By Sheila Walker, R.D.
The incidence of Type 2 diabetes (T2DM) is increasing dramatically in Canada. This will have a detrimental effect on our society. The burden of diabetes on the individuals affected and on the Canadian Health Care System is enormous.
Prediabetes precedes T2DM and includes either increased fasting and/or postprandial glucose levels. Every year about 5-10% of those with prediabetes will progress to T2DM (1).
The increase in both T2DM and prediabetes is due to a number of factors including:
- An aging population
- The increased rates of obesity
- The low levels of physical activity
- 77% of new Canadians come from populations that have higher risks of T2DM.
Diabetes educators will play an important role in helping those at risk modify their progression to diabetes. This paper will outline some of the strategies that have been found to be effective in reducing this risk.
Evidence-based research has produced a number of strategies, including life-style modification and drugs. Three prospective studies have shown these interventions can prevent T2DM. The Diabetes Prevention Program (DPP) (2) and the Finnish Diabetes Prevention Study (3) have both determined that lifestyle changes (diet and exercise) can reduce progression by 58% in subjects with prediabetes. The Da Qing study (4) found that diet and/or exercise could reduce risk by 31-46%.
Three medications have been shown to help prevent the development of T2DM. Metformin (850mg BID) taken for an average of 2.8 years in the DPP reduced progression by 31%. The STOP-NIDDM study (5) showed Acarbose (100mg TID) reduced risk by 30%. The DREAM trial (1) has shown that Rosiglitazone (8mg daily) reduced risk by 60%.
Diabetes Reduction Strategies
1. Lose Weight
The DPP (6) reported that modest weight loss (7% of initial body weight) coupled with exercise clearly reduced risk. Controlled-calorie diets (1200-2000) with 25% fat were used. Self-monitoring (fat, calories, activity, weight) was an important part of the study.
2. Increase Activity / Reduce TV Time
Regular exercise increases insulin sensitivity. The DPP participants exercised a minimum of 150 minutes a week (moderate pace equivalent to brisk walking). In a study of more than fifty thousand nurses (7), every two hours of TV watching was linked with a 14% increase in risk of diabetes. Minimal activity or walking around the home led to a 12% reduction.
3. Eliminate Trans Fatty Acids
Dr. Bruce Holub, a professor of Nutritional Sciences at the University of Guelph has said that “trans fatty acids are 10-times more harmful than saturated fatty acids” (8). Trans fats tend to increase LDL cholesterol and decrease HDL cholesterol. Canadians consume 9-13 grams of trans fat per day – Dr. Holub suggests intake be restricted to 2 grams or less per day.
A 2001 study (9) which looked at the dietary records from the Nurses’ Health Study drew a link between consumption of trans fat and risk of T2DM. It should be pointed out however that it is difficult to assess disease risk from nutritional data (10).
Good fats, such as those in oils, nuts and fish appear to reduce risk. As prediabetes is associated with an increased risk of CVD, it would make sense to replace trans fats with the good ones.
4. Increase Whole Grain Consumption
High intakes of whole grains are associated with a reduced risk of T2DM. People who consume three servings per day are 20-30% less likely to develop T2DM over the next decade than those who consume less than three servings per week (11). As well, in individuals without diabetes, there appears to be an inverse relationship between whole grain consumption and fasting insulin levels.
5. Quit Smoking
Smokers are more likely to develop T2DM than non-smokers. One study has suggested that men who smoked 25 or more cigarettes daily had almost double the risk of diabetes as non-smokers (12). The association is unclear but may relate to the fact that smokers share similar risk factors for T2DM.
6. Assess Intake of Calcium and Vitamin D
The research in this area is described as ‘promising but not definitive’. In a study of 300 people age 65 or older (13), a third of whom had prediabetes, there was less rise in fasting blood sugar over three years in those given Vitamin D (700 IU per day) and calcium (500 mg per day) than a placebo.
7. Control Alcohol
A light to moderate alcohol intake has been associated with a reduced risk of T2DM. Data from the Nurses’ Health Study (1980 – 1996) suggest about three drinks per week for women (14). The Harvard School of Public Health suggests a drink a day for men is associated with reduced risk.
8. Include Nuts and Peanut Butter
There is a potential benefit from nut and peanut butter consumption. As part of the Nurses’ Health Study (15), women who ate 5 tbsp. of peanut butter each week reduced their risk of T2DM by over 20%. Women who ate 1 tbsp. of peanut butter or other nuts one to four times a week reduced their risk by 16%.
9. Control Red and Processed Meats
In women, higher intake of meat, especially bacon and hot dogs, increases their risk of T2DM (16). In men, processed and red meat was linked to an increased risk. A ‘western’ diet (red and processed meat, french fries, high fat dairy products, refined grains, sweets and desserts) increased T2DM risk whereas a ‘prudent’ diet (vegetables, fruit, fish, poultry and whole grains) offers protection (17).
10. Enjoy Some Coffee
High coffee consumption (7 cups per day) is associated with a reduced risk (18). This is difficult to explain but may relate partly to a reduced hepatic glucose output. Although this is an interesting finding, this result does not provide justification to suggest an increased coffee consumption. A high intake of boiled coffee has been shown to increase total and LDL cholesterol.
11. Individualize Carbohydrate Intake
The carbohydrate content should be individualized to meet nutrition goals and glucose targets. Reducing the meal carbohydrate will help to lower postprandial levels. Wolever and Mehling investigated the long-term effect of 3 different diets in subjects with IGT (19). The high MUFA diet (20% MUFA, 40% total fat, 45% carbohydrate) and the low GI diet (55% carbohydrate) significantly reduced mean postprandial levels as compared to the high GI diet (55% carbohydrate) over 4 months. A high MUFA diet may also be useful as a low calorie weight loss diet as it provides satiety.
12. Consider the Glycemic Index
The glycemic index has shown mixed results. The American Diabetes Association has concluded that the total amount of carbohydrate is more important than the source (starch or sugar) or type (low or high GI). The DPP trial did not appear to use the glycemic index (6). The Canadian Diabetes Association suggests choosing low GI over high GI foods within the same food category for those with T2DM (5).
The growing epidemic of T2DM is a call to action to help those at high risk. We know that modest weight loss and exercise works. The DPP has shown that long-term follow-up is essential to help motivate clients to meet their lifestyle goals. Dietitians can work with clients to select suitable strategies that may be beneficial. The optimal diet for diabetes prevention is likely as individual as our clients but we have many strategies that may help reduce risk of T2DM.
CVD cardiovascular disease
GI glycemic index, a scale which rates how quickly carbohydrates raise blood sugar
HDL the good cholesterol
LDL the bad cholesterol
MUFA monounsaturated fatty acids (good fats which help reduce cholesterol)
Trans fat also known as hydrogenated fats, found in some processed and fast foods
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