Vitamins and minerals are essential for the maintenance of good health and the prevention of a number of diseases. In this article we look at the properties of vitamins A, B, C, D, E, K, and common food sources.
Types of vitamins
There are two types of vitamins:
· water-soluble vitamins B and C
· fat-soluble vitamins A, D, E and K.
Water-soluble vitamins cannot be stored in the body, so you need to get them from food every day. They can be destroyed by overcooking.
Vitamins and minerals are found in a wide variety of foods and a balanced diet should provide you with the quantities you need.
Vitamin A (retinol)
This vitamin is essential for growth and healthy skin and hair. It is a powerful antioxidant that plays a key role in the body's immune system. Vitamin A is found in the following animal products:
· milk, butter, cheese and eggs
· chicken, kidney, liver, liver pate
· fish oils, mackerel, trout, herring.
Another source of vitamin A is a substance called beta-carotene. This is converted by the body into vitamin A. It is found in orange, yellow and green vegetables and fruits.
Vitamin B Complex
The complex of B vitamins includes the following group of substances:
· B1 - thiamine
· B2 - riboflavin
· B3 - nicotinic acid
· B6 - pyridoxine
· B12 - cobalamin
· folate - folic acid.
The body requires relatively small amounts of vitamins B1, B2 and B3.
Vitamins B6 and B12 help the body to use folic acid and are vital nutrients in a range of activities such as cell repair, digestion, the production of energy and in the immune system. Vitamin B12 is also needed for the breakdown of fat and carbohydrate. Deficiency of either vitamin will result in anaemia.
Vitamin B6 is found in most foods, so deficiency is rare.
The best dietary sources of the B vitamins, especially B12, are:
· animal products (meat, poultry)
· yeast extracts (brewers' yeast, Marmite).
Other good sources include:
· asparagus, broccoli, spinach, bananas, potatoes
· dried apricots, dates and figs
· milk, eggs, cheese, yoghurt
· nuts and pulses
· fish
· brown rice, wheat germ, wholegrain cereals
Dietary sources of vitamin B6 are similar to those for vitamin B12 and also include avocado, herring, salmon, sunflower seeds and walnuts.
Folic acid (folate)
Folic acid works closely in the body with vitamin B12. It is vital for the production of healthy blood cells.
Lack of folic acid is one of the main causes of anaemia, particularly in people whose diet is generally poor. Vitamins B6 and B12 help the body use folate, so are often given alongside folic acid supplements.
In pregnancy, low folate levels increase the risk of the baby's spinal cord system not developing completely (spina bifida). All women are now advised to take folic acid supplements in the first three months of pregnancy and preferably before conception.
Vitamin C
Vitamin C is one of the most potent antioxidant vitamins.
We need vitamin C for growth, healthy body tissue, wound repair and an efficient immune system. In addition, it's thought vitamin C can reduce cholesterol levels and regulate your blood pressure and your body's absorption of iron.
Fresh fruit and vegetables are the main source of vitamin C – eating your five a day will easily meet the body's needs.
Too much vitamin C can result in a sensitive, irritable stomach and mouth ulcers.
Vitamin C content of foods – an adult needs 60mg a day
Food | Serving size | Amount of vitamin C |
Strawberries | 1 bowl | 70-120mg |
Kiwi fruit | 1 fruit | 50mg |
Steamed broccoli | 1 serving (80g) | 50mg |
Orange | 1 large | 70mg |
Mango and passion fruit smoothie | 250ml glass/bottle | 48mg |
Frozen peas, cooked | 1 serving (85g) | 17mg |
Vitamin D (calciferol)
Vitamin D is essential for healthy bones and teeth. It helps the body to absorb calcium.
The action of sunlight on the skin enables the body to manufacture vitamin D – even on a cloudy day. For this reason, most people will get enough vitamin D through their everyday activities.
Foods rich in vitamin D are oily fish, liver, cod liver oil and dairy products.
Vitamin E
Vitamin E is important in cell maintenance and also plays an active role in the maintenance of a healthy heart, blood and circulation. It is one of the body's main antioxidants.
The following foods are rich in vitamin E:
· avocados, tomatoes, sweet potatoes, spinach, watercress, brussels sprouts
· blackberries, mangoes
· corn oil, olive oil, safflower oil, sunflower oil
· mackerel, salmon
· nuts, wholemeal and wholegrain products
· soft margarine.
Vitamin K
Vitamin K is involved in the blood clotting process and in the maintenance of strong bones. It is found in small quantities in meat, most vegetables and wholegrain cereals.
Your body also makes vitamin K in the large intestine, through the activity of 'healthy bacteria'. For this reason, there is no recommended daily amount.
These bacteria are also referred to as the gut flora. They form part of our defence against more harmful organisms.
Diets rich in fatty and sugary foods can adversely change the balance of the gut flora, as can the additives and pesticides that are often a part of modern food production.
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