The alkaline diet—which is also known as the alkaline ash diet, alkaline acid diet, acid ash diet, acid alkaline diet, and even pH diet—is based on the premise that acidic blood causes all sorts of health problems that can be countered by eating more alkaline foods.
Proponents of the alkaline diet claim it can help with weight loss and chronic diseases like type 2 diabetes and heart disease and even cure conditions like arthritis and cancer.
But is the alkaline diet all it’s cracked up to be?
While the alkaline diet includes many healthy suggestions—such as fruits, vegetables, and water galore—and cautions against the consumption of admittedly unhealthy substances such as alcohol, sugar, and processed foods, nothing you eat is going to have a dramatic effect on the pH of your blood.
But if the alkaline diet is all about creating the optimal conditions for health through the consumption of alkaline foods, how can this be the case?
The reason is that our bodies have mechanisms in place that keep the blood pH tightly regulated.
What’s more, eating too many alkaline foods and too few acidic foods may actually lead to amino acid nutritional deficiencies. And this can have disastrous consequences for everything from bone health to muscle mass to blood pressure.
The pH Balance Diet: Weighing the Scales Between Acidic and Alkaline
The pH is a measurement of how acidic or alkaline something is and is based on a scale of 0 to 14, where 0 is considered extremely acidic, 7 neutral, and 14 extremely alkaline.
The body’s pH actually varies considerably from one area to another. For instance, the normal pH of the blood is around 7.4, but the pH of the stomach remains between 1.5 and 3.5 to maintain the acidic environment necessary to break down the foods we eat.
Based on the premise that maintaining a blood pH above 7.4 helps improve overall health, the alkaline diet involves avoiding foods that may act to lower blood pH levels by increasing dietary acid load.
Instead, proponents of the alkaline diet advocate creating an alkaline environment in the body by eating mainly non-acid-forming foods, and even bicarbonate (HCO3–), which is a base that can neutralize acidic blood.
However, a high-protein diet, with its increased acid load, actually results in very little change in blood chemistry and pH, though the same diet does have a profound effect on urinary chemistry and pH.
The reason for this is that the body maintains tight control over blood pH, but urinary pH has the ability to move from an acid to alkaline state to help the pH of the blood stay in balance.
The alkaline diet is thus built on the notion that alkaline foods increase the pH of urine, thereby making urine less acidic and, by extension, blood less acidic.
But there are two problems with basing a dietary theory on urinary pH. First, urinary pH does not necessarily reflect blood pH. Second, aside from its role in contributing to kidney stones and gout, clinical trials supporting the claim that acidic urine results in adverse health outcomes are lacking.
Amino Acids and Blood pH
Our bodies absorb all the essential amino acids—the amino acids that must be obtained through dietary sources—needed for survival from the proteins we eat. And as you might guess from the name, amino acids are indeed acidic. This is reflected by the drop in urinary pH that occurs after consuming protein-rich foods.
The sulfur-containing amino acids, such as methionine and cysteine, are considered particularly problematic by proponents of the alkaline diet, as increased sulfur intake can result in the formation of sulfuric acid and present a significant acid load to the body.
And, as animal proteins are a good source of sulfur-containing amino acids, advocates of the alkaline diet caution against the consumption of these proteins.
However, there’s an innate fallacy in the assumption that sulfur has a negative effect on health. This is because sulfur plays many important roles in the body, and a sulfur deficiency can have many adverse effects.
In addition, dietary amino acids, including sulfur-containing amino acids, have only a transient effect on blood pH. As we alluded to earlier, this is a result of the body’s highly effective system for regulating blood pH.
How the Body Regulates Blood pH
The kidneys play an important role in maintaining a constant pH in the blood. For example, when the blood becomes acidic after ingesting amino acids, the kidneys excrete ammonia in the urine, which works to balance the acidic load in the blood.
So, while urine becomes more acidic after eating amino acids, this acidity is not reflected in the blood. Rather, urine becomes acidic to help prevent the blood from becoming acidic and to keep blood pH constant.
This is, in fact, a natural function of the kidneys, and there’s no evidence that high protein or amino acid intake has any detrimental effect on kidney function.
But the excretion of ammonia in the urine plays only a minor part in keeping blood pH in the normal range. The major mechanism for maintaining the proper balance of blood pH is actually the carbon dioxide (CO2)–HCO3– system.
While the kidneys play a significant role in helping to maintain blood pH, it’s actually the lungs that play the predominant part in maintaining the pH balance of the blood.
You see, the lungs excrete protons derived from dietary metabolism in the breath as CO2. And CO2 is acidic, while HCO3–, as we’ve discovered, is basic, or alkaline.
To keep the levels of CO2 and HCO3– in balance, the lungs and kidneys work together so that as HCO3– neutralizes excess acid and is thus lost from the body, more CO2 is produced and excreted in the breath. And the HCO3– lost to acid neutralization is then regenerated in the kidneys.
As this process demonstrates, the human body has a very efficient procedure for keeping blood pH tightly regulated—even after the consumption of a large amount of protein and/or amino acids.
The Flaw in the Alkaline Diet
As we've seen, the alkaline diet doesn’t account for the efficient regulation of blood pH by both the CO2-HCO3– system and urinary excretion of ammonia. And following the recommendation of proponents of the alkaline diet to avoid all animal proteins and thus all sulfur-containing amino acids will result in an inadequate intake of essential amino acids.
However, essential amino acids perform a wide range of important metabolic functions and contribute to a multitude of health benefits, so they must be present in the diet in adequate amounts for optimal health to occur.