The alkaline diet is used by many with the belief that it will help treat or prevent cancer, heart disease, low energy, osteoporosis, or enhance your endurance and power, or recover from training quicker. But does an alkaline diet really do this?
The alkaline diet is also known as the alkaline ash, acid ash, or acid alkaline diet. This type of diet is consumed with the belief that eating foods with different pH (acidity) levels will affect the pH balance of the body. It is believed that many diseases can be controlled if we control our body’s pH through the foods we consume.
The body’s blood pH or acidity is maintained within a range of 7.35 to 7.45 (1), through the strict control of the kidneys and respiratory system (1, 2). If our blood pH level drops to less than 7.35, it is referred to as acidosis, and if it goes above 7.45, alkalosis. Both can be potentially very serious for the body and often fatal if not treated. Avoiding foods that are naturally more acidic such as meats, poultry, cheese and grains can affect the pH of the urine and make it slightly more alkaline, but this pH difference is not translated to the blood pH level. There is also no correlation between urinary pH and the acidity of the body (1, 2).
In some specialised parts of the body the environment for the cells is either acidic or alkaline depending on the functioning and mechanisms of the body’s cells. It is desirable to have an acidic environment for the stomach (to aid digestion), skin, urine and vagina, (to limit microbial overgrowth), whereas the gall bladder and pancreas are alkaline environments to neutralize stomach acid, and aid digestion (1).
Research initially focused on an acidic diet affecting or contributing to bone mineral loss and leading to increased risk of osteoporosis. There has been considerable change in the net acid load in the human diet over time (1). The most dramatic increase has been a decrease in potassium compared to sodium and an increase in chloride compared to bicarbonate from in the diet (3).
In a systematic review to evaluate causal relationships between dietary acid load and osteoporosis, researchers found no evidence to support an alkaline diet being protective for bone health (3 – 5). Conclusions from this review are that further research is needed to determine whether fruit and/or vegetables are protective of bone health, and what are the ideal protein intakes for bone health. There are many other confounding factors that relate to osteoporosis risk, such as age, genetics,activity, gender, changes in dietary intake over time, overall health status of an individual and medications (3).
There has been no evidence in any literature that supports the use of an alkaline diet to improve exercise performance for endurance, strength or recovery from exercise (6).
In summary, alkaline diets appear to have weak evidence to support their use, providing you have a well-functioning renal and respiratory system.