And the newest "superfood" trend is... wait for it... fermented foods!

Yup, all those pickles, sauerkraut, and vinegary sauces your Grandma used to serve are where it's at in the latest health craze these days.

And no surprise, there have even been a lot of claims that fermented foods can help combat diabetes, by lowering blood sugar levels. Really?! We just HAD to investigate.

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This dLife article on the many nutritional qualities of fermented foods mentions briefly that, "the good bacteria in fermented foods break down carbohydrates into acids and promote the growth of more friendly bacteria." But how exactly might that work? And are nutrition professionals really on board recommending that PWDs (people with diabetes) start vinegar-loading?

We queried the following expert CDEs (Certified Diabetes Educators), who are all also registered dietitian nutritionists, to get the skinny:

Hope Warshaw, RD, CDE, nationally known dietitian and author of "Diabetes Meal Planning Made Easy"; 2016 president of the American Association of Diabetes Educators (AADE)

Toby Smithson, CDE, Registered Dietitian Nutritionist, diabetes lifestyle expert and founder of

Sarah Picklo, RD, CDE, Senior Manager, Clinical Resources at the Academy of Nutrition and Dietetics, and Type 1 / patient advocate herself

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As you will see, not all experts agree on exactly how this all works, but it does seem the operative terms here are fibers, microbiome, and probiotics (see insert for definitions).


DM) Ladies, can you help us understand how "the good bacteria in fermented foods break down carbohydrates"?

Hope W) Based on the research I’m familiar with this notion seems like a stretch. From a research standpoint, what we know is that viscous fibers – some of the fibers in beans/legumes and oats, can help to a small degree (important caveat: when eaten in sufficient quantity) lower total cholesterol and glucose levels. Keep in mind, these fibers are not lipid-improving or glucose-lowering medications, but any little bit helps. Other fibers, including resistant starches found in bananas (especially under-ripe) and cooked potatoes, fruits and vegetables, are fermented to a greater or lesser degree by the healthy bacteria in the gut (colon).

Sarah P) Some research has suggested that GI bacteria may play a role in fermenting carbohydrates in the large bowel. It is possible that the colonic bacteria present in one's gut may have an influence on blood glucose levels.

Toby S) Fermentation is by definition the breakdown by organisms (bacteria, yeast, etc.) of complex organic molecules like carbohydrates into simpler organic acids or alcohol in an anaerobic (absence of oxygen) environment. Some bacteria in the gut can be thought of as a sledgehammer, i.e. they have the role of breaking down nutrients. Bacteroides thetaiotaomicron takes on the role of breaking down carbohydrate foods.

Why is this food trend just coming out now? Are there significant new research findings?

Toby S) Of course, fermenting foods is one of the oldest food preservation techniques, but not until recently have they studied the potential health benefits on the microbiota of humans. And there is still more research to be conducted on how we can modify unhealthy gut patterns.

Sarah P) Research on the gut microbiome is a relatively new area, stemming from a 2007 NIH project identifying many different types of the bacteria in the gut (GI tract). Now that several bacteria have been identified, research is beginning to analyze the role they have on human health and disease. As more is learned about the function of the gut and the bacteria found in the gut, our understanding of how individual foods, diets, and bacteria impact human health is also advancing. 

Hope W) This is actually about the importance of eating more fibers (note the S) and as a source of fibers eating more fermentable fibers, which is not new. The push on fiber has been in the U.S. Dietary Guidelines and the ADA nutrition guidelines for several iterations. Yet, as a whole Americans have not responded to this guidance. Maybe this trend can help -- although every diet trends come with a lot of hype and a bevy of not-scientifically-founded articles and food products to “feed” the trend du jour. I would caution readers to seek and consider the real scientific research evidence and to avoid turning their eating habits upside-down with every new trend.

Are you aware of any research that substantiates the health properties of fermented foods? In particular re: helping to keep blood glucose in check?

Toby S) There are numerous studies over the past 10 years revealing that microbiota may play a major role in regulation of metabolism in health and disease. A microbial imbalance has been associated with insulin resistance.  It’s hypothesized the gut microbiota may have an influence on insulin and leptin signaling and food intake.

A six-week study using fermented milk with type 2 diabetes subjects, revealed a decrease in fructosamine levels and a reduction in A1C levels. The healthy bacteria in fermented milk (yogurt) is Lactobacillus.

When we ingest enough probiotics, they will improve the microbiota. Probiotics change the gut to a healthier environment. L. casei CCFM419, which is found in ripened cheddar cheese, showed a regulation effect on blood glucose, reduced fasting blood glucose level and improvement in A1C levels.

Sarah P) I am aware of some microbiome research that was done to combine traditional measures of diabetes management (A1c, BMI) with additional considerations of gut bacteria found in the colon. This model allowed researches to predict postprandial glucose levels (after-meal blood glucose) more accurately than could be achieved with carbohydrate counting. However, the subjects in the study were healthy individuals, so additional research will need to be done to evaluate this for persons with diabetes. But the inclusion of fermented foods for the purpose of improving blood glucose has not been adequately studied as a strategy to improve blood glucose values in persons with diabetes.

So the actual research we should be paying attention to is about eating more fiber in your diet?

Hope W) Essentially yes. There's a growing body of research, including in the area of prevention of type 2 diabetes, of the value of consuming an eating plan that is higher in all types of dietary fibers. The reality is there are hundreds of dietary fibers in our foods and fermentable fibers is just one category of those. For more detail, I would highly recommend reading my RDN/CDE colleague Jill Weisenberger’s recent article on What You Need to Know About High Fiber Foods.

Got it. But do you recommend fermented foods to your patients? If so, which? And what advice do you give them?

Hope W) Yes, but the caveat is I recommend that people eat more of all types of dietary fibers. We need them all for a healthy gut, disease prevention (like colon cancer), weight control and more. Reality is on average Americans consume barely half of the recommended intake of dietary fiber. The recommended amount is 25 grams/day for women and 38 grams a day for men. Think about the foods that contain fibers – whole grains, fruits, vegetables and legumes – yes, all carbohydrate containing foods. Reality is people simply can't eat a variety of dietary fibers or a sufficient total amount of dietary fiber if you’re avoiding whole grains, legumes and fruits. This is a downfall of consuming a low-carbohydrate intake. There is research showing that people who consume a healthy vegetarian or vegan eating plan have healthier guts, have less type 2 diabetes, and stay at a healthier weight.

One can certainly tank up on vegetables and if desired eat them as sauerkraut, pickles, kimchi, vinegar-based cole slaw and the like, but with that alone, you're still not going to consume the amount and variety of fibers one needs for health.

Toby S) With the recent literature about the microbiome, I have started advising on the use of probiotics. Yogurt, especially Greek yogurt with live and active culture, has multiple health benefits. Healthy bacteria are important defenders for a healthy gastrointestinal and immune systems. Greek yogurt contains a perfect combination of protein and carbohydrate to make it a favorite go to probiotic food to recommend as a bedtime snack for people with diabetes. Plus it is a good source of calcium.

Vinegar used as a sauce, dressing or as a marinade can easily be incorporated into a healthy eating plan for people with diabetes. Vinegars contain very low to no carbohydrates and are very low in sodium.

Tempeh (fermented soy beans) is a food I often recommend which is an excellent source of a plant-based protein.

While sauerkraut, kimchi, miso, pickles and olives are also on the list of beneficial fermented foods, I caution with my recommendations of these choices due to the higher sodium content.

It’s important to note that consuming a fiber-rich diet (especially fruits and vegetables) are equally as important as including probiotics as part of a healthy eating plan. Without adequate fiber in the diet, probiotics will not be able to survive long enough to produce the beneficial short-chain fatty acids present in some dietary fibers that lead to GLP-1 (glucagon-like peptide (GLP)-1) and reduce weight and insulin resistance.


Wow, thanks to these diabetes nutrition experts for their insights! Fiber up, Friends.