Although food traditions vary from country to country, many traditional healthy diets are rooted in wholesome plant foods like fruits, vegetables, and whole grains. In a study of 1404 people who had been diagnosed with colorectal cancer at least six years prior, researchers analyzed their eating patterns based on how closely they aligned with a Mediterranean diet (fruits, vegetables, grains, unsaturated fats, legumes, moderate alcohol) and a healthy Nordic diet (fish, root vegetables, whole grain bread and oatmeal, apples, pears, cabbage). Those who most closely followed a Mediterranean diet were significantly less likely to die during the study period than those not following a Mediterranean diet. Similarly, each 1-point increase on the Modified Mediterranean Diet Score or the Healthy Nordic Food Index was linked with improved survival.
Journal of Nutrition. 2017 Apr;147(4):636-644. (Ratjen I et al.)

Childhood obesity is a growing problem around the world, and in developed countries, it is estimated that ⅓ of children are overweight or obese. In a study of 1,032 Greek teenagers (average age = 14), researchers tested a 6-month school-based nutrition education intervention, based on the principles of the Mediterranean Diet. Following the intervention, the researchers found significant decreases in overweight and obesity, abdominal obesity (specifically waist circumference), and blood pressure.
European Journal of Clinical Investigation. 2017 Apr 13. [Epub ahead of print] (Bacopoulou F et al.)

Although fruit has naturally occurring sugars, research continually demonstrates that fruit is an important part of a healthy diet, even for people with diabetes. In a large study of nearly half a million adults in China, researchers found that those eating fresh fruit daily were 12% less likely to develop diabetes over the 7-year study than those who rarely or never ate fresh fruit. Additionally, adults who had diabetes at the beginning of the study were 17% less likely to die over the study period, and were 13-28% less likely to have blood vessel complications.  
PLoS Medicine. 2017 Apr 11;14(4):e1002279. (Du H et al.)

Olive oil is a staple of the Mediterranean diet, an eating pattern praised for its links to good health and wellbeing. To see how olive oil relates to type 2 diabetes, researchers in Europe analyzed data from 4 cohort studies (following people over time and monitoring their health) and 29 clinical trials (randomly assigning people to diets with or without olive oil). They found that those consuming the most olive oil had a 16% lower risk of developing type 2 diabetes than those consuming the least olive oil, with every 2 teaspoon increase in olive oil daily linked with a 9% lower risk. For patients who already had type 2 diabetes, adding olive oil to their diet significantly lowered their HbA1c, an indicator of better blood sugar control.
Nutrition & Diabetes. 2017 Apr 10;7(4):e262. (Schwingshackl L et al.)

Pulses are the food group that comprises beans, peas, chickpeas, and lentils. To see how these foods might be related to diabetes prevention, researchers analyzed data from 3,349 Spanish adults from the PREDIMED trial. Those eating the most pulses (about ⅓ cup per day) were 35% less likely to get type 2 diabetes over the 4-year study period, even after adjusting for overall diet and BMI. Those eating the most lentils (about 1 ½ tablespoons per day) were 33% less likely to get type 2 diabetes, but the relationship was not significant for other types of pulses. Researchers found that by replacing just a half serving of whole grain bread, white bread, rice, or baked potatoes with a half serving of pulses was linked with a 44%, 47%, 52%, and 51% lower risk of diabetes, respectively.
Clinical Nutrition. 2017 Mar 24. pii: S0261-5614(17)30106-1. (Becerra-Tomas N et al.)

In the UK, moderate alcohol intake is defined by up to 3 drinks per day for men and up to two drinks per day for women. To see how drinking alcohol relates to heart disease risk, British researchers analyzed the drinking habits and health outcomes of nearly 2 million adults (although they did not differentiate between beer, wine, and other alcoholic beverages). They found that, compared to moderate drinking, both nondrinkers and heavy drinkers (exceeding the guidelines described above) were significantly more likely to suffer from heart failure, stroke, and death from heart disease, among other (but not all) heart problems. The scientists caution that “there are safer and more effective ways of reducing cardiovascular risk,” than taking up drinking (such as diet, exercise, and quitting smoking), and suggest that “a more nuanced approach to the role of alcohol in prevention of cardiovascular disease is necessary.”
BMJ. 2017 Mar 22;356:j909. (Bell S et al.)

Plant-based diets, which focus on fruits, vegetables, grains, and pulses, can be a great tool for eating healthy. In a small study in New Zealand, researchers randomly assigned overweight and obese adults to either a whole foods plant-based diet (with vitamin B12 supplementation) or a control group with no special diet for six months. Although the plant-based diet was not calorie restricted, those in the diet group lost on average 24 pounds after one year, and after excluding dropouts (49 of the 65 participants completed the study), the diet group also significantly improved their cholesterol.
Nutrition & Diabetes. 2017 Mar 20;7(3):e256. (Wright N et al.)

Eating a healthy diet may help benefit both your body and your brain. Researchers analyzed data from 9,700 primary and secondary schools in California to find any potential connections between nutritional quality of school lunches and test score data. They found that using a healthy meal vendor (defined by a Healthy Eating Index score above the median score among all vendors) was associated with significantly higher test scores in students. This relationship was strongest for students from low-income households, possibly because they are more likely to eat the school lunch. However, the researchers did not find that working with a healthy lunch provider reduced percentage of overweight students.
National Bureau of Economic Research. 2017 Mar. 1-45. (Anderson ML et al.)

Many patients who respond well to a gluten free diet, but don’t test positive for celiac disease, are thought to have non-celiac gluten sensitivity. However, a closer look at this population is raising some doubts. Researchers in Spain analyzed data from 10 studies comprising 1312 adults, all of which were double blind, placebo controlled gluten challenges (meaning that neither the researchers nor the participants knew if they were getting a gluten-free diet or the gluten-containing placebo).  Only 16% of the non-celiac gluten sensitivity patients showed gluten-specific symptoms when exposed to the gluten-containing diet, and 40% of them had similar or increased symptoms when on the gluten-free control diet. The researchers conclude that these results “cast doubt on gluten as the culprit food component in most patients with presumptive [non-celiac gluten sensitivity].”  
Perspectives in Clinical Gastroenterology and Hepatology. 2017 Mar:15(3):339-348. (Molina-Infante J et al.) 

For couples trying to get pregnant, a healthy diet may help tilt the odds in their favor. To see what types of foods are associated with better male fertility and healthy sperm quality, researchers analyzed data on eating patterns and male fertility in 35 observational studies from around the world. They found that a healthy diet (e.g. a Mediterranean diet) with lots of seafood, poultry, vegetables, fruits, low fat dairy, and grains is associated with better sperm quality. They also found that in some studies, processed meat, soy foods,  potatoes, full fat dairy, coffee, alcohol, sugary drinks, and sweets were linked with poor sperm quality and male infertility.
Human Reproduction Update. 2017 Mar 10:1-19. (Salas-Huetos A et al.)

For those without a medically diagnosed gluten issue (such as celiac disease), the support for gluten-free and low-gluten diets appears to be more fad than fact. In a study of nearly 200,000 health professionals, researchers at Harvard found that eating lower amounts of gluten is related to a higher risk for type 2 diabetes. In fact, those in the top 20% of gluten intake were 13% less likely to get type 2 diabetes over the 30-year study period, even after adjusting for family history, exercise habits, weight, and calorie intake. (Note that research presented at meetings is considered preliminary until published in a peer reviewed journal.)
Presented at the American Heart Association’s Epidemiology and Prevention / Lifestyle and Cardiometabolic Health 2017 Scientific Sessions. Portland, OR. March 9, 2017. (Zhong G et al.)

Despite heavy marketing of the Paleo diet and lifestyle, very little is known about what our early human ancestors actually ate. To learn more about their diets, scientists in Australia studied the DNA of dental plaque from the teeth of Neanderthals (relatives of early humans) who went extinct about 40,000 years ago. While there was evidence of a meat-based diet (including wooly rhinoceros and sheep) in what is today Belgium, the Neanderthal diet in what is today Spain indicated a vegetarian diet, including mushrooms pine nuts, and moss.
Nature. 2017 Mar 8. [Epub ahead of print] (Weyrich LS et al.)