The study, "Acute and second-meal effects of peanuts on glycaemic response and appetite in obese women with type 2 diabetes risk: a randomized cross-over clinical trial," was conducted jointly by Purdue University and the Federal University of Vicosa in Brazil. The principal investigator, Dr. Richard Mattes of Purdue University, explained, "If you include peanut butter or peanuts at breakfast, you not only diminish the rise in blood sugar at breakfast but also again after lunch, helping to reduce blood sugar over a very large portion of the day."
During three phases of the study, 1.5oz. of peanuts, 3tbs of peanut butter, or no peanuts or peanut butter were consumed with a breakfast consisting of orange juice and cream of wheat followed by a lunch consisting of white bread and strawberry jam. Blood samples and appetite ratings were taken over a series of three hours following breakfast and again after lunch to assess glucose control and satiety; participants were also asked to keep a food diary for the remainder of the day after leaving the testing site.
Results showed that peanut butter or peanuts included with breakfast promotes secretion of the appetite-suppressing hormone peptide YY (PYY). In addition, participants who consumed peanut butter or peanuts with breakfast reported a lower desire to eat for up to 8-12 hours later and maintained lower blood sugar following a high carbohydrate lunch compared to participants that did not include peanut butter or peanuts. Peanut butter had a slightly stronger effect, possibly because the cell walls of the peanut are ruptured during processing and may help slow the rate that carbohydrates are absorbed from the gut, resulting in a lower glycaemic response in the blood.
The researchers suggest that it is the synergy of components in peanuts, including the high protein, high fiber, and healthy oils that help to maintain blood sugar control, as well as contribute to feelings of fullness. According to the latest USDA National Nutrient Database, peanuts contain more protein than any other nut, with about 8g of protein per 1oz. portion, and they are also a good source of fiber with about 2.5g of fiber per 1oz. serving.
"Combined with findings from other work, this new research provides additional reasons to start your day with peanut butter and include a snack of peanuts in the late afternoon if you want to control your appetite and blood sugar too," said Pat Kearney, MEd, RD, program director for The Peanut Institute.