Sugar-free alkaline diets won’t ‘starve’ cancer

15 June 2023
What was claimed

Cutting out refined sugar and eating an alkaline diet will starve cancer cells.

Our verdict

Cutting out refined sugar will not mean the body has no glucose, which is what the cancer cells use for energy. There is no strong evidence that the ‘alkaline’ diet is effective in the treatment or prevention of cancer.

A Facebook video with over 22,000 likes claims that sugar-free diets can “starve” cancer cells, and suggests cutting out “acidic” foods as a way to fight the disease. This isn’t supported by the evidence.

The video features Barbara O’Neill, a naturopath banned for life in 2019 from providing any health-related services by the New South Wales Health Care Complaints Commission, which said in its findings that she “poses a risk to the health and safety of members of the public”.

The video caption contains a “disclaimer” that “we are not offering health, financial or legal advice on this page”. It also links to a blog that makes more claims about sugar and health. We have not fact checked this blog in detail, but the sources it cites don’t substantiate the claims made in the video.

False, misleading or unevidenced claims about cancer can cause harm if people make treatment decisions based on them. We have written about claims that certain foods or alternative therapies can cure or prevent cancer many times before. Delays in getting effective cancer treatment can have serious results.

Honesty in public debate matters

You can help us take action – and get our regular free email

Sugar, glucose and keto

The video starts by telling us that cancer “loves” sugar. It goes on to say that there is “nothing wrong with the sugarcane” but that refined sugar is the problem. Refined sugar is usually sucrose, a type of sugar that is broken down in the body into glucose and fructose.

Cancer cells do rely on glucose for energy, as do all cells in the human body. They also need other nutrients to grow and spread. And as Cancer Research UK says, “there’s no way of telling our bodies to let healthy cells have the glucose they need, but not give it to cancer cells”.

The person in the video says “cancer hates it when you stop the sugar”. But cutting out sugar doesn’t mean there will be no glucose for cancer cells to feed on.

Glucose used for energy in the body comes from many different types of food or drink. This includes sugar, but also very often carbohydrates from things like bread, which can be broken down into it. Glucose is also stored as glycogen, and this can be broken down when blood sugar levels drop between meals.

When there are no dietary sources of glucose, and all your glycogen is used up, the human body can make glucose from proteins and fats via a process called gluconeogenesis. 

It is possible to put your body into a state called ketogenesis, where products of fat breakdown are used by the body's cells for energy, instead of glucose. This is difficult to maintain, but can be done by eating a very high fat diet and no carbohydrates. The foods described in the video (sugarcane and vegetables) and in alkaline diets would not produce this state.

The evidence we have so far does not support a ketogenic diet to fight cancer in general, though it is an area of ongoing research and it may provide benefits in preventing certain side effects from certain cancer treatments. In general, other diets high in plants are better for reducing the risk of developing cancer.

One suggested food to eat in the video is vegetables. These contain carbohydrates that will be broken down to glucose during digestion and some will contain sugar as well. Vegetables in general will release glucose into the blood, albeit more slowly than refined sugar or foods like white bread. Sugarcane, which does contain more nutrients than refined sugar, also contains a lot of glucose.

When Full Fact asked the Facebook page which posted the video about the evidence for its claims on sugar, it referred us to this long review article which was published last year, but this doesn’t appear to add any evidence to substantiate the claims in the video.

The alkaline diet

The person in the video states “cancer is not happy when you create an alkaline environment”.

A 2016 systematic review published by the British Medical Journal found no evidence to support claims that an alkaline diet can change the likelihood of getting cancer, or the outcomes after diagnosis.

Cancer Research UK advises that “there is no scientific evidence that alternative diets can cure cancer”, including the alkaline and ketogenic diets in this category.

The video talks more generally about acidity or alkalinity of the body and how this relates to diet, saying that refined sugar is the “most acid substance you can put in your body”. However, many foods including fruits and vegetables have a lower pH (the measure of how acidic something is) than sugar, and therefore are more acidic.

It is not possible to make your body as a whole more or less alkaline through food. The pH of blood is very strictly regulated through processes in the body. Eating something very acidic or very alkali could change the pH of your urine as the excess is secreted to maintain the normal balance.

When we asked the Facebook page which posted the video about the alkaline diet claims, it referred us to a small study in cancer patients, published in 2020, which compared a group who had chemotherapy to a group who had an alkaline diet as well, and found better survival outcomes in the latter. However this study didn’t collect any data on the diet of the first group or confirm that both groups had the same chemotherapy regimes, and as a single retrospective cohort study, it doesn’t outweigh the much stronger evidence we discuss above.

We also contacted Barbara O’Neill for comment but did not receive a response.

Featured image courtesy of Commonwealth Scientific and Industrial Research Organisation

Full Fact fights bad information

Bad information ruins lives. It promotes hate, damages people’s health, and hurts democracy. You deserve better.