Dr. Christopher D. Gardner has a PhD in Nutrition Science and is a Professor at the Stanford School of Medicine and the Director of the Clinical and Translational Research Core in the Stanford Diabetes Research Center. His work focuses on the study of dietary strategies and their impact on participant health outcomes such as weight, insulin and glucose dynamics and related parameters. He recently spoke at the 79th American Diabetes Association (ADA) Meeting in San Francisco on the role of nutrition in diabetes prevention. Dr. Gardner sat down with us to talk about the nutritional guidelines from the Standards of Medical Care in Diabetes 2019 report by the ADA and his recommendations.
What changes that were made to the American Diabetes Association nutritional guidelines this year stand out to you? What triggered those changes?
I would say there were three in particular.
The first was the decision to take on dietary patterns by looking beyond “food” and focusing on “food patterns”. By this, I am referring to diets such as Mediterranean, Vegan, Asian, Paleo, Low-Fat or Low-Carb which represent emphases on specific food groups rather than individual foods. The advantage of making suggestions based on food patterns is that they are more generalizable and adaptable. On the other hand, food patterns tend to be less specific and harder to follow for people who are looking for more structure in their diet. The new guidelines reflect consensus across different food patterns in its summary statements and encourages intake of vegetables and whole grains while minimizing processed foods and added sugars. Because of the emphasis on reducing added sugar and refined grains, this approach suggests a much lower overall carbohydrate intake which is corroborated by a growing body of evidence for the benefits of lower carbohydrate diets on glycemic control.
The second related point that stood out to me from the recent update in the guidelines was the shift to taking a stronger positive stance on lowER carbohydrate diets. I emphasize the “ER” portion of the term because there remains little consensus on “how low is low” when it comes to carbohydrates. Although a considerable body of evidence supports the benefits of low-carbohydrate diets for glycemic control, there is a paucity of data on whether low-carbohydrate diets have a significant benefit for long-term morbidity or mortality. All the available data for this outcome comes from “Low-Fat” studies. Unfortunately, diet studies with morbidity and mortality outcomes are challenging to fund and take many years to conduct. This was acknowledged in the newly released Consensus statement.
Thirdly, the panel was tasked with addressing pre-diabetes. This was in contrast to previous reports which restricted their work to Type I and II diabetes. However, current trends suggest that unless an emphasis is placed on preventing people from becoming diabetic, an unprecedented number of humans are likely to have the disease in the near future. The group of people with pre-diabetes is most likely to make that transition soon and is therefore the focus of the effort to prevent diabetes.
One ADA recommendation is to encourage diabetics to reduce their consumption of sugar sweetened beverages. In this context, what is your view of the effectiveness of the so-called 'soda tax' on changing consumer behavior?
Preliminary data from Berkeley and Mexico – two of the first to implement soda taxes – supports a benefit in terms of influencing consumer behaviors. A definitive answer in the area of health benefits will not be available any time soon. That is because the time frame of studying stability or change in human behavior can be very brief, whereas tracking the health impacts of those behavioral changes (e.g., morbidity, mortality) is a very extensive and intensive undertaking.
For people who consume foods sweetened with non-nutritive sweeteners in lieu of sugar-sweetened foods, what are some of the risks of non-nutritive sweeteners?
The major problem with the consumption of beverages sweetened with non-nutritive sweeteners is the issue of “compensation” – psychological and physiological. The psychological compensation may come from choosing a diet soda rather than a regular soda for lunch and feeling so good about that choice that the person might reward themselves with a sweet treat for dessert that they may not have consumed otherwise. In this case, the sugar and calories from the cake likely diminish or even negate the benefit of the diet soda. The physiological compensation may plausibly come from the body sensing that an incoming sensation of sweetness would be linked with a proportional level of caloric intake that in fact isn’t there. This in turn potentially leads to sub optimal food choices in the future. In addition, chronic consumption of artificial sweeteners could be linked to an increased obesity and type 2 diabetes risk. That said, it is important to note that many of these potential risks have not been proven and are currently plausible rather than definitive.
What, in your experience, is the most common problem diabetic patients face with respect to nutrition?
Although I don’t see patients, my sense is that the most common problem stems from focusing on carbohydrate counting without simultaneously developing a full appreciation of the variability in quantity and quality of carbohydrates across a wide range of food groups – vegetables, nuts and seeds, fruits, whole intact grains. In the past the focus has been on what NOT to eat, rather than also providing guidance on what to include.
The guidelines mostly focus on recommendations for Type 2 diabetics, saying 'There is inadequate research in type 1 diabetes to support one eating plan over another at this time'. Given that type 1 diabetes often has an onset in childhood, do you anticipate there being significant differences in nutrition guidelines for type 1 diabetics?
While there may be certain circumstances that lead to a need for separate dietary guidelines for type 1 vs. type 2 diabetes, in general the broad characteristics of a healthy diet for people with type 1 diabetes is are more similar than different for those with type 2 diabetes.
Dr. Gardner has worked tirelessly over the past 20 years to improve our understanding of the role of nutrition and dietary strategies in the management of diabetes and educate the public on good dietary practices. He also studies the impact of social factors such as the climate change movement and animal welfare concerns that could help people make positive dietary changes. He was instrumental in helping draft the nutritional guidelines section of the American Diabetes Association report on Diabetes Care.
Harini Chakravarthy is a science writer for the Stanford Diabetes Research Center.