Lower-Limit of BMI, Tofu as a Source of Calcium & Yogurt as Fruit

Q: Why is there a lower limit set for a healthy body mass index (BMI)? Isn’t the lowest possible weight the healthiest?
Q: Is it true that tofu is a good source of calcium?
Q: Does the fruit in yogurt count as a serving of fruit?


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

Q: Why is there a lower limit set for a healthy body mass index (BMI)? Isn’t the lowest possible weight the healthiest?
A: Excess weight raises risk of cancer, diabetes and heart disease, but weight that is too low can be unhealthy also. Severely restricted eating, associated with a BMI less than 18.5, usually means that nutritional needs are not met. Weight this low is also tied to eating disorders. In some cases, excessively low weight may not cause poor health, but may be a sign of poor health, as in some respiratory and other chronic illnesses. Studies consistently link low BMI with osteoporosis and low bone mineral density. Examples of low weights associated with unhealthy BMIs are someone who is 5 feet 5 inches tall and weighs 105 pounds or less, and someone who is 5 feet 9 inches tall and weighs 120 pounds or less. Note that standard cut-offs defining healthy and unhealthy BMIs do not apply to children, teenagers, athletes, and pregnant women.

Q: Is it true that tofu is a good source of calcium?
A: The calcium content of tofu depends on how it is made. Tofu is made by curdling soymilk, just as cheese is produced by curdling dairy milk. If calcium sulfate is used to make tofu it can be a good source of calcium, with at least 400 milligrams (mg) in a four-ounce serving (about one-half cup). That’s even more than you’d find in a cup of milk (which has about 300 mg). The recommended daily total of calcium is 1,000 mg for most adults (1,200 mg for those over age 50). Tofu made using nigari (magnesium chloride) provides only a small amount of calcium, and tofu made with a combination of calcium sulfate and nigari provides some calcium, but not as much as a cup of milk. If you are looking for tofu with calcium, make sure you check the label.

Q: Does the fruit in yogurt count as a serving of fruit?
A: Most commercial fruit yogurts contain about two tablespoons of fruit preserves per serving, too little to be considered a fruit serving. One serving of fresh, canned or frozen fruit is a half-cup. A quarter-cup of dried fruit (such as raisins) is also considered a serving. For a more nutritious fruit yogurt that includes a serving of fruit, spoon some plain yogurt into a bowl and add a half-cup of one or more of your favorite fruits. You can flavor your yogurt with a little vanilla and a teaspoon of sugar, or simply start with vanilla yogurt. Your home prepared fruit yogurt will be higher in fiber and vitamins, and fresher tasting. It may also be lower in calories and less expensive. According to the American Institute for Cancer Research, eating an abundance of fruits and vegetables each day is one of the most important steps we can take to lower our risk of cancer. Finding ways to add an extra serving or two of fruit to our diets is worth the effort.

Reprinted with permission from the American Institute for Cancer Research www.aicr.org

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