Potassium

Of all the essential minerals potassium is probably the least understood by the general public. But it is absolutely essential for a number of reasons. It's needed to maintain the balance between acids and alkalis in all the body fluids and cells, a balance that is vital for survival and for which the difference between life and death is very small. Potassium also plays a key role in the transmission of nerve impulses throughout the body and in the prevention of calcium being lost in the urine. The other major function of this mineral is to promote muscle activity and prevent cramp, and it's in this area that most people will have heard about its importance.

Athletes have always been plagued by cramp and the fear of getting it at crucial moments and until quite recently the common perception was that cramp is caused by the amount of salt lost through sweating. This is the reason why so many athletes used to take salt tablets - and many still do - to prevent cramp, in the belief that this would make up for the sodium excreted with sweat. Even holidaymakers strolling on the sunny beach packed them in their holiday first aid kit in case they got cramp trying to get off the sunbed. Not only are salt tablets ineffective in the relief or prevention of cramp but they also increase the risk of high blood pressure, strokes and heart disease. Moreover, excessive salt intake causes oedema - swelling of the hands, feet and legs due to fluid retention.

You are now used to seeing tennis players munching on bananas in the middle of a match, footballers and all sorts of other professional athletes packing them in their sports kit. I take much of the credit for the switch from salt tablets to bananas as, back in the 1960s and 70s, I was heavily involved in tennis and treated many of the world's leading players. I advised them all to throw away the salt tablets and eat bananas, which supply easily digestible carbohydrates for energy and loads of potassium to prevent cramp and keep their muscles working.

Excessive consumption of sodium from salt in any form, taking water tablets (diuretics), cortisone medication and too much alcohol can all reduce your levels of potassium. All fruits and vegetables, along with instant coffee and red wine contain potassium. But boiling your vegetables halves the content as the mineral ends up in the cooking water, so make sure you use it in soups and gravies - our grannies used to drink the greens water and they weren't daft.

Blood loss, chronic diarrhoea or vomiting, diabetes, kidney disease or prolonged use of laxatives or diuretics can all cause potassium deficiency and this can be a particular worry in older people who tend to have lower intakes of most nutrients. A lack of potassium can cause muscle weakness, cramp, disorientation, mental confusion, depression and, if severe enough, heart attacks. Potassium supplements can help lower high blood pressure and reduce the risk of strokes, irregular heart rhythms and heart attacks. It's also effective in preventing kidney stones in people excreting too much calcium in their urine.

The average adult needs 3500 mg of potassium daily. Supplements of 2000-3000 mg per day are adequate for the majority of people.

BEST SOURCES

BANANAS
400 mg / 100 g
Percentage of daily requirement: 11% from average banana
Potassium score: 2/10

DRIED APRICOTS
As well as potassium, apricots provide huge amounts of betacarotene and fibre making them a nutritional superbooster
1880 mg / 100 g
Percentage of daily requirement: 43% from 10 apricots
Potassium score: 5/10

BAKED POTATO IN JACKET
An average baked potato also gives half your day's dose of vitamin C, lots of fat free energy and plenty of fibre
630 mg / 100 g
Percentage of daily requirement: 32% from average baked potato
Potassium score: 4/10

READY TO EAT PRUNES
760 mg / 100 g
Percentage of daily requirement: 41% from 10 prunes
Potassium score: 5/10

ALMONDS
780 mg / 100 g
Percentage of daily requirement: 22 % from a pack
Potassium score: 2/10

DRY ROASTED PEANUTS
730 mg / 100 g
Percentage of daily requirement: 21 % from a pack
Potassium score: 2/10

STIR FRY VEGETABLES
COURGETTE, CHINESE CABBAGE, LEEK, ONION, GARLIC AND SPINACH
490 mg / 100 g
Percentage of daily requirement: 28% from a 200g portion
Potassium score: 3/10

TOMATO PUREE
1150 mg / 100 g
Percentage of daily requirement: 13% from 2 tablespoons
Potassium score: 1.5/10

GRILLED CHICKEN BREAST
460 mg / 100 g
Percentage of daily requirement: 28% from average portion
Potassium score: 3/10