At a wedding, a tablemate groaned, “This is all delicious—the bread, the pasta, the cake—but so many carbs! I’ve been trying to avoid them because I have a family history of heart disease.” I knew what she meant, since some research indicates that carbohydrates may be as dangerous to our hearts as the dreaded saturated fat.
However, a recent study in Archives of Internal Medicine confirmed that we needn’t renounce all carbs, just those with a high glycemic index (GI)—meaning those that cause rapid spikes in blood sugar and insulin levels, which can be hard on the body. Study finding: Compared with women whose diets included the fewest high-GI carbs, women whose diets included the most carbs with a high GI were about twice as likely to develop coronary heart disease (narrowing of the blood vessels that supply blood and oxygen to the heart).
Surprising: High-GI foods include not only the usual carbo culprits (white bread, sweets) but also some foods that we normally think of as healthful, such as brown rice.
After that wedding, I contacted James Shikany, DrPH, of the University of Alabama at Birmingham School of Medicine, who has studied the connection between GI and chronic diseases for many years. He explained that, over time, a diet full of high-GI foods can lead to chronic high blood levels of insulin. This can have multiple adverse metabolic effects—for instance, on cholesterol levels, blood clotting factors and body weight—potentially increasing heart disease risk.
Here’s what women need to know about GI to keep their hearts healthy or to minimize the danger if they already have heart disease…
Demystifying the Glycemic Index
Scientifically speaking, the glycemic index is a measure of how quickly and dramatically equal amounts (usually 50 grams) of various carbohydrate foods will raise blood sugar levels. Based on that, a food is ranked on a scale ranging from 0 (meaning it causes no alteration in blood sugar) to 100 (reflecting an extreme spike in blood sugar equal to that of pure glucose). A GI of 70 or more is considered high.
Tricky: Some high-GI foods don’t really deserve a bad rap. For instance, although watermelon is a healthful fruit, it rates a high GI of 72. Dr. Shikany said that this stems from a glitch in the GI concept that arises with foods that are relatively low in carbohydrates—because you would have to eat almost five cups of watermelon to consume 50 grams of carbs! To get around that problem, you also should consider the newer concept of glycemic load (GL), which takes into account a food’s GI and its standard portion size. A report from the Harvard School of Public Health classifies a high GL as 20 and up… a GL of 10 or less is considered low. Watermelon’s GL is a very reasonable four.
It would be convenient if we could just check product labels to learn a food’s GI or GL, but unfortunately such information is not listed. What’s more, food processing and preparation methods can affect those numbers. For example, cooking carrots increases their glycemic ratings because heat breaks down the cell walls, making the carbohydrate more available, Dr. Shikany said. Thus, we must dig deeper to figure out which foods are best and worst for our hearts.
You might assume that you can just follow the often-heard advice to stick mostly to complex carbohydrates, such as whole grains. Yet when it comes to GL, that doesn’t necessarily hold true. For example, the GL of mass-produced whole-wheat bread tends to be only slightly lower than that of white bread.
What matters more, Dr. Shikany said, is to have soluble fiber in your food. Soluble fiber slows digestion and absorption and thus helps keep blood sugar levels more stable. Good sources include barley, oats and wheat bran… beans of many types… certain fruits (apples, citrus fruits, mangoes, pears, strawberries)… some vegetables (asparagus, Brussels sprouts, turnips)… flax and psyllium seeds.
A great way to be sure that you’re eating a low-glycemic diet is to look up favorite foods at www.GlycemicIndex.com. This database from the University of Sydney in Australia lists the GL (and GI) of many foods. If a food has a GL of 20 or more, instead eat something similar that has a lower GL. Example: Rather than white rice (with a GL as high as 43, depending on brand) or even brown rice (with a GL as high as 33), eat pearled barley (with a GL of nine to 12).
Of course, I realize that you won’t always have time to check the database, so I asked Dr. Shikany for some simple low-GL strategies. His suggestions…
- Eat foods that are as close to their natural states as possible. For instance, the GL of apple juice is about 13, whereas raw apples have a GL of just four to six.
- Breakfast cereals in particular have a wide GL range. Rule of thumb: Anything puffed, ground or flaked tends to have a higher GL than oatmeal or All-Bran.
- Whenever you eat carbs, have some protein and a bit of fat at the same time. This slows carbohydrate absorption, keeping blood sugar levels more stable… and keeping your heart healthier.