The recently reported push by the National Food Authority to have some breakfast cereal manufacturers reduce the levels of added vitamins and minerals in their products must have caused some people to wonder, after years of worrying that their diets were lacking in vitamins, whether perhaps they might be overdosing instead.
The question of just how much of a good thing is too much of a good thing is problematic. The conservative view is that people should be able to get all of their vitamin requirements from a balanced diet without any need for vitamin pills or foods supplemented with vitamins and minerals.
Such a diet, leaning heavily towards fruit, vegetables and whole grain cereals and breads, with moderate amounts of meat, fish and diary products, will provide the vitamins and minerals a human body needs to function properly.
People on restricted diets for cultural or religious reasons could be at risk, as could people attempting to lose weight, heavy drinkers, the poor and people suffering from diseases which inhibit the absorption vitamins, for example coeliac disease and cystic fibrosis.
Taking certain medications, such as the contraceptive pill, or laxatives, can alter the body’s response to vitamins. Vitamin needs are higher for people recovering from surgery or major illness, pregnant women and women who are breastfeeding.
Vitamins come in two forms: fat soluble and water soluble
- The B vitamins and Vitamin C are water soluble, along with niacin, folic acid, pantothenic acid and biotin.
- The fat soluble vitamins, such as Vitamins A, D, E and K, are less easily lost during cooking and can be stored in human liver and fat tissue, to be released by the body as needed.
The thing to remember about the water soluble vitamins is that they can rapidly disappear into cooking water, which is why vegetables should be prepared immediately before consumption and be cooked for as short a time as possible, in as little water as possible.
Where practical, water used to cook vegetables should be reused in gravies or soups. Copper and brass cooking pots, as well as the use of bicarbonate of soda in the cooking water, can destroy vitamins.
Most of the water soluble vitamins are not stored effectively by the body (because they are water soluble they tend to be excreted in urine), so foods containing them need to be eaten very regularly.
Examples of the toxic effects of large doses of vitamins include:
- Eczema, fatigue, joint paints,vomiting and eventual liver damage from vitamin A. People who drink large amounts of carrot juice can experience yellowing of the skin and the whites of the eyes.
- An increased risk of kidney stones and possible effects on fertility and control of blood glucose levels from Vitamin C.
- Headaches, vomiting, high calcium levels in the blood and calcium deposits in soft tissue from Vitamin D, the most toxic of the vitamins.
- Of course, the effects of vitamin deprivation are equally dangerous, ranging from blindness, in severe cases of Vitamin A deficiency, to neural tube defects in foetuses whose mothers do not take enough folic acid during pregnancy.