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Does alkaline water or an alkaline diet change your body's pH?
Food and water change urine pH, not blood pH, and no trials show alkaline diets prevent cancer or bone loss.
What you hear: “Alkaline water and an alkaline diet change your body's pH and help prevent or fight disease, including cancer.”
What the studies found
Studies show diet can change the pH of urine but not of blood, which the body keeps in a narrow range. A systematic review screened 8,278 papers on diet acidity, alkaline water and cancer, found no randomised trials and only one usable study, which showed no link with bladder cancer. A review of 22 randomised trials and other studies on bone found no evidence that an alkaline diet protects bones.
What you could do
Plain water is fine; the vegetables and fruit in 'alkaline' diets are good for you for other reasons, not because of pH.
See it in the habit library, with what it means for your own longevity score.
Not medical advice. General information from published studies, not a diagnosis or a treatment plan. Talk with your doctor before starting a supplement or changing a medicine, especially if you are pregnant, take other medicines or have a health condition.
How we judged it
Doesn't hold up: Good studies looked and found no benefit, or the claim is plainly false. We judge the claim as it is usually said online, not the habit itself. Trials assign people at random, so they can show cause; observed studies follow people and show a link, not proof. Last checked: October 2026.
The studies, in their own words
- Fenton & Huang, BMJ Open 2016
Promotion of alkaline diet and alkaline water to the public for cancer prevention or treatment is not justified.
- Fenton & Huang, BMJ Open 2016 (full text)
Studies show that while urine pH changes in response to diet changes, blood pH does not.
- Fenton et al. Nutr J 2011
A causal association between dietary acid load and osteoporotic bone disease is not supported by evidence and there is no evidence that an alkaline diet is protective of bone health.
More claims, checked
- Doesn't hold upA glass of red wine for your heart
- Doesn't hold upHigh-dose vitamin D for everyone
- Doesn't hold upYou need 8 glasses of water a day
- Backed by trialsA 10-minute walk after meals
- Partly trueIntermittent fasting and time-restricted eating
- Partly trueApple cider vinegar before meals
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