Vegan for Life - Jack Norris [72]
Some nutritionists believe that people who cook with olive oil, which is rich in monounsaturated fat, are likely to consume more vegetables (because the olive oil makes them taste so good). So it may be that vegetables are the protective factor and olive oil is just an innocent bystander. But olive oil also contains compounds that affect blood-clotting factors associated with heart disease risk.12 This suggests that small amounts of olive oil could be beneficial—or at the very least not harmful. While nobody knows exactly how much fat is ideal, it seems clear that a very low-fat diet is not the answer for everyone who needs to reduce disease risk.
Another type of fat in foods—trans fats—should definitely be avoided.13 Although small amounts of trans fats are found naturally in foods, most comes from processed foods made with partially hydrogenated fats. Hydrogenation is the process that turns vegetable oils into solid fat. Consuming trans fat raises the levels of bad LDL-cholesterol, reduces protective HDL-cholesterol, and is associated with a higher risk of both heart disease and diabetes. The American Heart Association recommends limiting trans fat to 1 percent of total calories. That’s such a tiny amount that practically speaking, it means you should just avoid all foods that list “partially hydrogenated” oils on the label. (If the label says “fully hydrogenated” or “hydrogenated,” the fats have been turned into saturated, not trans, fats. And it’s still a good idea to avoid saturated fats.)
Although the amount of trans fat in a food must be listed on the label by law, if the amount is less than ½ gram, the label can say that the food contains “0” grams of trans fat. Since the upper limit for trans fat intake on an 1,800-calorie diet would be two grams per day, eating foods with small amounts of trans fat can add up quickly.
THE GLYCEMIC INDEX: HOW CARBOHYDRATES AFFECT DISEASE RISK
Carbohydrates are digested and absorbed into the bloodstream as glucose, sometimes called blood sugar. When glucose levels rise, the hormone insulin is released into the blood. Insulin helps cells absorb fat and glucose from the blood, allowing the cells to use these nutrients for energy. Some carbohydrates are converted to glucose more gradually than others. The glycemic index (GI) is a measure of how quickly carbohydrates are broken down and absorbed into the blood. A meal with a high GI causes a surge in the release of insulin, which is associated with increased risk for CVD, diabetes, and possibly cancer.
Foods with a low GI can help with weight control since they help promote the use of body fat for energy, and they also tend to be more satisfying.14 Diets that are very high in protein are based on the idea that carbohydrates—because of their effects on insulin—are responsible for weight gain. But vegans are typically closer to their ideal body weight than omnivores, despite their higher carbohydrate intakes. And the PCRM studies showed that people on very high carbohydrate diets lose weight and have better blood-glucose control.
The key is to choose carbohydrate-rich foods with low GIs, which means eating more unprocessed, whole plant foods in place of refined carbohydrates. Most types of processing seem to affect the GI. For example, while beans typically have a low GI, the index tends to rise the longer the beans are cooked. And grinding grains into flour increases the GI. The amount of fiber in a food affects its GI, but other factors, some of them fairly obscure, are even more important.
In fact, sometimes the glycemic index makes no sense. Because the type of starch in a food impacts its GI, pasta made from white flour actually has a lower GI than brown rice.
And the glycemic index doesn’t always tell the whole story about the effects of a food on blood glucose. Some foods have a high GI, but they contain so little carbohydrate that it doesn’t matter. Carrots are a prime example.
Finally, foods that