The alkaline diet, also known as the acid-alkaline or alkaline ash diet, is based on the idea that replacing acid-forming foods with alkaline-forming foods can improve your health. Proponents of this diet even claim that it can help fight serious diseases like cancer. But what does the science actually say? This article examines the science behind the alkaline diet.
What is the Alkaline Diet?
The alkaline diet claims to improve your health by balancing your pH through diet. Under the premise of the alkaline diet, working toward a healthy, balanced pH involves making smarter eating choices to emphasize consuming alkaline-forming foods, which are plant-based foods.
The pH Scale
pH is a measure of acids and alkalis in a substance on a zero to 14 scale, with seven being neutral.
- Acidic: 0.0-6.9
- Neutral: 7.0
- Alkaline (or basic): 7.1-14.0
The Core Principle: Metabolic Waste and Ash
Metabolism is like a chemical reaction converting food into energy and leaving behind an “ash” residue known as metabolic waste. This waste consists of acidic, neutral, or alkaline ash. Proponents of this diet argue that the acidity of the ash affects your body’s acidity. Alkaline ash is thought to protect you from illness, while acidic ash can make you vulnerable. By choosing more alkaline foods, you may be able to “alkalize” your body and improve your health.
Food components that leave acidic ash include protein, phosphate, and sulfur, while alkaline components include calcium, magnesium, and potassium.
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Food Categorization
Certain food groups are considered acidic, alkaline, or neutral:
- Acidic: meat, poultry, fish, dairy, eggs, grains, alcohol
- Neutral: natural fats, milk, starches, sugars
- Alkaline: fruits, nuts, legumes, vegetables
Monitoring pH Levels
Many proponents of the alkaline diet suggest that people monitor the pH of their urine to ensure that it’s 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’s no set level.
The Reality of pH in the Human Body
The pH value measures a substance’s acidity or alkalinity. For example, stomach acid is highly acidic, while blood is slightly alkaline.
Your stomach is loaded with hydrochloric acid, giving it a pH of about 1.5-2.0, 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 7.35-7.45. When your blood pH falls out of the normal range, it can be fatal if left untreated.
The pH of your blood needs to remain constant for you to stay healthy, and your body has several effective ways to regulate it. Food won’t usually cause a major change in the pH of your blood. However, food can change the pH value of your urine - though the effect is somewhat variable. Excreting acids in your urine is one of the main ways your body regulates its blood pH. For example, if you eat a large steak, your urine will become more acidic afterward as your body gets rid of the metabolic waste. Therefore, urine pH is a poor indicator of overall body pH and general health. It can also be influenced by factors other than your diet.
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In healthy people, diet doesn’t significantly affect blood pH, but it can change urine pH.
Health Claims vs. Scientific Evidence
The alkaline diet may support health by limiting processed foods and promoting more whole foods. However, it doesn’t help fight disease by affecting your body’s pH levels.
Osteoporosis and Bone Health
The alkaline diet theory claims that to maintain a constant blood pH, your body takes alkaline minerals from bones to buffer acids from acid-forming foods. This is called the “acid-ash hypothesis of osteoporosis,” and implies that acid-forming foods can cause bone mineral density loss. However, this theory ignores the function of your kidneys and your lungs.
The blood can contain different acids, which are either “metabolic” (fixed) or “respiratory” (volatile). Fixed acids are excreted in the urine, whereas volatile acids are excreted by the lungs. One volatile acid is carbonic acid, which is formed by the lungs as part of your breathing process. This increases the acidity of your blood. The kidneys, meanwhile, are reabsorbing bicarbonate, which comes from the carbonic acid in the blood. This entire process resists change to the pH to allow you to stay in the necessary pH range for life.
The acid-ash hypothesis also overlooks the role of collagen loss in osteoporosis. Ironically, low levels of orthosilicic acid and vitamin C in your diet are strongly linked to such collagen loss.
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Keep in mind that recent scientific evidence suggests no link between dietary acid and bone health. In fact, a high protein, acid-forming diet may be linked to better bone health due to increased calcium retention and activation of IGF-1 hormone.
Research does not support the theory that acid-forming diets harm your bones. Protein, an acidic nutrient, even seems to be beneficial.
Cancer
In the past, comprehensive reviews on the relationship between diet-induced acidosis - or increased blood acidity caused by diet - and cancer concluded that there is no direct link. Newer research suggests that there might be a link between the acid in food and cancer. However, this research does not reflect blood acidity. It is also unclear if dietary acid load definitively causes cancer. In fact, experiments have also successfully grown cancer cells in an alkaline environment. And while tumors grow faster in acidic environments, the tumors create this acidity themselves. It’s not the acidic environment that creates cancer cells, but cancer cells that create the acidic environment.
There’s no link between an acid-forming diet and cancer. Cancer cells also grow in alkaline environments.
Evolutionary Perspective
Examining the acid-alkaline theory from both an evolutionary and scientific perspective reveals discrepancies. One study estimated that 87% of pre-agricultural humans ate alkaline diets which formed the central argument behind the modern alkaline diet.
Keep in mind that our remote ancestors lived in vastly different climates with access to diverse foods. In fact, acid-forming diets were more common as people moved further north of the equator, away from the tropics. Current studies suggest that about half of ancestral diets were acid-forming, especially among people who lived far from the equator.
Practical Considerations
Is It Easy to Follow?
Overall, the diet’s general guidelines are simple to follow, but it may not be difficult to follow for a long period of time. Adhering to the alkaline diet takes work. Proponents of the alkaline diet claim the human body can “acidify” with too many acidic foods. Keep in mind that as a general rule of thumb, if you want to stick to the alkaline diet, 80% of what you eat (by volume) should be alkalizing foods, with 20% acid-forming.
Cutting out so many foods is not sustainable in the long term.
Weight Loss Potential
You may lose weight on the alkaline diet in the short term, but this is likely due to increasing your intake of fruits and vegetables and eliminating processed, sugary and high-fat foods. This is likely because you are consuming more fruits and vegetables and cutting out many food groups.
Potential Health Benefits
Considering the alkaline diet emphasizes eating a plant-rich diet, this approach could be effective in fighting inflammation. That’s because fruits and vegetables are high in flavonoids, compounds that naturally occur in plants and contain anti-inflammatory properties.
Potential Health Risks
Even if the science behind the alkaline diet isn’t quite sound, the diet’s emphasis on fresh fruits and vegetables should keep you covered in terms of meeting your nutritional needs.
- Calcium: Because the alkaline diet calls for no dairy, which is a rich source of calcium, getting adequate amounts of calcium on this diet may be a challenge. There are some dairy-free sources of calcium that may be appropriate.
- Vitamin D: Depending on your individual vitamin D needs, it may be difficult to get all the vitamin D you need from food alone on the alkaline regimen.
Top Alkaline-Forming Foods
The primary alkaline-forming foods food categories are vegetables, fruit, nuts, and legumes. 10 examples include:
- beets
- broccoli
- mushrooms
- peas
- tomato
- apple
- cherries
- pineapple
- almonds
- pumpkin seeds