For optimum health, the body needs balanced quantities of acid and alkaline foods, and it functions at its best when its internal environment is slightly alkaline.

Almost all foods after being digested, absorbed, and metabolized in the body, release either an acid or an alkaline base into the bloodstream. The modern diet largely consists of foods like grains, fish, meat, poultry, cheese, and milk, which all produce acid. If the body is not balanced with the intake of alkaline foods (vegetables and fruits, primarily) it becomes prone to weak bones, joints and muscles, and more susceptible to disease in the long term. Therefore, for health and longevity, the body is reliant on the correct acid alkaline balance.

Metabolic acidosis occurs when the body has more acidity then alkalinity in it. Eating a diet of excessive meats, grains and breads, dairy products, sugar, overcooked, refined and processed foods and fast foods, can lead to an acidic pH balance. Other factors that can cause acidosis include exposure to pollutants, chemicals and stress.

It is not so much as any particular food, but rather the cumulative effect of a highly acidic diet over many decades that can cause problems for health. Alkaline bodies are also much more resistant to infection and cancer.

To rectify this problem, the key is to make the body's internal environment alkaline and to adopt a healthy lifestyle in general. Here are a few guidelines to achieve this:

• Increase the amounts of alkaline foods like fruit and vegetables, whilst decreasing the amount of acid-forming foods you eat. One way to do this is to eat a salad with every meal, or try to include alkaline foods with every meal. Drinking fresh juices is another way to increase your alkaline food intake. All vegetables in general, but particular green vegetables (salad greens, cabbage, broccoli, spinach, cucumber, courgette, etc) are the best sources of alkaline minerals.

• The method of cooking a food will also have either an acidic or alkaline reaction. For example, a potato that is baked or boiled in its jacket is alkaline food, whereas a fried potato is acid-forming. Slicing or shredding fruit makes it more alkaline, because the contact of the pulp with air allows some of its acid content to oxidize.

• Just because a fruit or vegetable may be acid, that doesn't mean it will be acid when it is digested. When foods are digested, they turn into "ash". This ash is what determines if a food is acid or alkaline. For example, fruits like berries and citrus fruit are known to contain acid, but when they are eaten, their acids are oxidized and they are metabolized and transformed into alkaline elements in the body.

• Drink plenty of water. Drinking lots of water is an effective was to deacidify the body, as water can neutralize many acids. Water generally has a neutral or slightly alkaline pH level of 7 and many bottled mineral waters have a pH over 7, making them more alkaline.

• stress contributes to the body's acid/alkaline balance - it increases its acidification through the physiological disturbances it creates. Therefore try to reduce your stress levels and find ways of relaxing.

• exercise will make the body more alkaline, but exercising excessively will cause it to become acid-forming. Moderate physical activity on a daily basis is most effective because it aids the oxidation and elimination of volatile acids as they are produced.