Health Studies

Paleo diets tend to be high in meat and vegetables, while restricting all grains and dairy products. In this study, researchers analyzed the microbiome of 44 people who had been following a Paleo diet for at least 1 year, and 47 people who eat a healthy diet reflective of dietary guidelines. Those strictly following a Paleo Diet and those eating a standard healthy diet ate significantly more fiber than those only loosely following a Paleo diet. However, those who strictly followed the Paleo diet (eating the lowest levels of whole grains and total grains) were significantly more likely to have higher levels of TMAO (a compound generated by the gut microbiome that is associated with plaque buildup in the arteries). The authors also added that “the rationale to exclude whole grains is not supported by data presented here; being inversely associated with body weight and TMAO concentrations.”
European Journal of Nutrition. 2019 Jul 5. doi: 10.1007/s00394-019-02036-y. [Epub ahead of print] (Genoni A et al.)

Gluten is a compound found naturally in wheat, barley, and rye that helps dough stretch and bread rise. Many misguided dieters today choose to go gluten-free, even though only about 1% of the population has celiac disease (an autoimmune disorder where gluten must be avoided). In this review, researchers analyzed studies on the nutritional adequacy of gluten-free diets. They found that gluten-free diets tend to have less fiber, calcium, magnesium, zinc, vitamin B12, folate, and vitamin D, and tend to have more saturated fat and exposure to arsenic. The researchers note that “the majority of persons adopting a [gluten-free diet] have no medical basis for doing so,” and that “only persons with [celiac disease], [wheat allergy], or [non celiac gluten-sensitivity] should follow a [gluten-free diet], and they should do so under medical supervision.”
Journal of Nutrition and Metabolism. 2019 Jul 1;2019:2438934. doi: 10.1155/2019/2438934. [Diez-Sampedro A et al.]

Longevity is fascinating to study, but what is perhaps more important than the years in your life is the life in your years – the ability to age successfully from a medical, social, and lifestyle point of view. In this study, researchers evaluated whole grain intake and measured “successful aging” (using social, lifestyle, and medical indicators) in a group of 3,349 adults ages 50+. Those eating the most whole grains (about 7 servings per day) were significantly more likely to score higher on the “successful aging index” than those eating the least whole grains (about 1.5 servings per day). Those eating the most whole grains were also less likely to have high blood pressure, diabetes, and high cholesterol.
Nutrients. 2019 May 29;11(6). pii: E1221. doi: 10.3390/nu11061221. (Foscolou A et al.)

Many ultra-processed convenience foods are designed to keep us coming back for more. In this study, researchers randomly assigned 20 adults to a diet of ultra-processed foods (packaged pastries, chicken nuggets, American cheese, deli meats, flavored fruit drinks, etc.) or unprocessed foods (spinach, nuts, fruit, chicken breast, plain Greek yogurt, avocado, sweet potato, bulgur, farro, etc.) for 2 weeks, immediately followed by the other diet for the next 2 weeks. The meals on both diets had the same number of calories, carbohydrates, fat, protein, sugar, sodium, and fiber, but participants could choose to eat as much or as little of the food that they wanted. People tended to eat 500 more calories on the ultra-processed diet, and gained about 2 pounds, while people tended to lose 2 pounds on the unprocessed diet. The categorization of ultra-processed vs unprocessed/minimally-processed is based on the NOVA system of food classification. While there are some concerns about the classifications used in the NOVA system (such as white rice and white flour being included in the “minimally processed” category alongside intact whole grains), helping direct consumers towards more wholesome, minimally-processed foods may be one strategy to address overeating and associated weight gain.
Cell Metabolism. 2019 May 16. pii: S1550-4131(19)30248-7. doi: 10.1016/j.cmet.2019.05.008. (Hall KD et al.)

Insulin is a hormone that helps your body manage your blood sugar, by keeping it from getting too high or too low. In this study, 13 adults with “pre-diabetes” were given a diet with either whole grains or refined grains for 8 weeks, then given a glucose test to assess how well their blood sugar was being managed. They then had a washout period of their normal diet for 8-10 weeks, before switching to the other diet for 8 weeks and taking the glucose test again, thus serving as their own controls. The whole grain diet improved the function of beta cells (the cells that secrete insulin) compared with the refined grain diet, and this effect was found to be independent of gut hormones (such as grehlin, the “hunger hormone”).
Molecular Nutrition and Food Research. 2019 Apr;63(7):e1800967. doi: 10.1002/mnfr.201800967. (Malin SK et al.)