The word vitamin, derived from vital amine, was coined in 1912 to describe a class of organic compounds, amines, required in small amounts for normal health. The first vitamin discovered, thiamine (vitamin B1), has an amino group in its structure. We now know that most vitamins are not amines but the name persisted.
Vitamins are essential substances that our bodies need to function normally. The 13 known vitamins are (chemical names in parentheses) vitamin A (retinol), C (ascorbic acid), D (calciferol), E (tocopherol), K (phylloquinone); and the B vitamins: B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folic acid) and B12 (cobalamin). Certain minerals are also essential for health, including calcium, phosphorus, potassium, sodium, chloride, magnesium, iron, zinc, iodine, sulphur, cobalt, copper, fluoride, manganese and selenium.
The body requires vitamins in order to facilitate the proper operation of cellular metabolism. Many vitamins act as cofactors essential to the functioning of certain enzymes vitally important in human metabolism. Most vitamins are readily obtained from a balanced diet of plant and animal foods, and vitamin deficiency is rarely seen any more in the developed world. Our intestinal bacteria are also a natural source of vitamins.
Poor nutrition still causes vitamin deficiency diseases in impoverished countries. But even in developed countries people on very specialised diets could develop vitamin-deficiency diseases – for example, most plants do not contain cobalamin, and individuals on strict vegetarian or vegan diets are at higher risk of developing cobalamin deficiency leading to anaemia and should consider taking vitamin supplements pills.
MG’s impressive small hybrid undercuts Toyota and Renault on price
‘We need the Irish because God gave us the gift of the gab’: Irish-Americans rally behind Kamala Harris
Buying a home on your own: Here is how to navigate the perils and pitfalls
‘Our daughter blames us for not realising years ago that she was autistic’
Many vitamins were discovered through studying nutritional deficiency. For example, in the 17th-18th centuries, scurvy was a common disease among sailors on long voyages. This was correlated with the unavailability of fresh fruit on these voyages, and a remedy preventing scurvy was discovered mid-18th century – a daily ration of limes. The vitamin involved here is vitamin C.
[ Most things you’ve heard about eating meat are wrong, say Irish scientistsOpens in new window ]
Biochemists have traditionally separated vitamins into two groups – water-soluble and fat-soluble vitamins. Vitamins A, D, E, and K are fat-soluble. Vitamin C and all the B vitamins are water soluble. Fat-soluble vitamins are stored in fatty tissue and the liver, and reserves of these vitamins can remain in the body for days and sometimes months. Water-soluble vitamins do not stay in the body for long and cannot be stored, exiting the body in the urine. People therefore need a more regular supply of water-soluble than fat-soluble vitamins.
The body doesn’t synthesise vitamins in sufficient amounts to meet its needs and therefore these essential vitamins needed must be obtained from the diet or from some synthetic source. It is believed that, because essential vitamins are readily available from eating a normal diet, humans gradually lost the ability to independently synthesise their own vitamins.
It is accepted general medical knowledge that the average person eating a balanced diet is in no need of vitamin supplementation. Nevertheless, taking supplementary multivitamin pills to guard against vitamin deficiency is widespread and is a multibillion dollar industry globally.
A Johns Hopkins survey has shown 33-50 per cent of American adults take multivitamin supplements. The US Preventive Services Task Forces (SPSTF) reviewed the impact of multivitamin supplements on all causes of mortality and found “insufficient evidence to determine benefits or harms”.
The study involved 400,000 participants and 164,000 deaths (Chuck Dinerstein, American Council on Science and Health). It seems that multivitamin supplements are generally just expensive placebos.
When I studied for my science degree in biochemistry at UCD in the 1960s, Prof Don Hingerty presented most of our medical biochemistry lectures. One of us asked him in class one day about the value of taking vitamin supplements.
Prof Hingerty told us that the net effect was to enrich Dublin Bay in vitamins. In other words, if you eat an adequate diet, you ingest all the vitamins you need and excess vitamin intake is simply excreted from the body. He was an Irish international rugby veteran and would talk for hours about rugby. He loved to organise groups of us to play tip-rugby at lunchtimes or on Saturdays – games in which he would enthusiastically participate.
William Reville is an emeritus professor of biochemistry at UCC