Whole grains

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.)

Numerous studies have been published on diet and diabetes risk, but the quality of these studies varies widely, making it hard to compare the risks and benefits of different food choices. In this analysis, researchers reviewed 53 studies on diet and type 2 diabetes risk, and evaluated their strength and validity. There was high evidence that 30g per day of whole grains was linked with a 13% lower risk of developing type 2 diabetes and that 10g per day of fiber from grains was linked with a 25% lower risk of developing type 2 diabetes. There was also moderate evidence that 0.5-1 ounce of alcohol per day was linked with a 25% lower risk of type 2 diabetes than not drinking at all. On the other hand, eating 3.5 ounces of red meat daily, 2 ounces of processed meat daily, 2 slices of bacon daily, or one serving of sugar sweetened beverages were all strongly linked with a higher risk of type 2 diabetes.
BMJ. 2019 Jul 3;366:l2368. doi: 10.1136/bmj.l2368. (Neuenschwander M et al.)

Hepatocellular carcinoma is the most common form of liver cancer. In this study of 125,455 adults in the U.S., eating more whole grains was linked with a significantly lower risk of developing hepatocellular carcinoma over the 24-year study period. The results were statistically significant for whole grains overall and were not statistically significant when looking at bran intake, germ intake, or fiber from whole grains, thus indicating that the whole grain is greater than the sum of its parts.
JAMA Oncology. 2019 Jun 1;5(6):879-886. doi: 10.1001/jamaoncol.2018.7159. (Yang Y 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.)

Eating a healthy diet can help protect our health from a number of conditions and complications, so researchers wonder how diet might relate to cancer risk. In this study, researchers used models and dietary data to analyze the cancer cases from 2015. They found that 5.2% of all new cancer cases in 2015 could be attributed to poor diet, with 1.8% attributable to low whole grain consumption, 1.2% attributable to low dairy consumption, and 1% attributable to processed meats. The link with colorectal cancer shows the strongest relationship with diet, as poor diet is linked with 38.3% of all new colorectal cancer cases.
JNCI Cancer Spectrum. 2019 May 22;3(2):pkz034. doi: 10.1093/jncics/pkz034. (Zhang FF 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.)

Hepatocellular carcinoma, a common type of liver cancer, has been on the rise in the US, and researchers wonder if eating habits might play a role. In a study of 125,455 adults followed for 24 years, those eating the most whole grains (33g per day, or about 2 servings) were 37% less likely to develop hepatocellular carcinoma than those eating the least whole grains (7g per day, or less than half a serving). When looking at the isolated relationship of fiber, bran, and germ, the results were not statistically significant, indicating that whole grains are greater than the sum of their parts.
JAMA Oncology. 2019 Feb 21. doi: 10.1001/jamaoncol.2018.7159. [Epub ahead of print] (Yang W et al.)

Whole grains are one of the most popular food sources of fiber, and both whole grains and fiber are important for overall health. In this study, researchers analyzed data from more than 200 studies encompassing 4,635 participants to better understand fiber and whole grains’ relationship with disease prevention. Fiber was linked with a 15-30% lower risk of heart disease, stroke, type 2 diabetes, colorectal cancer, and death, with similar findings for whole grains. The researchers noted a dose-response relationship for both whole grains and fiber, indicating that those who eat the most may confer an even greater benefit.
The Lancet. 2019 Feb 02;393(10170):434-445. doi: 10.1016/S0140-6736(18)31809-9 (Reynolds A et al.)

Diet is intimately linked both to human and environmental health. In this article, a commission of distinguished scientists from different fields set out to examine the components of a healthy diet and the link between diet and environmental health. Through an extensive review of literature, the researchers found that an ideal diet that meets basic nutritional needs and can be sustainably produced is mostly plant-based. Specifically, this diet is based around about 11 ounces vegetables, 9 ounces of dairy foods (a little over a cup of milk) 8 ounces of whole grains (about 8 servings, such as a slice of bread or a ½ cup cooked grains), 7 ounces of fruit, 3 ounces of legumes, 2 ounces of nuts, and an optional 2 ounces of other animal foods (like eggs, poultry, or meat) per day. The authors suggest that a global shift towards these dietary principles can prevent approximately 11 million deaths per year, and can sustainably produce enough food for the growing population without further damage to the environment.
Lancet.  2019 Feb 2;393(10170):447-492. doi: 10.1016/S0140-6736(18)31788-4. (Willett W et al)

White rice has displaced many traditional whole grains across Asia, so researchers wonder how white rice might relate to diabetes risk. In a study of 45,411 Chinese adults followed for 11 years, researchers found that replacing white rice with white bread and whole grain bread can reduce type 2 diabetes risk by 10% and 18% respectively, and that replacing white rice with noodles, red meat, or poultry might actually increase diabetes risk. Rice intake itself was not associated with higher type 2 diabetes. The authors conclude that “recommendations to reduce high white rice consumption in Asian populations for the prevention of [type 2 diabetes] may only be effective if substitute foods are considered carefully.”
European Journal of Nutrition. 2018 Dec 10. doi: 10.1007/s00394-018-1879-7. [Epub ahead of print] (Seah JYH et al.)