Vitamin A is a fat soluble vitamin. It is found in two forms – vitamin A (retinol) and provitamin A (beta-carotene).
Food sources for provitamin A are brightly coloured fruit and vegetables such as apricots, mangoes, peppers, tomatoes, carrots, spinach and green vegetables such as broccoli.
Food sources for retinol are liver, cheese, oily fish, eggs, butter and margarine.
If you are pregnant or planning to get pregnant, do not eat liver or liver products (e.g. pate), as they contain high levels of vitamin A and may harm the unborn baby.
In general, the amount of vitamin A adults need is:
- 0.7mg a day for men
- 0.6mg a day for women
Also known as thiamin, this is a water soluble vitamin. Main sources of vitamin B1 are wholegrain cereals, wholemeal breads, liver, kidneys, red meat and pulses. The recommended nutrient intake is 0.4mg/1,000Kcals for men and women. Deficiency will result in loss of appetite and energy, beri-beri and pain in the calf muscles. Excess intake of thiamin will not result in any toxic effects as the excess will be excreted in the urine.
Vitamin B6 (Pyridoxine)
Vitamin B6 is a water soluble vitamin, essential for the formation of red blood cells and the metabolism and transport of iron. Together with folate and vitamin B12, vitamin B6 is required for maintenance of normal blood homocysteine levels. Raised homocysteine is a risk factor for cardiovascular disease. It also promotes carbohydrate, fat and protein metabolism, promotes healthy skin and hair formation. Food sources are poultry, white fish, milk, eggs, whole grains, soya beans, peanuts and some vegetables.
The Department of Health advices that you should be able to get all the vitamin B6 you need by maintaining a balanced diet. Do not take more than 10mg of vitamin B6 a day in supplements.
Toxicity may result in loss of nerve sensation and unusual gait (walking stride). Deficiency will result in irritability, convulsions and aneamia.
The recommended intake of vitamin B6 is 1.4mg/day for men and 1.2mg/day for women.
This is a water soluble vitamin. Main food sources are meat, fish, shell fish, poultry, liver, eggs, dairy products, yeast extract and fortified breakfast cereals, soya proteins and milk.
A lack of vitamin B12 could lead to vitamin B12 deficiency anaemia. It is involved in fat, protein and carbohydrate metabolism and the formation of red and white blood cells. It is also required for normal growth and development of nerve, gut and skin tissues. Recommended nutrient intake for men and women is 1.5mg/day.
Vitamin B9 – folic acid
Folic acid is the synthetic form of folate and is a water soluble B vitamin. It is used in supplements and for food fortification.
There is conclusive evidence that supplements of 400μg/day of folic acid taken before conception and during the first 12 weeks of pregnancy prevent the majority of neural tube defects (e.g. spina bifida) in babies. Therefore, it is recommended that all women of childbearing age who are planning a pregnancy take a daily supplement as it is difficult to achieve 400μg/day from diet alone.
Main food sources of folate are liver, meat, green vegetables (e.g. sprouts), yeast extract, pulses and fruit. In various parts of the world such as the USA, Canada and Chile, folic acid is added by law to flour and bread. The UK is still considering this fortification as there are concerns that high intakes of folic acid may mask vitamin B12 deficiency in older people.
A water soluble vitamin. Vitamin C has antioxidant properties, potentially protecting cells from oxidative damage caused by free radicals. Vitamin C is also involved in the synthesis of collagen. This is required for the normal structure and function of connective tissues (skin, cartilage and bones). It is also involved in the normal structure and function of blood vessels and neurological function. Vitamin C increases the absorption of non-haem iron (iron from plant sources) in the gut. Main food sources are fresh fruit (especially citrus fruits), green leafy vegetables, broccoli, potatoes, peppers, tomatoes, berries and currants.
Deficiency will result in weakness, slow wound healing, infections, bleeding gums and anaemia.
The recommended intake to avoid deficiency is 40mg per day.
Dietary vitamin D exists as either ergocalciferol (vitamin D2) or cholecalciferol (vitamin D3). Dietary sources are relatively insignificant compared with the synthesis in the skin from exposure to sunlight or ultraviolet rays, because there are not many rich food sources of vitamin D.
Vitamin D is a fat soluble vitamin. Main food sources are liver, oily fish, eggs, fortified dairy products, cereals and margarine. Vitamin D increases calcium absorption from the intestine and promotes and helps regulate bone formation. Lack of vitamin D will result in rickets in children and osteomalacia in adults.
It is recommended that pregnant and lactating women and people aged 65 years and over take vitamin D supplements (10µg per day). For other ‘at risk’ groups, for example ethnic groups that have limited sun exposure because of their style of dress, supplements may also be necessary. Infants are recommended to receive supplements containing 7-8.5µg of vitamin D.
Vitamin K is a fat-soluble vitamin. It is an essential component in the body’s normal blood clotting process. The main food sources are dark green leafy vegetables (such as cabbage, sprouts, cauliflower and spinach). Besides getting vitamin K from food, we also get it from our own bodies as it is produced by bacteria in the bowel. Anybody who undergoes a long course of treatment with antibiotics is at risk of a vitamin K deficiency as the antibiotics will kill off the gut flora, thus putting them at risk.
The dietary reference value for vitamin K is between 0.5-1.0µg/kg/day.
When the number of calories consumed through food equals the calories the body expends (through normal physiological processes and physical activity) body weight will remain the same.
If weight loss is desired the calories consumed must be less than the calories expended. A calorie shortage of 500 Kcal per day will produce roughly 1lb of weight loss per week.
Even a small calorie excess can eventually cause weight gain. A surplus 100Kcal per day (such as 1 biscuit) over a year would lead to weight gain of about 10lb.
Zinc is a trace element that has several important functions in the body including cell reproduction. It is also involved in the metabolism of carbohydrates, fats and protein and helps with the healing of wounds.
Good food sources of zinc include meat, shellfish, dairy foods and cereals. The amount of zinc you need is about:
- 5.5-9.5mg a day for men
- 4-7mg a day for women