An alkaline diet can benefit health by limiting processed foods and promoting a higher intake of whole foods. However, it does not help fight disease by changing the body’s pH levels.
The alkaline diet is based on the idea that replacement acid-forming foods with alkali-forming foods can improve health.
Proponents of this diet even claim that it can assist in fighting serious diseases, such as cancer.
This article studies the science behind the alkaline diet.
What is the Alkaline Diet?
The alkaline diet—also known as the acid-alkaline diet or alkaline ash diet—suggests that consuming certain foods can alter the body’s pH.
Metabolism works like a chemical reaction that converts food into energy, leaving behind a residue of “ash” known as metabolic waste.
This waste can be acidic, neutral, or alkaline. Proponents of this diet argue that the ash’s acidity influences the body’s overall acidity.
Alkaline ash is believed to protect against disease, while acidic ash can increase vulnerability to it. By choosing more alkaline foods, a person can theoretically “alkalinise” the body and improve health.
What Do You Eat on an Alkaline Diet?
Dietary ingredients that produce acidic ash include proteins, phosphates, and sulfur; in contrast, alkaline ingredients include calcium, magnesium, and potassium.
Several food groups are classified as acidic, alkaline, or neutral:
- Acidic: Meat, poultry, fish, dairy products, eggs, grains, and alcohol.
- Neutral: Natural fats, milk, starches, and sugars.
- Alkaline: Fruits, nuts, legumes, and vegetables.
Regular pH levels in your body
pH is a quantity of how acidic or alkaline a substance is. The pH scale series from 0 to 14:
- Acidic: 0.0 – 6.9
- Neutral: 7.0
- Alkaline (or basic): 7.1 – 14.0
Many advocates of the alkaline diet suggest monitoring your urine pH to ensure it is alkaline (above 7) rather than acidic (below 7).
However, it is important to remember that pH varies greatly in different parts of the body. While some parts are acidic, others are alkaline; there is no single, fixed pH level throughout the body. Your stomach is full of hydrochloric acid, giving it a pH of around 1.5-2.0, which is highly acidic. This acidity is required to break down food.
On the other hand, human blood is always somewhat alkaline, with a pH of 7.35-7.45. When the blood pH drops outside this normal range, it can be fatal if left unprocessed.
Though this only occurs in certain pathological states, such as ketoacidosis produced by diabetes, starvation, or alcohol consumption.
Food affects the pH of your urine but not your blood
Your blood pH should remain within a healthy range, and your body has several effective mechanisms to regulate it.
Generally, foods do not cause significant changes in blood pH. However, diet can alter urine pH, though this effect tends to be somewhat variable.
Excretion of acids through urine is one of the primary mechanisms by which the body regulates blood pH.
For example, if you eat a large steak, your urine will become additional acidic as your body eliminates metabolic waste products.
Because of this, urine pH is an unreliable indicator of both overall body pH and overall health status. Additionally, it can be influenced by factors unrelated to diet.
Acid-forming foods and osteoporosis
Osteoporosis is a liberal bone disease characterised by decreased bone mineral content. This is particularly prevalent in postmenopausal women and can greatly increase the risk of fractures.
The alkaline diet theory holds that, to maintain a consistent blood pH, the body draws alkaline minerals from the bones to neutralise acids produced by acidic foods. This theory, known as the “acid-ash hypothesis” in the context of osteoporosis, suggests that acidic foods may lead to damage to bone mineral density.
However, this theory ignores the role of the kidneys and lungs. The blood can contain a variety of acids, which are classified as “metabolic” (fixed) or “respiratory” (volatile).
Fixed acids are excreted in the urine, while volatile acids are excreted through the lungs. An example of a volatile acid is carbonic acid, which is formed in the lungs as part of the respiratory process; This process increases the acidity of the blood. For their part, the kidneys reabsorb bicarbonate, which is derived from carbonic acid in the blood. This entire process acts as a buffering mechanism against changes in pH, ensuring it remains within the range essential for life.
Furthermore, the “acid-ash” theory ignores the role that collagen loss plays in the development of osteoporosis. Ironically, low levels of dietary orthosilicic acid and vitamin C are closely associated with collagen loss.
It is important to note that recent scientific evidence (from reliable sources) indicates no association between dietary acid intake and bone health. In fact, a diet rich in protein—even though it has the potential to acidify—may be associated with better bone health, as it promotes greater calcium retention and stimulates the activation of the hormone IGF-1.
Acidity and Cancer
Previously, comprehensive reviews of the relationship between dietary acidosis—or the increase in blood acidity caused by food intake—and cancer concluded that there was no direct link.
Newer research suggests that there may be a connection between dietary acidity and cancer.
However, these studies do not reflect actual blood acidity levels. It is also unclear whether dietary acid load specifically causes cancer. In fact, various experiments have successfully cultured cancer cells even in an alkaline environment.
And while tumours grow faster in acidic environments, they also create that acidity. It is not the acidic environment that makes the cancer cells; rather, the cancer cells create the acidic environment.
Ancestral diets and acidity
An examination of the acid-alkaline theory—from both evolutionary and scientific perspectives—reveals some discrepancies.
It is estimated that 87% of pre-agricultural humans consumed alkaline diets; this figure serves as the primary argument supporting the modern alkaline diet.
It is important to note that our ancestors lived in a range of climates and had access to diverse foods. In fact, acid-forming diets became more common as populations moved north of the equator, away from tropical regions.
Frequently Asked Questions
What are the 10 most alkaline foods?
The main categories of alkaline foods are vegetables, fruits, nuts, and legumes. Below are 10 examples:
- beets
- broccoli
- mushrooms
- peas
- tomatoes
- apples
- cherries
- pineapples
- almonds
- pumpkin seeds
What is the fastest way to alkalize the body?
There is no quick fix for making the body alkaline, nor is there conclusive evidence that doing so is necessary. The body’s pH levels are tightly controlled, and diet has little influence on blood pH; however, it may affect urine pH.
Conclusion
The alkaline diet is healthy because it emphasises whole, unprocessed foods. However, claims that this diet improves health by altering pH levels lack scientific support based on reliable studies.
A low-protein variant of this diet may be beneficial for individuals with chronic kidney disease, although there is no evidence that it affects pH levels.