While browsing the grocery store or scrolling online, you may have seen water or foods labeled as “alkaline.” These products often claim you need alkaline water and foods for peak performance. More recently, these products and their supporters have also claimed that alkaline water and foods fight cancer. The “alkaline diet” has grown in popularity in online conversations about cancer and nutrition. Is the alkaline diet really effective at fighting cancer? Do you really need alkaline water to stay healthy? Let’s explore.
What is the alkaline diet?
The alkaline diet is sometimes also called the acid-alkaline diet, alkaline acid diet, or acid ash diet. Supporters of the alkaline diet claim that when the body’s environment becomes “acidic,” the risk for cancer increases. This claim came from a finding that cancer cells in laboratory animals and cell studies live in an acidic (low pH) environment. This led to the assumption that eating foods that are alkaline (high pH) will stop cancer growth by creating a high pH environment in the body. Supporters call this “alkalizing the body.” The theory that what you eat can alter the acidity or alkalinity (the pH level) of your blood is the basis of the alkaline diet. However, this is an unproven claim in humans. The findings only apply to cells in lab experiments.
The Acid Alkaline Association (AAA)’s version of this diet recommends eating 80% alkaline foods (most vegetables and fruits) and 20% acid-producing foods (meats, poultry, dairy, eggs, coffee, whole grains, beans, sugar, and alcohol). Foods are categorized based on their effect on the body, especially the potential renal acidity load (PRAL). Certain fruits, vegetables, and seeds are emphasized. Processed foods are largely avoided. In addition to classifying foods by their pH, the AAA promotes 10 levels of the alkaline diet with more restrictions as the levels progress, including avoiding certain food combinations.
Does the alkaline diet actually change pH levels in the body?
You cannot change the pH of your blood by changing the foods that you eat or the combinations of the foods that you eat. The primary claim of the alkaline diet is not true.
Scientific evidence tells us that the human body has a powerful system to keep the blood pH levels in a tight range, pH 7.35 to 7.45, which is a neutral pH. The kidneys and respiratory system work around the clock to maintain a safe pH level in the blood. If the pH of blood changes quickly, it is life threatening. Your food choices have little to no effect on the pH of your blood. Some alkaline diet plans recommend checking your urine pH often. Urine pH has no relationship to your blood pH or cancer risk.
Some acids in the body actually work to benefit us in many ways. How? Many areas of our body must be acidic to work correctly, like the acidic levels in our stomach for proper digestion.
Is the alkaline diet safe for all cancer patients?
Some patients find the strict rules of the alkaline diet, such as only eating specific foods together, to be stressful. As a patient progresses through the advanced levels of the alkaline diet, consuming adequate calories may become difficult because of increasing restrictions. One version of the alkaline diet recommends 64 ounces of water daily which may not be appropriate for all cancer patients. The restrictive nature of the alkaline diet can also put patients at risk for nutrient deficiencies from not consuming enough dietary protein, Vitamin B12, Vitamin D, iron, and calcium by limiting beef, poultry, eggs and dairy foods.
Does the alkaline diet offer any benefits?
The alkaline diet’s emphasis on increasing fruits and vegetables and avoiding processed foods, sugar, and alcohol is a good thing. Studies of plant-based diets show that meals full of plants, including fruits, vegetables, and whole grains, and less animal protein reduce the risk of cancer and other chronic diseases like high blood pressure, heart disease, and diabetes.
The basic recommendations of the alkaline diet—eating a plant-based menu and eating multiple meals throughout the day—do offer benefits. Eating multiple times throughout the day may also help people feel less hungry and more energized since they have a regular source of fuel.
What’s the bottom line?
Your overall pattern of eating is more important than a single food in managing cancer or risk of cancer. There are no large, well-designed clinical trials that prove an acidic (lower) pH blood level in humans increases cancer risk. Cancer cells create an acidic environment. The acidic environment does not create the cancer. There is also no scientific evidence that proves the claim that maintaining an alkaline pH in the blood reduces cancer cell growth, cures cancer, or prevents cancer recurrence.
Some acids in the body actually benefit us by adding in digestion, for example. Acids are vital for health and immunity like the amino acids that are the building blocks of dietary protein and healthy fatty acids for your heart. Enjoying a variety of foods, especially fruits and vegetables, provides many health benefits. Focus less on the alkalinity and acidity of foods, and focus more on colorful, plant-based meals.
Remember, the alkaline diet is NOT a substitute for cancer treatments such as a chemotherapy, radiation or surgery.
Always talk to your healthcare team before making any changes to your diet or lifestyle.
 O’Brien, S et al: “Diets, Functional Foods and Dietary Supplements for Cancer Prevention and Survival,” Oncology for Clinical Practice, Chapter 8, page 62-65, 2013, Oncology Nutrition Dietetic Practice Group of the Academy of Nutrition and Dietetics.
 Leech, Joe. (2017, June 9). “The Alkaline Diet: An Evidence-Based Review.” Healthline. Retrieved from https://www.healthline.com/nutrition/the-alkaline-diet-myth#section1.
 The American Institute for Cancer Research. “Alkaline diets.” Retrieved from http://www.aicr.org/patients-survivors/healthy-or-harmful/alkaline-diets.html?_ga=2.250217038.992419478.1533654035-1668668041.1493149900.
 Cunningham, Eleese. (2009). “What Impact Does pH Have on Food and Nutrition?” Journal of American Dietetic Assoication, 109(10), 1816. Retrieved from https://jandonline.org/article/S0002-8223%2809%2901521-1/abstract.
 Foroutan, Robin. (2016, April 28). “Alkaline Diet: Does pH Affect Health and Wellness?” Food & Nutrition. Academy of Nutrition and Dietetics. Retrieved from https://foodandnutrition.org/may-june-2016/alkaline-diet-ph-affect-health-wellness/.