Vitamins and minerals: health benefits and risks explained

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Vitamins, dietary minerals and trace elements are essential to the healthy function of the human body. Vitamins are organic compounds that are vital to, but not always produced by, the body and so have to be obtained through the diet. Similarly, dietary minerals (e.g. calcium and phosphorous) and trace elements, of which even smaller amounts are required (e.g. zinc and selenium), are acquired through food. For the majority of people, a balanced, nutritious diet satisfies the body’s vitamin and mineral requirements.[1]

There are two types of vitamins; fat soluble and water soluble. Fat soluble vitamins are found mainly in fatty foods and animal products, such as oils, butter, eggs, liver and oily fish. Whilst the body requires a constant supply of these vitamins, the tiny quantities needed coupled with their storage in the liver and fatty tissue for use when required mean that it is not vital to consume them every day. In fact large doses of fat soluble vitamins can be harmful. For example, the risk of lung and stomach cancers is increased in those who consume 20-30mg/day of B-carotene.[2] However many of the side effects seen with excess vitamin intake are not likely to happen as a result of dietary intake, but rather by exceeding the recommended dose with supplementation.[3], [4], [5] 

Water soluble vitamins such as vitamin C, folic acid and niacin are found in a wide range of foods including vegetables, fruit, potatoes, grains and dairy food.[6] These water soluble vitamins are less stable than fat soluble vitamins. They are often destroyed by heat or air, meaning that they cannot be stored by the body and excesses are excreted in urine. The consumption of foods containing water soluble vitamins is therefore needed more often, to maintain the body’s supply. As they are excreted in the urine, water soluble vitamins are generally less harmful than fat soluble vitamins, although very high doses may have an adverse effect on the body.[7] For example, large doses vitamin C can cause diarrhoea,[8] while excess folic acid can have effects that range from abdominal cramps and nausea to confusion and increased seizure frequency.[9]

Dietary minerals and trace elements have many functions including building strong bones and teeth, regulating the composition of the fluid inside and surrounding cells, and converting food to energy.[10] However high doses taken over a long period can be harmful, as demonstrated by the doubling of hospital admissions for gastrointestinal problems, 17% increase in kidney stones and 20-40% increase in the risk of a heart attack in those taking calcium supplements.[11]

Despite the fact that a varied, healthy diet will provide adequate amounts of all essential vitamins, minerals and trace elements for most people, the use of dietary supplementation is increasing. There is no real evidence, that taking synthesised vitamins and mineral supplements has any real benefit to health. Furthermore, in addition to a lack of proven efficacy, the manufacture of dietary supplements is not regulated as stringently as that of medicines. This is because they are not classified as a food or a drug, and as such, they are not technically permitted to make any health claims. More worryingly, no clinical trials are required prior to their production and sale. Many supplements are manufactured by synthetic methods and contain additives such as sweeteners, which may be harmful to health, and they can interact with prescribed medications with serious and even life-threatening results.[12]

In conclusion, naturally occurring vitamins and microelements are an important part of our diet. Whilst many synthetic supplements are available that contain high doses of these essential nutrients, it is often the case that our dietary intake is sufficient, except in cases of diseases or conditions that result in a vitamin deficiency. The potential for damaging effects seen with high intake of certain man made vitamins, coupled with the possibility for drug interactions means that you could be doing more harm than good by taking these ‘healthy’ supplements.


[1]  FAO/WHO (2001) Human vitamin and mineral requirements. Retrieved April 2016 from,

[2]  Druesne-Pecollo N, et al. (2010) Beta-carotene supplementation and cancer risk: a systematic review and metaanalysis of randomized controlled trials.Int J Cancer. 127(1). 172-84.

[3] Schwalfenberg, GK. & Genius, SJ. (2015) Vitamin D, Essential Minerals, and Toxic Elements: Exploring Interactions between Nutrients and Toxicants in Clinical Medicine.ScientificWorldJournal. 318595.

[4]  Brown, AC. (2016) An overview of Herb and dietary supplement efficacy, safety and government regulations in the United States with suggested improvements. Part 1 of 5 series. Food Chem Toxicol. [epub ahead of print] doi: 10.1016/j.fct.2016.11.001.

[5] Brown, AC. (2016) Liver toxicity related to herbs and dietary supplements: Online table of case reports. Part 3 of 6. Food Chem Toxicol. [epub ahead of print] doi: 10.1016/j.fct.2016.07.001.

[6] CSU (2012) Water-soluble vitamins: B-complex and vitamin C. Retrieved November 2016 from,

[7]  CSU (2012) Fat-soluble vitamins: A, D, E, and KB-complex and vitamin C. Retrieved November 2016 from,

[8] Mulholland, CA, Benford, DJ. (2007) What is known about the safety of multivitamin-multimineral supplements for the generally healthy population? Theoretical basis for harm. Am J Clin Nutr. 85(1). 318S-322S

[9] Rogovik, AL, Vohra, S, Goldman, RD. (2010) Safety considerations and potential interactions of vitamins: should vitamins be considered drugs? Ann Pharmacother. 44(2). 311-24.

[10] Shenkin, A. (2006) Micronutrients in health and disease. Postgrad Med J. 82(971). 559-567.

[11] Reid, IR, Bristow, SM, Bolland, MJ. (2015) Calcium supplements: benefits and risks. J Intern Med. 278(4). 354-68.

[12] Williamson, EM. (2003) Drug-interactions between herbal and prescription medicines. Drug Saf. 26(15). 1075-92.


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Wow! I was sure that the more vitamins I eat, the healthier I get. Fruits and vegetables became my main food, anything to get more vitamins. I've never thought vitamins can be harmful. My diet definitely will be revised :)

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I knew that you cannot be overdosed with vitamins, given a body consumes as much as it needs and anything over needed is excreted without any adverse consequences. It turns out such an opinion is a wide-spread misconception.

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Why don't you provide figures? How much vitamin should one eat to exceed the recommended amount? What is the recommended amount? I see the references, but it takes a lot of time to find something in the source. That would be great if these figures were included into the article, it is certainly relevant and important info. 

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