Minerals have three main functions in the body: as constituents of the bones and teeth, as regulators of body fluid composition and as part of chemical reactions involving enzymes in the release of energy. The main minerals required in the diet are calcium, magnesium, phosphorus, potassium, sodium, chlorine and sulphur. Other minerals which are required in only tiny quantities (less than 100mg/day) are called trace elements.
Calcium, the most abundant mineral in the body is involved in muscle contraction (including the heart), nerve function, enzyme activity and blood clotting. The key to bone strength, calcium is stored in the skeleton as calcium phosphate and the bones act as a reservoir with calcium constantly being withdrawn and redeposited at controlled rates. Vitamin D is essential to the absorption of calcium and is especially important in childhood and adolscence when its influence on bone growth and density is most marked. If you have chosen to follow a vegan diet then it is especially important to maintain your vitamin D intake (most efficiently through outdoor exposure to sunlight) in order to ensure calcium absorption. Low sodium (including salt) intake and high potassium intake help maintain calcium levels as does a reduction in tea and coffee drinking. The avoidance of oxalic acid foods such as spinach, chard and rhubarb in calcium rich meals is also effective. Calcium is found in dairy milk, cheese and yoghurt, leafy green vegetables, almonds, sesame seeds, dried fruit, tofu, pulses, fortified breakfast cereals and soya milks.
Iron is required mainly for the production of haemoglobin in the blood and maintenance of the muscle protein myoglobin.. The body is very efficient in recycling iron as it renews blood cells but growing infants, children and women have enhanced needs for iron.
The maintenance of healthy iron levels is important on any diet, indeed iron intake of women in the general population is below the recommended level of 14.8 mg per day. Calcium, proteins,and phytates all affect the absorption of iron whereas vitamin C has a beneficial effect on iron absorption. Vegetarian sources of iron include pulses, tofu,sprouted beans and seeds, fortified breakfast cereals and bread, green leafy vegetables, nuts, dried fruit and molasses. (See iron factsheet)
Magnesium is required for strong bones and the production of enzymes involved in energy release. It is found widely in plant foods and magnesium deficiency is very rare. Occuring together naturally with phosphorus in chlorophyll - the green pigment in plants - magnesium is found green leafy vegetables, bread, cheese, peanuts, yeast extract and is abundant in a varied and balanced vegetarian diet.
Phosphorus is the second most common mineral in the body and, in the form of phosphates, has many functions including bone mineralisation and in conjunction with the B vitamins, the metabolism of fats, proteins and carbohydrates. Phosphorus is found in green leafy vegetables, bread, cheese, peanuts, yeast extract and is abundant in a varied and balanced vegetarian diet.
Potassium is present in fluids inside cells and its action is closely linked to that of sodium. Potassium is involved in heart function and along with calcium and magnesium has been found to have a beneficial effect on blood pressure. Potassium is widely found in plant foods, especially in wholegrain cereals, bananas, raisins, muesli, root vegetables and yeast extract.
Sodium is present in the fluid system outside cells and is important in blood composition along with chloride. They are both essential in small amounts for maintaining the body's water balance and in the nerve activity that controlls muscle contraction. It is the kidneys' role to keep sodium and chloride blood levels within a very narrow range and the kidneys of older adults and very young infants cannot tolerate high sodium intakes. Sodium chloride (salt) in the diet is the main source of both these substances. Processed food, crisps and shop-bought cakes and biscuits often contain high levels of hidden salt whereas a diet of predominantly wholegrains, vegetables, pulses, nuts, and fruit is naturally low in sodium and chloride. Yeast extract often recommended as part of vegetarian diets as a source of B vitamins and potassium should be consumed in a low-salt form to avoid an excessive sodium intake. Sodium (including salt) intake should be no higher than 6mg a day for adults. High sodium intake is linked to high blood presssure.
Sulphur plays a role in some enzyme systems. Most dietary sulphur is in the sulphur-containing amino acids methionine and cysteine in protein. There is no indication of sulphur deficiency except in association with protein deficiency.
Trace elements are minerals that are required by the body in much smaller quantities than the other major minerals. Trace elements though are essential to many functions in the body. Vegetarians and vegans should be especially aware of the need for iodine, selenium and zinc.
Copper is essential for red blood cell formation and many enzyme function and is found in wholegrain foods, potatoes, green vegetables, wheatgerm and nuts. Chromium is necessary for maintenance of blood glucose levels, good sources include wholegrain cereals, pulses, nuts and brewer's yeast. Cobalt can be ultilised by the body only as part of vitamin B12 , good sources include nuts, green leafy vegetables and and cereals. Fluoride helps form strong bones and teeth. The main dietary source is fluoridated water. In some areas of low natural fluoridation fluoride is added to the drinking water but fluoride is not available as a supplement. Iodine is essentail for the production of thyroid hormones which control body metabolism. Iodine levels in food are linked to levels in the soil or animal feed. Cereals are a key source of iodine and if dairy milk products are consumed then iodine levels will be satisfactory. Edible seaweeds such as Nori and Kombu eaten in moderate amounts are valuable sources of iodine especially for vegans with 0.5mg od iodine per day being the upper limit for iodine intake. Manganese is required for enzyme activity and also muscle function. Found in green vegetables, wholegrain cereals, nuts, spices Deficiency has never been observed. Molybdenum is essential part of some enzyme systems and is involved in DNA metabolism. It is found in higher concentrations in plants that grow above ground such as peas and leafy vegetables and particularly in oats. Selenium is involved in thyroid function, immunity and acts as an antioxidant. Selenium intake in the general population has fallen in the last twenty years. Sources in the vegetarian diet include: Brazil nuts, wheat bread, cereal products and eggs. Zinc plays a role in a wide range of enzyme systems and is essential for growth as it plays an essential role in the protein synthesis involved in bone development. Vegetarian diets tend to contain less zinc than meat-based diets and excessive phytic acid found in cereal foods tends to inhibit the absorption of zinc. Good sources of zinc include cheese, sourdough bread, pulses, green vegetables, sesame and pumpkin seeds.
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