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Harvard Commentaries
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Harvard Commentaries
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Food for Thought Food for Thought
 

Alkaline Diets and Cancer: Fact or Fiction?


January 16, 2013


By Stephanie Vangsness, M.S., R.D., L.D.N.
Brigham and Women's Hospital

Advocates of alkaline diets claim that they help you lose weight, increase your energy, and even reduce your risk of heart disease and cancer. While their arguments sound persuasive, they ignore all the facts.

The body performs any number of intricate balancing acts daily. One of them is to make sure that the body's fluids, tissues and cells aren't too acidic or alkaline, but stay in a healthy pH range. If you recall high school chemistry, pH measures the concentration of hydrogen in a solution. The more hydrogen, the more acidic it is (low pH); the less hydrogen, the more alkaline it is (high pH).

Proponents of alkaline diets claim that when the body's pH is too acidic, your risk for many conditions, including cancer increases. They also claim that eating too much of certain foods–animal protein, sugar, caffeine, and processed foods–makes your body more acidic and that changing what you eat will change your pH.

We know that people whose diets are high in fat and low in fiber are at higher risk of certain types of cancer. But claiming that restricting certain foods and eating others will make your pH “alkaline enough” to prevent cancer is more fiction than fact. Here are answers to questions I frequently get about these diets.

Can You Make Your pH More Alkaline?

Your body has a complex system of checks and balances to keep its pH in a normal and healthy range: 7.35 to 7.45. When your pH shifts outside this range and becomes too acidic or too alkaline, your body automatically corrects itself to bring things back to normal by:

  • Increasing or decreasing respiration — When you breathe more rapidly, you blow out more carbon dioxide. This raises your pH so it becomes more alkaline and less acidic. Conversely, slowing down your breathing causes you to release less carbon dioxide, which lowers your pH making it more acidic and less alkaline.
  • "Mopping up" excess hydrogen ions — Neutralizing substances in the blood, such as bicarbonate and hemoglobin, mop up excess hydrogen ions and prevent pH from becoming too acidic.
  • Eliminating the excess — Your kidneys excrete excess acidic substances into urine to prevent pH from becoming too low. Conversely, if your pH starts to become too high or alkaline, the body uses similar tools in reverse to bring down the pH.

The bottom line: The body fights hard to keep your pH balanced. It's nearly impossible to achieve and maintain a high-alkaline pH for a prolonged period of time.

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Can an Alkaline pH "Kill" Cancer Cells?

First of all, there are no human studies supporting alkaline diets for the prevention or treatment of cancer. Test-tube studies, however, have shown that some cancer cells grow faster in an acidic solution. They've also shown that some chemotherapy drugs become more effective if the area around a tumor cell is altered to be more alkaline. However, we can't assume that what happens in a test-tube also happens in the human body. In fact, the opposite effect could occur and have dangerous consequences.

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Can Diet Change the pH Balance of the Body?

The body's pH levels may change slightly as a result of eating some foods, but will remain in the tightly held range of 7.35-7.45. For instance, some fruits and vegetables as well as dairy products may raise the pH of your urine, whereas meat products and cranberries may lower the pH of your urine. However, even if you eat large quantities of these foods, your blood pH will barely change and only for a short time.

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Are Urine and Saliva pH Test Strips a Good Way To Measure the Body's pH?

The only way to directly measure the body's pH is by testing your blood. Testing your urine only tells you the pH of your urine. Urine is naturally more acidic and has a lower pH (~ 6.0). Similarly, saliva test strips only measure the pH of your saliva, not the pH of your blood.

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Can an Alkaline Diet Be Harmful?

Alkaline diets promote the exclusion of many foods. Excluding an entire family of foods can result in some vitamin and mineral deficiencies. You may also miss out on some potential anti-cancer benefits. A list of foods often restricted on an alkaline diet is listed below, along with reasons why these foods shouldn't be eliminated.

Food Group

Benefits of the Food Group

Fats and Oils
Provide essential fatty acids (EFAs). EFAs are needed to make healthy cells, maintain immunity, and combat inflammation.
Dairy
An excellent source of protein and vitamins, specifically vitamin D and calcium. Adequate vitamin D intake has been linked to increased survival from cancer.
Beans and Legumes
Rich in phytonutrients, substances also found in colorful fruits, vegetables, which help lower cancer risk and boost the immune system. Beans and legumes are rich in fiber, which is good for gastrointestinal health and may help prevent colon cancer. Also a good source of vegetarian protein. Protein needs are higher in cancer patients, especially those receiving chemotherapy.
Fruits
Contain phytonutrients, vitamins and fiber.

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Do Dietitians and Other Health Care Professionals Recommend Alkaline Diets?

No. Studies of alkaline diet are limited to animal and test tube trials. While research is currently in progress looking at the correlation between alkaline diets and bone health, there are unfortunately no major human studies in regards to alkaline diets and cancer at this time.

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Stephanie Vangsness, M.S., R.D., L.D.N., received her master’s degree in nutrition and health promotion from Simmons College, Boston. She is a senior clinical nutritionist at Dana-Farber Cancer Institute and Brigham and Women's Hospital.

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