Once you've digested the reality that veggies, fruits and whole grains are the easiest forkway to health, it might be time to get really picky. Like, wrap your head around the fact that according to a growing body of research, apples rule over bananas, yams over potatoes and pumpernickel over whole wheat bread.This school classifies carbs according to something called the glycemic index, a measure that tells us how fast the digestive system turns a particular munchable into blood glucose (sugar).
White bread, jelly beans and short-grain white rice rate high on the index -- no surprises there. But some other foods rated high aren't so obvious: stuff like parsnips, dried dates, corn flakes and rice cakes. In the moderate group are buckwheat, sweet corn, pasta and cantaloupe; foods low on the index include lentils, plums, chickpeas and barley. Check out www.glycemicindex.com for complete info.
High blood glucose levels are toxic and have to be brought down quickly. To restore balance, your pancreas pumps out insulin, a hormone that moves glucose out of the blood and into your muscles and fat. If you constantly eat foods high on the glycemic index, you have to produce a lot of insulin to bring your blood glucose down. Chronic high insulin is associated with diabetes and heart disease, and there's some evidence that it contributes to cancer too.
But is sticking strictly to foods low on the index the be-all and end-all of health? As with most dietary rules, things aren't cut and dried. Foods high in fat won't raise your blood sugar quickly, but can have other negative effects. And fructose, a sugar low on the index, seems to encourage diabetes.
Moderate indulgence in foods rated high is OK, if you make sure to eat lots of stuff that's rated low at the same meal. Apparently, adding lemon juice or vinegar to a meal, say as salad dressing, helps keep blood sugar even. Cooking pasta al dente will also lower its glycemic hit.
Beans and veggies, as a rule of thumb, will temper the glucose-raising impact of your meals. Thankfully, chocolate is low on the index, but you gotta buy fair trade and watch out for the fat.
"It would generally be beneficial for people to keep their insulin levels low. There are all these correlations between cardiovascular disease and insulin. Just cutting out high GI foods doesn't have any particular benefit. You need to bring in the low GI foods while maintaining a high carbohydrate diet. I personally think disease prevention is the strongest place for looking at GI. Once we already have a disordered metabolism in a big way, dietary effects are relatively small in comparison to drugs. With prevention, relatively small changes are happening day in and day out."
THOMAS WOLEVER, MD, PhD, department of nutritional sciences, U of T, division of endocrinology and metabolism, St. Michael's Hospital
"If you have less insulin, you'll be less likely to store fat. The same foods that have a lower glycemic index act to lower blood triglycerides and cholesterol. When my clients start eating foods lower on the glycemic index, their mood improves, because there's a constant even release of sugar. And the fat starts coming off and sometimes cholesterol starts going down."
MARINA GANGE, certified nutritional practitioner
"Eating foods lower on the glycemic index helps people lose weight, because they're more satiated. People report feeling fuller longer, less hungry, and as they lose weight their sugar levels improve. It is indeed the case that acids help prevent quick blood sugar rises. That's probably why sourdough bread is low on the glycemic index. We'll probably be hearing about this soon. Sauerkraut might help. Pickled beets might help. The theory needs to be researched more. But I don't think acid is going to hurt anybody."
SANDI WILLIAMS, MEd, RD (registered dietitian), certified diabetes educator
"We are looking at different sugars and their effect on obesity and insulin resistance, the condition that occurs before the development of diabetes. We've found that we need to clearly watch for certain sugars such as fructose. It can cause insulin resistance, and that can cause high blood fat. Prepared foods have fructose as a supplement. It's added as a sweetener. Table sugar has fructose and glucose."
KHOSROW ADELI, professor of laboratory medicine, U of T, director, clinical biochemistry, Hospital for Sick Children