Sphingolipids in food and the emerging importance of sphingolipids to nutrition

Eukaryotic organisms as well as some prokaryotes and viruses contain sphing olipids, which are defined by a common structural feature, i.e., a "sphingo id base" backbone such as D-erythro-l,3-dihydroxy, 2-aminooctadec-4-ene (sp hingosine). The sphingolipids of mammalian tissues, lipoproteins, and milk include ceramides, sphingomyelins, cerebrosides, gangliosides and sulfatide s; plants, fungi and yeast have mainly cerebrosides and phosphoinositides. The total amounts of sphingolipids in food vary considerably, from a few mi cromoles per kilogram (fruits) to several millimoles per kilogram in rich s ources such as dairy products, eggs and soybeans. With the use of the limit ed data available, per capita sphingolipid consumption in the United States can be estimated to be on the order of 150-180 mmol (similar to 115-140 g) per year, or 0.3-0.4 g/d. There is no known nutritional requirement for sp hingolipids; nonetheless, they are hydrolyzed throughout the gastrointestin al tract to the same categories of metabolites (ceramides and sphingoid bas es) that are used by cells to regulate growth, differentiation, apoptosis a nd other cellular functions. Studies with experimental animals have shown t hat feeding sphingolipids inhibits colon carcinogenesis, reduces serum LDL cholesterol and elevates HDL, suggesting that sphingolipids represent a "fu nctional" constituent of food. Sphingolipid metabolism can also be modified by constituents of the diet, such as cholesterol, fatty acids and mycotoxi ns (fumonisins), with consequences for cell regulation and disease. Additio nal associations among diet, sphingolipids and health are certain to emerge as more is learned about these compounds.