Written by Gouri Ajith and Edited by Myra Ali
Every day, consumers are bombarded with both subliminal and overt messages that vitamins will not only counteract deficiencies, but also optimize and augment human health. As the popularity of vitamins has steadily increased over the last century, general perceptions about the supplement continue to be influenced more by marketing campaigns than by science. What are vitamins, and why does our body need them?
A vitamin is a compound that the body requires to function but cannot produce in sufficient quantities by itself [1]. The human body requires 13 vitamins (A, D, E, K, C, and the eight B vitamins) to perform various biochemical processes such as metabolism and cell growth [1]. While severe deficiencies of certain vitamins can cause symptoms like blindness or scurvy, it has not been proven that excess quantities of vitamins prevent or treat the development of certain conditions such as cancer or heart disease [1]. People who either have extremely limited exposure to the sun, are elderly, or follow a vegan diet may be at risk of developing a vitamin deficiency. Such risks can be confirmed by a simple blood test; a vitamin supplement can then be recommended by a doctor [2]. Conversely, those who eat a sufficiently varied diet and do not have a medical condition or lifestyle that limits vitamin absorption do not need supplemental vitamins to maintain their health [2]. The one exception is pregnant women, for whom folic acid supplements are recommended, to help prevent birth defects of the spinal cord and brain [2].
While vitamins have been demonstrated to benefit the health of people with vitamin deficiencies, they could have negative consequences depending on the dosage and on the individual’s own health.. Not only can some supplements pose a risk by interacting with certain medications, it is possible to overdose on vitamins by surpassing the recommended limits. The American Institute of Medicine of the National Academies has set tolerable upper intake levels (ULs), which describe the maximum dosages of vitamins that do not cause adverse side effects [3]. The risk of overdosing depends on whether the concerned vitamin is water-soluble or fat-soluble. If water-soluble vitamins, such as C and B, are consumed in quantities that exceed what the body requires, then the excess vitamins are simply excreted from the body through urine. However, it is possible for large doses of water-soluble vitamins to cause negative side effects such as kidney stones and diarrhea. Conversely, excess amounts of the fat-soluble vitamins A, D, E, and K, are stored in the body’s fat cells; therefore, excess fat-soluble vitamins can accumulate in toxic amounts and cause organ damage. It is possible for vitamin overconsumption in general to cause symptoms such as nausea or vomiting or, more rarely, hypervitaminosis, a condition in which abnormal consumption of vitamins leads to serious illnesses [3]. On the other side, certain proponents of alternative medicine claim that excess amounts or megadoses of vitamin C, in particular, can treat or cure diseases such as cancer and AIDS [4]. However, much of these claims are based either on theoretical speculation or scientific trials that could not be verified through further experimentation [5].
It is important to consider that vitamins are chemically active compounds that can interact with various drugs, and that vitamin supplements are not synonymous to being healthy [6]. It should also be noted that the Food and Drug Administration does not require supplements to be proven as safe in order to be put on the market [1]. Thus, consumers of vitamin supplements should be aware of recommended daily limits and consult a health care provider before taking vitamins if they smoke, are pregnant, are going to undergo surgery, or have certain medical conditions. Furthermore, those who are generally healthy and want to prevent potential vitamin deficiencies should look towards the original vitamin source: food.
References:
[1] “Frequently Asked Questions (FAQ).” National Institutes of Health Office of Dietary Supplements, https://ods.od.nih.gov/Health_Information/ODS_Frequently_Asked_Questions.aspx.
[2] “Should You Take Dietary Supplements? A Look at Vitamins, Minerals, Botanicals and More.” NIH News in Health, https://newsinhealth.nih.gov/2013/08/should-you-take-dietary-supplements.
[3] “Nutrient Recommendations: Dietary Reference Intakes (DRI).” National Institutes of Health Office of Dietary Supplements, https://ods.od.nih.gov/Health_Information/Dietary_Reference_Intakes.aspx.
[4] Eliseo Guallar, MD, DrPH; Saverio Stranges, MD, PhD; Cynthia Mulrow, MD, MSc, Senior Deputy Editor; Lawrence J. Appel, MD, MPH; Edgar R. Miller III, MD, PhD. 2013. Enough Is Enough: Stop Wasting Money on Vitamin and Mineral Supplements. Annals of Internal Medicine. 159:850-851.
[5] Fortmann SP, Burda BU, Senger CA, Lin JS, Whitlock EP. 2013. 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 Internal Medicine.159:824-34.
[6] Farin Kamangar and Ashkan Emad. 2012. Vitamin and Mineral Supplements: Do We Really Need Them? Int J Preventive Medicine. 3: 221–226.