The alkaline diet, or acid–ash diet, is based on the theory that the food that we eat has the potential to change the acid-base balance of our body. The theory states that we should eat an alkaline diet as acidic foods put us at risk of diseases such as cancer, osteoporosis and cardiovascular disease.
AcidAlkalinediet.com goes as far as claiming it can cure cancer:
“Many people believe that an alkaline pH can not only protect the body against cancer, but can even help to cure it once it has developed.”
This theory is based on bad science. I’m going to tell you why…
So quick recap on what acid and alkaline actually means.
The pH is a measure of how acidic or alkaline something is. We measure the pH of something on a scale which runs from 0-14, 7 being neutral. So anything below 7 is acidic and anything above is alkaline.The pH is a logarithmic scale – so a difference of 1 in on the pH scale is x 10 difference.
Brain overload, or are you still with me?
Our bodies are tightly regulated to stay within 7.35-7.45 but don’t worry this is all taken care of behind the scenes by your lungs and kidneys. The only time this scale tips out of balance is when either the lungs or kidneys are not working correctly, or something pathological, i.e. harmful, is going on inside the body. When someone comes into hospital very unwell, we check the pH of their blood through an arterial or venous blood gas. This gives doctors a quick snapshot as to what might be going on and what bodily system is affected.
Although the pH of our blood can change when something goes wrong in our biological system, the foods that we eat however do not change the pH of your blood.
I can hear advocates of the diet screaming through my laptop screen “but my urine pH changes depending on the foods that I eat!”
Yes, it is true that food can influence the your urine pH. Your urine is a fluid full of waste products and is a reflection of a number of metabolic and digestive processes. Excess acidity is eliminated in the kidneys and this can be manipulated by your diet. Certain foods can leave end-products referred to as ‘ash’. This ‘ash’ can be acid or alkaline. Foods which are ‘alkaline’ include fresh fruit and vegetables, and foods which are ‘acidic’ include animal products and whole grains. So eating more ‘acidic’ foods can make your urine as a result more acidic – but just your urine, not your blood, or cells, or brain, or your large toe.
Furthermore, it is pretty easy to measure your urine pH with test strips that you can purchase in pharmacies and online, and I think this is one of the driving forces behind the success of the diet.
We all get satisfaction from seeing measurable ‘improvements’ in our health.
We are obsessed with our weight, our blood pressure, our cholesterol levels, our blood glucose, and so having the ability to manipulate the pH of your urine offers people the ‘proof’ that it’s working. In reality, your urine pH is not an indicator of your health.
Followers of the diet also propose that in order to balance the blood pH from an acidic diet, the body pulls minerals from our bones to neutralize the acid.
Therefore acid forming foods such as meat, dairy and grains, overtime lead to osteoporosis. This hypothesis stems from the observation that a diet high in acidic foods often leads to an increase in urinary calcium, so it was assumed that this calcium was taken from the bone.
However, this has been extensively researched and it has been concluded that an ‘acid-ash’ does not increase the risk of bone loss or osteoporosis.
There is no evidence from superior quality balance studies that increasing the diet acid load promotes skeletal bone mineral loss or osteoporosis. Changes of urine calcium do not accurately represent calcium balance. Promotion of the “alkaline diet” to prevent calcium loss is not justified.
In summary, there is no scientific basis to the alkaline diet. However, it may have some inadvertent health benefits as it involves following a plant based diet with lots of fresh fruit and vegetables.
My advice? Aim to increase your fruit and vegetable intake and don’t stress about the pH of your pee.
- Nutritional disturbance in acid–base balance and osteoporosis: a hypothesis that disregards the essential homeostatic role of the kidney.
- Causal assessment of dietary acid load and bone disease: a systematic review & meta-analysis applying Hill’s epidemiologic criteria for causality.
- Meta-Analysis of the Effect of the Acid-Ash Hypothesis of Osteoporosis on Calcium Balance
- The Alkaline Diet: Is There Evidence That an Alkaline pH Diet Benefits Health?
- NHS CHOICES: THE ALKALINE DIET.