Leslie Beck, a Toronto-based private practice dietitian, is Director of Food and Nutrition at Medcan.
If nuts aren’t a staple in your daily diet, they ought to be. That’s especially true if you’re at increased risk for type 2 diabetes.
According to researchers from Pennsylvania State University, eating an average of 52 grams of nuts a day can reduce the likelihood of developing insulin resistance, a precursor to type 2 diabetes. It’s estimated that up to 50 per cent of people with insulin resistance will develop diabetes if they don’t make lifestyle changes.
Previous studies have suggested that eating nuts regularly is tied to better blood glucose (sugar) control and protection from type 2 diabetes. Most studies, however, were observational, not randomized controlled trials, and therefore don’t prove cause and effect.
The new research, published this month in the American Journal of Clinical Nutrition, was a review of data pooled from 40 randomized controlled trials that examined nut consumption on blood glucose control in 2,832 people with and without diabetes.
The studies looked at all types of nuts: tree nuts (e.g., almonds, Brazil nuts, cashews, hazelnuts, macadamia nuts, pecans, pine nuts, pistachios, walnuts) and peanuts, which botanically speaking are legumes, not tree nuts.
Blood tests that were reviewed included fasting blood sugar, hemoglobin A1C (one’s average blood sugar level over the past three months) and fasting insulin. The researchers also looked at insulin resistance.
Insulin resistance occurs when your cells become less sensitive to the blood-sugar-clearing effects of the hormone insulin. This signals your pancreas to produce more of the hormone, driving up insulin levels.
Over all, there was no effect of eating tree nuts or peanuts on fasting blood sugar or hemoglobin A1C. However, when the researchers looked at specific types of nuts, they found that eating pistachios was associated with a significant reduction in fasting glucose.
Eating nuts was also tied to significantly reduced fasting insulin and insulin resistance, especially in people with prediabetes. No one particular type of nut accounted for this effect.
Prediabetes occurs when fasting blood sugar is higher than normal (6.1 – 6.9 millimoles a litre), but not yet high enough to be considered diabetes (7.0 mmol/L or higher). Some of the longterm complications of diabetes, such as heart disease and nerve damage, may begin during prediabetes.
Nuts are high in healthy unsaturated fats, fats thought to help improve insulin sensitivity. Dietary fibre and magnesium in nuts may also play a role.
Pistachios and walnuts are a good source of alpha linolenic acid (ALA), an omega-3 fatty acid linked to protection from type 2 diabetes.
Scientists also speculate that the unique combination of unsaturated fats and antioxidants in pistachios may be responsible for their effects on insulin sensitivity.
What about weight gain?
Nuts are high in calories, due mainly to the fats they contain. The concern: Eating nuts every day can lead to weight gain therefore undoing their health benefits.
The current analysis of 40 studies, though, revealed that the beneficial blood glucose effects of eating nuts did not differ whether participants lost or gained weight during the study duration.
Even so, 52 grams of nuts, the average daily intake across the 40 studies, is equivalent to 300 calories worth of almonds (43 nuts), 340 calories of walnuts (26 halves) or 290 calories of pistachios (74 kernels).
To prevent adding excess calories to your diet, swap nuts for snacks such as granola bars, crackers, cookies and chips. Substitute nuts for granola as a topping on yogurt.
Replace meat in stir-fries with nuts, which, in addition to unsaturated fat and fibre, add plant-based protein.
Measure and preportion nuts for snacks. Eating nuts in the shell, such as pistachios, can also help control portion size since it takes more time to crack and eat them.
Fending off type 2 diabetes
The new findings suggest that adding nuts to your daily diet can help improve insulin sensitivity. But it’s not the only dietary strategy that can help prevent, or delay, the development of type 2 diabetes.
Higher dietary intakes of magnesium have been linked to a lower risk of insulin resistance and diabetes. Magnesium-rich foods include black beans, chickpeas, tempeh, spinach, Swiss chard, pumpkin seeds, sunflower seeds, almond butter, quinoa, brown rice and salmon.
Limiting red meat intake and avoiding sugar-sweetened beverages (e.g., soft drinks, fruit drinks, iced tea, energy drinks) are also thought to guard against type 2 diabetes.
And importantly, if you’re overweight, a modest weight loss of 5 to 7 per cent of body weight combined with 150 minutes of exercise a week has been proven to prevent diabetes in people with prediabetes.
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