Nut consumption offers weight, cardiometabolic benefits
CHICAGO — Two studies presented at the American Heart Association Scientific Sessions indicated that higher levels of nut consumption appear to have certain weight and cardiometabolic benefits.
In one study, increasing daily consumption of nuts in lieu of other foods reduced risk for obesity. In another, substituting Brazil nuts for pretzels increased satiety, decreased anxiety and mitigated increases in blood glucose and insulin.
Variety of nuts
In the study on consumption of a variety of nuts, the researchers analyzed 25,394 men from the Health Professionals Follow-up Study between 1986 and 2010, 53,541 women from the Nurses’ Health Study between 1986 and 2010 and 47,255 women from the Nurses’ Health Study II between 1991 and 2011. All participants were free from chronic disease and obesity at baseline.
“Once weight has been gained, it is hard to lose. Thus, one of the most effective strategies to prevent obesity is to minimize the gradual weight gain instead of weight loss,” Xiaoran Liu, PhD, MSc, research associate in the department of nutrition at Harvard T.H. Chan School of Public Health, told Cardiology Today. “Nuts are nutrient-dense foods rich in unsaturated fatty acids, vitamins, minerals and fiber. Their high fat content leads some to perceive nuts as unhealthful and to be avoided by those attempting to manage or lose their body weight. The consumption of nuts and seeds increased during the last 2 decades in the U.S.; thus, we are interested in investigating the associations between long-term weight change and the changes in intake of nuts.”
Nut consumption was determined by a semiquantitative food frequency questionnaire given every 4 years. The researchers examined associations between changes in nut consumption and concurrent weight change, RRs for weight gain of at least 5 kg and incidence of obesity, defined as BMI of at least 30 kg/m2.
According to the researchers, an increase by one serving per day in consumption of the following nuts was not associated with weight gain over 4 years (P < .01 for all):
total nuts: –0.35 kg; 95% CI, –0.38 to –0.31;
peanuts: –0.24 kg; 95% CI, –0.31 to –0.17;
walnuts: –0.64 kg; 95% CI, –0.78 to –0.5; and
other tree nuts: –0.65 kg; 95% CI, –0.74 to –0.56.
Liu and colleagues determined that each increase by one serving per day in consumption of nuts was linked to reduced likelihood of weight gain of at least 5 kg over 4 years (RR for total nuts = 0.91; 95% CI, 0.88-0.93; RR for peanuts = 0.94; 95% CI, 0.9-0.97; RR for walnuts = 0.8; 95% CI, 0.74-0.87; RR for other tree nuts = 0.8; 95% CI, 0.76-0.84).
The following nuts were associated with reduced risk for incident obesity per increase of one serving per day over 4 years: total nuts (RR = 0.95; 95% CI, 0.93-0.98), walnuts (RR = 0.79; 95% CI, 0.71-0.9) and other tree nuts (RR = 0.81; 95% CI, 0.76-0.87).
“Our research extends previous work by demonstrating the consistent inverse associations between total nuts — particularly specific types of nuts — and gradual weight gain, and risk of obesity,” Liu said in an interview. “Results from the present study add to the evidence that increased consumption of nuts, including peanuts, despite their calorie content, appears to protect against gradual weight gain and risk of becoming obese. In addition, because weight changes occur gradually at the population level, our analytical approach examined the concurrent changes in intakes of nuts and weight change over a 4-year period approximates an intervention study in examining weight change in response to a change in diet.”
Substituting one serving of nuts per day for one serving of red meat, processed meat, french fries, desserts or potato chips conferred less weight gain (P < .05 for all), according to the researchers.
“In the case of nuts, and like any other type of food, one size doesn’t always fit all,” Liu said. “For patients who want to lose weight, the synergetic effects of adapting an overall healthy dietary pattern including nuts at the expense of unhealthy foods or snacks offers more robust effect on weight loss and weight management. Adding nuts into one’s diet as a substitution of unhealthy foods is one of the key messages from our work. Patients who are learning about weight management shall be mindful on their calorie intake; however, the improvement of overall dietary quality is more important and critical than simply counting the calories of the diet.”
For the Brazil nut study, 22 healthy adults (mean age, 25 years; mean BMI, 22.3 kg/m2) consumed 36 g of pretzels and 20 g of Brazil nuts, separated by a 48-hour washout period.
The researchers measured satiety at baseline, 20 minutes and 40 minutes; anxiety at baseline and 40 minutes; and blood glucose, insulin and antioxidant levels at baseline and 40 minutes.
“We decided to undertake this study because there has been a notable amount of literature regarding the positive effects of selenium on many health outcomes. Selenium has demonstrated a role in increasing antioxidant capacity, improving blood glucose and insulin responses, and elevating mood. Since Brazil nuts are the highest known food source of selenium, we wanted to investigate if consumption of Brazil nuts showed results as promising as those previously found with selenium,” Mee Young Hong, PhD, RN, professor in the School of Exercise and Nutritional Sciences at San Diego State University, told Cardiology Today. “Additionally, there have been many studies that demonstrated positive health effects for other tree nuts, but very few have been done for Brazil nuts specifically.”
Compared with pretzels, Brazil nuts were associated with greater satiety at 40 minutes (P < .05) and less anxiety at 40 minutes (P = .02), according to the researchers.
Although pretzel consumption was associated with increased blood glucose and insulin levels at 40 minutes (P < .001 for both), Brazil nut consumption was not. Neither food affected antioxidant capacity.
“Brazil nuts did not significantly elevate either blood glucose or blood insulin levels at 40 minutes post-consumption. This indicates that Brazil nuts may help prevent the hyperglycemic conditions that could lead to diabetes,” Hong said in an interview. “Also, Brazil nut consumption demonstrated satiety for a longer period of time than consumption of the pretzel control. This suggests that Brazil nuts may play a role in reducing overall food intake, which may help with weight management and/or weight loss. Considering other food sources of selenium, including breads, grains, meat, poultry, fish and eggs, one or two Brazil nuts would be sufficient to achieve daily recommendation of selenium. Brazil nuts are also a good option for patients on a vegetarian or vegan diet because they are plant-based sources of protein and healthy fats.” – by Erik Swain
Hong MY, et al. Presentation Sa1297.
Liu X, et al. Presentation 284. Both presented at: American Heart Association Scientific Sessions; Nov. 10-12, 2018; Chicago.
Disclosures: The study by Liu and colleagues was funded by the NIH and the California Walnut Commission. The study by Hong and colleagues was funded by the AHA. Hong and Liu report no relevant financial disclosures.