In the Nurses’ Health Study, which tracked 85,000 women for 16 years, those with the healthiest lifestyles had about a 90 percent lower risk of diabetes than those with unhealthy lifestyles (though something else about those women may explain some of that lower risk).1
Other evidence from studies that observe people instead of enrolling them in programs:
Unhealthy carbs. “Cutting back on unhealthy carbohydrates—basically white flour and other refined starch, sugar, and potatoes—is helpful,” says Walter Willett, chair of the nutrition department at the Harvard T.H. Chan School of Public Health. In his recent study on 70,000 women, those who ate more starch and less fiber had a higher risk of diabetes.2
Sugar drinks. “There’s about a 25 percent increase in the risk of diabetes for each 12 oz. serving of sugar-sweetened beverages per day,” notes Willett.3 And only about half of that increased risk is due to weight gain. “It’s also probably due to the high amount of unhealthy carbohydrate that is gulped down in a few minutes.”
Meat. “Both processed and unprocessed red meat are related to a higher risk of type 2 diabetes,
consistently and quite strongly in all of our studies,” says Willett.4 “If you want to keep diabetes risk low, replace red meat with some beans, nuts or other plant sources of protein, or some dairy, poultry, or fish.”
Dairy. “There is always hype about the benefits of dairy,” says Willett. “We need more studies, but so far it looks like yogurt—but not overall dairy—seems to reduce the risk of type 2 diabetes.”5
What about studies reporting a lower risk of diabetes in people with high blood levels of dairy fat.6 “Those levels are not good measures of dairy intake,” he explains. “And they’re influenced by an individual’s metabolism. That’s tricky because diabetes is a disease of disturbed metabolism.”
Coffee. In Willett’s studies, each daily cup of coffee was linked to a 4 to 8 percent lower risk of diabetes.7 “It’s probably due to the flavonoids and antioxidants in coffee,” he notes, “because it looks like decaffeinated coffee has a similar benefit.”
Magnesium. People who consume more magnesium-rich foods—like leafy greens, beans, nuts, and whole grains—have a lower risk of progressing from prediabetes to diabetes.8 But something else about those people may account for their lower risk.
Vitamin D. People with low vitamin D levels have a higher risk of diabetes. But so far, most studies that give vitamin D or a placebo to people with prediabetes have come up empty.9 Stay tuned.
Selenium. People over age 62 who were given selenium supplements (200 micrograms a day) for roughly three years were twice as likely to get type 2 diabetes as those who got a placebo.10 Stick to a multivitamin with no more than about 100 mcg.
How quickly can you expect changes?
“If you make a change in your diet or lifestyle today, you’re taking your foot off the accelerator, and that happens almost overnight,” says Willett. “If you exercise today, your insulin resistance goes down within hours. And if you keep up the daily exercise, within a day or two your risk of diabetes drops.”
Changing your diet might take longer to make a difference, but it’s a matter of weeks, not years. “Even if you’re right at the brink of diabetes, you can still rapidly reduce your risk,” says Willett.
1 N. Engl. J. Med. 345: 790, 2001.
2 Am. J. Clin. Nutr. 102: 1543, 2015.
3 Diabetes Care 33: 2477, 2010.
4 Am. J. Clin. Nutr. 94: 1088, 2011.
5 BMC Med. 12: 215, 2014.
6 Circulation 133: 1645, 2016.
7 Am. J. Clin. Nutr. 97: 155, 2013.
8 Diabetes Care 37: 419, 2014.
9 J. Clin. Endocrinol. Metab. 99: 3551, 2014.
10 J. Natl. Cancer Inst. 108: djw152, 2016.