By Louise D Metz, MD
What vitamins and supplements should I take? This is a question that we hear a lot from our patients. Many are already taking multiple supplements and want to know if they should continue. According to the U.S. Preventive Services Task Force, 49% of adults in the U.S. reported using at least 1 dietary supplement, and 32% reported taking a multivitamin supplement between 2007 and 2010. In addition, the National Health Interview Survey Alternative Medicine Supplement in 2012 found that about 18% of adults reported using herbal and other natural products. Many people take supplements with the intent to decrease their chance of heart disease or cancer or osteoporosis; others to increase energy, sleep better, decrease infections, or decrease inflammation. We like to think that we can control our health and improve our quality of life by adding in supplements, and we hear this message along with messages about diets and nutrition throughout our culture. Let’s delve into some of the research to determine if there is evidence to support this frequent use of vitamins and supplements.
Starting with heart disease and cancer prevention: A recent meta-analysis in the Annals of Internal Medicine looked at 24 different supplements, including vitamins, minerals, antioxidants, and omega-3 fatty acids, and their effect on heart disease and mortality. The authors found no convincing evidence that supplements prevent heart disease or extend life. The U.S. Preventive Services Task Force (USPSTF) in 2014 also compiled the literature on vitamin supplements, and did not find evidence of benefit of any supplements on risk of heart disease or for prevention of cancer.
How about bone health? We hear a lot about Calcium and vitamin D for prevention of osteoporosis. Calcium and vitamin D supplements have been shown to improve bone density, but it is not clear whether they actually decrease the risk of osteoporotic fractures. In the past, healthcare providers typically recommended 1200 mg of calcium in the form of supplements for all women. However, we now know that 1000-1200 mg of calcium is the appropriate total amount of calcium from dietary plus supplement sources, and that higher doses could have negative health consequences. Many people easily consume this amount of calcium in their diet in the form of dairy, greens, certain nuts, beans, or fortified foods, though some need an additional low dose supplement. For vitamin D, the literature suggests that around 800 IU is an optimal daily intake, and at least some of this total can be obtained through milk products and sun exposure.
There are certainly some other specific clinical indications for particular supplements. For instance, we have strong data for the use of folic acid in pregnant individuals, as this supplement in a dose of 400 mcg per day has been shown to decrease the risk of neural tube defects. Omega-3 fatty acids and inositol have been demonstrated to have efficacy in the treatment of polycystic ovarian syndrome. There are also several supplements that have been shown in small randomized controlled trials to decrease the frequency of migraine headaches, including magnesium, riboflavin, coenzyme Q10, and melatonin. Vitamin B12 has been touted as a supplement that can give us more energy. In reality, vitamin B12 supplementation in the form of pills or injections is only indicated for individuals who have a low vitamin B12 level, often either due to an auto-immune condition known as pernicious anemia or due to a vegan diet that does not contain vitamin B12. Similarly, iron supplements and higher dose vitamin D supplements are helpful if levels of these vitamins are detected to be low.
We should also consider the potential harms of supplements, which are often assumed to be safe because they are “natural”. Vitamins and herbal supplements are minimally regulated by the FDA, and manufacturers of supplements do not have requirements to demonstrate the safety or efficacy of these products. Supplements can have impurities or inaccurate labeling, such as the popular adrenal support supplements, which in some cases have been found to contain potentially harmful thyroid or steroid hormones. It is important to note that even “natural” products can have potential adverse effects and drug interactions. Some other examples: beta-carotene has been found to increase the risk of lung cancer, vitamin E in some studies has been associated with an increase in mortality risk, multiple drug interactions can occur with St.John’s wort, high dose vitamin C or calcium can cause kidney stones, and some literature points towards an increase in cardiovascular risk with high dose calcium.
Putting all of this together, supplements, including multivitamins, are not needed for general health or prevention of disease for most individuals with adequate and varied nutritional intake. Exceptions to this include adding calcium and vitamin D supplements if dietary sources are inadequate, and folic acid during pregnancy. Other vitamins and supplements may be needed and beneficial for particular health conditions or deficiencies, and for individuals in areas with limited resources and food insecurity. Many of the supplements and herbs that are commonly used lack any evidence of benefit, and some can cause harm. Consider checking in with your healthcare provider about whether a supplement may be helpful and safe for you. Though it may certainly be indicated depending on your health conditions and nutritional needs, you may also be able to save some time and money, and minimize risks by avoiding those that are not beneficial.
References:
Fortmann et al. Vitamin and mineral supplements in the primary prevention of cardiovascular disease and cancer: An updated systematic evidence review for the U.S. Preventive Services Task Force. Annals of Intern Med. 2013 Dec 17; 159(12):824-34.
Khan et al. Annals of Internal Medicine. 7/9/2019 Effects of Nutritional Supplements and Dietary Interventions on Cardiovascular Outcomes: An Umbrella Review and Evidence Map [Epub ahead of print 9 July 2019] doi: 10.7326/M19-0341.
Clarke et al. Trends in the use of complementary health approaches among adults: United States, 2002-2012. Natl Health Stat Report. 2015 Feb.
Akturk et al. Over-the-Counter “Adrenal Support” Supplements Contain Thyroid and Steroid-Based Adrenal Hormones. Mayo Clin Proc. 2018;93(3):284.
Tai et al. Calcium intake and bone mineral density: systematic review and meta-analysis. BMJ. 2015;351:h4183. Epub 2015 Sep 29.
Chung et al. Vitamin D with or without calcium supplementation for prevention of cancer and fractures: an updated meta-analysis for the U.S. Preventive Services Task Force. Ann Intern Med. 2011;155(12):827.
Zhao et al. Association Between Calcium or Vitamin D Supplementation and Fracture Incidence in Community-Dwelling Older Adults: A Systematic Review and Meta-analysis. JAMA. 2017;318(24):2466.
Rothman et al. Teratogenicity of high vitamin A intake. N Engl J Med. 1995;333(21):1369.
Fairfield, K. Vitamin supplementation in disease prevention. (2019). In L. Kunins (Ed.), Uptodate.
Saper, R. Overview of herbal medicine and dietary supplements. (2019). In L. Kinins (Ed.) Uptodate.
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