The humble bean and lentil could provide a simple way of helping people with type 2 diabetes to control their blood sugar levels and might even reduce their risk of heart attacks and strokes.
Researchers have found that compared with a diet rich in whole grains, eating beans and lentils every day led to small drops in an important measure of blood sugar as well as in blood pressure and cholesterol levels.
In the study carried out in Toronto, Canada, participants were put on a bean, lentil and chickpea diet for three months and their estimated 10 year risk of cardiovascular disease fell from 10.7% to 9.6%.
‘We know from our previous research that foods low on the glycemic index scale are helpful in lowering blood glucose levels,’ said Dr. David Jenkins, lead author of the study and director of Risk Factor Modification Centre at St Michaels Hospital.
‘But this is the first study of its kind to specially look at legumes’ effect on cardiovascular risk factors and find they also have a blood pressure lowering effect in diabetic patients,’ he added.
Dr. Jenkins said that focusing on the health impact of a specific food like legumes, among the lowest glycemic index foods, rather than the glycemic index as a whole, simplifies the take home message for patients.
The glycemic index was founded by Dr. Jenkins and is used to measure the extent to which a particular food will raise blood sugar levels. Foods high on the glycemic index scale are ones that cause a spike in blood sugar levels such as white breads and sugary treats. Those low on the index have a stable effect on blood sugar levels and include foods like legumes, apples and berries.
The study randomly assigned 121 patients with type 2 diabetes to one of two groups. The control group ate a healthy but not a low glycemic index diet that included more insoluble fibre in the form of whole wheat grains. The test group was given a low glycemic index diet specifying eating at least one cup of legumes per day.
The participants’ blood pressure, body weight, blood glucose levels, blood fat and hemoglobin A1c (HbA1c), the gold standard for diabetes control, were measured before and after the three month study.
The results showed a beneficial effect on all measurements except blood pressure for the control group, whereas the test group had a beneficial effect on all measurements as well as a significant reduction in HbA1c values and risk for coronary heart disease, both driven by a reduction in blood pressure.
‘Legume consumption of approximately one cup per day seems to contribute usefully to a reduction in blood pressure which is hugely important for diabetic patients. High blood pressure is a big contributor to renal failure in these patients, and so if you can control both their blood pressure and glucose levels together, you have a very powerful treatment advantage,’ said Dr. Jenkins.
Separately, Dr. Jenkins’ colleague Arash Mirrahimi, a research assistant at the Risk Factor Modification Centre, found that people who ate foods high on the glycemic index scale were up to 14% more likely to be at risk for an acute heart attack or death due to coronary heart disease than those who ate foods low on the index.
Mirrahimi and colleagues reviewed and pooled results from 12 studies that looked at the risk of having coronary heart disease based on the types of diets participants were eating.
They found that women who ate higher glycemic index diets were particularly susceptible and had a 26% higher risk for coronary heart disease than women with lower glycemic index diets.