Macrominerals


These are the minerals that are found in larger amounts in the body and include; calcium, phosphorus, magnesium, potassium, chloride and iron.

Calcium

The amount of calcium which adults are advised to take every day is at least 700mg, though in certain circumstances (e.g. adolescence, pregnancy, and osteoporosis) the level should be at least 1,000mg.

The following foods are valuable sources of calcium in our diets:

  • Glass of whole milk (190ml) - 226mg
  • Glass of semi- skimmed milk (190ml) - 232mg
  • Glass of skimmed milk (190ml) - 236mg
  • Pot of yoghurt (150g) - 225mg
  • Small pot of fromage frais (100g) - 86mg
  • 1oz (28g) cheddar type cheese - 210mg
  • 2tbsp (20g) grated hard cheese - 148mg
  • Cheese spread triangle (25g) - 150mg
  • Small pot cottage cheese (115g) - 90mg
  • Cream cheese (in sandwich – 30g) - 29mg
  • Scoop ice cream (60g) - 66mg
  • Thick slice white bread - 37mg
  • Thick slice wholemeal bread - 20mg
  • Crumpet (40g) - 60mg
  • Scone (48g) - 90mg
  • Bowl muesli (50g) - 55mg
  • Kellogg's Nutri-Grain bars (37g) - 200mg
  • 2oz (57g) drained sardines - 310mg
  • Shelled prawns (60g) - 90mg
  • 1 egg - 32mg
  • 4oz (110g) green vegetables - 35mg
  • Small can baked beans (150g) - 80mg
  • 2 tbsp red kidney beans (70g) - 50mg
  • Large orange (210g) - 70mg
  • 7 dried apricots (56g) - 52mg
  • 1 tbsp sesame / sunflower seeds (12g) - 80mg

Although dairy products may contain higher amounts of calcium, beans and seeds may have amounts which are more bioavailable, i.e. we absorb a higher percentage of the calcium from these foods.


Iron

Foods rich in iron fall into two main groups:

  • Animal sources - haem iron
  • Plant sources - non-haem iron

Animal sources tend to be better absorbed than plant sources, but try to consume a variety of foods from both sources

Animal sources

  • All red meat, game, liver, kidney, sausages, beef burgers
  • Egg yolk
  • Fish (not as high as red meat), but reasonable sources are pilchards and sardines, especially those canned in tomato sauce
  • Poultry (not as high as red meat)

Plant sources

  • Pulses – butter beans, broad beans, haricot (baked) beans, lentils, red kidney beans, chick peas
  • Green leafy vegetables e.g. brussel sprouts, spinach, cabbage, lettuce, etc – but a large portion needs to be eaten for a good iron intake
  • Flour products – bread, pasta, biscuits, cakes – wholemeal varieties are higher in iron
  • Breakfast cereals – many are fortified with iron, check the packet. Especially good are Branflakes, Weetabix, All-bran, Shredded wheat

Miscellaneous
The following contain some iron but in smaller amounts:

  • Dried fruits - apricots, figs, prunes
  • Dark chocolate, cocoa, liquorice, black treacle, gingerbread

Vitamin C and Iron
Vitamin C can help iron be more easily absorbed by the body, by changing it into a form more easily used. Therefore eat foods rich in vitamin C with foods rich in iron:

  • Fresh fruit - especially citrus fruit, strawberries, blackcurrants; including fruit juice and tinned fruit
  • Fruit squashes - vitamin C enriched cordials including orange squash, blackcurrant
  • Vegetables - especially tomatoes, green leafy vegetables and potatoes. Most vitamin C is found just under the skin so is lost in peeling. Some is also lost in cooking and letting food stand for a long while. To minimise losses avoid peeling where possible, prepare foods just before meal times and cook in minimal water with the lid on

Calcium and Iron
Calcium can inhibit iron absorption. It is recommended to consume calcium-rich foods, especially dairy products, away from iron rich foods. But, do not omit calcium-rich foods from your diet, as they are needed for healthy bones and teeth.

Bran and Iron
The use of raw bran is not recommended, as it contains phytate which 'binds' dietary iron, making it unavailable for absorption. You still need to have a good fibre intake, so continue to consume wholemeal products, fruit and green vegetables, which are high in iron.


Magnesium

Magnesium is the fourth most abundant mineral in the body. Most is found in bone, but there are also high amount in cells of tissues and organs. Magnesium is involved in a huge amount of biochemical reactions in the body, including helping to maintain normal muscle and nerve function, keeping heart rhythm steady, supporting a healthy immune system and keeping bones strong. Magnesium also helps to regulate blood sugar levels, promotes normal blood pressure, and is known to be involved in energy metabolism and protein synthesis.

Dietary magnesium is absorbed in the small intestines and its metabolism is closely linked to calcium. Magnesium is excreted through the kidneys.

Magnesium deficiency is characterised by progressive muscle weakness, neuromuscular problems, heart problems and eventual death. Adult males should aim for 300mg per day, females 270mg per day.

Green vegetables contribute a good proportion to magnesium intake because the chlorophyll, which gives greens their green colour, contains magnesium. Wholegrain cereals are also great sources, but refined grains are low in magnesium as refining removed the magnesium rich germ and bran, so some cereal products are fortified with magnesium. Tap water can also be a source of magnesium but the amount varied according to supply; 'hard' water contains more magnesium than 'soft' water.

  • Spinach (130g) – 45mg
  • Muesli (95g) – 95mg
  • All-bran (45g) – 95mg
  • Bran Flakes (45g) – 60mg
  • Shredded Wheat (2 biscuits) – 55mg
  • Weetabix (2 biscuits) – 48mg
  • Special K (35g) – 19mg
  • Porridge oats (100g) – 18mg
  • Wheatgerm (2 tbsp) – 35mg
  • Wheat bran (2 tbsp) – 45mg
  • Wholemeal bread (1 slice) – 55mg
  • Granary bread (1 slice) – 40mg
  • Brown rice (50g) – 55mg
  • Almonds (25g) – 80mg
  • Cashew nuts (25g) – 75mg
  • Peanuts (25g) – 50mg
  • Peanut butter (25g) – 50mg
  • Mixed nuts (25g) – 65mg
  • Soya beans, cooked (100g) – 63mg
  • Kidney beans (50g) – 75mg
  • Chick peas (50g) – 65mg
  • Baked beans (200g) – 62mg
  • Potatoes, baked with skin (150g) – 48mg
  • Banana – 45mg
  • Avocado – 25mg
  • Halibut (85g) – 90mg
  • Natural yoghurt, low fat (150g) – 45mg
  • Plain dark chocolate (100g) – 100mg
  • Milk chocolate (100g) – 100mg

Phosphorous

Most phosphorous in the body is present in the bones helping provide rigidity to the skeleton. It is also present in soft tissues as inorganic phosphate. It is involved in metabolism in high energy phosphate compounds, eg as adenosine triphosphate (ATP).

Around 80% of dietary phosphorous is absorbed. Requirements are set equal to dietary calcium, and adults should aim for 800mg per day. Symptoms of phosphorous deficiency include progressive muscle weakness, fatigue, arthritis, tooth decay, fragile bones and stunted growth.

Phosphorous is a major constituent of plant and animal cells, therefore is abundant in the diet and present in all natural foods. It is also present in many food additives. Especially good sources include:

  • Tuna
  • Mackerel
  • Salmon
  • Sardines
  • White fish eg cod, plaice
  • Liver
  • Kidney
  • Chicken
  • Turkey
  • Eggs
  • Pine nuts
  • Pistachios
  • Pumpkin seeds
  • Sesame seeds
  • Sunflower seeds
  • Walnuts
  • Almonds
  • Brazil nuts
  • Cashews
  • Peanuts
  • Pecan nuts
  • Chickpeas
  • Lentils
  • Soya beans
  • Garlic
  • Popcorn
  • Cheese
  • Wheat bran
  • Wheatgerm
  • Brown rice
  • Buckwheat
  • Oats
  • Rye
  • Wheat
  • Chocolate
  • Kelp
  • Yeast

Zinc

Zinc is an essential mineral present in small amounts in all tissues. Bones and teeth contain more, as does the pancreas and there is around 0.7mg/100ml blood. It is however, only needed in small amounts from the diet. Even though we only need small amounts, some people do not have high zinc levels because only 20-30% of the zinc we consume is actually absorbed in the intestine. Absorption is decreased by dietary fibre, calcium, copper, phytate (from raw unprocessed bran), and phosphate. The presence of amino acids and peptides in the gut increase zinc absorption. Adult males require 9.5mg of dietary zinc per day, females 7mg per day.

The following foods are significant sources of zinc:

  • Fortified breakfast cereals
  • Brazil nuts
  • Pumpkin seeds
  • Almonds
  • Other nuts and seeds
  • Red meat
  • Poultry
  • Pork
  • Dairy products (especially yoghurt and hard cheese)
  • Beans
  • Lentils
  • Chickpeas
  • Peas
  • Wholegrain foods
  • Wholewheat flour
  • Rye, rye flour and rye bread
  • Oats and oat flour
  • Free range eggs
  • Wheatgerm