Onion Consumption May Slow Down Bone Loss

Tears of Joy

Sure, onions can add flavor to your favorite dishes. But did you know that they can help in preventing osteoporosis, too? Scientists at the University of Bern, Switzerland, have discovered that a chemical compound found in onions appears to retard bone loss.

Researchers analyzed the active chemical components of white onions and ascertained that a peptide called GPCS was most likely responsible for this benefit. This information adds to other studies, which have also found benefits in eating onions. Last month I told you about a study conducted at Cornell University that found that onions with the strongest flavor, such as New York bold onions, western onions, and yellow shallots, seem to inhibit the growth of liver and colon cancer cells (5/19/05 eTip, subject line: “Nothing to cry about”).

In the Swiss study, the researchers obtained a group of isolated bone cells from newborn rats and exposed the cells to parathyroid hormone to stimulate bone loss. They then exposed the treated cells to the peptide compound GPCS. They found that exposure to the compound helped to significantly inhibit the loss of bone minerals, including calcium.

This is great (if not surprising) news; onions contain the antioxidant polyphenol, specifically the flavonoid quercetin. It is widely believed that polyphenols play a role in preventing the onset of all sorts of serious health conditions — from certain cancers to cardiovascular disease. Now it looks like we can add osteoporosis to that list as well.

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Diet and Potassium

Q: I know that bananas, raisins, prunes, and potatoes are all good sources of potassium. But those foods are a concern for those of us who suffer from Type 1 diabetes and must maintain strict control over our blood sugar levels. Can you tell me some low glycemic sources of potassium that I might add to my diet?

JVW: You are right to be concerned. A food’s glycemic index rates the speed at which your body metabolizes carbohydrates and the food’s ability to increase blood sugar. Avoiding foods that create too much of an insulin reaction in your body is the key to controlling diabetes. Unfortunately, as you have found, many foods that are rich in potassium also rate high on the glycemic index.

There are other foods that are known to be rich in potassium, but please check with your doctor to make sure they are right to include in your diet, and to get details about how much or how often they should be added.

Sun-dried tomatoes are an excellent source of potassium. So are sweet potatoes, which are on the lower end of the glycemic index. Beet greens, celery, carrots, radishes, tomatoes, Swiss chard, squash, and spinach are other good sources and can be added as your diet permits. White beans or soy beans, seeds, and nuts, (which are also a good source of protein), are high in potassium, too.

Taking a potassium supplement may be your best bet if you can’t get enough potassium through diet alone. If you are following a low-carbohydrate diet and are not eating at least five to six servings of vegetables every day, make sure you take at least 400 to 500 milligrams of potassium daily.

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What is …the glycemic index?

The glycemic index rates the speed at which various carbohydrates are metabolized and ranks their ability to raise blood sugar.

Glucose is used as the reference point for the index, with a rating of 100 on the scale. Table sugar has a rating of 65; a bagel 72; sweet potatoes earn a 54; an apple ranks a 36, while watermelon comes in at 72. Basically, the higher the rating on the glycemic index, the bigger impact the food will have on your blood sugar level.

Yours in good health,
Amanda Ross
Managing Editor Nutrition & Healing

Sources:

Wetli HA, et al. “A -Glutamyl Peptide Isolated from Onion (Allium cepa L.) by Bioassay-Guided Fractionation Inhibits Resorption Activity of Osteoclasts.” Journal of Agricultural and Food Chemistry 2005; 53(9): 3,408-3,414.