The Complete Book of Men's Health - Part 3: Nutrition and Lifestyle

• No RDAs, but these intakes are deemed both safe and adequate.

Source: The Dietary and Nutritional Survey of British Adults (OPCS) HMSO Publication SS1241.

CALCIUM

Calcium is needed for the growth and development of strong, healthy bones and teeth. Ninety-nine per cent of the body's stores are in the bones, with the other 1 per cent playing a crucial role in blood clotting, muscle contraction, nerve conduction, the production of energy, and immunity.

A dietary deficiency at any stage in life results in raids being made on bone stores which significantly increases the risk of developing osteoporosis (brittle bones) in later life.

In general, exercise strengthens bones, and due to increased mineralization the calcium needs of athletes increase. If the diet is relatively poor in calcium, sports training may result in inadequately mineralized bones, weakened bones and stress fractures.

• EC/UK RDA: 800 mg/day.

• US RDA: 1,200 mg/day.

The National Osteoporosis Society is lobbying for these recommendations to be raised to at least 1000 mg per day for adult men.

• UK average dietary intake: 400­1,600 mg/day.

• Some sports nutritionists suggest that athletes need supplements of 400­1,600 mg/day. Intakes of up to 2,500 mg/day seem safe, although higher intakes may result in kidney stones.

• Foods rich in calcium include:

milk

yoghurt

cheese

green vegetables

oranges

bread.

Vitamin D is needed for absorption of calcium from the digestive tract. Usually only a small fraction of dietary calcium is taken up (typically less than 40 per cent); the remainder is lost in bowel motions.

It is relatively easy to increase calcium intake. Drinking an extra pint of skimmed or semi-skimmed milk per day provides as much calcium as whole milk (700 mg) but without the additional saturated fat.

By law in the UK, white and brown flour must be fortified with calcium ­ but this does not apply to wholemeal flour.

Men with a tendency to kidney stones should avoid calcium supplements unless medically supervised.

CHLORIDE

Chloride is a negatively charged electrolyte that, together with sodium (outside the cells) and potassium (inside the cells), controls our fluid and electrolyte balance.

Most adults in the Western World obtain too much salt (sodium chloride). This is a mineral on which you need to cut down, rather than worry about deficiency.

Don't add table salt to food, avoid salted snacks and try not to add salt during cooking either.

MAGNESIUM

Magnesium is the third commonest mineral inside body cells after potassium and phosphorus. It is an integral part of over 300 enzymes and is needed for every major biological process, from the synthesis of protein and nucleic acids to glucose metabolism, muscle contraction and energy production. It is essential for burning carbohydrate as a fuel.

• EC/UK RDA: 300 mg/day.

• US National Research Council recommendation: 350 mg/day.

• UK average daily intake: 323 mg/day. Intakes range from 150­550 mg.

• Active sportspeople need more magnesium than sedentary men to assist muscle contraction and to replace magnesium lost in sweat. Deficiency can cause poor appetite, tiredness, muscle cramps, tics, twitching and weakness.

• Some sports nutritionists prescribe magnesium supplements of 400­1,000 mg per day for athletes in full training. There is no evidence of toxicity at doses of up to 6,000 mg per day, so long as kidneys and heart are functioning normally.

• Foods rich in magnesium include:

dark green, leafy vegetables

nuts

seafood

seaweed

soya beans

meat

eggs

dairy products

wholegrains.

• Drinking water from hard-water areas is another important source.

A diet high in refined and processed foods will be deficient in magnesium as well as other important minerals, vitamins and fibre.

PHOSPHORUS

Ninety per cent of body phosphorus is associated with calcium in the bones. The remainder forms essential, energy-rich molecules (e.g. ATP, ADP) that are instrumental in controlling metabolic reactions concerned with burning fuel.

• EC/UK RDA: 800 mg/day.

• Most adult men obtain more than this. The only men who may develop deficiency are those using antacids containing aluminium hydroxide. This impairs absorption of phosphates from the digestive tract.

Sodium phosphate supplements do seem to improve athletic performance. Tests with endurance athletes (e.g. cyclists) showed that megadose supplements of sodium phosphate (4 g per day) for three days prior to an event decreased lactic acid accumulation, increased oxygen consumption by 11 per cent and lengthened by 20 per cent the amount of time before they felt exhausted. Other studies suggest that sodium phosphate supplements can increase maximal power output by up to 17 per cent.

Potassium phosphate is currently being researched to see if it has the same effect. Calcium phosphate has no beneficial ergogenic effect at all. Phosphate fuel products which boost athletes' intake are now available.

POTASSIUM

Potassium is the main positively charged electrolyte found inside cells. It balances the sodium ions found in the extra-cellular fluid and is essential for muscle contraction, nerve conduction and for the production of nucleic acids, proteins and energy. Deficiency causes fatigue, weakness and muscle pains, although this usually only occurs when taking non-potassium-sparing diuretic drugs. Potassium chloride is considered a healthier alternative to sodium chloride. Diets high in potassium and low in sodium are linked with a lower risk of high blood pressure and stroke.

• EC/UK RDA: 3,500 mg/day.

• UK average dietary intake: 3,187 mg/day. Observed intakes range from 1,700­4,800 mg.

Athletes need more potassium than sedentary men. They can lose up to 800 mg potassium in sweat per day, and studies show that many athletes are potassium deficient.

Intakes are easily maintained by eating seafood and plenty of fresh fruit and vegetables. Avoid processed, canned or any prepacked foods as these usually have a reversed sodium: potassium ratio. Stick to fresh wholefoods instead.

Sports nutritionists prescribe potassium supplements of 100­500 mg per day for some athletes ­ although a medium-sized banana would provide the same amount.

SODIUM

Sodium is the main positively charged electrolyte outside of cells. A pump in the cell membrane maintains high potassium levels inside cells to offset the sodium in the extracellular fluid.

• EC/UK RDA: 1,600 mg/day.

• UK average intake: 3,380 mg/day. Intakes range from 1,550­5,600 mg.

Some Western men eat as much as 12 g salt (sodium chloride) per day, which is putting health at risk through rising blood pressure and increased chance of a stroke (see Chapter 12).

Most athletes do not need sodium supplements, even in the form of electrolyte drinks. Sweating makes you lose more water than sodium, and after a good work out you will have a higher relative proportion of sodium to water than before you started. You need water first (see fluid intake after the event) and then carbohydrates (see carbohydrates after exercise) but not salt.

Athletes should never take salt tablets ­ just the reverse. Don't add salt to food during the cooking or at the table. This will knock around 3 g off your daily salt intake. Concentrate on potassium instead. Apart from anything else, your lifetime's exposure to salt is linked with your risk of developing high blood pressure.

CHROMIUM

Chromium is essential for the normal metabolism of glucose, insulin and fatty acids, and for muscle growth. Adequate intakes are therefore vital for athletes.

Chromium is needed in trace amounts to form an organic complex called Glucose Tolerance Factor (GTF). This contains vitamin B₃ (niacin) and three amino acids as well as chromium. It is essential for the interaction between the hormone insulin and its cell wall receptors.

• US National Research Council suggested intake: 50­200 mcg/day.

• The optimum chromium intake is unknown.

• The average intake is below 50 mcg and it is thought that only 2 per cent is in an absorbable form. Deficiency is therefore common and seems to be associated with poor glucose tolerance, as is seen in diabetes.

Body stores of chromium are rapidly depleted by following a high carbohydrate/sugar diet and through exercise. Running significantly increases the urinary loss of chromium. Athletes therefore need more than sedentary men.

Chromium in the form of picolinate has been shown to help muscle cells take up more amino acids than any other form of chromium supplement.

Some interesting studies done in the UK have shown the benefit of chromium picolinate to soccer players undergoing weight training.

Those given 200 mcg chromium per day for six weeks gained an average of 1.7 lb more lean muscle weight than did controls, and lost 2.6 per cent more body fat. Larger men weighing over 75 kg (165 lb) did not benefit ­ possibly because they needed higher doses. Some sports nutritionists prescribe chromium picolinate supplements of between 200 and 800 mcg per day for athletes in training.

There is no evidence that trivalent chromium, the form found in food, is toxic. Hexavalent chromium or chromate (the type found on car bumpers) is highly toxic, however.

The richest known source of natural GTF is brewer's yeast, whose GTF is 10 times more active than that from any other food. Chromium-enriched yeast, with an even higher content of GTF, has now been developed.

• Dietary sources of chromium include:

brewer's yeast

black pepper

thyme

wheatgerm

wholewheat bread

meats

cheese.

NB Most refined carbohydrates have had their chromium content removed.

COPPER

Copper is essential in very small amounts for healthy functioning of many enzymes in the liver, brain and muscles. It is involved in the utilization of oxygen and in the production of adrenaline-like hormones.

Copper is also essential for the production of melanin pigment and for collagen synthesis, maintaining healthy bones, cartilage, hair and skin. Copper-containing enzymes are important antioxidants which either inhibit the production of free radicals or mop them up once they are formed.

• Desirable copper intakes are not yet agreed. Safe intakes for optimum health in men are thought to be 1.5­3 mg/day.

• UK average intake: 1.6 mg/day. Intakes range from 0.7­3.4 mg.

• Active athletes should aim for an intake of 2­3 mg per day.

Only 30 per cent of dietary copper is absorbed, as the presence of raw meat, excessive vitamin C, zinc and calcium in the intestines impairs bioavailability. The ideal ratio of dietary copper to zinc is 1:10.

• Foods rich in copper include:

crustaceans

shellfish

nuts

dried stone fruits

dried peas or beans

green vegetables.

• Plant copper levels vary depending on the copper content of the soil in which they were grown.