The alkaline diet has made big headlines over recent years, often for all the wrong reasons. We look into this contentious diet and ask whether it is safe, effective and scientifically sound.


What is the alkaline diet?

An alkaline diet is based on the theory that you can change the pH balance of your body and blood through the food you eat – despite there currently being no sound evidence to suggest this is possible.

Advocates of the diet have claimed that high levels of ‘excess’ acid in the body, caused by our modern diets, contribute to a range of health conditions including arthritis, osteoporosis, kidney and liver disorders, and even cancer.

Advocates cite ‘acid-producing’ foods to be meat, wheat and other grains, refined sugar, dairy products, caffeine, alcohol and processed foods. Foods that are considered ‘alkaline’ include fruit and vegetables.

The diet was originally developed to help prevent kidney stones and urine infections, as the pH of your urine changes depending on what you eat. However, there is no evidence to suggest that this alters the pH of the rest of the body. Blood pH is tightly regulated by our kidneys and is not affected by diet.

Cancer Research UK says that there is no good evidence to prove that diet can manipulate the pH of the body, or that ‘acidic’ diets increase the risk of cancer.

Health experts warn that the alkaline diet lacks sound evidence, and advise against cutting out whole food groups, as some versions of the diet suggest. However, it is worth saying that the recommendations to eat more fruit and vegetables and cut down on sugar and alcohol are in line with current healthy eating guidelines.

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We asked registered nutritionist Kerry Torrens for her view…

Does the alkaline diet work?

Without doubt our modern diets are prone to being rich in saturated fat, simple sugars and salt and are low in alkalising minerals like magnesium and potassium. However, the premise that by following an 'alkaline' diet, you will promote a preferential blood pH – to help maintain a healthy weight and optimise well-being – is strongly disputed. This is because your body is designed to do this anyway, aiming to keep the blood pH at a constant slightly alkaline level of between 7.35 and 7.45.

That said, the foods recommended by the alkaline diet are good for you and, in fact, are largely those promoted for healthy weight management. So, if you are cutting down on meat, swapping fatty, processed foods, refined sugars, caffeine and alcohol for more plant-based foods like fruit, vegetables, nuts and seeds and drinking water, you are more than likely going to experience some weight loss.

Are there other health benefits when following an alkaline diet?

This way of eating may have additional benefits – a plentiful intake of plant-based foods improves the balance of potassium to sodium which helps manage blood pressure and may improve heart health.

As for the evidence supporting other specific health benefits, such as the effects on bone health, muscle wastage and the possible alleviation of back pain, there are currently limited scientific studies to support such claims. Although, it may be argued that more research is needed.

A plentiful intake of fruit and vegetables, as advocated by the diet, has been claimed to enhance bone health and possibly protect against osteoporosis because of its high potassium content and lower levels of 'acidic' dietary protein. However, the evidence is inconsistent and studies involving a more 'alkaline' diet and supplements have not shown to be of benefit to bone health. In fact, in the elderly an inadequate protein intake can be a greater problem for bone health.

What are the long-term effects of the alkaline diet?

The long-term effects of an alkaline diet will vary depending on the version of the diet adopted. A strict eating plan that eliminates grains, dairy and animal foods may be deficient in protein as well as vitamins and minerals including vitamin D, vitamin B12, calcium and iron.

However, if you follow a balanced version of the diet that does not eliminate food groups, and includes some grains and animal protein along with plenty of plant-based foods, the long-term effects may be more positive. Eating in line with healthy weight loss advice and maintaining a healthy weight may lead to a lower risk of cardiovascular disease, although this benefit may also be obtained by following any healthy, varied balanced diet.

Is the alkaline diet safe for everyone?

As with all diets, pregnant and breastfeeding women as well as diabetics on medication, should seek medical advice before embarking on a restricted eating programme. Furthermore, this sort of diet may be unsafe for teenagers and children, who may, should they eliminate certain food groups, miss out on crucial nutrients needed for growth. For example, cutting out whole food groups such as dairy, can lead to nutritional inadequacies. In order to address this, followers need to find alternative food sources and consume them in appropriate amounts to ensure an adequate intake of key nutrients like calcium and vitamins A and D.

For those with chronic illnesses including cancer, it is important to note that there is no clinical evidence supporting the value and safety of an 'alkaline' diet, and in some cases it may prove detrimental.

If you have no pre-existing health condition, the alkaline diet is generally safe, but it is important that you understand how to obtain enough protein and calories from plant sources, to satisfy your needs.

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Please note, if you are considering adopting any form of restrictive eating or diet, please consult your GP or a registered dietician to ensure you can do so without risk to health.

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This article was reviewed on 21 March 2022 by Kerry Torrens.

Kerry Torrens BSc. (Hons) PgCert MBANT is a registered nutritionist with a post-graduate diploma in Personalised Nutrition & Nutritional Therapy. She is a member of the British Association for Nutrition and Lifestyle Medicine (BANT) and a member of the Guild of Food Writers. Over the last 15 years she has been a contributing author to a number of nutritional and cookery publications including BBC Good Food.


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