The RCT, conducted by Peking University and supported by the Key Projects of Beijing Science & Technology, is said to be the first to trial the effects of the ingredients on pre-diabetic individuals.
It showed that individuals who had taken the mixture had reduced glucose, insulin, and c-peptide levels, which are all interlinked.
This is because insulin and c-peptide levels are regulated by the glucose levels.
Findings of the study were published in the Journal of Functional Foods.
Sixty-five pre-diabetic subjects aged 45 to 65 completed the RCT which took place between October and November 2018.
As pre-diabetics, their fasting plasma glucose was in the range of 5.6 to 6.9 mmol/L or haemoglobin A1c (the average level of blood sugar) levels in the range of 5.7% to 6.4%.
The experiment group took a brown powder containing 0.5g of mulberry leaf extract and 1.0g of white kidney bean extract with 100g of white bread and 200ml of plain water.
Their blood samples were then collected at the 30th, 60th, and 120th minute.
The results showed that the post-meal glucose level in the experiment group had lowered, especially at the 30th and 60th minute.
However, at about the 90th min onwards, the glucose level in the experiment group started to increase and even surpassed that of the control group.
Overall, when measuring the ‘area under a curve’ between the 0 and 120th minute, there was a 38.19%, 40.55%, and 40.21% drop in the glucose, insulin, and c-peptide level of the experiment group.
No long-term effect?
Aside from the 120 minutes trial, the researchers also conducted a four-week RCT, however there was no significant improvements in the glucose level.
In the four-week RCT, the same group of individuals from the experiment group was required to consume 1.5g of mulberry leaf and white kidney bean extract mix three times per day after their usual meals.
On the 15th and 29th day, all subjects ate 100g of white bread and 200ml of plain water in 10 minutes. On these two days, their blood samples were collected 30, 60, and 120 min after they started the meal.
Findings showed that there was a fluctuation in glucose, insulin, and c-peptide levels in the experiment group when the measurements were taken on these two days.
For example, although the glucose level on day 15 of the trial saw a drop from the baseline level, it increased again on day 29 of the trial.
“A potential explanation for our results was that the duration of MWEM supplementation might not have been enough to significantly improve glycaemic control, which might be partly due to the long lifespan of HbA1c (average blood sugar level in the past two to three months) and glycated serum protein (GSP) (an intermediate marker of glucose),” the researchers explained.
The researchers believe there is a need for future trials to be conducted over a longer period so as to find out the optimal duration for the supplementation to work.
The researchers said that mulberry and white kidney beans could have lowered the glucose level by decreasing the digestion and absorption of carbohydrates.
The bioactive compounds involved are α-amylase inhibitor in the white kidney beans and 1-deoxynojirimycin in mulberry leaves.
These compounds could have blocked the active site of the starch-degrading enzymes in the digestive tract, in turn decreasing the digestion and absorption of carbohydrates.
The researchers said that there was a need for future studies to find out the optimal dose, proportion of ingredients used, and the optimal duration of consumption for achieving the best results.
They also added the need to recruit more subjects for future trials.
“Although we confirmed that the mulberry leaves and white kidney bean extract mix can help to decrease almost all the indicators mentioned above in pre-diabetic individuals, the additive effects cannot be judged from the evaluation of a single combination of the extracts,” the researchers explained.
“For this purpose, further studies using both the combination of the extracts with different proportions and each extract separately with different doses are needed,” they said.
Source: Journal of Functional Foods
Effects of mulberry leaf and white kidney bean extract mix on postprandial glycaemic control in pre-diabetic subjects aged 45–65 years: a randomized controlled trial
Authors: Yan Liu and et al