Phospholipids: Structure Plus Functionality
By Angela M. Miraglio, R.D.
Physiologically, phospholipids (PLs) play manyessential roles in cellular structure and function. Small quantities of PLs occur naturally in a wide variety of foods, andfrequently formulators use them as emulsifiers in processed products. Because our bodies synthesize PLs from other nutrients and metabolites, thehealth significance of ingested PLs is difficult to assess. To date, healthauthorities recognize only one component of these diverse compounds—choline—asa nutrient. But others believe that supplemental PLs offer some advantages inheart health and cognitive functioning.
PLs consist of fatty acids and aphosphate-containing compound attached to glycerol or the amino alcoholsphingosine, resulting in compounds with fat-soluble and water-soluble regions. Cell membranes utilize the dual hydrophilic and hydrophobic characteristic ofPLs to maintain structure and transport materials. Glycerol-containing PLsinclude 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-systemconduction and protection, memory storage and muscle control. Choline, a majorcomponent of PC and SPH, functions as a methyl donor and a precursor to theneurotransmitter acetylcholine.
All plant and animal foods contain some PLs as part of their cell membranes. The phosphate-containing component and fatty-acid composition variesaccording to the source. Dairy PLs include PC, PE, PS and SPH, while lecithinconstitutes the PLs in soy and eggs. Considered synonymous with PC, lecithinactually contains a mix of PLs and some triglycerides. For example, soy lecithinincludes PA, PC, PE, PI and PS. Egg lecithin with considerable PC qualifies asan excellent source (more than 110 mg per serving per FDA) of choline with 280mg per large egg, while beef contributes enough choline to qualify as a goodsource (more than 55 mg per serving). Marine PLs incorporate valuable omega-3 fatty acids in a form that increasestheir levels in the brain, according to animal studies.
In general, little research exists on the requirementsor intake of PLs. Michael Schneider, Ph.D., from Lecithos, Freinsheim, Germany, and aconsultant to Cargill Lecithin Group, Minneapolis, says no known symptoms areassociated with PL malnutrition, except choline deficiency. While some researchindicates that choline helps with fetal brain development and memory, cholinedeficiency manifested as liver dysfunction with fatty liver in studies withhealthy men and people on total parenteral nutrition. Therefore, ingredients with PC, such as lecithin, and SPH offer knownnutritional value because they contribute choline to the diet.
“Althougheggs contain reasonably high concentrations of PLs, soybean oil is one of themost-common sources of lecithin, a predominant PL for product development andhealth ingredients,” says Jennifer Causey, Ph.D., nutrition manager, Lipid Nutrition, a divisionof Loders Croklaan B.V., Wormerveer, the Netherlands. “Lecithin is animportant component of our diet. Unfortunately, the economically driven processing and purification of foodingredients often leads to a decrease in natural PL sources important to brainand cardiovascular health.”
The level and types of PLs in food ingredients vary. Causey says that LodersCroklaan produces high-quality liquid PL products with concentrations rangingfrom 30% to 35% PC, and adds, “While the market in the United States is a hotup-and-coming venue from a health perspective, PC is sold extensively in the EUas a nutritional ingredient with a growing market anticipated globally.”
According to Schneider, Cargill manufactures two deoiled soy lecithinproducts 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). Arange of new products are under development, as are novel processes that willadd value to existing products.
Typical whey protein concentrates contain some PLs, but a specialized wheyprotein concentrate from Glanbia Nutritionals, Inc., Monroe, WI, aimed at thesports nutrition market features PS and PC levels approximately double that inWPC 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 wellas purify and refine individual components to provide high-quality material forsupplemental purposes.
The emulsifying properties of PLs contribute functionality to many foods andbeverages. However, Schneider says, “Usually the emulsifier dosage is belowany effective dose, but this does not mean you could not add more to make use ofthe dual functionality (emulsifier and health ingredient).” He notes thateffective or therapeutic doses range from 100 mg per day for PS to 5 and gramsmore per day of deoiled soy lecithin, adding that 1 gram of PC supplies 156 mgof choline and with 1.2 grams PC providing enough for liver effectiveness. “Theincorporation of an effective dose is very much dependent on the type oflecithin and/or PL product. Food product examples can be bars, confectioneries,spreads and yogurts, and lecithin granules for direct consumption and foodsupplements, of course,” he states.
In the dietary supplement world, lecithin and choline health claims includeimprovement of exercise endurance, dementia in Alzheimer’s patients, memory,thinking ability and muscle control, and reduction of liver degeneration—withlittle or no scientific evidence to support them, according to “The AmericanDietetic Association’s Health Professional’s Guide to Dietary Supplements,2nd Edition” (2003). It also states that claims about PS raising IQ andreducing production of cortisol, thereby inhibiting muscle breakdown, lacksufficient data. However, in 2003, FDA approved a qualified health claim forsoy-derived PS dietary supplements and the potential reduction of risk fordementia and cognitive function in the elderly, with the caveat that verylimited and preliminary scientific research suggests these effects. FDAconcludes that little scientific evidence supports the claim. FDA also specifiedthat no level can be suggested as the effective dose. Obviously, divergent viewsexist on PLs’ role in disease prevention and treatment. Hopefully, futureresearch will provide guidance for developing PL-fortified products.