Phospholipids: Structure Plus Functionality
By Angela M. Miraglio, R.D.
Contributing Editor
Physiologically, phospholipids (PLs) play many essential roles in cellular structure and function. Small quantities of PLs occur naturally in a wide variety of foods, and frequently formulators use them as emulsifiers in processed products. Because our bodies synthesize PLs from other nutrients and metabolites, the health significance of ingested PLs is difficult to assess. To date, health authorities recognize only one component of these diverse compounds—choline—as a nutrient. But others believe that supplemental PLs offer some advantages in heart health and cognitive functioning.
Phospholipids basics
PLs consist of fatty acids and a phosphate-containing compound attached to glycerol or the amino alcohol sphingosine, resulting in compounds with fat-soluble and water-soluble regions. Cell membranes utilize the dual hydrophilic and hydrophobic characteristic of PLs to maintain structure and transport materials. Glycerol-containing PLs include phosphatidic acid (PA), phosphatidylcholine (PC), phophatidylethanolamine (PE), phophatidylinositol (PI), and phosphatidylserine (PS). Sphingomyelin (SPH), the other major PL, consists of sphingosine and PC. Phospholipids contribute to lipoprotein formation in the liver, nervous-system conduction and protection, memory storage and muscle control. Choline, a major component of PC and SPH, functions as a methyl donor and a precursor to the neurotransmitter acetylcholine.
All plant and animal foods contain some PLs as part of their cell membranes. The phosphate-containing component and fatty-acid composition varies according to the source. Dairy PLs include PC, PE, PS and SPH, while lecithin constitutes the PLs in soy and eggs. Considered synonymous with PC, lecithin actually contains a mix of PLs and some triglycerides. For example, soy lecithin includes PA, PC, PE, PI and PS. Egg lecithin with considerable PC qualifies as an excellent source (more than 110 mg per serving per FDA) of choline with 280 mg per large egg, while beef contributes enough choline to qualify as a good source (more than 55 mg per serving). Marine PLs incorporate valuable omega-3 fatty acids in a form that increases their levels in the brain, according to animal studies.
Adding value
In general, little research exists on the requirements or intake of PLs. Michael Schneider, Ph.D., from Lecithos, Freinsheim, Germany, and a consultant to Cargill Lecithin Group, Minneapolis, says no known symptoms are associated with PL malnutrition, except choline deficiency. While some research indicates that choline helps with fetal brain development and memory, choline deficiency manifested as liver dysfunction with fatty liver in studies with healthy men and people on total parenteral nutrition. Therefore, ingredients with PC, such as lecithin, and SPH offer known nutritional value because they contribute choline to the diet.
“Although eggs contain reasonably high concentrations of PLs, soybean oil is one of the most-common sources of lecithin, a predominant PL for product development and health ingredients,” says Jennifer Causey, Ph.D., nutrition manager, Lipid Nutrition, a division of Loders Croklaan B.V., Wormerveer, the Netherlands. “Lecithin is an important component of our diet. Unfortunately, the economically driven processing and purification of food ingredients often leads to a decrease in natural PL sources important to brain and cardiovascular health.”
The level and types of PLs in food ingredients vary. Causey says that Loders Croklaan produces high-quality liquid PL products with concentrations ranging from 30% to 35% PC, and adds, “While the market in the United States is a hot up-and-coming venue from a health perspective, PC is sold extensively in the EU as a nutritional ingredient with a growing market anticipated globally.”
According to Schneider, Cargill manufactures two deoiled soy lecithin products with minimum 97% acetone insolubles (70% to 75% PLs consisting of 18% to 25% PC, 18% to 22% PE, 13% to 19% PI, 4% to 8% PA and 0.10% to 1.31% PS). A range of new products are under development, as are novel processes that will add value to existing products.
Typical whey protein concentrates contain some PLs, but a specialized whey protein concentrate from Glanbia Nutritionals, Inc., Monroe, WI, aimed at the sports nutrition market features PS and PC levels approximately double that in WPC 80 (PS 247 mg versus 135 mg and PC 1,000 mg versus 553 mg per 100 grams). Several soy-based and marine-based ingredients also modify PLs profiles as well as purify and refine individual components to provide high-quality material for supplemental purposes.
The emulsifying properties of PLs contribute functionality to many foods and beverages. However, Schneider says, “Usually the emulsifier dosage is below any effective dose, but this does not mean you could not add more to make use of the dual functionality (emulsifier and health ingredient).” He notes that effective or therapeutic doses range from 100 mg per day for PS to 5 and grams more per day of deoiled soy lecithin, adding that 1 gram of PC supplies 156 mg of choline and with 1.2 grams PC providing enough for liver effectiveness. “The incorporation of an effective dose is very much dependent on the type of lecithin and/or PL product. Food product examples can be bars, confectioneries, spreads and yogurts, and lecithin granules for direct consumption and food supplements, of course,” he states.
In the dietary supplement world, lecithin and choline health claims include improvement of exercise endurance, dementia in Alzheimer’s patients, memory, thinking ability and muscle control, and reduction of liver degeneration—with little or no scientific evidence to support them, according to “The American Dietetic Association’s Health Professional’s Guide to Dietary Supplements, 2nd Edition” (2003). It also states that claims about PS raising IQ and reducing production of cortisol, thereby inhibiting muscle breakdown, lack sufficient data. However, in 2003, FDA approved a qualified health claim for soy-derived PS dietary supplements and the potential reduction of risk for dementia and cognitive function in the elderly, with the caveat that very limited and preliminary scientific research suggests these effects. FDA concludes that little scientific evidence supports the claim. FDA also specified that no level can be suggested as the effective dose. Obviously, divergent views exist on PLs’ role in disease prevention and treatment. Hopefully, future research will provide guidance for developing PL-fortified products.
Angela M. Miraglio, M.S., R.D., is a Fellow of the American Dietetic Association from Des Plaines, IL. Her firm, AMM Food & Nutrition Consulting, provides communications and technical support to the food and beverage industry. She can be reached at ammiraglio@aol.com.
