- Researchers from Beth Israel Deaconess Medical Center recently found through a brain imaging study that eating walnuts activates an area in the brain associated with regulating hunger and cravings.
- Ten volunteers diagnosed as obese reported feeling less hungry while consuming walnut-containing smoothies than while receiving placebo smoothies. When the participants were shown pictures of highly desirable foods, functional magnetic resonance imaging revealed increased activity in a part of the brain controlling desire after they consumed the five-day walnut-rich diet compared to when they had not.
- "This is a powerful measure," study leader Christos Mantzoros, director of the Human Nutrition Unit at the medical center and professor of medicine at Harvard Medical School, said in a release about the research. "We know there's no ambiguity in terms of study results. When participants eat walnuts, this part of their brain lights up, and we know that's connected with what they are telling us about feeling less hungry or more full."
In a separate study conducted at the University of Georgia and reported in the journal Nutrition, researchers found that 26 millennial participants felt fuller when they consumed foods containing polyunsaturated fatty acids — often abbreviated as PUFAs — such as walnuts, hummus and salmon.
According to the study authors, more research is needed to assess the long-term impact of a PUFA-rich diet and to determine whether any specific foods have a greater impact than others.
Nuts typically contain a high level of monounsatured fat, but walnuts are unique because they also contain a relatively high level of PUFAs — 13 out of 18 grams of total fat per one-ounce serving. They are also the only nut with a significant amount of plant-based omega-3 alpha-linolenic acid, with 2.5 grams per ounce.
Fats are not created equal, and the 2015 to 2020 Dietary Guidelines for Americans recommends consuming PUFAs and monounsatured fats in place of saturated fats. One ounce of raw walnuts — about 12 to 14 halves — contains 190 calories and 18 grams of fat.
Consumers have heard the good news about walnuts, which is reflected in annual consumption. For the 2015 to 2016 marketing year, walnut consumption totaled more than 133 million pounds, which is about 10% more than the previous year. Crop yields are at record levels due to increased planting, and the U.S. is the single largest consumer of shelled walnuts (and the second-largest producer following China).
Manufacturers use walnuts in prepared foods such as trail mix, ice cream and candy, and turn them into walnut oil, walnut butter and even a liqueur. The crushed shells are marketed for use in biodegradable industrial applications.