Much has been said about the dietary factors that may contribute to the development of type 2 diabetes. Now a lot of new research gives us a clearer picture of the specific factors involved in this global health problem – and it sure is interesting…
Registered dietician Dr Ingrid van Heerden reports back on a talk by Prof Renée Blaauw, presented at the South African Sugar Association’s Nutrition in Non-Communicable Diseases Prevention Roadshow in 2015.
Type 2 diabetes is associated with chronic, low-grade inflammation, particularly in fat tissue. Signals from the inflamed tissue interfere with the working of insulin and promote insulin resistance – the forerunner of type 2 diabetes. When this type of inflammation occurs, thin and obese people react differently.
Thin people produce macrophages, a type of white blood cell that engulfs and removes harmful components in the body, and which have anti-inflammatory effects. The fat tissue of overweight and obese people, on the other hand, produces inflammatory cytokines – proteins that either regulate or interfere with cell signalling.
The fact that cytokines can have either a positive or negative effect, particularly when inflammation is present, has been linked to the development of insulin resistance. If this isn’t counteracted by a healthy diet, weight loss and exercise, it can progress to type 2 diabetes.
Strategies to reduce inflammation in the body include weight loss and eating plenty of protective vegetables, fruits and whole grains.
Protein intake and type 2 diabetes
Research shows that a high protein intake promotes weight loss which, in the short term, improves glucose control. However, long-term studies show that a high-protein intake could be risky.
In a 12-year follow-up study with more than 27,000 participants, it was found that high-protein diets caused an increased risk of type 2 diabetes. This result is a direct contradiction of the message proposed by promoters of high-protein, high-fat slimming diets who maintain that these diets will reduce the risk of type 2 diabetes.
During the study, conducted in Sweden among subjects between the ages of 45 and 74, dietary data was collected in order to determine the macronutrient intake (i.e. the protein, fat and carbohydrate intake) of the population.
When the subjects’ protein intake was increased, thus replacing fat or carbohydrate in the diet, the risk of developing type 2 diabetes increased by 67% in the group of people eating the most protein (mainly processed meats and eggs). Interestingly, the study participants who ate more carbohydrates or fats didn’t show this increased risk of type 2 diabetes.
The researchers also found that the subjects who ate more fibre-rich bread and cereals (grains) were less likely to develop type 2 diabetes, which lead them to suggest the following: “Replacing protein with carbohydrates may be favourable, especially if fibre-rich breads and cereals are chosen as carbohydrate sources.”
This recommendation was supported by a meta-analysis done by researchers in Norway who consulted 16 studies that investigated the influence of various types of grains on the risk of developing type 2 diabetes.
Fibre and reduced risk of type 2 diabetes mellitus
In view of the positive findings reported by the Norwegian researchers, Prof Blaauw identified another meta-analysis conducted in China that combined the results of 17 other studies to determine if dietary fibre can help to protect us against type 2 diabetes.
In total, these combined study results showed that dietary fibre can decrease the risk of developing type 2 diabetes by 19%, and that cereal fibre and insoluble fibre (as found in unprocessed wheat, for example) can lower the risk by 23% and 25%, respectively.
Yao and co-workers identified what’s called a “dose-response effect” for dietary fibre. This means that, as the dose of a beneficial compound (a food, a medication or a nutrient) increases, so does the beneficial effect.
In the case of the study by Yao et al., people eating 15g of dietary fibre a day had a 2% reduced risk of developing type 2 diabetes, while people consuming 35g of dietary fibre a day reduced their risk by 34%.
How can we increase our dietary fibre intake?
This high level of fibre in the diet mirrors the dietary patterns of our ancestors, and some rural people who still follow a diet rich in unprocessed grains. A fibre-rich diet also contains very little animal protein. These populations had/still have a low incidence of type 2 diabetes – something that’s often been ascribed to their intake of unprocessed grains, wild vegetables, roots, nuts and fruits.
While it may not possible to return fully to the eating habits of our ancestors, we can make a concerted effort to increase our dietary fibre intake by eating high-fibre foods as often as possible. Try to select unprocessed foods that are rich in dietary fibre, and low in fat and salt.
Legumes (beans, peas, lentils, soya and products made from soya beans), home-cooked oats, quinoa, brown rice, unsifted wheat, sorghum, millet and maize, breads with a high fibre content, and oat or wheat bran, should help you achieve an intake of 35g of dietary fibre a day.
Slowly increase dietary fibre
It wouldn’t be wise to change from a typical Western diet (based on highly processed “white” grains and cereals) to traditional grains overnight, as this is guaranteed to cause digestive problems, which may put you off dietary fibre for life!
Start off slowly by introducing one item of high-fibre food to your diet a week, such as 1 teaspoon of wheat bran added to your breakfast cereal, fruit juice or smoothie. Continue for 1 to 2 weeks until your digestive tract and its population of microorganisms have adjusted to handle the extra 5g of daily dietary fibre.
Now add a bit more fibre to your diet. For example, add a small serving of legumes which, when properly prepared, shouldn’t cause bloating. (Soak the legumes overnight and discard the water. Boil in water and discard the water. Then boil again in water until soft. Allow the legumes to soak up sufficient water with the second cooking to be soft and digestible.)
By slowly adding fibre-rich foods to your diet over a period of 2 to 3 months, you’ll reach the desired level of intake. In most cases, the transition will be relatively painless.
If you develop symptoms of discomfort and bloating when you increase your dietary fibre intake, despite a careful, gradual introduction, you may be intolerant or allergic to soya or gluten. If this is the case, it’s important to have tests done to confirm your allergy or intolerance. Consult a registered dietician to assist you with a diet that avoids the offending foods without causing any other complications.
1. Aune D et al, (2013). Whole grain and refined grain consumption and the risk of type 2 diabetes: a systematic review and dose-response meta-analysis of cohort studies. Eur J Epidemiol, 28(11): 845-58.
2. Blaauw R (2015). Dietary Factors for the Prevention of Diabetes Mellitus. Lecture presented on 12 February 2015, at the SASA Nutrition in NCD Prevention Roadshow, Pretoria.
3. Ericson U et al, (2013). High intakes of protein and processed meat associated with increased incidence of type 2 diabetes. Br J Nutr, 109(6): 1143-53.
4.Yao B et al, 2014. Dietary fibre intake and risk of type 2 diabetes: a dose-response analysis of prospective studies. Eur J Epidemiol, 29(2):79-88.