Eukaryotic organisms as well as some prokaryotes and viruses contain sphingolipids, which are defined by a common structural feature, i.e. , a "sphingoid base" backbone such as D-erythro-1,3-dihydroxy, 2-aminooctadec-4-ene (sphingosine). The sphingolipids of mammalian tissues, lipoproteins, and milk include ceramides, sphingomyelins, cerebrosides, gangliosides and sulfatides; plants, fungi and yeast have mainly cerebrosides and phosphoinositides. The total amounts of sphingolipids in food vary considerably, from a few micromoles per kilogram (fruits) to several millimoles per kilogram in rich sources such as dairy products, eggs and soybeans. With the use of the limited data available, per capita sphingolipid consumption in the United States can be estimated to be on the order of 150-180 mmol (approximately 115-140 g) per year, or 0.3-0.4 g/d. There is no known nutritional requirement for sphingolipids; nonetheless, they are hydrolyzed throughout the gastrointestinal tract to the same categories of metabolites (ceramides and sphingoid bases) that are used by cells to regulate growth, differentiation, apoptosis and other cellular functions. Studies with experimental animals have shown that feeding sphingolipids inhibits colon carcinogenesis, reduces serum LDL cholesterol and elevates HDL, suggesting that sphingolipids represent a "functional" constituent of food. Sphingolipid metabolism can also be modified by constituents of the diet, such as cholesterol, fatty acids and mycotoxins (fumonisins), with consequences for cell regulation and disease. Additional associations among diet, sphingolipids and health are certain to emerge as more is learned about these compounds.

The measurement of estradiol in biological fluids is important in human biology from cradle to grave. In addition to its centrality in sexual development, it has significant effects on skin, blood vessels, bone, muscle, coagulation, hepatic cells, adipose tissue, the kidney, the gastrointestinal tract, brain, lung, and pancreas. Alterations in its plasma concentration have been implicated in coronary artery disease, stroke, and breast cancer. Although modern immunoassays and liquid chromatography/tandem mass spectrometry-based methods for estradiol are reasonably well suited to the diagnosis and management of infertility (nonetheless, imprecision and method-to-method differences remain problematic), the very low concentrations that appear to be crucial in nonreproductive tissues are a separate and more difficult issue. Such levels of estradiol are too low to be routinely measured accurately or precisely, and further evolution of analytical methods and the way in which estradiol is standardized is needed.

Reference ranges generated in a community-based sample of men provide a rational basis for categorizing testosterone levels as low or normal. Men with low TT or FT by these criteria had higher prevalence of physical dysfunction, sexual dysfunction, and diabetes. These reference limits should be validated prospectively in relation to incident outcomes and in randomized trials.

Harmonized normal range in a healthy nonobese population of European and American men, 19 to 39 years, is 264 to 916 ng/dL. A substantial proportion of intercohort variation in testosterone levels is due to assay differences. These data demonstrate the feasibility of generating harmonized reference ranges for testosterone that can be applied to assays, which have been calibrated to a reference method and calibrator.

Objective: We applied VDSP protocols to existing ELISA-derived serum 25(OH)D data from the Irish National Adult Nutrition Survey (NANS) as a case-study survey and evaluated their effectiveness by comparison of the protocol-projected estimates with those from a reanalysis of survey serums by using liquid chromatography-tandem mass spectrometry (LC-tandem MS). Design: The VDSP reference system and protocols were applied to ELISA-based serum 25(OH)D data from the representative NANS sample (n = 1118). A reanalysis of 99 stored serums by using standardized LC-tandem MS and resulting regression equations yielded predicted standardized serum 25(OH)D values, which were then compared with LC-tandem MS reanalyzed values for all serums. Results: Year-round prevalence rates for serum 25(OH)D concentrations ,30, ,40, and ,50 nmol/L were 6.5%, 21.9%, and 40.0%, respectively, via original ELISA measurements and 11.4%, 25.3%, and 43.7%, respectively, when VDSP protocols were applied. Differences in estimates at ,30-and ,40-nmol/L thresholds, but not at the ,50-nmol/L threshold, were significant (P , 0.05). A reanalysis of all serums by using LC-tandem MS confirmed prevalence estimates as 11.2%, 27.2%, and 45.0%, respectively. Prevalences of serum 25(OH)D concentrations .125 nmol/L were 1.2%, 0.3%, and 0.6% by means of ELISA, VDSP protocols, and LC-tandem MS, respectively. Conclusion: VDSP protocols hold a major potential for national nutrition and health surveys in terms of the standardization of serum 25(OH)D data.Am J Clin Nutr 2013;97:1235-42.