New Scientist, 30 August 2014

Vitamins, minerals, fish oils… the list of nutritional supplements you can buy keeps growing. Find out which supplements are worth it, and which ones aren't. (A collaborative article by a number of New Scientist staff)

Image: Angus Greig

Image: Angus Greig

N 1911, Polish chemist Casimir Funk made one of the most influential biomedical discoveries of all time. He learned that a disease called beriberi affected those who ate a diet of mainly white rice, but not those who ate mostly brown rice. He isolated a chemical from rice bran, showed it could prevent beriberi, and called it "vitamine".

We now call that compound vitamin B1. It is one of many essential nutrients that the human body cannot produce in sufficient quantities and that we must obtain from food. Casimir's breakthrough led to similar discoveries, including the compounds that prevent scurvy and rickets. In 1920, the British chemist Jack Cecil Drummond proposed dropping the "e" and using the umbrella term "vitamin".

Early success at identifying, preventing and curing nutritional deficiencies naturally led to the idea that dietary supplements were good for everybody. Science now recognises around a dozen essential vitamins, as well as some20 minerals considered essential in small amounts. In the US, iodine was added to table salt in 1924 to prevent goitre, vitamin D to milk in 1933 to prevent rickets, and several vitamins and minerals were added to flour in 1941.

Public awareness of vitamins grew, and with it, a desire to take personal control. Single vitamin supplements became available in the US in the 1930s, and multivitamins went on sale a decade later.

Though health authorities emphasise that most of us should be able to get all of the vitamins and minerals we need from a balanced diet, the industry has boomed. The list of supplements now numbers in the hundreds. It is estimated that about half of the US population now takes some form of supplement each day, while nearly a third of people in the UK do the same. All those pills and powders add up: the industry is worth roughly $30 billion in the US, and some £675 million in the UK.

But in recent years doubts have emerged over whether these supplements actually work, and whether they are always safe – particularly when they supply vitamins that can slowly build up to dangerously high levels in body fat. Over the next five pages, we look at the latest evidence for and against the 20 most popular.

The information in this feature summarises published research and guidance and is not intended as individual medical advice.

Vitamin A

Back in 1500 BC the ancient Egyptians noted that eating liver cured night blindness. Only in the early 20th century was it discovered that this was due to vitamin A.

"Vitamin A" is an umbrella term for several compounds, including retinol and retinoic acid, that we get from our diet. It is vital for growth, vision and development. Dairy products and fish oils are rich sources. Provitamin forms, such as the orange pigment beta carotene, get converted into vitamin A in the body. Just half a carrot meets your daily need for 0.6 to 0.7 milligrams.

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