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For Immediate Release: November 13, 2009

NW: Questions about body pH and cancer, METs, stevia

Week of December 14, 2009
Contact: Alice Bender, (202) 328–7744

Nutrition Wise
Karen Collins, MS, RD, CDN
American Institute for Cancer Research

Q: Can diet affect cancer risk by changing body pH?

A: The term pH is a measure of acidity or alkalinity. A number of books and supplement advertisements suggest that a “body pH” that is too high or too low can be responsible for cancer, diabetes, lack of energy and overweight. Following the recommended diet or taking the supplement being advertised supposedly can keep your pH right. However, no solid research supports such claims. There is no single measure of “body pH,” because our blood, mouth, urine and stomach all differ in acidity somewhat. Food choices may affect the pH of the urine, though research is not consistent even on that. Although it’s true that our body needs to maintain its pH within a relatively narrow range, we have many intricate body systems to take care of it without any effort on our part. Unless someone has kidney disease that prevents their system of acid–base regulation from working, you can forget about body pH. Instead, concentrate on the food choices that significantly lower cancer risk, such as eating plenty of vegetables and fruits that help with weight control and offer many protective nutrients, phytochemicals and fiber.

Q: When recommendations about exercise refer to METs, what does that mean?

A: METs (also known as metabolic equivalents) measure the intensity of any kind of physical activity. Moderate activity, such as walking at three or four miles per hour, water aerobics or general gardening, is defined as 3.0 to 5.9 METs by the 2008 Physical Activity Guidelines for Americans. Vigorous activity, such as race–walking or jogging at least five miles per hour or heavy gardening in which you feel your heart rate increase, is defined as 6.0 or greater METs. These guidelines say adults should accumulate at least two–and–a–half–hours of moderate activity each week; similar benefits can also come from 75 minutes a week of vigorous activity. For some people, activity defined on these scales as moderate may be so difficult that it is really vigorous activity, or may even be physically impossible. For them, basing their activity goals on other scales of intensity is recommended. Their physician or a certified fitness professional can teach them to judge intensity based on their heart rate. The federal guidelines note that people can also judge intensity simply by how it feels to them. Moderate activity feels like 5 or 6 on a scale of 0 (sitting) to 10 (highest effort possible); vigorous activity feels like 7 to 8 on that scale. Inactive, unfit adults should not do relatively vigorous activity when they first start to become active. People without diagnosed diabetes, heart conditions or arthritis and without dizziness, chest pain or joint pain do not need to consult a doctor to begin increasing activity. Others should see their doctor so they can get cleared for the right activity for them. Appropriate activity offers too many benefits – and feels too good – to pass up.

Q: Do stevia sweeteners offer any special advantage beyond being natural?

A: Stevia, now approved by the FDA for use as a sweetener, is currently available in several brands. Since it’s 200 to 300 times sweeter than sugar, it is essentially calorie–free in the amounts used. Keep in mind that “natural” on food labels has no legal definition. No research identifies any clinical advantage over other zero–calorie sweeteners. Like the others, it does not raise blood sugar and it seems that it does not promote dental cavities. Substituting sweeteners like this for a single teaspoon of sugar only saves 16 calories, but in foods or drinks with larger amounts of sugar, stevia and other zero–calorie sweeteners can make a significant calorie difference over time.



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