multivitamin Summary: Key Takeaways

As this is a long article, here are the key takeaways so you can quickly reference them:

Whole-Food Vitamins vs Synthetic Vitamins

I like to break down multivitamins into two broad categories: whole-food derived (found in natural, whole foods) and synthetic (created in laboratories). Without getting too technical, it is important to understand that just because something has been synthesized in a laboratory doesn’t necessarily mean it is not the same as what is found in nature. However, it is often different – for instance, synthetic Vitamin E is structurally unique from that of natural Vitamin E.

With both types of vitamin on the market, the argument against using synthetic – which include chemical distillates – is that they are not recognized and used by the body the same way vitamins from whole foods are. In research on scurvy (a disease defined by a Vitamin C deficiency), for example, it was found that whole foods containing Vitamin C quickly eliminated the illness while ascorbic acid (the distillate) supplementation had little effect.1 Whole food vitamins (in their highest quality form) contain the vitamin complexes as they exist in nature, and are theoretically recognized by the body as whole foods.

Vitamins Do Not Have To Be Tested Before Appearing On Store Shelves

Although the FDA has established “current Good Manufacturing Practice” (cGMP) regulations (requiring that vitamin manufacturers evaluate their products by testing purity, strength, and composition), because vitamins are classified by the FDA as general food products under the category of dietary supplements, and no testing is required before the manufacturer brings a product vitamin to market.

The primary safety concern with multivitamins is toxicity from over ingestion of a vitamin, or mineral, leading to increased risk of illness. For example, ingesting too much zinc interferes with copper and iron absorption. Since people do not need to consult a doctor before ingesting vitamins, you can potentially take vitamins that interact with one another in ways that can hurt, rather than help, your health.

Additionally, as with any nutritional supplement, there is a risk of impurities in the product, which can have severe consequences. For example, a contaminated batch of tryptophan from a particular manufacturer in Japan was linked to 37 deaths and 1500 cases of permanent disability.2

Long Term Health Benefits of Multivitamins Are Inconclusive

Diets high in fruits and vegetables reduce the risk of diabetes, cancer, heart disease, and a host of other medical conditions.345 It’s hypothesized the high concentrations of anti-oxidants & fiber reduce inflammation and protect against chronic disease. So, the natural progression from this is the belief that supplementing with isolated forms of the anti-oxidants and nutrients found in fruits and vegetables would confer the same benefits.

The research, however, on the benefits (and harms) of vitamin supplementation in the general population is inconsistent. Supplementation of a nutrient confers health benefits if a person is deficient in that nutrient. That should be obvious, but that is not what this article is about. The question we need to know the answer to is: will taking a multivitamin make us live longer or perform better?

The gold standard of research study design is a randomized, placebo controlled trial, in which subjects are divided into experimental and “control” groups, with the experiment group receiving a placebo, or inactive substance, and the experimental group receiving the substance to be studied.

Last year, the Journal of the American Medical Association published the results of the first large scale, placebo controlled trial examining the long-term effects of multivitamin supplementation on cancer. The researchers found an 8% decrease in total cancer incidence in men taking a multivitamin. However, other observational studies find no association between multivitamin use and lower cancer rates, and some even find evidence that supplemental intake of certain vitamins may actually increase risk of certain cancers.

To further complicate matters, the few randomized controlled trials that have been done have produced conflicting results. Some show decreased cancer incidence6 and others show no effect or elevated risks.7

As far as improving performance, the research is also equivocal. For example, a study published in the Journal of the American Society of Clinical Nutrition shows no performance improvement in runners after 3 months of multivitamin supplementation. Similarly, a study entitled “Chronic multivitamin-mineral supplementation does not enhance physical performance” concluded just that.8A study from 2006 in Research and Sports concluded that a liquid multivitamin supplement had no effect on “Anaerobic Exercise Performance” in people consuming an adequate diet.

Herein lies the problem and its resulting million dollar questions: What is an adequate diet and does the definition change depending on exercise habits and goals?

Multivitamin Recommendations

The research on multivitamins is lacking overall and even the research that has been done shows conflicting results. So what are we to do?

Ideally, an individual should strive to eat a variety of fresh fruits and vegetables (10+ servings) every day. Few people would disagree that this is the best way to get nutrients, improve energy and performance, and guard against disease. There is certainly a synergistic health effect from the contents of fruit and vegetables (both the things we know about and probably things we don’t know about), as nature’s design is most likely the best. The problem lies in executing this type of plan over the long run.

This is especially true for people who are trying to restrict calories to lose body fat, as 10 pieces of fruit would provide about 1000 calories per day. So what is the next best thing to eating that much produce? The makers of Centrum will say that taking a Centrum a day is the best alternative. Companies that sell whole food vitamin supplements will tell you that taking Centrum will do more harm than good, as the body doesn’t recognize and utilize synthetic vitamins the same way it does natural micronutrients. Unfortunately, there is no clear answer provided by research.

If eating 10+ servings of fruit and vegetables per day is not feasible for you, the next best thing is a product that most closely approximates it, namely, a “super greens and reds powder,” which is essentially fruit and vegetables concentrated down into a powder to be taken daily. This bypasses the issue of poor use of isolated nutrients and the idea that nutrients in real food exist in combinations impossible to replicate in a lab. There are many of them out there, but Lindberg Fruits & Greens+ is my choice.

If using a super foods powder is not feasible, the next best thing is a whole food multivitamin. It is very important to scrutinize the label of whatever product you’re thinking about buying, as often times products label “whole food multivitamins” are actually synthetic compounds combined with yeast (a whole food). Megafood, makes a good product, as does Garden of Life.

I recommend against the routine use of traditional multivitamins, unless you are part of a special population that research has shown to benefit from them. Still, if you are a hard training athlete, or are at risk for deficiencies due to restricted nutritional plans, you will likely derive more benefit from supplementation with traditional products than none at all. It is, however, a much better idea to use a preparation that more closely mimics eating real food.

In conclusion, there are no clear answers, and in the end the decision to supplement with multivitamins needs to be tailored to the situation of each individual. For most of the population, and especially athletes and people looking to improve body composition, a whole food derived nutrition supplement is a solid bet.

Show 8 References

  1. THE POTATO IN SEA-SCURVY. The Lancet. 1970;38(992):789.
  2. Toyo’oka T, Yamazaki T, Tanimoto T, et al. Characterization of contaminants in EMS-associated L-tryptophan samples by high-performance liquid chromatography. Chem Pharm Bull. 1991;39(3):820-2.
  3. Bazzano LA, He J, Ogden LG, et al. Fruit and vegetable intake and risk of cardiovascular disease in US adults: the first National Health and Nutrition Examination Survey Epidemiologic Follow-up Study. Am J Clin Nutr. 2002;76(1):93-9.
  4. Cohen JH, Kristal AR, Stanford JL. Fruit and Vegetable Intakes and Prostate Cancer Risk. JNCI Journal of the National Cancer Institute. 2000;92(1):61-68.
  5. Bazzano LA, Li TY, Joshipura KJ, Hu FB. Intake of fruit, vegetables, and fruit juices and risk of diabetes in women. Diabetes Care. 2008;31(7):1311-7.
  6. Blot WJ, Li J, Taylor PR, et al. Nutrition Intervention Trials in Linxian, China: Supplementation With Specific Vitamin/Mineral Combinations, Cancer Incidence, and Disease-Specific Mortality in the General Population. JNCI Journal of the National Cancer Institute. 1993;85(18):1483-1491.
  7. Omenn GS, Goodman GE, Thornquist MD, et al. Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease. N Engl J Med. 1996;334(18):1150-5.
  8. Singh A, Moses FM, Deuster PA. Chronic multivitamin-mineral supplementation does not enhance physical performance. Med Sci Sports Exerc. 1992;24(6):726-32.


  • Flor Rodriguez says:

    I take a multivitamin mostly because I am low on iron no matter how much spinach and other iron rich foods I eat. It gets so bad that my hair thins out if I stop taking vitamins. I haven't had any issues with my women's one a day. Could the hazards show up later down the line? Is there something I could take just for iron?

    • Charlie Seltzer says:

      This is something I would discuss with your doctor. You appear to fall in one of the "special populations" that do benefit from traditional multivitamin supplementation. Unless your doctor disagrees, and since you seem to get good benefits from your vitamin, I would continue it.

  • Aaron says:

    Thank you for this article. It makes sense that people will seek out the most efficient ways to optimize their health but it's important to identify areas where we actually need them. The living enzymes in raw food are essential to nutrient delivery. Organic fruits and vegetable are more available in most areas and when you consume organic vegetation you need less volume than conventional produce. This means price should be considered proportionate to the amount of food you actually need for optimal health rendering multi-vitamins useful only in certain environments like remote deserts or space stations. Juicing fruits and vegetables is probably the most necessary time saving method to adopt as we don't all have the time to eat vegetables all day long.

  • Jenny says:

    I thought a fruit and veggie serving wad a half cup, one full cup for green leaf ones like spinach, cabbage, etc.

  • Charlie Seltzer says:

    Regarding serving sizes, I guess it depends on what your source is.

  • Michael says:

    Exellent! I loved reading this I often have asked these questions to myself. Great research and a topic well worth the effort!

    Good work BuiltLean & Charlie

    • Charlie Seltzer says:


  • Katie says:

    Thanks for a helpful article. There is so much controversy on this subject that it's very useful to see the issues set out with scientific studies referenced.

    Personally, I used multivitamins last year when I was losing weight on a 1200 calorie diet, but now I've lost the weight and I'm back to eating normally I find it easy to get enough vitamins & minerals through a balanced diet, so I've ditched the multivitamins for now.

    Recently I've also been including flax seeds / flax seed oil in my diet to try to get my alpha-linoleic acid - it would be interesting to see an article here about the pros and cons of this, especially for vegetarians who can't rely on fish for Omega-3. Thanks!

    • Charlie Seltzer says:

      There are vegan omega-3 products out there, but I can't personally vouch for them as I don't have any direct experience with them. Flax is healthy, but does contain omega-6 fatty acids as well. Since most of us already get too much omega-6s versus omega-3s, I think it makes more sense to go with a pure omega-3 formulation.

  • john Bryson says:

    A thoughtful and responsible article on a very important topic. The supplement companies are certainly making a killing these days, and, it seems, they go mostly unchallenged with their claims. I'd encourage follow up articles to focus on some of the more popular supplements out there today. It drives me crazy to see Dr. Oz claiming this or that supplement can be such a game-changer for people. Good lifestyle choices are what we need to promote. Too boring, I guess! Thanks for this, and, all your articles!

  • Lee says:

    Great article Charlie and thank you Marc for providing such a great resource of information! I had not heard of “super greens and reds powder” before, so this and juicing may be a great option for me as I find it difficult to get all my fruit and veggies in a day.

    Thanks again,


    PS - received error on initial submission and had incorrect email - so sorry if you see this twice :)

    • Marc Perry, CSCS, CPT says:

      Happy to hear you learned something new and you find BuiltLean to be a great resource!

  • Leah says:

    Great informative and resourceful article.. I think I have a good balanced diet but have been reading lately and wonder if you have an opinion on acidic diets including caffeine, alcohol, high protein and high magnesium causing calcium loss from the body and if a calcium supplement would be likely indicated in such instance?
    Just interested, Thanks for any input offered!

    • Charlie Seltzer says:

      I have spent the past hour reviewing medical literature on the acid diet hypothesis and bone demineralization. My conclusion is that there is no merit behind these claims. Here are three large review/meta-analyses to support my conclusion:

    • Charlie Seltzer says:

      Thanks for the feedback. Nothing is ever simple, and results of research on the benefits of calcium and magnesium supplements has been mixed. As far as high protein diets, there's been some good research showing that high protein diets are actually associated with a decreased risk of bone fractures, especially in older women. The reasoning is that the extra muscle that higher protein intakes support help protect bones. Alcohol and caffeine certainly have their place in any moderate, maintainable lifestyle, though like with anything, moderation is key. Specifically with regard to calcium supplementation, the decision should be made based on individual factors and only after carefully weighing the risks versus the benefits. Sorry I can't be more specific. I hope this helped.

  • Ronni says:

    Thanks for providing us with such an informative and unbiased article.
    It is really frustrating that there is still not enough information about multivitamins. Really wish there was more concrete evidence about the benefits of multivitamins to different demographics.

    • Kristin says:

      We completely agree - that's why we make a point to present both sides of the equation. We want to give you as much information as possible about the pros and cons so that you can make the best decision for yourself. Glad you enjoyed the article!
      -Kristin, BuiltLean Coach & Managing Editor