Platelet-Activating Factor (PAF) Antagonists in Foods:  A Study of Lipids with PAF or Anti-PAF-like Activity in Cow's Milk and Yogurt

Yogurt, a food with indisputable nutritional value, is also used for therapeutic purposes. Milk derivatives are blamed for some pathological effects of yogurt noted in selected subjects such as sensitive newborns or infants. In this study, we investigated the probable existence of platelet-activating factor (PAF) and lipids inhibiting PAF action in raw and incubated milk and yogurt. Detection of these substances may explain the controversial properties of these milk products. The in vitro biological study of lipids in washed platelets showed little production of PAF in incubated milk (0.3−0.8 ng/100 mL sample) although the concentration of PAF in milk fat remained constant during the majority of the incubation time. Yogurt lipids of intermediate polarity presented stronger inhibitory activity against PAF than lipids corresponded to raw or incubated milk. Our data demonstrated that Streptococcus thermophilus and Lactobacillus bulgaricus biosynthesize important quantities of PAF inhibitors, whereas random contamination of milk leads to the production of small amounts of PAF and PAF inhibitors.