2012年9月14日 星期五

Potassium - Why You Need It in Your Diet and Which Foods Are Rich In It


Potassium is a major mineral, and one of the four electrolytes. It is chemically very similar to the electrolyte sodium, and like all the electrolytes it is present in a dissolved state in body fluids. 95% of it is stored in the fluid within the cells of the body, whereas sodium and chloride reside mainly in the fluid outside the cells.

In a typical 60kg (132lb) person, there is around 210g of potassium. It is the third most abundant mineral in your body (after calcium and phosphorous).

Functions

One of the chief roles is to regulate the function of muscles and nerves. Potassium is the principal positively charged ion inside cells. It works closely with sodium, in what is known as the 'sodium - potassium pump' whereby the electrical charge in cells is changed to activate your muscles to relax and contract. This process also activates nerve transmission throughout the body, a role shared by the other electrolytes, which by definition are strong conductors of electricity when dissolved in water.

A particularly important muscle that potassium helps regulate is the heart, particularly the heartbeat.

Potassium also works with sodium to ensure optimum fluid balance between the cells and the bloodstream. If cells become too full of fluid they would burst, and if the bloodstream is too full of fluid, high blood pressure results. It also helps reduce acidity in the body.

Your metabolism is aided by potassium, which assists in the storage of glucose in the form of glycogen in the liver and muscles. This is why athletes low in potassium are prone to fatigue more easily and perform less well; their glycogen stores are not as efficient.

Potassium also helps bone strength and density. High salt diets can leech calcium from your bones, and potassium helps to counteract this.

Food sources

The three foods richest in potassium are boiled spinach, chard, and crimini mushrooms. Bananas are a good source but contrary to popular belief, not the number one source. What bananas do have in their favour is that they are one of the most convenient potassium-rich foods to eat, and are particularly useful foods for the elderly and young children, being sweet and easy to chew and swallow.

Other good sources include Brussel sprouts, tomatoes, broccoli, yams, dried apricots, almonds, and avocados. Meat, fish and dairy contain some potassium, but not nearly as much as the top vegetable sources.

Deficiency and excess

Symptoms of deficiency include muscle cramps, fatigue, muscle weakness, poor reflexes, and high blood pressure. Many factors can cause deficiency. Diets high in processed and junk-food can lead to deficiency as the manufacturing process depletes potassium in foods. High salt in your diet can disturb the delicate balance between potassium and sodium in the body, which requires more potassium than sodium, the opposite of the ratios found in junk food.

Not only salt, but also caffeine, sucrose, smoking, and drug-taking all have the effect of reducing your body's ability to absorb potassium. And because the body doesn't readily conserve potassium, it's vital to consume potassium-rich foods every day. The daily recommended intake is 3,000 - 4,000mg, and people with poor diets consume less than half that amount.

Other causes of deficiency are excessive fluid loss (sweating, diarrhoea, vomiting, abuse of diuretic medicines and laxitives), fasting (which can lead to heart failure in extreme cases, due to potassium levels falling dangerously low), and malabsorbtion disorders such as Crohn's disease.

It is rare to suffer ill-effects from excessive intake of potassium, as the kidneys are efficient at flushing excess out in the urine. However, kidney patients and the elderly can suffer an excessive build-up of potassium in the blood (hyperkalemia) which can cause irregular heartbeat.

If you consume plenty of fresh vegetables, steer clear of junk food and processed foods, keep your salt intake low, and avoid smoking, you'll consume and absorb enough potassium for it to fully perform its vital roles in your body.




Dominic Londesborough is a top Personal Trainer in London





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