Your vital guide to vitamins

By LUCY ELKINS , Daily Mail

Last updated at 16:16 05 October 2004

We've all known for years that vitamins are good for us - but only now are we discovering just how good. Scientists found recently that having enough Vitamin B3 in the diet can help prevent Alzheimer's, and Vitamins D and C are being investigated for their potential role in the prevention of cancer.

However, one problem is that opinions differ on what is a safe limit for vitamin consumption - EU guidelines, for example, are at odds with the UK's own less-generous RDA (recommended daily allowance). And much of the research into vitamins involves doses far higher than the RDA.

Many nutritionists recommend that you aim to get your vitamins solely from food, as this way it is impossible to overdose.

Here, we look at the main vitamins, the conditions they can help prevent and treat, which foods contain them, and the safe daily intake.

VITAMIN A

Night vision:

Increasing the amount of Vitamin A in the diet can help improve your vision in poor light. The vitamin helps convert light into electrical signals that are then distinguished by the brain. As it can be absorbed only with fat, Vitamin A deficiency is a common problem among people on lowfat diets or those with Crohn's disease.

Colds and infections:

Vitamin A has an important part to play in the immune system, and people without enough of it in their diet are more prone to colds, flu and even cold sores.

Acne:

Vitamin A plays a vital role in maintaining healthy skin and reducing the risk of infection, and it has been found to be an effective treatment for acne. Treatments containing Vitamin A such as creams, lotions and gels are now available on prescription.

Food sources: Full-fat dairy products; liver; vegetable oil; red, yellow and orange fruit and vegetables; margarine; egg yolks.

RDA: Vitamin A can be toxic if taken in excess. The recommended daily maximum dose is 700microgram (mcg) for a man and 600mcg for a woman. It should be avoided by pregnant women, as excess Vitamin A has been linked to birth defects.

VITAMIN B2

Migraines:

Vitamin B2 has been found to treat migraines and reduce the number of painkillers needed to deal with them. German researchers found that 400mg a day (many times the recommended maximum) halved the number of migraines that regular sufferers experienced.

Food sources: Eggs; fortified cereals; meat; milk; kidneys; green vegetables.

RDA: 1.3 milligrams (mg) per day.

VITAMIN B3

Alzheimer's:

Researchers at the Institute For Healthy Ageing in Chicago recently discovered that people who eat a diet low in Vitamin B3 (12mg or less per day) are 80 per cent more likely to suffer from Alzheimer's. Those who take in plenty of the vitamin not only have a lower risk of developing the disease, they were also found to retain their general mental agility for far longer.

Cataracts:

Studies have found that people taking Vitamin B3 together with Vitamin B complex supplements were half as likely to develop cataracts than those who did not.

Depression:

Vitamin B3 is sometimes prescribed to help lift mild depression. It is normally given with the amino acid tryptophan; this combination helps produce serotonin - the natural feel-good chemical that enhances mood.

Food sources: Poultry; fish; liver; eggs; nuts; seeds; wholemeal bread. Vitamin B3 is sometimes called niacin.

RDA: The RDA is only 18mg per day, so few people are deficient.

VITAMIN B6

Carpal tunnel syndrome:

This condition causes pain and numbness in the fingers, and is common in arthritis sufferers and pregnant women. A recent study found that increasing Vitamin B6 intake reduced the symptoms in 85 per cent of cases.

Pre-menstrual syndrome:

The B vitamins, and B6 in particular, have been found to relieve the symptoms of PMS. It can help moderate mood swings, and reduce breast tenderness and water retention. It also helps in the production of serotonin - trials have found that Vitamin B6 is good for alleviating mild depression. It works best when taken with magnesium or other B vitamins.

Food sources: Chicken; turkey; avocado; cod; bananas; liver.

RDA: 1.3mg per day.

VITAMIN C

Eye disease:

Taking Vitamin C together with Vitamin E helps slow the progress of the age-related eye disease macular degeneration, the leading cause of blindness in the over-65s. The condition is caused by a deterioration in the retina. It is thought that Vitamin C helps in the absorption of lutein and lypocene - nutrients found in fruit and vegetables that are needed to maintain the health of the retina.

Back pain:

Vitamin C is needed for the production of collagen - the basis of healthy cartilage, ligaments and tendons. It also stimulates the bone-building cells and boosts calcium absorption. Researchers found that people who suffered back pain because of damaged discs found their pain reduced (and, in some cases, the need for surgery was overcome) after taking Vitamin C daily.

Rheumatoid arthritis:

People with low levels of Vitamin C are more likely to develop rheumatoid arthritis, which leads to swelling and stiffness in the joints of the knees, wrists and ankles. Studies at Manchester and Cambridge Universities found that people who ate plenty of dietary sources of Vitamin C, such as fruit and vegetables, substantially reduced their risk of developing the disease.

Heart attacks and strokes:

An American study found that just a fraction of the recommended daily dose of Vitamin C -

0.5mg - can reduce the risk of a heart attack or stroke by 11 per cent. Another study found that people who do not get enough Vitamin C are almost four times more likely to suffer a heart attack than those who do.

Low sperm count:

Vitamin C can help overcome fertility problems associated with a low sperm count. Studies have found that 500mg of Vitamin C twice a day can boost sperm count by a third while also reducing the numbers of abnormal sperm - which can't fertilise an egg - by the same amount.

Food sources: Citrus fruits; peppers; green leafy vegetables; strawberries; kiwi fruit.

RDA: 40mg a day - the equivalent of, say, a kiwi fruit and a peach.

VITAMIN D

Diabetes:

Vitamin D may reduce the risk of developing Type 1 diabetes, the most serious form of the disorder, which can be controlled only with insulin injections. Finnish studies found that babies given Vitamin D supplements have an 80 per cent reduced risk of developing the condition in later life, although as yet scientists are not sure why.

Osteoporosis:

Vitamin D helps those with the bone-thinning disease osteoporosis, as it plays a key part in the absorption of calcium, which is vital for bone strength. Studies have found that a Vitamin D supplement, taken with calcium, can help reduce the rate of fractures (a common side effect of the condition) by 45 per cent. Most people get enough Vitamin D through diet and exposure to the sun, but elderly people may benefit from a supplement.

Osteoarthritis:

American studies have found that low levels of Vitamin D increase the amount of wear and tear in the joints of the hip and knee, which can lead to osteoarthritis - a bone condition that affects half of those over the age of 60. The Arthritis Research Campaign is funding further research to see if Vitamin D could be used to combat osteoarthritis of the knee in future.

Food sources: Oily fish; egg yolks; margarine. Another source (through the skin) is moderate exposure to the sun.

RDA: There is no RDA for Vitamin D.

VITAMIN E

Heart attacks:

Many studies have found that people with enough Vitamin E in their diet have a reduced risk of heart attacks. It can also reduce the risk of further attacks in people who have already suffered one. Vitamin E reduces cholesterol and inflammation, and so helps prevent blood vessels becoming furred or inflamed. However, the studies found that the benefits are gained only from dietary sources of Vitamin E, not supplements.

Menopause:

Vitamin E may help treat a number of menopausal symptoms. It is found by some to help combat hot flushes, and may also help with mood swings caused by hormonal imbalances. However, the evidence is largely anecdotal.

Pre-eclampsia:

Researchers at St Thomas's Hospital in London found that pregnant women could reduce the risk of pre-Eclampsia - which causes a huge surge in blood pressure and kidney damage, and can prove fatal to mother and baby - by taking Vitamins E and C. The study found that taking 400mg of Vitamin E and 1,000mg of Vitamin C reduced the risk by almost ten per cent. It is thought the two vitamins help "mop up" the toxins released into the body through the kidney damage.

Food sources: Unroasted nuts such as almonds and walnuts; sesame and sunflower seeds; spinach; oily fish.

RDA: More than 3,000mg a day can be toxic.