Effect of kefir and soy yogurt consumption on serum IGF-1 levels in young healthy women

Background:Milk and dairy product intake are associated with higher IGF-1 concentrations, a well-known factor promoting adverse events such as carcinogenesis. Different associations with high levels of IGF-I were found for dairy protein such as milk and derivatives, and soy protein. In this contest, fermented milk product (kefir)exhibits a growing number of health-promoting effects including stimulation of the immune system, and antimutagenic and anticarcinogenic activity, but there is a lack of data on healthy humans. Objectives: We aimed to determine the serum IGF-1 profiles of young healthy volunteers of the female sex after kefir or soy yogurt consumption during a Mediterranean diet.Materials and Methods: The study was conducted by monitoring the serum IGF-1 levels of female participants, following a normocaloric and normoproteic Mediterranean Diet, at the baseline (T0) and after 40 days of which the first 20 days (T1) consuming 125g of kefir, and the last 20 days (T2) consuming 125g of soy yogurt. Results: A total of 10 female participants were enrolled in the study (age=26.1± 2.9). The IGF-1 level was in the range of normality for all the participants except for one participant (T0=245 ± 61, T1=227 ± 58, T2= 239 ± 55). The mixed-model analysis revealed statistically significant differences in IGF-1 levels by diet (p=0.014; η2p=0.49). In particular, post-hoc analysis revealed a lower value after 20 days of kefir diet compared to both baseline (p= 0.014) and 40 days of diet (p=0.163). Conclusion: Caloric and protein intake have been suggested to influence circulating IGF-I, promoting carcinogenesis. Kefir consumption could improve the IGF-1 levels. Our data suggest that the inclusion of whole milk kefir in a normocaloric and normoprotein diet promotes blood IGF-1 levels in healthy young women as compared to soy yogurt consumption, reinforcing the beneficial effect of fermented milk on metabolic disorders. The interpretation of this result will need to be better investigated in further studies on large sample sizes.Keywords: IGF-1, Kefir, normocaloric diet, soy yogurt