Sterols in human milk during lactation: bioaccessibility and estimated intakes.

Human milk (HM) is the exclusive food during the first 4-6 months of an infant's life. Breastfeeding has been related to significant health benefits for infants, and hence it is of interest to study the bioactive compounds present in HM, such as sterols (cholesterol being the most abundant). The aim of this study was to determine the contents of sterols (cholesterol, desmosterol, lathosterol, lanosterol, campesterol, stigmasterol and ß-sitosterol) in 10 pools of colostrum, transitional milk, and 1, 3 and 6 month HM obtained from Spanish volunteers from two different geographical areas (coastal and central) and to estimate the intake and bioaccessibility (BA) of sterols in order to ascertain the fate of sterols after digestion. The results showed that the total sterol contents decreased to half the initial level during lactation (24-11 mg per 100 mL) and was significantly higher in samples from the coastal area. Total and animal sterol intakes were between 200 and 400 times higher than plant sterol intakes and were significantly higher in samples from the coastal area. However, no statistically significant differences were found in cholesterol and plant sterol intakes between areas. The BA of total sterols ranged from 45% to 69% and was higher in the first month, which coinciding with the highest fat content of milk. In conclusion, the sterol content varies depending on the lactation stage and the geographical area, and the BA of sterols can be positively affected by a higher lipid content. All these data may contribute to the development of infant formulas that are more similar to HM in terms of composition and behaviour after digestion, according to the lactation stage involved.

Cholesterol Content in Human Milk during Lactation: A Comparative Study of Enzymatic and Chromatographic Methods.

This study validates a gas chromatography (GC) method for determining the sterol profile of human milk (HM) and compares it with an enzymatic-spectrophotometric (E-S) method. Good linearity ( r > 0.97) and low limits of detection and quantification were obtained with the GC method (<1.8 and <6 µg/100 g of HM, respectively). Suitable intra- and interassay precisions (all <18%) and satisfactory recovery percentages (80-109%) were obtained for both methods. In addition, both methodologies were used to assess cholesterol evolution in HM during lactation, showing a 50% decrease at 6 months versus colostrum. The E-S method overestimated cholesterol content by <20% versus the GC method. The results indicate that both methods may be used by the industry and in research to better understand the differences between the sterol profiles of infant formulas and HM.

Impact of Lipid Components and Emulsifiers on Plant Sterols Bioaccessibility from Milk-Based Fruit Beverages.

Sterol bioaccessibility (BA) of three plant sterol (PS)-enriched milk-based fruit beverages (MFb) with different fat contents (1.1-2.4%), lipid sources (animal or vegetable), and without or with emulsifiers (whey proteins enriched with milk fat globule membrane (MFGM) or soy lecithin) was evaluated after simulated gastrointestinal digestion. The BA of total PS followed the order 31.4% (MFbM containing milk fat and whey proteins enriched with MFGM) = 28.2% (MFbO containing extra virgin olive oil and soy lecithin) > 8.7% (MFb without fat addition). Total and individual PS content in the bioaccessible fractions followed the order MFbM > MFbO > MFb. Consequently, formulation with MFGM is proposed in beverages of this kind to ensure optimum bioavailability of PS. Our results suggest that the BA of PS is influenced by the type and quantity of fat and the emulsifier type involved.

Plant sterols and antioxidant parameters in enriched beverages: storage stability.

Plant sterols (PS) stability, antioxidant parameters, and color were studied during 6 months of storage at 4, 24, and 37 °C in three PS-enriched functional beverages. Beverages were skimmed milk with fruit juice and PS (MFJPS), fruit juice and PS (FJPS), and skimmed milk with PS (MPS). No loss in total PS content occurred during storage observing the same values at any given storage time point. Total carotenoids decreased 36% with storage at two months and then remained stable. Total polyphenols showed fluctuations throughout the storage, remaining stable at 6 months and reaching initial values. The antioxidant capacity (TEAC method) increased 18% at 6 months, and there was an increase in color over time and temperature, probably due to Maillard reaction compound formation. The increase in total antioxidant capacity might have helped PS maintenance throughout storage, these beverages being a good PS source even after 6 months of storage.

Effects of phytosterol ester-enriched low-fat milk on serum lipoprotein profile in mildly hypercholesterolaemic patients are not related to dietary cholesterol or saturated fat intake.

Phytosterols (PS) are recommended to reduce LDL-cholesterol. However, the influence of cholesterol and fat intake on the lipid-lowering effect of PS in mildly hypercholesterolaemia is unclear. Thus, the aim of the present study was to evaluate whether the efficacy of PS is related to the composition of saturated fat and dietary cholesterol intake. Additionally, serum carotenoid content was analysed to evaluate to what extent it was undermined by PS. This was a 3-month randomised, parallel trial with a three-arm design. Patients were divided into three groups: healthy diet (n 24), healthy diet+PS (n 31) and free diet+PS (n 29), receiving 2 g/d of PS. Healthy and free diets were characterised by a daily ingestion of 6.8 % of saturated fat and 194.4 mg of cholesterol and 12.7 % of saturated fat and 268.1 mg of cholesterol, respectively. After PS therapy, patients receiving the healthy diet+PS or a free diet+PS exhibited a similar reduction in total cholesterol (6.7 and 5.5 %), LDL-cholesterol (9.6 and 7.0 %), non-HDL-cholesterol (12.2 and 8.9 %) and apo B-100/apo A-I ratio (11.5 and 11.6 %), respectively. In patients following the healthy diet, (ß-carotene concentration rose by 26.9 %, whereas the ß-carotene and lycopene levels dropped by 21.0 and 22.8 % in the group receiving the free diet+PS, respectively. No change was observed in carotenoid levels in healthy diet+PS group. In conclusion, the efficacy of PS in relation to lipoprotein profile is not influenced by saturated fat or dietary cholesterol intake, which confirms the positive effect of healthy diet therapy in improving the negative effects that PS exert on carotenoid levels.

Fortification of milk with calcium: effect on calcium bioavailability and interactions with iron and zinc.

Calcium solubility, dialysability, and transport and uptake (retention + transport) by Caco-2 cells as indicators of calcium bioavailability have been estimated in the in vitro gastrointestinal digests of milk and calcium fortified milk. A significant linear correlation (p < 0.05) was obtained between calcium uptake and the amount of soluble calcium added to the cells, and also between percentage calcium uptake and the calcium measured in the analyzed samples. The solubility, dialysis, transport, and uptake values are higher (p < 0.05) for calcium fortified milks than for nonfortified milks; that is, calcium fortification increases not only calcium content but also its bioavailability. An inhibitory effect of calcium from fortified milks upon iron absorption was found. The observed effect of calcium from fortified milks upon zinc bioavailability depends on the in vitro method used, zinc solubility and dialysis decrease in calcium fortified milks, and percentage zinc uptake remains unchanged.