Glucagon-like peptide 1 (GLP-1) is a hormone that plays a key role in regulating blood glucose, insulin secretion, appetite, and energy balance. It is mainly produced by the cells in the gut in response to food intake. However, in some metabolic conditions, such as obesity and type 2 diabetes, GLP-1 secretion may be impaired, leading to poor glucose control and increased risk of complications. A recent review published in The American Journal of Clinical Nutrition explores how dietary factors can influence GLP-1 secretion and offer a new perspective in diabetes and obesity treatment.
GLP-1: a promising target for metabolic disorders
GLP-1 has multiple beneficial effects on metabolic health. It stimulates insulin secretion from the pancreas, inhibits glucagon release, slows down gastric emptying, reduces food intake, and promotes weight loss. It also has protective effects on the cardiovascular system, the liver, and the brain. GLP-1 analogs, which are synthetic versions of the hormone that resist degradation by enzymes, have been approved as effective drugs for type 2 diabetes and obesity. However, these drugs are expensive, require injections, and may cause side effects such as nausea, vomiting, and pancreatitis. Therefore, enhancing endogenous GLP-1 secretion, which is the natural production of the hormone by the body, through dietary interventions may be a more feasible and sustainable approach.
Dietary factors that affect GLP-1 secretion
The review summarizes the current evidence on how different dietary factors can modulate GLP-1 secretion in various metabolic conditions, such as normal weight, overweight, obesity, impaired glucose tolerance, and type 2 diabetes. Some of the dietary factors that have been shown to influence GLP-1 secretion are:
- Macronutrients: The amount and type of carbohydrates, proteins, and fats in the diet can affect GLP-1 secretion. Generally, high-protein and high-fat diets tend to increase GLP-1 secretion more than high-carbohydrate diets. However, the quality and source of the macronutrients also matter. For example, complex carbohydrates, such as whole grains and fiber, may stimulate GLP-1 secretion more than simple sugars. Similarly, plant-based proteins, such as soy and pea, may have more potent effects than animal-based proteins, such as whey and casein. Moreover, unsaturated fats, such as olive oil and fish oil, may enhance GLP-1 secretion more than saturated fats, such as butter and lard.
- Micronutrients: Some vitamins and minerals may also have an impact on GLP-1 secretion. For instance, vitamin D, magnesium, zinc, and chromium have been reported to increase GLP-1 secretion in animal and human studies. However, the optimal doses and forms of these micronutrients for GLP-1 secretion are still unclear and need further investigation.
- Phytochemicals: These are bioactive compounds found in plants that may have beneficial effects on health. Some phytochemicals, such as polyphenols, flavonoids, and terpenoids, have been shown to stimulate GLP-1 secretion in vitro and in vivo. For example, quercetin, a flavonoid found in apples, onions, and berries, can increase GLP-1 secretion by activating G-protein-coupled receptors on the gut cells. Other phytochemicals, such as curcumin, resveratrol, and capsaicin, may also have similar effects.
- Prebiotics and probiotics: These are dietary components that can modulate the gut microbiota, which is the collection of microorganisms that live in the digestive tract. The gut microbiota can influence GLP-1 secretion by producing short-chain fatty acids (SCFAs), such as acetate, propionate, and butyrate, from the fermentation of dietary fiber. SCFAs can stimulate GLP-1 secretion by activating G-protein-coupled receptors and enhancing the expression of GLP-1 genes in the gut cells. Prebiotics, such as inulin, fructooligosaccharides, and galactooligosaccharides, are types of fiber that can selectively feed the beneficial bacteria in the gut and increase SCFA production. Probiotics, such as Lactobacillus and Bifidobacterium, are live bacteria that can colonize the gut and modulate the gut microbiota composition and function.
Implications and recommendations
The review suggests that dietary factors can have a significant impact on GLP-1 secretion and metabolic health. By choosing the right foods and nutrients, people with metabolic disorders, such as obesity and type 2 diabetes, may be able to boost their endogenous GLP-1 secretion and improve their glucose control and weight management. However, the review also acknowledges that there are many gaps and inconsistencies in the current literature and that more research is needed to establish the optimal dietary patterns, doses, and combinations of dietary factors for GLP-1 secretion. The review also emphasizes that dietary interventions should be tailored to individual characteristics, such as age, sex, genetic background, and metabolic status, as these may affect the response to dietary factors. Furthermore, the review calls for more studies on the long-term effects and safety of dietary factors on GLP-1 secretion and metabolic outcomes.