Nut-Based Better Than Cereal-Based Snacks for Blood Sugar Control in Prediabetes
High-protein nut-based snacks cause a smaller rise in blood sugar levels than high-carbohydrate cereal-based snacks in overweight people with prediabetes, a randomised study reports.
Remarkably, consuming the high-protein nut-based snack with white bread reduced blood sugar levels by 30% compared to eating white bread alone.
The study, “A higher-protein nut-based snack product suppresses glycaemia and decreases glycaemic response to co-ingested carbohydrate in an overweight prediabetic Asian Chinese cohort: the Tû Ora postprandial RCT,” was published in the Journal of Nutritional Science.
Lowering the glycaemic index or glycaemic load of a meal can lower blood sugar levels and potentially reduce the risk of type 2 diabetes and cardiovascular disease. Previous studies show that including peanuts and tree nuts such as almonds in the diet may reduce the risk of type 2 diabetes.
Nuts are good sources of plant protein and polyunsaturated fats known to improve blood lipid profile. Nuts also reduce insulin resistance, inflammation, oxidative stress, and promote satiety. Interestingly, eating nuts with high-carbohydrate foods causes a smaller rise in blood sugar levels than eating high-carbohydrate food alone. Due to their health benefits, various nutrition guidelines recommend eating 28g of nuts daily as part of a healthy balanced diet.
Dried fruits with their high fibre, potassium, magnesium, and antioxidant compounds may also lower type 2 diabetes risk. However, few studies have investigated the impact of eating nut and dried fruit-based snacks on blood sugar levels in people with prediabetes.
A team of scientists in New Zealand sought to investigate the effect of eating a high-protein snack containing nuts and dried fruit with and without white bread on blood sugar levels in overweight prediabetic Chinese adults. They also investigated blood sugar levels in these participants after eating a high-carbohydrate cereal-based snack containing the same amount of calories with and without white bread.
All participants provided blood samples to measure their fasting blood glucose. They also underwent a dual-energy x-ray absorptiometry (DEXA) scan to measure their body fat levels, and magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) scans to measure abdominal, pancreas and liver fat.
Participants were given five different meals on five separate days, and their blood sugar levels were measured at 15-minute intervals over two hours. The meals included:
- A high-protein nut-based snack bar
- A high-carbohydrate cereal-based snack bar
- A high-protein nut-based snack bar eaten with white bread
- A high-carbohydrate cereal-based bar eaten with white bread
- White bread only
The high-protein nut-based snack bar, providing approximately 241 kcal, contained almonds, peanuts, dehydrated apple, dehydrated blueberry, chicory oligofructose, rolled oats, kawakawa leaves, sunflower oil and soya lecithin. Conversely, the high-carbohydrate cereal-based snack bar, providing approximately 235 kcal, contained rolled oats, white flour, canola oil, rice malt syrup and baking soda.
A total of ten adults, two males and eight females, with a mean age of 47 years and a body mass index of 25.5, were enrolled in the study. The mean fasting blood glucose was 6.0 mmol/L, indicating prediabetes. All participants had high abdominal fat, and half of the cohort had higher than normal pancreas or liver fat.
Participants’ average fasting blood glucose before eating all meals was similar. However, the average blood glucose levels at 60 mins and 120 mins after eating the meals was significantly lower for the high-protein nut-based snack than all other meals. Remarkably, the average blood glucose levels at 60 mins and 120 mins after eating the high-protein nut-based snack was approximately 6.5-fold and 10-fold lower, respectively, than the high-carbohydrate cereal-based snack.
Furthermore, eating the high-protein nut-based snack with white bread reduced blood glucose levels by 30% compared to eating white bread alone. Interestingly, when participants ate the high-carbohydrate cereal-based with white bread, their blood glucose levels were not lower.
“The fibre of the test formulation is likely to have played a major role in our present study observations, since dietary fibre is strongly associated with improved insulin sensitivity and consequent lower circulating insulin and glucose levels, including in patients with established type 2 diabetes.
Soluble fibre is known to increase distension within the stomach and viscosity in the small intestine and decrease the rate of nutrient absorption. Hence, CHO [carbohydrate] absorption and postprandial appearance of glucose in blood is significantly altered,” the scientists wrote.
The levels of fat in the participant’s pancreas and liver were varied. After eating all meals, those with higher pancreas and liver fat content experienced significantly higher rises in blood glucose levels than those with lower fat content.
“Also of note in our present trial was the exaggerated postprandial [after eating] response to all meal treatments in the high-organ-fat sub-cohort….there was up to a 20% increase in area under the blood glucose curve over the 2 h test in individuals with… ectopic pancreas and/or liver fat infiltration,” they wrote.
The researchers highlighted two study limitations: only measuring blood glucose and including only one ethnicity.
Still, “in this study of overweight prediabetic Chinese adults, we showed that the incorporation of the recommended daily intake of mixed nuts (16-28 g) plus dried fruit into a higher protein, higher fibre, higher unsaturated fat snack formulation, in bar format, resulted in a significant suppression of glycaemic response, in strong contrast to an energy-matched high-cereal higher-CHO [carbohydrate] snack bar.
While this was as expected, even in this dysglycaemic [abnormal blood sugar] population, notably, the nut-based product also ameliorated the postprandial hyperglycaemia of a high CHO, high GI food item, name, WB [white bread]. Co-ingestion with the nut-based snack bar decreased the overall glycaemic impact by approximately 30% in this high-risk group, even though the total CHO content ingested was increased,” the scientists wrote.
Besides the beneficial effect of high-protein, nut-based snacks on blood glucose control, this study also shows that fat levels in the liver and pancreas may affect blood glucose levels.
“We have also shown preliminary data that support the hypothesis that the postprandial glycaemic response to a meal is dependent, at least in part, on fat deposition within key organs of pancreas and liver,” the team wrote.
The researchers recommend larger studies with multiple ethnicities to corroborate and further investigate these findings.
Eat a low glycaemic index diet is the best way to maintain healthy blood glucose levels. If you have prediabetes, it is better to choose low glycaemic foods more frequently than high glycaemic foods.
And when eating foods with a high glycaemic index such as white rice or white bread, pairing them with quality proteins and fat can significantly reduce blood glucose spikes. Remember though, that portion size matters.