Introduction
Vitamins and minerals are essential for health and normal development. Most cannot be manufactured in sufficient quantities by the body so have to be obtained from the diet, and a normal balanced diet is usually sufficient. However, certain groups of people are at greater risk of developing a deficiency, such as the elderly who are more likely to have malabsorption disorders or appetite loss, vegetarians who may lack vitamin B12, pregnant and lactating women who have higher nutritional needs, alcoholics who often have impaired vitamin B12, folic acid and thiamine absorption, and dieters.
The sources and functions of the main vitamins and minerals are listed in the following table.
Vitamin or mineral Function in body Dietary sources

A (retinol) Healthy eyes, skin and mucus membranes, immune system Dairy products, eggs, oily fish, carrots, liver
B1 (thiamin) Carbohydrate metabolism, healthy nerves and muscles Yeast, liver, cereals, milk, eggs, fresh and dried fruit
B2 (riboflavin) Healthy skin, eyes, nerves and mucus membranes, iron absorption, production of steroids and red blood cells Cereals, milk, eggs, rice, mushrooms
B6 (pyridoxine) Protein and carbohydrate metabolism, formation of haemoglobin White meat, whole cereals, eggs, fish, vegetables, peanuts, milk
B12 (cyanocobalamin) Blood production Yeast extract, meat, fish, dairy products, eggs
Nicotinic acid (part of the B complex) Enzyme systems Meat, fish, wholemeal flour
Folic acid (part of the B complex) Reduces the risk of neural tube defects (eg. spina bifida) in unborn babies, red blood cell production Green leafy vegetables, chickpeas, brown rice, fortified cereals, bananas
C (ascorbic acid) Iron absorption, maintains healthy cells Citrus fruit, berries, green vegetables
D (calciferol) Calcium and phosphorous metabolism Oily fish, eggs, fortified cereals
E (tocopherol) Antioxidant Plant oils, nuts, seeds, wheatgerm
K (phytomenadione) Wound healing, blood clotting Green leafy vegetables, vegetable oils, cereals
Iron Red blood cell formation Liver, meat, beans, nuts, dried fruit, dark green leafy vegetables, whole grains
Calcium Strong bones and teeth, regulates muscle contraction Dairy products, green leafy vegetables, soya products
Magnesium Food metabolism Green leafy vegetables, nuts
Phosphorous Strong bones and teeth, releases energy from diet Red meat, dairy products, fish, poultry, oats, rice

Tonics often contain bitter ingredients, such as gentian infusions, which are thought to stimulate the appetite. In addition to vitamins and minerals, tonics often contain caffeine and glycerophosphates.

When to refer
• Anyone who doesn’t feel better after taking a tonic or vitamin supplement for two weeks or longer.
• Patients requesting an iron supplement who has not seen a GP.

Associated advice
• Tonics can contain considerable amounts of alcohol, so be aware of the risk of drug interactions.
• Women are recommended to take a folic acid supplement while trying to conceive and during the first trimester of pregnancy. The usual dose is 0.4mg per day, though women whose babies are considered at high risk of neural tube defects should take 5mg (though this must be prescribed).
• Iron preparations should not be taken unless recommended by a GP.
• Iron tablets can cause constipation, diarrhoea and gastrointestinal disturbances. They are generally best taken after food.
• Iron supplements should not be taken at the same time as indigestion remedies or tetracycline antibiotics.