Selenium.

Selenium is an important antioxidant trace mineral that works with vitamin E to protect the immune system, keep the liver healthy and combat the ageing process. Selenium is also used to make thyroxine, the thyroid gland hormone regulating metabolism. Most multivitamin preparations include low doses of selenium but these are to combat any deficiency in the diet rather than for therapeutic effect. Larger doses (up to 200mcg daily) are needed to boost the body's production of anti-inflammatory prostaglandins and bring effective pain relief to arthritis sufferers Selenium occurs naturally in the soil and enters the food chain through plants. Populations of countries with poor soil or using intensive farming methods usually have low levels of selenium and an increased risk of cancer and heart disease.

RDA is between 60mcg and 200mcg. Selenium supplements usually include vitamin E and are available in strengths of 100mcg or 200mcg.

Good food sources: meat, fish, shellfish, dairy products and wholemeal bread and grains.

Thiamin - vitamin B1.

The first of the B complex group of vitamins, used by the body to release energy from food and to maintain the health of the digestive and nervous systems. Older people, anyone recovering from illness or under stress, smokers, contraceptive pill users and alcoholics need extra thiamine. The vitamin also helps prevent air and seasickness and some travellers find a 100mg dose effectively deters biting insects! RDA is 1.4mg.

Good food sources: wheatgerm, wholemeal bread, fortified cereals, brewer's yeast, oats and pork.

Valerian.

A popular natural remedy for anyone suffering from anxiety-related insomnia. This popular herb's soothing and calming properties help calm nerves, soothe irritable bowl syndrome and ease period and muscle cramps and spasms.

Zinaxin.

The world's first standardised natural treatment for arthritis with no known side-effects. Made from the extracts of two species of ginger, the active plant components are carefully preserved by a unique extraction method. Zinaxin works by fixing the biochemical imbalance in the joint and stops production of inflammatory substances like prostaglandins. Unlike anti-inflammatory drugs, Zinaxin does not block the enzymes produced by these substances, so causes no gastric upsets. By inhibiting inflammation and pain, further deterioration in affected joints is prevented.

Zinc.

A trace mineral, essential to over 80 body processes that helps maintain a healthy immune system. The body uses the mineral for tissue repair and renewal, so zinc supplements promote healing and may improve the skin's condition. Human fertility is also affected by zinc levels in the body - low levels in men may result in reduced sperm count, and pregnant women deficient in zinc are more likely to give birth to smaller babies. Zinc deficiency also causes loss of taste and smell and may be a contributing factor in anorexia nervosa, the slimmer's disease. A poor appetite is often the first sign of a zinc deficiency. To top up dietary levels, 5-10mg of organic or chelated zinc should be taken daily. RDA is 15mg. Other useful zinc products include lozenges for sore throats and zinc and castor oil cream to prevent and treat nappy rash.

Good food sources: Oysters, tinned sardines and other sea foods, baker's yeast, wholemeal bread, nuts, seeds, beef, liver, eggs and cheese.

Catherine Beattie is a health and travel writer and founder of Discovery Books.