A High-fiber diet feeds gut microbes, lowering blood sugar

High Fibre Essential to Lowering Blood Sugar

Updated May 29, 2024

Plenty of fibre: That’s long been the recommendation for a healthy diet. But why?

The primary rationale has been that fibre is made up of undigestible bulk that prevents people from eating unhealthy food — and helps keep the digestive tract regular. However, new research suggests that dietary fibres play a critical role in feeding the trillions of microbes that reside in our bodies, known collectively as the microbiome. Precisely, for people with type 2 diabetes, a high-fibre diet and a favourable gut microbiome can control patients’ blood sugar and body weight.

The Role of Fibre in Blood Sugar Regulation

Researchers in China pinpointed the specific “good” bacteria that ferment fibre into acids and ultimately improve insulin regulation. According to lead investigator Liping Zhao, chair of applied microbiology at Rutgers University, these bugs create an acidic microenvironment in the gut that helps beneficial, blood-sugar-lowering bacteria proliferate — and might even keep pathogens at bay. This discovery underscores the importance of dietary fibre in managing blood sugar levels and highlights the intricate relationship between diet, gut microbiota, and metabolic health.

Mechanisms Behind Fibre’s Benefits

New findings suggest that promoting the growth of fibre-loving bacteria may help manage type 2 diabetes. “The study gets at the mechanistic reasons of why these fibre-rich, plant-based diets may be helpful, especially in patients with type 2 diabetes,” Clare Lee, an endocrinologist at Johns Hopkins University, tells STAT News. “It’s an exciting step towards understanding potential mechanisms to help us prevent and treat diabetes.”

In the study, microbiologist Liping Zhao of Rutgers University and his colleagues fed a group of 27 type 2 diabetes patients a diet of whole grains, traditional Chinese medicinal foods, and prebiotics for up to 86 days, while a group of 16 patients ate a similar diet with less fibre. All patients were treated with the diabetes drug acarbose, which helps transform starch into a fibre.

For the first four weeks, haemoglobin A1c, a measure of blood sugar, fell in both groups. After day 28, however, those in the group that ate more fibre showed more significant drops in blood sugar levels compared with the individuals who ate less fibre. At the end of the study, 89 per cent of people on the high-fibre diet reached adequate blood sugar levels, while only 50 per cent did on the lower-fibre diet.

The Gut Microbiome and Blood Sugar

Scientists say they’ve found a direct connection between blood sugar and gut bacteria. By exploiting that connection with a very high-fibre diet, they’ve successfully treated a small group of people with type 2 diabetes. The finding could be important not only for the 100 million American adults with diabetes or prediabetes but also for anyone who’s trying to manage their weight.

What hasn’t been well understood is precisely how fibre gives you these benefits. Evidence has been mounting that fibre plays a vital role in the types of bacteria that thrive in our guts and how they work. Last year, new research from the Finnish Diabetes Prevention Study showed that people who ate more fibre had more of an anti-inflammatory chemical in their blood called indole propionic acid, which is made by gut bacteria. They were also less likely to go on to get type 2 diabetes.

“Overall, this study adds to what we know about how important the gut microbiota is when it comes to the development of some chronic diseases, like type 2 diabetes,” says Vanessa de Mello Laaksonen, PhD, an assistant professor in nutrigenomics at the University of Eastern Finland.

Fibre and Insulin Sensitivity

A high-fibre diet has been shown to improve insulin sensitivity, which is crucial for managing type 2 diabetes. Insulin sensitivity refers to how responsive the body’s cells are to insulin. When cells are more sensitive to insulin, they can more effectively take up glucose from the bloodstream, lowering blood sugar levels. Research has demonstrated that dietary fibre, particularly soluble fibre, can enhance insulin sensitivity by slowing down the digestion and absorption of carbohydrates, leading to a more gradual rise in blood sugar levels.

Types of Fibre and Their Benefits

There are two main types of dietary fibre: soluble and insoluble. Soluble fibre dissolves in water to form a gel-like substance, which can help lower blood cholesterol and glucose levels. Insoluble fibre, on the other hand, adds bulk to the stool and helps food pass more quickly through the stomach and intestines. Both fibre types are essential for overall health, but soluble fibre is particularly beneficial for blood sugar control.

Sources of High-Fibre Foods

Incorporating various high-fiber foods into your diet can help manage blood sugar levels. Some excellent sources of dietary fibre include:

Whole grains: Oats, barley, quinoa, and brown rice are fibre-rich and can help regulate blood sugar levels.
Fruits: Apples, pears, berries, and citrus fruits are high in soluble fibre and can aid in blood sugar control.
Vegetables: Broccoli, Brussels sprouts, carrots, and sweet potatoes are excellent sources of fibre.
Legumes: Beans, lentils, and chickpeas are fibre-packed and can help improve insulin sensitivity.
Nuts and seeds: Almonds, chia seeds, and flaxseeds are high in fibre and can provide additional health benefits.

Fibre Supplements and Blood Sugar Control

Fibre supplements can be helpful for individuals who struggle to get enough fibre from their diet alone. Supplements such as psyllium husk, inulin, and glucomannan have been shown to improve blood sugar control and support overall digestive health. However, it is essential to consult with a healthcare provider before starting any new supplement regimen.

The Impact of Fibre on Weight Management

In addition to its benefits for blood sugar control, a high-fibre diet can also aid in weight management. Fibre-rich foods tend to be more filling and can help reduce overall calorie intake by promoting a feeling of fullness. This can be particularly beneficial for individuals with type 2 diabetes, as maintaining a healthy weight is crucial for managing the condition.

Fibre and Cardiovascular Health

A high-fibre diet is also associated with improved cardiovascular health. Soluble fibre can help lower LDL (harmful) cholesterol levels, reducing the risk of heart disease. Given that individuals with type 2 diabetes are at a higher risk for cardiovascular complications, incorporating more fibre into the diet can provide additional protective benefits.

Practical Tips for Increasing Fibre Intake

Here are some practical tips for increasing your fibre intake:

Start your day with a high-fibre breakfast: Choose whole-grain cereals, oatmeal, or whole-wheat toast to kickstart your day with a fibre boost.
– Incorporate more fruits and vegetables: Aim to fill half your plate with fruits and vegetables at each meal.
– Choose whole grains: Opt for whole-grain versions of bread, pasta, and rice instead of refined grains.
– Snack on nuts and seeds: Keep a stash of almonds, walnuts, or sunflower seeds for a fibre-rich snack.
– Add legumes to your meals: Incorporate beans, lentils, and chickpeas into soups, salads, and stews.
– Stay hydrated: Drinking plenty of water is essential when increasing fibre intake to help prevent digestive discomfort.

Conclusion

The evidence is compelling: a high-fibre diet is beneficial for lowering blood sugar levels and managing type 2 diabetes. This conclusion is supported by an array of studies and expert opinions that underline the multifaceted role of dietary fibre in metabolic health.

Firstly, dietary fibre enhances the growth of beneficial gut bacteria, producing short-chain fatty acids like butyrate. These fatty acids have been shown to improve insulin sensitivity and reduce inflammation, which are critical factors in diabetes management. Dr. Liping Zhao, chair of applied microbiology at Rutgers University, emphasizes that “creating an acidic microenvironment in the gut helps beneficial, blood-sugar-lowering bacteria proliferate, which may keep harmful pathogens at bay and improve overall metabolic health.”

Furthermore, fibre’s role in slowing down the digestion and absorption of carbohydrates cannot be overstated. This mechanism leads to a more gradual rise in blood sugar levels, thereby preventing the spikes harmful to individuals with type 2 diabetes. According to a study published in the *Journal of Nutrition*, individuals who increased their soluble fibre intake experienced a significant reduction in both fasting blood sugar and HbA1c levels, markers crucial for long-term blood sugar control.

The link between fibre intake and reduced risk of developing type 2 diabetes is also well-documented. Research from the Finnish Diabetes Prevention Study found that participants who consumed more fibre had higher levels of indole propionic acid, an anti-inflammatory compound produced by gut bacteria. These participants were significantly less likely to develop type 2 diabetes, highlighting the preventive potential of a high-fibre diet.

Moreover, fibre’s benefits extend beyond blood sugar regulation, including weight management and cardiovascular health. A comprehensive review in the American Journal of Clinical Nutrition concluded that high-fibre diets are associated with lower body weight and reduced risk of cardiovascular diseases, which are often comorbid with diabetes.

Dr. Clare Lee, an endocrinologist at Johns Hopkins University, points out that “understanding the mechanistic reasons behind the benefits of fibre-rich, plant-based diets opens new avenues for preventing and treating diabetes.” This sentiment is echoed by numerous experts who advocate for dietary fibre as a cornerstone of diabetes management and overall health.

Incorporating a variety of high-fibre foods into your diet—such as whole grains, fruits, vegetables, legumes, nuts, and seeds—helps control blood sugar levels and contributes to a healthier, more balanced diet. Practical tips like starting your day with a high-fibre breakfast, choosing whole-grain products, and snacking nuts and seeds can make a significant difference.