The effects of dietary soy phosphatidylcholine on neutrophils

Abstract

Effects of oral soy phosphatidylcholine (PC), on polymorphonuclear leukocyte (PMNL) phagocytosis and killing of Candida albicans (c.a.) and on PMNL fatty acid composition were followed in eight normal adults in an open cross-over study. Twenty-seven grams of PC delivering 18g linoleic acid (LA) or placebo were provided daily for three days. Bloods were drawn for PMNL assays at baseline and four, seven and fourteen days post ingestion. In response to PC but not to placebo, PMNL phagocytosis and killing of c.a. increased 2.0 fold (p[less than]0.01) and 2.6 fold (p[less than]0.01), respectively; PMNL phospholipid arachidonic acid (PL-AA) content increased 2.9 (p[less than]0.01) to 3.7 fold (p[less than].001) and stimulation of PMNL with c.a. resulted in a 5.3 fold increase in PL-AA release (p[less than]0.001) which correlated with PMNL killing (r=0.932) and phagocytosis (r=0.872). In separate experiments, a minimum of 18g of oral PC was required to produce similar changes. Leukotriene B4 generation increased four-fold when PMNLs of 4 subjects were exposed to calcium ionophore (A21387) and [less than]1,900 fold when exposed to N-f-met-leu-phe (fMLP). Ingestion of equivalent amounts of LA as soy or safflower oil did not effect PMNL function or PL-AA composition. In another experiment the ingestion of 40 grams of PC by two test subjects significantly increased total leukocyte choline from 92.6[plus or minus]21.4 pmol/10 superscipt 6 pMNLs at baseline to 168.2[plus or minus]1.7 pmol/10 superscipt 6 pMNLs at 48 hours (P=0.04). This supports the hypothesis that oral phosphatidylcholine not only reaches the bone marrow precursor PMNL pool, but that there is a significant incorporation. This is the first demonstration in that a dietary supplement significantly increases polymorphonuclear leukocyte phospholipid-arachidonic acid, the major eicosanoid precursor.