The pH scale measures whether a substance is more acid or base (alkaline). Foods low in acid are considered alkaline, meaning they have an alkaline effect on the body and may counteract acids that are formed in the body, thus balancing the body's pH level.
The range for pH is from 0 to 14. A pH of 7 is considered to be neutral, neither acidic nor alkaline. Liquids that have a pH below 7 are acidic while those with a pH above 7 are considered to be alkaline.
The bodily fluids must remain between 7.35 and 7.45 on the pH scale for the body to function properly. If the fluids become too acidic, a condition called acidosis occurs. If the body becomes too alkaline, the condition is called alkalosis. Both conditions can be fatal.
The body does a good job at regulating its own pH levels. While acids are formed during metabolism, digestion, and the ingestion of acid-forming foods, there are mechanisms in place to buffer them and keep the body in balance. Eating alkaline-forming food prevents these buffers from overwork, but doesn't actually reduce the acidity in the body.
Vegetables, such as asparagus, lettuce, onion, cauliflower, peas, red cabbage and carrots are naturally low in acidity. Most leafy greens are low in acidity. The only fruits considered alkaline are lemons, limes, avocados, tomatoes, rhubarb and grapefruit. A few nuts, seeds and grains are low in acidity. They include almonds, pumpkin, sunflower, sesame, flax, buckwheat groats, spelt and lentils. Some of the oils considered to have an alkaline effect are flax, hemp, avocado, olive, evening primrose, borage and coconut oil.
Theories about "alkalining" or "alkalising" have circulated ever since Dr. William Hay introduced his book, A New Health Era, in 1933. He theorised that most diseases are caused by the body being too acidic and the need to eat more alkaline-forming foods.