These diets attribute their health benefits mostly to the increase in nutrients, such as vitamins, minerals and fibre etc., which are needed for biochemical and metabolic processes. However, there is another major physiological effect of these foods that is often overlooked and not included in standard guidelines—the effect on acid-alkaline balance.
The importance of acid-alkaline balance
Every part of the body needs different levels of acidity and alkalinity for the function of important physiological roles. The balance between alkalinity and acidity and is often termed pH balance, as pH is the measure of hydrogen ions (pH = potential hydrogen), which are acidic. This scale is measured numerically in which the value 7.0 is neutral, below 7.0 is acidic, and above 7.0 is alkaline.
Controlling extracellular pH in the correct range is critical for metabolic homeostasis.2 For example, research shows that even small changes in the pH levels towards acidity can lead to increased bone breakdown and reduced bone rebuilding.3 These small changes in pH are termed chronic low-grade or latent acidosis and although it is not as severe as metabolic acidosis (where there is a considerable decrease in blood pH), latent acidosis is more common and can have severe and long-term detrimental effects on health.4,5
The effects of chronic low-grade acidosis
If acid production increases more than the body can excrete (primarily via the kidneys), even healthy people are affected by chronic-low grade acidosis.6 Also, simply ageing has an impact as the glomerular filtration rate of the kidneys decreases by 50% from ages 20 to 80 years. This limits the kidney’s ability to excrete the excess acid produced endogenously during metabolism and from a dietary acid load.7 Conversely, excess acid from the diet can damage the kidneys, even in children, again reducing acid excretion and increasing tissue acidosis.8,9
According to research, the overproduction and accumulation of metabolic acids, a high dietary acid load, and chronic tissue metabolic acidosis may contribute to the development of numerous health issues,2,10 including:
· pain and inflammation
· fatigue and exhaustion
· cognitive decline
· insulin resistance
· cardiovascular risk
· glutathione depletion
· poor detoxification
· kidney disease
· bone demineralisation
· muscle breakdown
· gastrointestinal dysfunction
· developmental issues in children5,9
Chronic low-grade acidosis is often described as diet-induced because a high dietary acid load is a major determinant in the body’s acid-base balance.11 Conversely, a diet rich in alkalising foods will balance the acid levels and support the body’s acid buffering systems.
Diet and acid-base balance
The original ‘healthy’ Palaeolithic diet was made up of 35% meat and 65% plant matter12; however, the western or ‘modern’ diet now focuses on high-fat, high sugar, red meat, and refined grains, with very little intake of fruit and vegetables. This dietary pattern is linked with serious health conditions but is also highly acidic.13
Although diets, like the Mediterranean diet, are healthy, they can often be difficult for many people to follow in a balanced way. Additionally, regardless of the promotion of these diets, global trends in children and adults show an alarming increase in unhealthy foods, an abundance of animal protein, and a severe lack of adequate fruit and vegetable intake.9,14
Fruit and vegetables contain high levels of alkalising minerals, such as magnesium, calcium, and potassium, as well as metabolisable anions, including citrate. These anions consume acidic hydrogen ions when they are metabolised and by doing so increase the alkalinity of the body. Citrate bound minerals are also highly effective at neutralising acidosis, as citrate is very alkalising and has high bioavailability. Additionally, plant matter (vegetables and fruits) contains high levels of glutamate, which also consumes acidic hydrogen to help bring the body to a neutral position.15
Animal proteins and cereal grains, on the other hand, contain sulphur containing amino acids, which when metabolised produce the highly acidic non-metabolisable anion, sulphate.
In the acid-base balance approach, balance is the key word, with a general recommendation of at least two thirds alkalising foods (mainly vegetables with some fruit) and not more than 1/3 acid forming foods (meats, grains and dairy) at each meal.
Research shows following a moderate protein diet with an increased intake in vegetables and fruit can correct metabolic acidosis and improve numerous health outcomes.
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