What is the alkaline diet?

Does this diet really work and is there evidence to support the controversial claims made about its health benefits? We investigate the acid alkaline diet.

A selection of green vegetables

The alkaline diet has made big headlines over the last few years, and often for all the wrong reasons. We look into this highly 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 that you eat – despite there currently being no evidence to suggest that 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.

Foods that are cited as being ‘acid-producing’ by advocates of the diet include meat, wheat and other grains, refined sugar, dairy products, caffeine, alcohol and processed foods. Foods that are considered ‘alkaline foods’ 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.

The NHS says that the alkaline diet lacks evidence, and advises against cutting out whole foods groups, as some versions of the diet suggest. The NHS does acknowledge that the recommendations to eat more fruit and vegetables and cut down on sugar and alcohol are in line with current healthy eating advice.

A woman standing on bathroom weighing scales to read weight

We asked nutritionist Kerry Torrens for her view…

Does the alkaline diet work?

The premise that by following an 'alkaline' diet, you will promote a preferential blood pH, which helps your body maintain a healthy weight and optimise your well-being is fundamentally flawed. 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 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. This way of eating may have additional benefits because 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, if any, 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.

Is the alkaline diet safe?

The alkaline diet has been cited as a beneficial way of eating for those with chronic illnesses including cancer. However, to date there is no clinical evidence supporting the value and safety of an 'alkaline' diet for cancer patients, and in some cases it may prove detrimental

A plentiful intake of fruit and veg, 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 to date 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.

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, vitamin A and D.

Read more about why we need vitamins and minerals, and discover the best sources of calcium.

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 that is adopted. A strict eating plan which eliminates grains, dairy and animal foods may be deficient in protein as well as vitamins and minerals including vitamin D, vitamin B12calcium and iron.

However, if choosing a balanced version of the diet which 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 standard healthy weight loss advice and maintaining a healthy weight may lead to a lower risk of cardiovascular disease, although this benefit can be obtained by following any healthy, balanced diet.

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This article was reviewed on 6th November 2019 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.

All health content on bbcgoodfood.com is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other health care professional. If you have any concerns about your general health, you should contact your local health care provider. See our website terms and conditions for more information.

Comments, questions and tips

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7th Nov, 2017
A frequently misunderstood aspect of the alkaline diet is the errant notion that the blood pH becomes alkaline, when in actuality it is the metabolic energy sources (food) that are alkaline. That is, indeed your body maintains homeostasis and constant pH, but your body also has to counteract the acid/alkaline shifts generated by food sources by either producing acid or eliminating base in equal parts in order to maintain the constant pH. Thus if you load your dietary intake with alkalinity your body will have to react differently than if you were to load it with acidity; it will have to work completely differently and shift to acid generation and base elimination. Metabolic energy sources do make a significant difference, but the consequences are understudied and ill defined - and indeed warrant in depth analysis. For 200,000 years we evolved without many of the current foods we are exposed to (e.g. refined sugars, grains, dairy) and the entire simian kingdom gets by without it as well, and in many instances fares better. As far as controversial, well by definition this word means 'giving rise or likely to give rise to public disagreement' and given the significant public interest in this topic it is indeed controversial, whereas saying the world is flat, today, would not be controversial. I suggest caution with a couple of things: people who are quick to dismiss complexity and the pursuit of knowledge in exchange for the embrace of simplistic black and white views, and those who bully their position with derogatory statements such as 'snake oil.' These people needed decades of proof that radon blankets, thalidomide and smoking tobacco were not a good idea. That is not to say that exploitation of the meek is an unconscionable and despicable thing, but believing science and medicine are not biased or are more advanced than they truly are is not much different. Caveat emptor, and make your own decisions.
7th Nov, 2017
I would suggest that a 'controversial' diet is one which might have some weak evidence for success. When a diet such as the one you write about has no evidence of success I would tend to call it 'misinformation' or 'ineffective'. Using the word controversial is playing into the hand of those who sell snake oil. . . A bit like saying that the idea that the world is flat might be controversial.
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