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Vitamins
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Vitamins are nutrients required by the body in small amounts, for a variety of essential
processes.
Most vitamins cannot be made by the body, so need to be provided in the diet.
Vitamin D can be made by the body in the skin when it is exposed to sunlight.
Vitamins are grouped into fat-soluble vitamins (A, D, E and K) and water-soluble vitamins (C
and the vitamin B complex). Originally, vitamins were given letters but are now more
commonly referred to by their names, e.g. Ascorbic acid (vitamin C) and folate (vitamin B9).
Requirements for vitamins change across life stages.
Vitamin C
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 which is required for the normal
structure and function of connective tissues such as skin, cartilage and bones. It is therefore an
important nutrient for the healing process. It is also involved in the normal structure and function of
blood vessels and neurological function. Vitamin C also increases the absorption of non-haem iron
(iron from plant sources such as vegetables) in the gut.
Severe deficiency of vitamin C leads to scurvy. Signs of deficiency do not manifest until previously
adequately nourished individuals have been deprived of vitamin C for 4-6 months. Deficiency is
associated with fatigue, weakness, aching joints and muscles. Most of the other symptoms of scurvy
are due to impaired collagen synthesis and are characterized by bleeding gums, poor wound healing
and damage to bone and other tissues.
Vitamin C is found mainly in fresh fruit and vegetables especially citrus fruits and berries; green
vegetables, peppers and tomatoes. Vitamin C is also found in potatoes, especially new potatoes.
Vitamin C is very quickly and easily destroyed by the following conditions:
1. Heat – dry or moist;
2. Exposure to air – this leads to the oxidation of ascorbic acid into a form which is useless to
the body;
3. The presence of an alkali, such as bicarbonate of soda added to cooking water to prevent
colour loss, which causes vitamin C to be oxidised;
4. Water – vitamin C leaches into water, therefore cooking methods which us the minimum
amount of water should be used, e.g. steaming or microwaving.
Most cooking processes cause significant losses particularly dehydration, canning and freezing. To
prevent the loss of vitamin C, foods should be cooked and served as quickly as possible.
© British Nutrition Foundation 2015
www.foodafactoflife.org.uk
Activity
Using a nutritional analysis programme, such as Explore Food, food tables or the internet, investigate
the effect of different cooking methods on the vitamin C content of a variety of vegetables.
Firstly find the vitamin C content per 100g of the raw food and then complete the chart below,
following the example.
Food
Cooking method
Vitamin C content
per 100g
Reason for loss
Carrots - old
Carrots - old
Raw
Boiled in unsalted
water
6mg
2mg
N/A
Vitamin C leaches
into water
© British Nutrition Foundation 2015
www.foodafactoflife.org.uk
How could the
amount of loss be
reduced?
N/A
Eat raw
Microwave
Steam
Use cooking
water to make a
sauce or gravy