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updated: 6/14/2011 3:43 PM

Food a better source of potassium

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Q. I heard that coffee is one of the top sources of potassium in the U.S. diet. Is coffee high in potassium?

A. No, coffee is not nearly as high in potassium as many other foods. Coffee is one of the top five sources of potassium for U.S. adults, but that's because we drink so much of it and we don't eat enough of the foods that are the best sources of this important nutrient.

A potassium-rich diet helps to lower blood pressure, apparently counteracting to some degree the blood pressure-raising effects of sodium. Getting enough potassium may also help reduce bone loss with age; more research is needed.

Americans need to overcome two main obstacles to come closer to recommended levels. Fruits and vegetables are major sources of potassium, so working them into every meal to get at least seven servings each day is the first step.

We also need to expand our selection. Vegetables and fruits highest in potassium include spinach and other cooked greens, winter squash, white and sweet potatoes, tomato juice and sauce, bananas, citrus fruit, cantaloupe, dried apricots and raisins. Legumes (dried beans such as kidney and garbanzo) are also very high in potassium, as well as fiber and natural antioxidants that provide other health benefits.

In addition, choosing whole-wheat bread gives you two to three times the potassium of white bread.

Q. Should I try to follow a low glycemic index (low GI) diet to lower cancer risk?

A. You may have heard that eating foods with a high glycemic index (GI) makes blood sugars go up, causing increased levels of hormones like insulin that seem to promote development of some cancers.

However, while those effects have been seen in short-term studies and do make sense in theory, longer-term studies do not show consistent impact on hormone levels. There are plenty of reasons for the confusion.

Although you can find lists of foods with their GI value in books and on websites, actual blood sugar-raising effects of foods vary substantially with how they are cooked and whether they are eaten alone or along with sources of protein, fiber or fat, all of which blunt the effect.

Furthermore, a large portion of a "low GI food" could end up raising blood sugar as much as a small portion of a "high GI food."

Rather than focus specifically on the glycemic index of your diet, aim for an overall strategy to avoid elevated insulin with a diet that supplies nutrients and phytochemicals that reduce cancer risk.

To decrease insulin resistance, accumulate at least 30 minutes of moderate physical activity throughout the day, control portion sizes even of "healthy" food to achieve and maintain healthy weight, and make vegetables, fruits, whole grains and beans the largest part of your plate.

People with type 2 diabetes or the insulin resistance of pre-diabetes and polycystic ovary syndrome (PCOS) may be especially sensitive to foods' blood sugar-raising effects, but best advice for now seems to involve more than choosing low GI foods.

• Provided by the American Institute for Cancer Research. Learn more about the group and its New American Plate program at