Also known as Ascorbic acid, Vitamin C is essential for the production of collagen and therefore for healthy skin, bones, teeth and gums. It provides resistance to infection and promotes wound healing, energy production and growth. For vegetarians who have a relatively high-fibre diet Vitamin C plays a key role in non-haem iron absorption. Found in citrus fruits, blackcurrants, kiwifruit, passionfruit, guava, bitter gourd, cabbage, cauliflower, broccoli, spinach, lamb's lettuce, parsley, tomatoes and sweet peppers.
Influences calcium absorption and ensures continuous mineralisation of bones and teeth by supporting calcium blood levels. There are two forms of Vitamin D. Vitamin D3 (cholecalciferol) is produced by the action of sunlight on our skin and is found in animal products like eggs and milk. D3 is used to fortify foods as is the other form, Vitamin D2 (ergocalciferol) which is derived from plant sources. For most people the action of sunlight on the skin provides adequate levels of Vitamin D. With UK daylight, groups at risk from inadequate intake are pregnant women, people receiving less than 15 mins a day exposure to the sun on face and forearms particularly older people, some ethnic groups who wear enveloping clothes and people with dark skin colour. It is recommended by the Department of Health for all pregnant women to take a daily 10ug Vitamin D supplement. Excessive intakes of Vitamin D causes excessive absorption of calcium which can damage the kidneys.
Vitamin D sources suitable for vegetarians or vegans are dairy products and those margarines, breakfast cereals and soya milk brands which have all been fortified. Vitamin D is stable to heat and air.
Vitamin E is the name given to a group of substances called tocopherols. Tocopherols occur widely in plant foods and similarly to vitamin C and vitamin A have anti-oxidant properties which protect cells, particularly DNA and polyunsaturated fatty acids from the effects of free radicals. The destructive effects of free radicals against which vitamin E is protective are thought to be linked to cancer and atherosclerosis. Vitamin E is fat soluble and therefore stored in the body. Good sources include nuts, seeds and wheatgerm, corn, soya and olive oil. Small amounts occur in dairy products. Vitamin E is relatively stable but due to its anti-oxidant properties is reactive to air. High intakes of vitamin E from supplements for example can interfere with the function of vitamin K leading to problems with blood clotting.
Vitamin K is a fat soluble vitamin, stored in the liver. It plays an important role in blood clotting and in the production of certain proteins so-called ‘gla-proteins’ which are present in bone and connective tissues. Vitamin K is present in cow’s milk and dairy products but the best sources are dark leafy greens such as cabbage, kale, spinach and broccoli too. Oils and margarine, particularly those based on soya are good sources but freshness is important as vitamin K is damaged by UV light. The relatively widespread availability of vitamin K and the ability of the gut to synthesise a form of the vitamin means that deficiency is rare. In the UK vitamin K is routinely given to newborn babies as a precaution against a rare but serious blood disorder.
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