VITAMIN A

Found in cheese, oily fish, milk, liver.

Pros Maintains healthy skin, aids night vision, strengthens the immune system.

Cons Use of vitamin A supplements was linked in the study to a 16% increase in mortality. It can cause liver damage.

BETA-CAROTENE

The plant version of vitamin A, it is found in yellow fruits – mangoes, melons, apricots and leafy green vegetables.

Pros Boosts the body’s antioxidant levels.

Cons Use of beta-carotene as a supplement was linked in the study to a 7% increase in mortality. In previous studies, it was given to patients reduce the production of cancer-causing free radicals, which happens in smokers, but these were terminated because, apparently, it led to worse forms of cancerous tumour.

VITAMIN B12

Found in meat, eggs and dairy foods.

Pros Helps the creation of red blood cells and maintains the nervous system.

Cons Excessive intake may interfere with other nutrient absorption.

SELENIUM

Found in nuts, meat, fish and eggs.

Pros Necessary for the immune system and thyroid to function properly.

Cons None known.

VITAMIN C

Found in fruit and vegetables, especially oranges, kiwi fruit, peppers and broccoli.

Pros Vitamin C helps to protect cells, assists in healing wounds and iron absorption.

Cons May cause severe diarrhoea if an overdose of the supplement is taken. Uncertain whether the effect on the body of having to break down excessive levels of vitamin C may, in itself, generate free radicals.

VITAMIN D

Made by the body from sunlight; also found in oily fish and eggs.

Pros Helps to protect against cancer, heart disease, tuberculosis and diabetes. Regulates the levels of calcium and phosphates needed to maintain healthy bones and teeth.

Cons None known.

VITAMIN E

Found in olive, corn and soya oils, as well as nuts and seeds.

Pros Helps to prevent cell damage and boosts the immune system.

Cons Linked to up to a 4% increase in mortality by the study, when taken as a supplement.

ZINC

Found in nuts and red meat.

Pros Assists in healing wounds and the processing of dietary fats, carbohydrates and proteins.

Cons High doses interfere with the absorption of copper, which can lead to anaemia and weakened bones.

MAGNESIUM

Found in dairy products, leafy green vegetables, fish and seafood.

Pros Essential to the metabolic process of converting food into energy; supports bone health.

Cons Overdose can cause life-threatening diarrhoea and dehydration.

FOLIC ACID

Found in leafy vegetables.

Pros Helps to build healthy cells. Can prevent the incidence of neural birth defects in pregnant women.

Cons None known.