They're foods with big health benefits, yet they're often neglected, relegated to the back of the kitchen cupboard. Legumes - chickpeas, kidney beans, black beans, navy beans, lentils - help regulate blood sugar, lower cholesterol and blood pressure, and guard against heart attack and cancer.
Now, a new study in the August issue of Diabetologia adds to the growing evidence that beans are good for you, especially if you have diabetes. It seems that adding beans to your diet can improve blood glucose control.
More than two million Canadians have diabetes, a number that's expected to rise to three million by the end of 2010. What's more, the incidence of impaired fasting glucose, or pre-diabetes, is also on the rise. (People with impaired fasting glucose have a higher blood sugar level after an eight-to-12-hour fast than is normal, but not high enough to be diagnosed with Type 2 diabetes.
For people who have diabetes, controlling blood glucose is paramount in preventing long-term complications such as heart disease, nerve damage and kidney disease. For people with pre-diabetes, managing blood glucose levels can prevent a future diagnosis of Type 2 diabetes.
Diet is a key to blood sugar management, whether a person is taking diabetes medication or not. When added to a high-fibre diet or a low-glycemic diet (one with complex carbohydrates that allow the slow release of sugar into the bloodstream), legumes have been found to lower fasting blood glucose and insulin readings.
Research even suggests that eating legumes can substantially reduce the risk of developing Type 2 diabetes.
In the new study, researchers from the Risk Factor Modification Centre at St. Michael's Hospital in Toronto analyzed the results of 41 randomized controlled experimental trials to assess the evidence that beans benefit blood sugar control.
The trials were conducted in a total of 1,674 people with and without diabetes. The review included studies measuring blood glucose control when legumes were eaten alone, when added to a high-fibre diet, or when part of a low-glycemic diet.
When eaten on their own or part of a high-fibre or low-glycemic diet, legumes lowered fasting glucose and insulin levels. Legumes were also found to improve glycosylated hemoglobin (HbA1c), a marker for longer-term blood sugar control. (The HbA1c blood test provides an average of blood glucose measurements over the past six to 12 weeks.) In fact, when legumes were eaten as part of a high-fibre or low-glycemic diet, the significant reduction in HbA1c seen in people with Type 2 diabetes was comparable to that achieved by oral medications.
The blood-glucose-lowering effect of legumes was strongest for chickpeas. But benefit was also seen with black beans, pinto beans and red and white kidney beans. And it didn't take a large portion to see improvement in blood sugar control. Eating only ahalf cup (125 ml) lowered fasting glucose and insulin levels.
Legumes are an excellent source of fibre and vegetable protein, and contain slowly absorbed carbohydrate. With their low glycemic index, legumes slow the rise in blood sugar after a meal, fending off an outpouring of insulin.
Legumes are also a good source of many phytochemicals, some of which may aid in blood sugar control. Most beans are also chock full of folate, vitamin B6, magnesium, potassium, zinc and iron.
The health benefits of legumes go beyond diabetes control. Studies have revealed that eating legumes can help lower LDL (bad) cholesterol and reduce elevated blood pressure, and may even cut the risk of prostate and breast cancers.
It's a wonder, then, why legumes are so often neglected in our typical Western diet. Many of my private-practice clients tell me it's not because they dislike legumes. Instead, they don't know how to incorporate them into their diet, aside from making chili or opening a can of baked beans.
Legumes are one of the most versatile, nutritious and inexpensive foods available. You can buy legumes dried or already cooked in the can. If you buy them dried, you need to cook and soak them first. To save time, use the quick-soak method. Place washed beans in a large pot with three times the volume of cool water. Bring beans and water to a boil for two minutes, then remove from the heat. Cover and let stand for one hour, then drain and rinse in a colander.
If you prefer the convenience of canned legumes, you'll only have to drain them in a colander and rinse under cool running water to remove sodium and many of the carbohydrates that produce intestinal gas..
While beans don't always cause gas, some people are more sensitive to this potential side effect. If you're new to legumes, start slowly and gradually increase your portion size over a few weeks to give your gut time to adjust. If that fails, try Beano, a digestive enzyme supplement available in drug stores that breaks down the gas-causing sugars.
Health Canada advises eating beans and lentils in place of meat to reduce saturate fat and increase fibre. The Canadian Diabetes Association recommends adding legumes to your diet to help lower the glycemic index and increase the fibre content of your diet.
The following quick tips will help you add legumes to your meals on a regular basis:
Toss cooked legumes into leafy green and pasta salads.
Add chickpeas to your favourite Greek salad recipe for a boost of protein and fibre.
Serve soup made from dried beans or lentils. Try minestrone, split pea, black bean or lentil soup.
Make a mixed bean salad by combining red and white kidney beans with black beans.
Add cooked legumes to homemade or store-bought soups and stews.
Spread sandwiches with hummus, instead of butter or mayonnaise, before filling.
Add cooked chickpeas to grain dishes such as couscous or rice pilafs.
Add black beans to tacos and burritos. Use half the amount of lean ground meat you normally would and make up the difference with beans.
Add white kidney beans to a tomato-based pasta sauce for a Mediterranean-inspired meal.
Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is lesliebeck.com.