Vitamin B1 (Thiamin)

What it does

Vitamin B1, or thiamin, is essential for turning the food you eat into usable energy. In its active form (thiamin pyrophosphate) it acts as a helper molecule for enzymes that break down carbohydrates and sugars, feeding the reactions that release energy inside every cell. Because the brain and nervous system rely almost entirely on a steady supply of glucose for fuel, they are especially sensitive to a shortage of thiamin.

Thiamin is also needed for the normal functioning of nerves, muscles and the heart. It supports the manufacture of certain neurotransmitters and helps maintain the electrical signalling that nerves and muscle cells depend on. A prolonged deficiency causes beriberi, which can affect the nerves in the limbs (causing weakness and tingling) or the heart and circulation (causing swelling and heart strain).

The body stores very little thiamin, so a regular dietary intake matters. It is found in wholegrains, pork, pulses, nuts and fortified cereals, though it is easily lost when grains are refined or when food is over-boiled. Requirements rise when you burn more carbohydrate, and heavy alcohol use is a common cause of deficiency because alcohol interferes with both the absorption and the use of thiamin.