Alkaline diets are growing in popularity. Those who use them believe that the problem with the average Western diet is its acidity – having a pH lower than 7.0. They say a number of health problems are caused by this acidity and that it can even cause muscle loss. Is this true?
Here are the facts. Eating alkaline foods – foods with a pH greater than 7.0 – banishing acidic foods, and taking alkaline products won't do much to "restore the body's pH" and prevent these health conditions. These claims just aren't supported by science. Let's break it down.
Meat, dairy, and grains are generally acidic while foods such as fruits and vegetables are generally basic/alkaline.
Alkaline diets are high in fruit and vegetable consumption and limited in meat, dairy, and grains. Sugar is generally thought to be acidic and is restricted in alkaline diets, but sugar is actually neutral. Many individuals following alkaline diets consume lemon juice or apple cider vinegar because they are touted as basic, but these are also acidic. Vinegar is acetic acid and lemon juice contains citric acid.
Any slight variation of pH caused by dietary intake is rapidly regulated by the kidneys. Therefore, dietary acid intake cannot alter blood pH.
The kidneys play a key role in maintaining pH balance throughout the body. Normal physiological pH of blood is tightly controlled between 7.35 and 7.45. When blood becomes acidic, the kidney excretes H+ and produces bicarbonate ions which enter the blood and neutralize blood pH to keep it in this narrow range. As a result of the kidney's role in acid-base balance, urine pH can range from 4.5 to 8.2 and can be influenced by dietary intake. However, urinary pH is not a good measure of blood pH, which is maintained within a narrow range in individuals with normal kidney function.
Although blood pH is not altered by the diet in healthy individuals, advocates of the alkaline diet claim that humans evolved to eat low-acid diets. This is not true.
A recent study on the dietary patterns of pre-agricultural humans found that roughly half consumed an acidic diet. As a side note, I would also advise against making any dietary recommendations (for performance, health, or otherwise) off of the diets of pre-agricultural man, a population whose average life span was a fraction of ours today and who commonly died of starvation.
The acidic environment of the stomach and neutral-to-basic environment in the small intestine occur regardless of what food is consumed in the diet.
When food is swallowed, it enters the stomach where hydrochloric acid creates a pH range of 1.5 to 3.5. This acidic environment serves several purposes including: denaturing of proteins, activation of pepsin (an enzyme that breaks down protein), and protection from bacterial infection. Once food exits the stomach, it enters the small intestine where bicarbonate is released to neutralize the acidic pH. This allows enzymes in the small intestine to work at their optimal rate to digest proteins, carbohydrates, and lipids.
Due to the kidney's key role in regulation of blood pH, people with impaired kidney function are often susceptible to fluctuations in blood pH levels. Conditions such as diabetic ketoacidosis, alcohol toxicity, respiratory disorders such as emphysema, carbon monoxide poisoning, and others can alter blood pH. Remember, in healthy individuals blood pH is maintained between 7.35 and 7.45.
Consumption of large amounts of bicarbonate can alter stomach pH. However, this also results in GI symptoms/distress and may alter normal digestion of protein in the stomach since the low pH is an integral part of this process. Bicarbonate supplementation has been shown to increase blood pH by as much as 0.08 but this is a short-term increase that's quickly regulated.
Dietary acid may have a detrimental impact on oral health. Foods with pH less than 5.5 can damage tooth enamel. Therefore, excessive amounts of highly acidic foods or beverages (soda) should be avoided.
That aside, proponents of alkaline diets often cite a number of other health benefits including: better skin health, resistance to infection, and more energy. However, there's no scientific evidence to support any of these claims. As a whole, alkaline diets do not live up to the hype. Blood pH can't be altered through dietary acid intake in healthy individuals. As a result, health claims made by those who follow an alkaline diet are not supported by the scientific literature.
However, one thing we can take from the dietary practices of those who follow alkaline diets is a recommendation for a diet high in a variety of fruits in vegetables. These foods are beneficial for their nutrient content, not because they are alkaline foods. For individuals with normal kidney function, there's no need to worry about the pH of foods you're eating.
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