Plant-based, low-carb diet may boost longevity for people with Type 2 diabetes

Cutting some carbohydrates may help people with Type 2 diabetes live longer -- as long as they are swapping sugar for vegetables instead of steak, new research suggests.

The study, of more than 10,000 U.S. adults with Type 2 diabetes, found that those who ate relatively fewer carbohydrates were less likely to die over the next 30 years, versus those with a bigger taste for carbs.

But the quality of those lower-carb diets was key: People who ate a moderate amount of carbs but still fit in plenty of vegetables, fruit, fiber-rich grains and beans tended to live longer, versus people with higher-carb diets.

Then there were the folks with lower-carb diets that were heavy in meat and dairy. They saw no such survival advantage.

Experts said the findings, published in April issue of Diabetes Care, support a familiar piece of diet advice: Limit sugar and heavily processed foods, and eat more plants.

More than 37 million Americans have diabetes, the vast majority of whom have the Type 2 form, according to the U.S. Centers for Disease Control and Prevention. Type 2 diabetes arises when the body loses its sensitivity to the blood sugar-regulating hormone insulin.

The disease is often related to obesity, and diet changes, exercise and weight loss are cornerstones of managing it.

Low-carb diets are often promoted for weight loss and reining in blood sugar. But popular diets that strictly limit carbs, like the Keto diet, are very hard to maintain over time, said study author Yang Hu, a research associate at the Harvard T.H. Chan School of Public Health.

Plus, Hu said, not all carbs are alike. Avoiding sugar and starchy foods like white bread and processed snacks makes sense, especially for people with diabetes.

"But there are a lot of healthy carbohydrates, too, like vegetables and high-fiber whole grains," Hu said.

So he and his colleagues wanted to look at the way people with diabetes are really eating over the long haul -- including the quality of their carb choices. They turned to data from two long-running studies of U.S. health professionals, and zeroed in on over 10,000 participants who developed Type 2 diabetes after the studies' start.

Every few years, the participants filled out detailed dietary questionnaires. From that, Hu's team devised five different scoring systems: One was based on the simple amount of carbs people ate each day; the other four focused on the quality of people's lower-carb eating patterns -- whether they still ate healthy, plant-based carbs, or favored meat and other animal products, for instance.

Over a 30-year period, just under 4,600 study participants died. But those odds were lower among people whose diets were relatively lighter in carbs. When the researchers dug deeper into diet quality, only lower-carb diets high in plant foods appeared protective.

People who scored in the top 20% for a healthy lower-carb diet -- rich in plant foods, light in sugar and starch -- were about 30% less likely to die during the study period, versus people who scored in the bottom 20%.

It's important to point out that people's diets were not actually all that low in carbs, said Julie Stefanski, a registered dietitian and certified diabetes educator.

Even those who scored in the top 20% for restricting carbohydrates were typically getting about 40% of their daily calories from carbs. That's a lot more than strict low-carb diets allow.

That looser outlook on carbs is also necessary to fit in enough nutrient-rich plant-based foods, said Stefanski, a spokesperson for the Academy of Nutrition and Dietetics.

"We know that people with diabetes need to watch their carbohydrate intake," Stefanski said.

But, she added, it's also clear that high-fiber, nutrient-rich plant foods have a host of health benefits.

Stefanski noted that the study group was mostly white and composed of educated, higher-income health professionals. In the real world, many people managing Type 2 diabetes cannot easily find and afford healthy, fresh food.

There are ways to make it more feasible, Stefanski said -- like buying frozen vegetables to have on hand. You can have a healthy low-carb breakfast, for instance, by mixing some spinach into eggs, she said.

Ultimately, Stefanski said, there is no one-size-fits-all diet that works for everyone. People with diabetes who need help crafting a diet that is healthful, affordable and palatable can ask their doctor for a referral to a dietitian, she said.

Diet is only one part of the story, though. In this study, Hu's team found that the link between healthy eating and longer life was strongest among people who also exercised regularly, refrained from smoking and kept alcohol consumption to moderate amounts.

More information

The Academy of Nutrition and Dietetics has more on preventing and managing diabetes.