Diet plays a critical role in the management of many chronic diseases. It is well known that individuals with type 2 diabetes (T2D) need to pay close attention to foods rich in carbohydrates to better manage their blood sugar. Usually, individuals are told to increase their dietary fiber intake which is associated with better glycemic control and limit their overall carbohydrate consumption. However, there are many other cooking strategies available to reduce the glycemic response to meals rich in carbohydrates and with a high glycemic index, such as adding fats, proteins, or vinegar, modifying the cooking or preparation processes, and even the selection and storage of foods consumed. The aim of the present narrative review is to summarize some of these existing strategies applied to the cooking process and their ability to modulate glycemic response to meals in individuals with T2D.
The increase in the global prevalence of type 2 diabetes (T2D) and associated chronic diseases has prompted a lot of research into possible strategies to reduce its impact on society. Healthy eating is an essential component of treatment, and it is fundamental to identify and implement effective dietary strategies to prevent and treat the progression of the disease.
For people with T2D, nutritional goals should be the same as for the rest of the population: a healthy, balanced diet, adapted to each individual and incorporating foods from all groups. In addition to that, patients with T2D need to pay special attention to foods rich in carbohydrates that may be included in each meal, to avoid rapid changes in blood glucose.
According to the American Diabetes Association, the total amount of carbohydrates in a meal is the most important determinant of postprandial glycemic response. However, the quality of carbohydrate-rich foods may have additional benefits on post-meal blood glucose levels. One of the most common and usual ways of measuring the glycemic effect of food is by using the glycemic index (GI). This scale ranks a carbohydrate-containing food or drink by how much it raises blood glucose levels, compared with the effect caused by eating the same amount of glucose or white bread as a baseline. On the other hand, the concept of glycemic load (GL) refers to the hyperglycemic effect of a food, in this case, according to the amount of carbohydrates contained in the portion. However, the application of GI and GL concepts has important limitations, since there is a high intra- and interindividual variability in the glycemic response. One of the reasons is the high variability of dietary and cooking factors that can modify the glycemic index of foods, therefore influencing the glycemic response (GR). These include the combination of foods with different nutritional compositions, to handling techniques, and cooking processes. In the case of T2D, those that minimize GR are noteworthy.
This narrative review collects the evidence published to date on the ability of certain dietary and cooking strategies to reduce the GR of foods rich in carbohydrates. The objective is to review the magnitude of the impact that they can have and to reveal those that can be carried out in a simple and practical way on a day-to-day basis, both to help health care professionals when giving recommendations, and people with T2D.
Methods
The methodology of the current narrative review was based on searching the PubMed and Cochrane Library databases. The search was conducted from March 2021 to December 2021 with the use of different keywords related to diabetes and combinations, taking different spelling of search terms into consideration such as: (“glycemic/glycaemic index” OR “glycemic/glycaemic load” OR “glycemic/glycaemic response” OR “glycemic/glycaemic variability” OR “blood glucose response” OR “glucose absorption” OR “postprandial glycemia”) AND (“cooking” OR “culinary techniques” OR “cooling” OR “resistant starch” OR “retrogradation” OR “diet therapy” OR “dietary strategies”) AND (“type 2 diabetes mellitus” OR “diabetes mellitus” OR “diabetes management” OR “insulin resistance” OR “insulin sensitivity” OR “antidiabetic activity”), adding relevant cited sources and cross-references. Subsequently, titles, abstracts and finally full-text articles were examined by the scientific team about the suitability of the articles in terms of content and, in a subsequent step, in terms of quality. For the purposes of this review, studies included were limited to those published in English, conducted in healthy or individuals with T2D and carried out in the last 30 years.
Results
Combination of foods rich in carbohydrates and foods with different nutritional profiles
It is known that the GR of a food can be influenced by the simultaneous intake of other foods with a different nutritional profile. Specifically, the presence or combination of foods rich in fiber, fat and/or protein, or the addition of vinegar to foods rich in carbohydrates delays the so-called gastric emptying. That is, the combination of foods rich in carbohydrates with foods with a different nutritional profile (each with its corresponding absorption speed), slows down the time it takes for food to pass from the stomach to the intestine, slowing down the absorption of food and giving a lower GR. Below, is a detailed description of how the combination of foods rich in carbohydrates with foods with a different nutritional profile (fiber, fat, protein, and acetic acid) can particularly affect GR.
Fiber
Dietary fiber is a type of carbohydrate of plant origin present in fruits, vegetables, legumes, seeds, nuts and whole grains resistant to the action of digestive enzymes, without being able to be digested by the body and, therefore, without direct influence on the GR. It reaches the large intestine intact, where the intestinal bacteria will be able to metabolize, generating short-chain fatty acids (butyrate, propionate, and acetate) that are beneficial for the body. The higher fiber content of a meal can help lowering the GI of a food.
In previous research it was observed that the GR of a food with a high GI can be reduced if it is combined with foods rich in fiber, especially those rich in soluble fiber. Comparing a breakfast with a high GI (2.2 ± 0.2g fiber) to another with a low GI (4.9 ± 0.5g fiber), a 46% decrease in GR was observed in the latter, measured as the area under the curve (AUC). In the study by Guzman G, et al., where they compared the GR generated after the consumption of fruit juice with and without pulp, and from an entire piece of fruit, those who ate the entire fruit presented a significant decrease in AUC compared to those who consumed fruit juice with and without pulp (689 ± 70.7 mg/dl, 892 ± 70.7 mg/dl, 974 ± 70.7 mg/dl, respectively).
