Inadequate support: No evidence indicates that following an alkaline diet helps prevent or treat cancer more than a balanced diet.
FULL CLAIM: “[Cancer] means your body is full of acidity which occurs from over consumption of meat, acidic drinks and processed foods”; alkalizing your body prevents cancer
A Facebook video published in July 2022 claimed that the acidification of the body is the cause of cancer and suggested that consuming certain foods that reduce its acidity can prevent this condition. The Facebook post received more than two thousand interactions on the platform.
The idea that consuming acidic foods promotes various illnesses, including cancer, and that reducing the intake of such foods prevents these illnesses is a common myth. This myth is the basis of the alkaline diet, which avoids foods such as meat, fish, dairy, eggs, grain products, and processed foods in favor of a wide range of fruits, vegetables, and legumes.
As Health Feedback explained in previous reviews, the idea that an alkaline diet prevents or treats diseases, whether it is COVID-19, acquired immunodeficiency syndrome (AIDS), or cancer has no scientific basis. In the case of cancer, this idea is based on two assumptions. The first one is that cancer is caused by acidification of the body. The second one is that consuming certain foods can change the acidity of the body’s tissues. Both assumptions are incorrect, as we explain below.
Cancer is caused by mutations, not by body acidity
Claims that acidification of the body causes cancer seem to arise from a misinterpretation of the research conducted by the chemist and physician Otto Warburg. Warburg’s work was key for understanding the mechanisms of cellular respiration—the chemical process that allows cells to obtain energy from nutrients—and this work earned him the Nobel Prize for Physiology or Medicine in 1931.
Cellular respiration comprises several stages in which the mitochondria have a critical role, as the diagram below by National Geographic illustrates (Figure 1). Depending on the availability of oxygen, cells can use two different pathways to obtain energy. In the presence of oxygen, most cells preferentially use aerobic respiration (Figure 1, blue arrows). But when oxygen is unavailable, cells can produce energy through an alternative pathway called anaerobic respiration or anaerobic glycolysis, which relies on glucose fermentation (Figure 1, green arrows).
Figure 1. Diagram showing the processes involved in cellular respiration. By National Geographic.
While healthy cells generally use aerobic respiration to generate energy, Warburg found that cancer cells preferentially obtain their energy from fermenting glucose, even when oxygen is available. This preference for fermentation even in the presence of oxygen is called aerobic glycolysis and produces lactic acid as a by-product.
This particular metabolism of cancer cells is known as the Warburg effect. Indeed, tumors are often surrounded by an acidic environment partly created by their own production of lactic acid, which can serve as a hallmark of cancer progression. While a few studies show that acidic conditions might promote cancer growth, cancer cells can also grow in an alkaline environment[3,4]. In any case, these are laboratory studies that don’t necessarily reproduce what happens in the human body and therefore can’t be directly extrapolated to people.
As Health Feedback explained in a previous review, research has shown that the metabolic changes that Warburg described are likely a consequence of cancer, not its cause. Today, we know that cancer is caused by mutations, which arise due to different factors, including environmental factors that damage the DNA and random errors during cell division. In addition, certain inherited mutations can also increase a person’s likelihood of developing cancer.
Food intake can’t change the acidity of the body’s tissues and cells
Misinterpretation of the Warburg effect research has led to the idea that reducing the body’s acidity is effective at preventing or fighting cancer. Proponents of the alkaline diet believe this can be achieved by consuming certain foods they consider alkaline based on the potential renal acid load, which is the amount of acid the food produces in the kidney once digested. However, this is incorrect because food intake can’t change the tightly-regulated acid-base balance of the body. Acidity level is determined by the number of hydrogen ions in a solution, measured by the pH scale. The higher the pH, the fewer the number of hydrogen ions in the solution and the more alkaline the solution.
While the pH of certain body fluids, like urine or saliva, can indeed vary depending on our diet or overall health[5,6], the pH regulation of the tissues and cells is a critical and tightly controlled function. Most chemical reactions in the body take place within a very narrow pH range, and any significant deviation from this range could have serious consequences. For this reason, the body uses several strategies to keep a specific and constant pH in each tissue. For example, blood in healthy people has a slightly basic pH, ranging between 7.35 and 7.40. The kidneys and the lungs have a critical role in regulating the body’s pH, using bicarbonate and carbon dioxide, respectively. In addition, the liver is an important regulator of blood pH through lactic acid metabolism.
Therefore, if the alkaline diet provides any benefit, it is certainly not by altering the body’s pH. But could the alkaline diet combat cancer in other ways?
According to the American Cancer Society, “at least 18% of all cancers and about 16% of cancer deaths in the U.S. are related to excess body weight, physical inactivity, alcohol consumption, and/or poor nutrition”. Based on this, an alkaline diet that promotes the intake of vegetables and limits meat, processed foods, and alcohol could be considered a healthy dietary pattern in line with the recommendations from the American Institute of Cancer Research to reduce the risk of cancer.
But overall, current evidence doesn’t indicate that an alkaline diet prevents cancer or provides benefits to cancer patients, at least no more than a nutritionally balanced diet. A 2016 review evaluating the association between an alkaline diet and the incidence and clinical course of cancer found there was almost no research on this topic at that time and that promoting an alkaline diet to prevent or treat cancer was unjustified. The American Institute of Cancer Research explains that later research has been equally scarce and produced mixed results.
Finally, a healthy diet isn’t based on food acidity but on how much calories, nutrients, and fiber it contains. The Dietary Guidelines for Americans list several core elements that should be part of a healthy diet, including grains, dairy, lean meats, and nuts. All these foods would be considered acidic by proponents of the alkaline diet, but are actually rich in protein, omega-3 fatty acids, and carbohydrates necessary for the body. By avoiding such foods, a strict alkaline diet could potentially lead to nutritional deficiencies in the long run, particularly in physically active people.
The risks of cancer misinformation
Cancer, in particular cancer prevention and treatment, has been a common subject of misinformation for decades.
One study published in the Journal of the National Cancer Institute in July 2022 analyzed the most popular social media publications on cancer treatment for the four most common cancers in 2018 and 2019. The researchers found that 32.5% of the 200 publications evaluated contained false, inaccurate, or misleading information, most of it harmful. Furthermore, the average engagement for the articles containing misinformation was greater than that for articles containing factual information.
While many of these treatments aren’t necessarily harmful per se, they pose an indirect health threat as they can interfere with effective cancer treatments and may also lead some patients to delay or reject clinically proven treatments.
The relevance of these indirect negative effects is clearly illustrated by two studies published in JAMA Oncology and the Journal of the National Cancer Institute. These studies showed that patients who used alternative therapies—unproven therapies that replace proven effective treatments—and those who used complementary therapies in addition to at least one proven treatment were up to two times more likely to die than those who only received effective treatment. The higher mortality in the earlier groups appeared associated with the complete refusal of effective cancer treatment or the refusal of additional proven treatment proposals.
The claim that an alkaline diet prevents or treats cancer is false and based on the incorrect assumptions that cancer is caused by acidification of the body and that food intake can regulate this acidity. Cancer is caused by mutations, and the acidity that is often associated with tumors isn’t the cause of cancer but rather its consequence. Food intake can’t change the body’s pH unless a person has illnesses that affect organs responsible for regulating the body’s pH, such as the liver and kidneys. No evidence supports the claim that an alkaline diet can prevent or treat cancer more than a nutritionally balanced diet.
- 1 – Liberti and Locasale. (2016) The Warburg Effect: How Does it Benefit Cancer Cells? Trends in Biochemical Sciences.
- 2 – Webb et al. (2011) Dysregulated pH: a perfect storm for cancer progression. Nature Reviews Cancer.
- 3 – Rohani et al. (2019) Acidification of Tumor at Stromal Boundaries Drives Transcriptome Alterations Associated with Aggressive Phenotypes. Cancer Research.
- 4 – Martínez-Zaguilán et al. (1996) Acidic pH enhances the invasive behavior of human melanoma cells. Clinical and Experimental Metastasis.
- 5 – Welch et al. (2008) Urine pH is an indicator of dietary acid-base load, fruit and vegetables and meat intakes: results from the European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk population study. British Journal of Nutrition.
- 6 – Pedersen et al. (2018) Salivary secretion in health and disease. Journal of Oral Rehabilitation.
- 7 – Hamm et al. (2015) Acid-Base Homeostasis. Clinical Journal of the American Society of Nephrology.
- 8 – Scheiner et al. (2017) Acid-base disorders in liver disease. Journal of Hepatology.
- 9 – Fenton and Huang. (2015) Systematic review of the association between dietary acid load, alkaline water and cancer. BMJ Open.
- 10 – Johnson et al. (2022) Cancer Misinformation and Harmful Information on Facebook and Other Social Media: A Brief Report. Journal of the National Cancer Institute.
- 11 – Johnson et al. (2018) Complementary Medicine, Refusal of Conventional Cancer Therapy, and Survival Among Patients With Curable Cancers. JAMA Oncology.
- 12 – Johnson et al. (2018) Use of Alternative Medicine for Cancer and Its Impact on Survival. Journal of the National Cancer Institute.