The alkaline diet was originally developed with the idea of helping individuals with kidney disease. Since kidneys filter the blood and maintain acidity levels, the rationale was that when kidney function is compromised, adjusting the diet to reduce the acid load might slow progression of the disease.
However, the alkaline diet has become the latest fad adopted by normal, healthy people who claim that it lowers the acidity in their bodies.
The alkaline diet, also known as the alkaline-ash diet or acid alkaline diet, is built upon the notion that a high level of acidity in our bodies is linked to disease.
At a high-level, the claim is that eating more ‘alkaline producing’ foods – including vegetables, fruit, nuts, and legumes – can help to neutralise the acidity of your body. Conversely, eating ‘acid producing’ foods – such as meat, dairy, eggs, and grains – can be detrimental to your health.
Any eating plan that reduces ultra-processed food is good, which is what the alkaline diet has in its favour. However, it also cuts out some of the most nutritious foods – meat, fish, eggs and dairy products – and it has no means of delivering complete proteins.
The first point to make is that the body is extremely effective at maintaining a steady acidity/alkaline balance; this is scientifically known as your ‘pH level’. Low pH (0-6) means acidic, medium pH (7) means neutral, and high pH means alkaline (pH 8-14).
There are also very different pH levels in different parts of the body. For example, the stomach has a low pH (2-3) typically due to the presence of stomach acid, which breaks down food for digestion. The blood has quite a strict, neutral pH (7.35-7.45), and no foods you eat will change this. If your blood pH level does change out of these parameters, you will become very unwell, and it would likely be fatal.
Our bodies have complex systems in place to regulate the pH levels of our blood. For example, the kidneys. When blood is filtered by the kidneys, reabsorption and secretion of hydrogen (acidic) and bicarbonate (alkaline) ions occur. This is why urine pH changes: our kidneys remove excess acidity to be excreted in our urine.
This is also why using urine pH level to determine blood pH, as many studies cited in support of the acid-ash hypothesis do, is invalid.
Osteoporosis is a condition where your bones become brittle and fragile from loss of tissue. The hypothesis of the alkaline diet is that protein, in particular, animal protein, is acid-forming. In order to neutralise this acid, our bodies dissolve bone matter to release bicarbonate.
By this theory, protein should be detrimental to bone health and increase our risk of osteoporosis.
However, in a thorough systematic review of the evidence for the effect of an alkaline diet on bone health, this claim was not supported. In fact, randomized controlled trials demonstrated that protein has positive effects on bone density.
Interestingly, Dr William Davis explains in his book, ‘Wheat Belly’, that animal foods, although on the acidic side of the food table, are not as harmful to pH balance as this would suggest: ‘Animal protein exerts a bone-strengthening effect through stimulation of the hormone IGF-1, which triggers bone growth and mineralisation’.
He describes wheat, white flour, and pasta as the most acidic foods. He argues that society as a whole is greatly overconsuming these ultra-processed carbohydrates, and when confronted with such a sustained level of acidity, the body draws from its alkaline stores to compensate. Most notably that ‘the body will sacrifice bone health to keep pH stable’.
He also argues that sugary drinks are another source of acid and gives a particularly interesting example of the association between increased soft drink consumption and bone breakages: ‘The constant draw on calcium from bones is associated with fivefold increased fractures in high school girls who consume the most carbonated colas’.
We should be quick to remember that association does not mean causation, and it might be the case that high school girls consuming a lot of soft drinks are also falling down on other aspects of their diet.
Overall, it seems the alkaline diet does not reduce the risk for osteoporosis and could in fact harm rather than improve bone health.
Despite the media plugging the belief that the alkaline diet can prevent and even cure cancer, the scientific evidence is near to non-existent.
A systematic review, published by the British Medical Journal, explored the link between the alkaline diet and all types of cancer. A staggering 1 study was included in the review due to the lack of available, high-quality human trials.
The 1 study was a prospective cohort study that examined whether raised urinary pH effects bladder cancer. As discussed, any excess acid gets excreted in our urine, so this is an interesting avenue to explore. However, the single study exploring this link found no significant effect.
The lack of evidence does not mean that we can completely disprove the claim of the alkaline diet helping to prevent/ treat cancer, but points out that it was not built upon science.
Therefore, there is currently no reason to suggest that individuals with cancer would benefit from the alkaline diet, nor that it can help with prevention.
Those living with a medical condition should seek advice from a licensed medical professional. The pioneer of the alkaline diet, Robert Young, is now facing jail time for practising medicine without a license and wrongly treating cancer patients with the alkaline diet.
A final note to dispel some lingering concerns that come with the alkaline diet.
There is simply no science to suggest that drinking more ‘alkaline’ water has any health benefits. Basic tap water is usually alkaline. When water hits your stomach, which is acidic as previously mentioned, it is immediately neutralised. Paying £2.99 for 500ml of ‘miracle’ water is no guarantee that it is any different to what comes out of our taps for free.
Chlorophyll has attracted a lot of attention as a key alkaline-forming substance, to the extent that chlorophyll supplements are recommended. There are claims that it has ‘anti-cancer’ and ‘anti-bacterial’ properties and can ‘detox’ our bodies.
First, it is worth noting that as with anything we eat, chlorophyll will be digested and degraded and we don’t need to be ‘detoxed’ as our livers do a pretty good job of this.
Secondly, all of the evidence that might suggest ‘anti-cancer’ and ‘anti-bacterial’ properties are in vitro. This means they have been studied in a petri dish in a lab rather than on the human body.
Lastly, many supplements are actually categorised as food rather than medication and so don’t go through the usual safety checks and regulations a medicine would go through before being sold.
The bottom line is that many green vegetables and herbs contain chlorophyll, alongside other vitamins and minerals, such as spinach, parsley, and green beans. There is no evidence to suggest supplementing chlorophyll has benefits above and beyond healthy eating.
So what is our conclusion here? We would strongly recommend you don’t follow the alkaline diet word-for-word. However, there are two underlying themes that we agree on: