The alkaline diet is also known as the acid-alkaline diet or alkaline ash diet.

Its premise is that your diet can alter the pH value — the measurement of acidity or alkalinity — of your body.

Your metabolism — the conversion of food into energy — is sometimes compared to fire. Both involve a chemical reaction that breaks down a solid mass.

However, the chemical reactions in your body happen in a slow and controlled manner.

When things burn, an ash residue is left behind. Similarly, the foods you eat leave an “ash” residue known as metabolic waste.

This metabolic waste can be alkaline, neutral, or acidic. Proponents of this diet claim that metabolic waste can directly affect your body’s acidity.

In other words, if you eat foods that leave acidic ash, it makes your blood more acidic. If you eat foods that leave alkaline ash, it makes your blood more alkaline.

According to the acid-ash hypothesis, acidic ash is thought to make you vulnerable to illness and disease, whereas alkaline ash is considered protective.

By choosing more alkaline foods, you should be able to “alkalize” your body and improve your health.

Food components that leave an acidic ash include protein, phosphate, and sulfur, while alkaline components include calcium, magnesium, and potassium (1Trusted Source, 2Trusted Source).

Certain food groups are considered acidic, alkaline, or neutral:

Acidic: meat, poultry, fish, dairy, eggs, grains, alcohol
Neutral: natural fats, starches, and sugars
Alkaline: fruits, nuts, legumes, and vegetables

Regular pH levels in your body
When discussing the alkaline diet, it’s important to understand pH.

Put simply, pH is a measurement of how acidic or alkaline something is.

The pH value ranges from 0–14:

Acidic: 0.0–6.9
Neutral: 7.0
Alkaline (or basic): 7.1–14.0
Many proponents of this diet suggest that people monitor the pH of their urine to ensure that it is alkaline (over 7) and not acidic (below 7).

However, it’s important to note that pH varies greatly within your body. While some parts are acidic, others are alkaline — there is no set level.

Your stomach is loaded with hydrochloric acid, giving it a pH of 2–3.5, which is highly acidic. This acidity is necessary to break down food.

On the other hand, human blood is always slightly alkaline, with a pH of 7.36–7.44 (3Trusted Source).

When your blood pH falls out of the normal range, it can be fatal if left untreated (4Trusted Source).

However, this only happens during certain disease states, such as ketoacidosis caused by diabetes, starvation, or alcohol intake