The data are in: Eat right, reduce your risk of diabetes

Robert H. Shmerling, MD

Senior Faculty Editor, Harvard Health Publishing

Follow me on Twitter @RobShmerling

Here’s a new medical study with a conclusion that might just change your life: eat healthy.

Sure, you’ve heard it before, but this time the benefit is the prevention of diabetes. That’s a big deal, especially if, like so many other people, you are at risk for the disease. More on that in a moment.

First, let’s review the study. Researchers publishing in PLoS Medicine describe a study of more than 200,000 people in the U.S. who participated in health surveys over a 20-year period. They found that:

  • People who chose diets that were predominately of plant-based foods developed type 2 diabetes 20% less often than the rest of the study subjects.
  • For those with the very healthiest plant-based diets (including fruits, vegetables, nuts, beans, and whole grains), the reduction in type 2 diabetes was 34%.
  • On the other hand, those who made less healthy choices (such as sugar-sweetened beverages and refined grains) developed type 2 diabetes 16% more often than the rest.

It’s worth emphasizing that this was not a study of the effect of being a vegan or of following an expensive, pre-packaged diet plan that might be hard to maintain over time. This was a study of “normal” dietary choices across a spectrum, from largely animal-based to largely plant-based with all variations in between. That makes it more applicable to the average person.

While this type of study cannot prove that the reduction in diabetes was strictly due to the difference in diet, the “dose response” (the higher degree of protection with the very healthiest diets) is strongly suggestive of real effect due to diet.

Current recommendations

The USDA’s current dietary guidelines (called “MyPlate”) urge everyone to choose healthy foods. For example:

  • Half of each meal should consist of whole fruits and vegetables.
  • About a quarter of each meal should be made up of protein, and another quarter grains (especially whole grains).
  • Low-fat dairy products such as low-fat milk and yogurt are preferred over higher fat options.
  • Moderate total calorie intake (depending on your age, gender, size, and physical activity).
  • Reduce the intake of saturated fat, sodium, and added sugar. Read nutrition labels so you know what you’re eating.

According to the USDA’s website, the MyPlate diet “can help you avoid overweight and obesity and reduce your risk of diseases such as heart disease, diabetes, and cancer.”

Even more recently, the 2015 Dietary Guidelines Advisory Committee reported that a diet “that is higher in plant-based foods, such as vegetables, fruits, whole grains, legumes, nuts, and seeds, and lower in animal-based foods, is more health promoting.” And just this week, US News and World Report ranked plant-based diets (the DASH diet and the Mediterranean diet) as the healthiest.

These recommendations have been endorsed by nutritionists, doctors, and public health officials. But, the data on which they are based are not perfect. This new study is among the strongest to date supporting the notion that a healthy diet can lower your risk of a chronic disease such as diabetes.

Of course, there are caveats

Is this the last word on the connection between diet and prevention of diabetes? Not by a long shot.

For one thing, this study examined trends among thousands of people over time. While that allows some observations (and even predictions) about large groups of people in aggregate, it does not allow accurate predictions for an individual. You could follow a healthy diet all your life and still develop diabetes. And not everyone who chooses an animal-based diet that is high in refined sugars will develop diabetes.

The information about diet was self-reported, so some inaccuracy is inevitable. And for some foods, the designation of “healthful” is somewhat subjective.

In addition, such studies are unable to say that diet is the key reason for the findings. Some other factor — exercise, genetics, or a host of other possibilities in combination — might matter more than diet alone. However, the dose response (as defined above) does suggest that diet is playing a significant role.

And in conclusion….

Given the dramatic increase in the incidence of diabetes in this country, studies that identify preventive approaches are worthy of attention. Besides providing some of the strongest support to date for recommendations for healthier diets, perhaps the biggest impact of a study like this should be for people at increased risk of disease. For example, a person who is overweight, has “pre-diabetes” (a high blood sugar that’s not quite high enough to be diagnostic of diabetes), or a strong family history of diabetes might take this data to heart and commit to changing their diet.

Studying the impact of dietary (or any other) recommendations is an important way to validate the guidelines’ usefulness. This new study is a good example.


  1. Harveer Parmar

    Very Informative article. Thanks.

  2. glen small

    Avoid all grains.

  3. MIKE


  4. farhan

    what foods are good to control heart problems

    • Ken Walden

      Whole food, plant-based diet is the ONLY diet to have been shown to prevent and sometimes reverse heart disease.
      See “How to prevent and reverse heart disease” by dr. Caldwell Esselstyn of the Cleveland Clinic. NO other treatment has come close.

  5. ana north

    As a Physician I have a number of problems with this article – not the least of which is the lack of a clear distinction between Type one and Type two diabetes – it is true that insulin dependent diabetics can benefit from a healthy diet (can’t we all) but “Eat right, Avoid Diabetes” is flat out wrong and needs correction. I expect better from Harvard – this is not WebMD 🙂

  6. Bob

    “People who chose diets that were predominately of plant-based foods developed type 2 diabetes 20% less often than the rest of the study subjects.” Twenty percent of what? Presenting results this way (i.e., relative risk reduction) is misleading and almost always exaggerates the impact of whatever is being touted. In order to provide the true size of a benefit, the risk reduction should be presented on an absolute basis. You should know that. I expect better from Harvard.

  7. P M

    No wonder the percentages of patients who avoided diabetes on this plant-based diet are so low! Instead, skip the grains and the high sugar fruits. Drink water, coffee, tea — no sweetened drinks. Avoid sweeteners of any sort. After a couple of weeks, you won’t miss them at all. Eat a modest serving or two a day of grassfed/pastured/wild animal protein, plenty of healthy fats & oils (olive/coconut/grassfed butter/avocado/nuts), and all the vegetables you want. Stick to low sugar fruits, like berries and apples.

    Every person on this diet has either avoided or reversed diabetes. When will Harvard finally reject their corrupt pro-carbohydrate research from the past and do real research into real food? Saturated fats are not dangerous. They never were. Carbs cause high cholesterol, not fats. Nations around the world are changing their food pyramids to reflect this new research. It’s hard to take this newsletter seriously, when your information is decades old — and wrong.

    • Sandra Heyneman

      I agree! Come on Harvard! My blood sugar and cholesterol numbers went way down when I cut bad carbs, ate lots of organic eggs, beef, chicken, nuts, whole milk and yogurt and healthy fats like coconut oil.

    • Rita

      Totally agree–not to mention GMOs and Monsanto/chemicals in quite a bit of snack and processed foods. Time to re-think “healthy”–also exercise is important. No exercise is not an option.

    • Donald Morgan

      The whole My Plate program is nonsense and leads to more people staying on medications for diabetes, heart disease, many cancers, Alzheimer’s and so many more. You need to quit putting bad information out to the public. Unfortunately the poor public is caught in the cross hairs and they become even more confused. Do you have any idea how misconstrued our current dietary guidelines are? Very low carb is the answer and I can’t figure out why a very well respected school can’t figure that out. Please deliver the right message!

    • ken walden

      To read about effect of whole-food plant based diet on diabetes see;
      China Study by T. Colin Campbell
      Dr. John McDougal’s website. Search diabetes.
      Dr. Michael Greger’s website;
      Dr. Neil Barnards books.

      Civilization grew up on primarily starch based diets, ie, rice, potatoes, wheat, other whole grains. The incredibly high incidence of diabetes is a recent result of the SAD (standard American diet). Diabetes was virtually unknown decades ago until SAD came into their diets. China used to have one of the lowest rates of diabetes. Now, with the introduction of the SAD to their diet they have one of the highest rates. It’s the food…

  8. F Ornelas

    I have switched to a healthy diet and have seem the results. Measured lipids, and sugar levels before and after the change. This combined with daily 30 minutes briskly walk. The results spoke by themselves. The numbers improved a lot. I may add that cinnamon will also help to lower the HA1c, but use it wisely since you could see yourself making more trips to the bathroom.

  9. David Vose

    Do you think eating dead animals is right? First, they stink literally. Second, when you eat your dead animals do you go in the backyard to cut its throat, skin it and cut out their guts to eat?
    Also, experts put protein on the bottom of the list of our needs. A mothers milk between 3% and 5% protein. Pushing protein is what marketers use to sell products. You have some learning to do.

  10. Kelly

    The foods we eat can do more than help prevent diabetes. Eating a healthy diet can help prevent heart disease and many other diseases as well.

    I do believe a plant based diet is the way to go but I often find it hard for me to stick with it.

    Of course exercise does play a role but i think it is diet that is key.

    Here is a wonderful article I found discussing foods that help prevent diabetes.

  11. parul singh

    you need to understand how foods and nutrition affect your body for manage your diabetes.Good health depends on eating a variety of foods that contain the right amounts of carbohydrates, protein and healthy fats, as well as vitamins, minerals, fiber and water
    Doctors of medixpres suggest the plan of diet.

  12. Clive Burnard

    I wouldn’t listen to a corrupt Harvard University which, in the early 1960s, was bribed by the sugar industry to produce bogus studies linking saturated fat with heart disease when there is no such link.

    Of course, we now know that the real culprit in heart disease is in fact refined carbohydrates and sugar.

    Our bodies need lots of fat to be healthy, including saturated fat. Without a lot of fat in a meal we are unlikely to feel satiated so end up overeating and his gain weight hence the low-fat, high-carbohydrate dietary (bad) advice caused the obesity epidemic. Furthermore, without the full amount of fat in dairy products our bodies are unable to absorb the fat-soluble nutrients they contain.

    The best advice from a non-vested interest source is to switch back to healthy butter and whole milk and relish the delicious fat on meat.

  13. Ben Fury

    From the study:
    “… less healthy plant foods (fruit juices, sweetened beverages, refined grains, potatoes, sweets/desserts) and animal foods received reverse scores.”

    That lumps so many varied foods together as to make the conclusions completely meaningless. Dumping high sugar foods in with protein/fat foods is nonsensical. Another epidemiological fail.

  14. Roger Bird

    The recommendations here will cause very limp gains for people addicted refined carbs, but you can do MUCH better by going paleo.

  15. Dona C. Collins

    Dr. Robert some great insight.

    I have been in the field for over 20 years and I have to say that diabetes is on a rise and our eating habits are one of the major factors.

    In fact a recent article by Elisabeth Almekinder from who is a certified diabetes educator and a registered nurse talks about it in detail.

    It is surprising that at the same time an article on NYTimes says otherwise.

    I found this article by Dr. Jennifer Bowers great read which I believe you fill find interesting as well which is exactly on the same topic.

    Thank you
    Dona C. Collins

Commenting has been closed for this post.