The alkaline diet, sometimes known as the “acid, alkaline diet”, is based on the principle that certain foods either acidify or alkalise the body. The reason that this is considered important is that an acidic body can lead to ill-health – particularly cancer. But is it true?
Principles of the Alkaline Diet
According to the Acid Alkaline Association foods are classified as either acid-forming or alkalising, depending upon the effect they have on the body and not their own pH scale (how acid or alkaline that particular food item is).
Proponents suggest that acid-forming diets lead to acid indigestion that then creates a condition known as chronic acidosis, which causes the body tissues to become acidic. This then prevents optimal oxygen exchange in the cells, which then causes the immune system to malfunction leading to diseases such as cancer among others.
Chronic acidosis is a situation where the pH of the blood falls, causing severe damage to body tissues which ultimately leads to kidney failure and coma.
It is therefore a very serious condition that requires immediate medical attention.
There are two main types:
- Respiratory acidosis: your lungs’ function is to bring in oxygen from outside the body and expel carbon dioxide, but sometimes the body is unable to remove as much carbon dioxide as it needs to. Usually because of an existing medical condition such as a respiratory disease, or disease causing difficulties with breathing.
- Metabolic acidosis: the most common form of metabolic acidosis is one that can happen in people with diabetes, called ketoacidosis. This happens when there is a build up of ketones in the blood causing the blood to acidify. The main reason for metabolic acidosis is an issue with the kidneys not being able to clear acids from the blood sufficiently, or they clear too much alkaline compounds that stabilise the body’s pH.
In essence, acidosis is caused either by the lungs or the kidneys not doing their job effectively due to injury or disease (1).
Can foods cause acidosis?
According to the Acid Alkaline Association, yes. They suggest that the combination of a modern, stressful lifestyle combined with a typical western diet acidifies the body.
But are they right?
Your kidneys are excellent at maintaining an acid/alkaline balance which protects the body from acidosis, but emerging studies are suggesting that the modern diet that is heavily dependent on meat, cereal grains, eggs and dairy haven’t given the kidneys time to adapt (2).
Unfortunately, the science supporting this theory is very sparse. Some population studies are warning us that high acid-load diets can be damaging to the kidneys (3).
The main sources of acidifying foods include: meat, fish, dairy foods, and grains (especially rice).
Alkalising foods include fruit and vegetables, but also coco cola, alcohol, white sugar and margarine.
These are all based on what is called their PRAL (Potential Renal Acid Load) score (4), which influence the pH of the urine.
So what does the science say?
According to some studies, foods can affect the body’s acid/alkali balance but that may not have an affect on any disease studied such as hypertension (5,6), which is otherwise known as high blood pressure.
This is by no means conclusive as one study did show an association (7).
A recent study also suggested that there might be a weak association between acid diets and cardiovascular disease and deaths from all causes (8) but this was strongly criticised by some in the science community as being poor science (9).
Another population-based study found an independent association between an acidic diet and cardiovascular disease in Korean people (10).
However, there is no strong evidence to support the theory that a dietary acid load has any link with cancer (13), which is what the Acid Alkaline Association purport.
The problem with many of these studies is that they are not randomised controlled trials (considered the gold standard for finding true links), but population studies (known as epidemiology studies).
This can show an association but not a cause and effect. Therefore, you can conclude that there is a possible link, but not state for sure that it is actually due to the acidifying nature of the food.
Population studies on diet are racked with problems because it’s extremely difficult to control what people are eating and whether they are reporting it correctly.
Furthermore, diet is so complex that it would be difficult to state whether any one type of food has an affect unless you compare it with others.
As a very basic example, ten of us might eat an apple a day and ten of us might eat a pear. If five of the pear eaters had a heart attack and none of the apple eaters did, does this mean that apples are protective against heart disease? Or is there something else? So you need to control the diet to identify that nothing else is interfering with the results.
I think the alkaline diet is actually totally harmless. Maybe there is something in it, maybe there isn’t. But the fact that it encourages more fruit, more vegetables, and less meat and heavily processed food cannot be a bad thing.
I am not going to stand up and say that the alkaline diet is based on bad science like some might, but I will say that the science to back it up is not particularly robust as yet (that doesn’t mean it won’t be in the future).
If you are following this diet, then I wouldn’t encourage you to stop. If you have kidney disease and/or diabetes, then this diet would probably benefit you a great deal, but you should always follow the advice from a dietitian, particularly one that is specialised in the field of diabetes or kidney disease.
As for cancer, I agree that a diet high in fruit and vegetables might be protective – but not because it is less acidifying. Fruit and vegetables contain a wide range of plant compounds (called phytochemicals) that have strong antioxidant properties, and it is these that are more likely to protect you from cancer.
But guys, super restrictive diets are generally not good for health because they can cause us to obsess about food. And that obsession can lead to avoiding essential nutrients and malnutrition.
No diet is curative! Any diet or diet guru who says that their diet can cure you is lying.
Do eat more vegetables, more fruit, and less processed high fat/high sugar foods. But try and not obsess about food restrictions unless you have a medical reason to do so or you are ethically following a meat/dairy free diet.
Nathan Cowley – pexels.com
Seb is a writer and blogger of food and nutrition. He holds a bachelors and a masters degree in nutrition science, and has studied sports and exercise nutrition at postgraduate level. He specialises in plant-based nutrition and believes passionately that we can all live with a little less meat.