Alkaline water has become a popular drink trend, with many celebrities and fitness gurus touting its hydration and detoxification benefits. You may have also heard that alkaline water can prevent or treat cancer, but no studies have yet proven this to be true.

So what should people with cancer know about drinking alkaline water? Here, we talk about what alkaline water is, why the science doesn’t support its use for people with cancer, and general guidelines for ways to stay hydrated during your cancer treatment.

What is alkaline water?

Alkaline water is water that has a higher pH level than regular tap water. The pH of something refers to how acidic or basic (also called alkaline) it is on a scale of 0 to 14, with 1 being very acidic and 14 being very alkaline. Regular tap water typically has a pH of 7, which is considered neutral.

Alkaline water can come from natural springs that give the water a higher pH. Alkaline water can also be made by adding baking soda to tap water, by using a water ionizing machine, or by using a specific filtration system to create it. Alkaline water is now common to find in the water aisle at the grocery store.

Where did the idea that drinking alkaline water will prevent or treat cancer come from?

Some research has shown that tumors are acidic and that this acidity may help tumors grow and survive. Because of this, some people have hypothesized that eating alkaline foods or drinking alkaline water can help prevent or treat cancer.

The idea gained attention in 2002 with the publication of a series of pH Miracle books by Robert O. Young, who promoted the theory of an alkaline, or high pH, diet to treat and prevent disease, including cancer. Young later served time in jail and was ordered to pay over $100 million to a person with cancer who chose not to receive standard cancer treatment and instead followed his theories about an alkaline diet.

Does science support drinking alkaline water for cancer?

To date, no studies have shown that drinking alkaline water prevents or treats cancer. This may be because the human body naturally does an excellent job at keeping our blood at a steady 7.3 to 7.4 pH level. The body has several ways to balance the acidity and alkalinity of the blood. For example, people breathe out carbon dioxide during respiration to normalize the blood’s pH. The kidneys also secrete ions to help normalize the blood’s pH. It’s a finely tuned system that does not allow for much deviation.

Because the body is constantly working to balance pH levels, drinking something with a higher pH, like alkaline water, does not significantly affect the overall pH of the blood or the pH of the blood that would reach a cancer cell or tumor in the body. So while alkaline water is being promoted by some companies or individuals, science does not support its use for cancer prevention or treatment. However, some people may enjoy drinking alkaline water for its taste, and they may be willing to pay more for it to be bottled or ionized as alkaline water.

Julie LG Lanford, MPH, RD, CSO, LDN“Alkaline water does not kill cancer. Thankfully, our kidneys and lungs keep our pH tightly regulated, right where they should be. But don’t worryalkaline water won’t harm your body, just make your wallet smaller.” — Julie LG Lanford, MPH, RD, CSO, LDN, registered dietitian and nutritionist with 15 years of experience working in oncology nutrition

How much water should I drink if I’m receiving cancer treatment?

Staying hydrated is important for anyone with cancer, especially if you’re receiving cancer treatments such as chemotherapy, radiation therapy, and surgery. These treatments’ side effects include nausea and vomiting and diarrhea, all of which can cause dehydration. Your cancer medications, any infections you may experience, and your environment can also lead to dehydration. When you’re dehydrated, your body can’t function properly. This is because the body depends on water to perform certain functions, including transporting nutrients and oxygen, controlling heart rate and blood pressure, and regulating body temperature. Severe dehydration can lead to low blood pressure, fever, rapid heartbeat, and disorientation or confusion. Look for signs of dehydration, such as dry mouth, fatigue, dizziness, or headaches, and call your doctor if you suspect you’re becoming dehydrated.

That’s why it’s important to drink plenty of fluids throughout the day to stay hydrated. The U.S. Centers for Disease Control and Prevention (CDC) notes that several factors need to be considered in figuring out how much adults should drink per day. Ask your doctor or registered dietitian about how much water you should drink daily based on your health and treatment plan. Also, let them know if you are considering switching to alkaline water and discuss it with them.