Scientists discovered which carbohydrates boost immunity after weight loss

Scientists from NYU Langone Health and several other U.S. research centers have made an unexpected discovery: refined starch in the diet after weight loss activates immune cells significantly more than added sugar. The study was conducted on volunteers who had lost approximately 15% of their body weight by following a very low-carbohydrate diet before the experiment. The results were published in the journal Cell Press Blue.

The experiment enrolled 54 individuals with overweight or obesity who did not have cardiovascular disease or diabetes. After successfully losing weight, the volunteers were divided into three groups: the first continued following a very low-carbohydrate diet, while the other two switched to a high-carbohydrate diet. In one case, the primary source of carbohydrates was starch from refined grain products; in the other, it was added sugar. The caloric content of the diets was identical, and the experiment itself lasted ten weeks.

The most pronounced changes were recorded in those who consumed refined starch. These participants experienced a sharp increase in the activity of several types of immune cells: natural killer cells, which are responsible for destroying infected and altered cells, monocytes, T-lymphocytes, and neutrophils. Genetic analysis confirmed the enhancement of processes associated with both innate and adaptive immunity, as well as with defense against bacteria and fungi. The group consuming added sugars, however, demonstrated the opposite pattern: over the ten weeks, the activity levels of immune and metabolic processes in these participants generally decreased compared to baseline levels.

Among the probable mechanisms behind this effect, the scientists highlight the complement system — a component of immune defense that helps the body recognize and destroy foreign objects. Participants in the "starch" group showed elevated levels of adipsin, also known as complement factor D, which triggers the activation of this mechanism. According to the authors, sharp postprandial glucose spikes may be linked to enhanced complement activity and subsequent mobilization of immune cells.

The researchers emphasize that it is premature to extrapolate the results to the general population, since the experimental conditions were quite specific — the participants had obesity and were on a strict diet. Nevertheless, the authors are convinced that their data point to the importance of carbohydrate composition for immune processes in the body.