Acidic or alkaline? Its link to cancer is not what you think

Have you ever heard of the so-called “alkaline diet”? If not, let me tell you about the rumors surrounding it.

According to its proponents, the alkaline diet can prevent—and even treat—diseases, especially cancer, by making the body more “alkaline.” The idea is based on the belief that cancer “thrives” in acidic environments, and that certain foods we eat create the acidic conditions cancer supposedly likes.

So, how true is this claim? Let’s listen to the scientific facts.

Alkaline diet: eating based on your blood’s pH level

Alkaline” (basic) and “acidic are terms used to describe a substance’s pH value—how acidic or basic it is. A pH below 7 is considered acidic, while above 7 is alkaline. Human blood has a pH of about 7.4.

The alkaline diet is an eating approach aimed at reducing the body’s acidity. It favors foods said to be alkaline, such as leafy green vegetables, fresh fruits, nuts, and seeds.

No evidence it prevents or treats cancer

Current data show no proven effect of the alkaline diet in treating cancer.

While there have been some early studies, mostly on animals, suggesting a potential link, they are very limited. In humans, there is no reliable scientific evidence supporting the claim.

A large 2016 systematic review combining 252 studies on alkaline water and cancer found no evidence that drinking alkaline water or following an alkaline diet could influence cancer development or treatment. Only one study found a weak link—between bladder cancer and urine pH—and even that was minimal.

Another review in 2022 examining over 30 human and lab studies found no scientific evidence that alkalinizing therapies—including the alkaline diet—affect cancer development or treatment. The studies were conducted in both human and laboratory settings, but the evidence was not found to be sufficient for treatment.

The Turkish Society of Medical Oncology emphasizes that apart from nutritional support prescribed by doctors, there is no proven benefit for cancer patients from diets like the alkaline diet.

The U.S. National Cancer Institute also states there is no evidence that an alkaline diet can slow, cure, or prevent the recurrence of diseases like cancer.

No matter how alkaline or acidic your diet is, you can’t change your blood pH

The claims about the alkaline diet rest on the idea that it can make the body more “alkaline.”

However, according to the American Institute for Cancer Research, there’s a key problem: no matter what you eat, your body tightly regulates your blood pH on its own. It can retain or excrete certain substances as needed. Your diet simply does not change your blood’s pH level.

Nutritionist Karen Collins from the Institute explains:

“Yes, protein-rich foods like meat can produce some acid when digested. And fruits and vegetables contain minerals that have a more ‘alkaline’ effect when digested. But these differences do not alter the body’s overall pH balance.”

Advocates often suggest measuring urine pH. But urine pH only shows what your body is excreting—not that your overall pH balance has changed. In fact, alkaline urine means the body is getting rid of alkalinity, not holding onto it. So alkaline urine is not proof the diet “works.”

Acidic environments are a result of cancer, not the cause

In the early 1900s, Nobel Prize–winning scientist Dr. Otto Warburg suggested that cancer cells thrive in low-oxygen, acidic environments and produce energy by fermenting sugar. This idea laid the foundation for the acid–alkaline diet belief. But science has advanced considerably since then, and we now know far more about cancer and nutrition.

Research shows that cancer cells can grow in alkaline—or non-acidic—conditions as well.

Modern evidence indicates that an acidic environment is the result of cancer, not the cause. Cancer cells produce large amounts of energy quickly and slow blood flow, creating acidity around them.

In other words, the belief that “cancer loves acidic environments” is not scientifically accurate.

Balanced eating is what’s truly healthy

According to Cancer Research UK, while the alkaline diet is rich in fruits and vegetables, it restricts many other foods and may not provide a balanced, adequate diet for cancer patients. In particular, reduced intake of protein and dairy products over time can lead to deficiencies in iron, calcium, zinc, vitamin B12, and vitamin D.

Healthy, balanced eating is known to help reduce cancer risk not just for cancer prevention, but for overall well-being. Experts recommend a diet rich in fiber, adequate fruits and vegetables, and sufficient protein. They also stress avoiding tobacco products and maintaining an active lifestyle.

Why do such myths spread?

This claim is an example of the false certainty or “illusion of certainty”, presenting unproven methods as if they guarantee results, often relying on personal stories instead of scientific evidence.

Such information spreads quickly because it sounds hopeful and harmless. Sometimes it appeals to emotions through personal testimonies, and sometimes it undermines trust with “they’re hiding the truth from you” rhetoric.

The real danger lies in trusting these unproven claims: they can delay effective medical treatment or foster false hope. Statements like “cancer cannot survive in an alkaline body” distort scientific facts and can be exploited by those selling false hope.

Yes, we all want to help our loved ones. But no matter how promising something sounds, it’s always best to turn to evidence-based, trustworthy sources.