The Alkaline Diet and Cancer: What Does the Evidence Say?

In the world of cancer nutrition, few topics stir as much curiosity—and confusion—as the alkaline diet. Promoted widely online and in wellness circles, this diet claims to prevent or even cure cancer by altering the body’s pH. But what does the science actually say?

Let’s take a closer look.

What Is the Alkaline Diet?

Also known as the Acid-Alkaline Ash diet, the alkaline diet is based on the idea that the foods we eat can influence the body’s pH levels. The theory suggests that acidic foods (like meat, dairy, and grains) disrupt the body’s natural balance, while alkaline foods (like vegetables and fruit) restore it—creating an internal environment that discourages disease, including cancer.

Foods are often classified using a calculation called the PRAL score (Predicted Renal Acid Load), which estimates how acidic or alkaline a food is once metabolised.

Typical recommendations include:

✅ High intake of green vegetables, low-sugar fruits, and alkaline water

❌ Avoidance of meat, dairy, grains, sugar, and legumes

Some proponents even encourage monitoring urine pH to track progress—though this isn’t a reliable indicator of blood pH.

What Does the Science Say?

Despite its popularity, there is no scientific evidence that the alkaline diet can prevent or cure cancer.

Here’s what we do know:

• Human blood pH is tightly regulated at around 7.4 by the kidneys and respiratory system. Diet does not alter this.

• Urine pH may change based on food intake, but this does not reflect changes in blood pH or cancer risk.

• While some cancer cells may thrive in acidic environments, others (like leukaemias) prefer alkaline conditions. Tumour cells are also highly adaptable.

• There is no evidence that diet can meaningfully alter the pH of the tumour microenvironment.

  
  

In short: the body’s pH balance is not something we can manipulate through food alone.

Could It Cause Harm?

Yes—especially for people living with cancer.

The alkaline diet is highly restrictive and often low in protein due to the exclusion of meat, dairy, and pulses. For individuals already at risk of malnutrition due to cancer or its treatment, this can further compromise nutritional status, appetite, and enjoyment of food.

Other concerns include:

• Increased cost and time demands (e.g., specialist waters, alkalising machines)

• Misclassification of foods, leading to confusion and unnecessary avoidance

• Emotional pressure to “eat perfectly” in the hope of curing cancer

At Flourish, we believe that nutrition should support—not stress—the healing process.

A Gentle Reminder

It’s natural to seek out dietary solutions during cancer. But it’s equally important to ground those choices in evidence and compassion. If you’re considering a new diet, especially one that’s restrictive, speak with a qualified oncology dietitian. Your nutritional needs are unique—and they deserve care that’s both scientifically sound and emotionally safe.