Visual function in patients undergoing long-term total parenteral nutrition

Article Abstract:

Nutritional deficiencies can lead to dysfunction of one or more body systems, including vision. Patients who undergo long-term total parenteral nutrition (TPN; feeding by intravenous means only) are particularly subject to nutritional disorders, either because of the underlying disorder that required treatment by TPN, generally poor nutrition during the disease state, or because TPN may lead to an unacknowledged lack or excess of particular nutrients. Visual function was assessed in 12 children and 27 adults who were medically stable and being treated with long-term TPN due to a variety of gastrointestinal disorders. Inspection of the retina showed granularity of tissue, but the prevalence of these differences in pigmentation was not significant. Many of the subjects, about one half of children and one third of adults, had one or more abnormalities in retinal function associated with either rod or cone cells (which differ in their participation in night and color vision). Of the nutrients which affect vision, zinc and vitamin E levels were normal, while vitamin A was high in 10 adults. The element selenium was low in all 10 children who were tested and in 17 of 21 adults who were tested. Levels of two important fats, linolenic and linoleic acids, were also in the low range, as was taurine, an amino acid. However, the only nutrients that correlated with retinal function were zinc and vitamin E. Duration of TPN therapy did not correlate with levels of nutrients or retinal function. Visual acuity was normal in all but two patients. The relationship between blood and tissue levels of these nutrients is unclear, and further study of the association between these nutrients, TPN, and visual function is needed. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Physiological aspects, Parenteral feeding, Parenteral nutrition, Vision

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Fat absorption in neonates: comparison of long-chain-fatty-acid and triglyceride compositions of formula, feces, and blood

Article Abstract:

Premature infants have a decreased ability to absorb fat because of their small amount of bile acids (needed for fat metabolism) and inadequate lipolytic activity, or reduced ability to break down fat. Human milk contains fat that is more bioavailable, or accessible for metabolic needs, than the fat in infant formulas. Human milk contains lipases, enzymes that break down fats, and specific types of triglyceride structures. For example, in human milk, the fatty acid called palmitic acid is attached to the triglyceride at a specific site, the sn-2 position, which may enhance fat absorption. However, studies showed that infant formulas that were modified to contain this palmitic acid did not result in better fat absorption in premature infants as compared with standard infant formulas. The absorption of fat was assessed in 22 premature infants who were fed a lard-modified fat formula, containing the palmitic acid attached to the sn-2 position of the triglyceride. The results were compared with those of 14 premature infants who received a standard infant formula. More than 90 percent of the lipid contained in the feces of the infants from both groups was composed of free fatty acids. The specific amounts and types of these fatty acids were related to the formula fatty acid composition. The levels and nature of cholesterol esters and triglycerides in the feces were similar for the two groups. Lipolysis, or fat breakdown, in the colon accounts for fat metabolism in the intestine and limited fat absorption. The presence of triglycerides in the colon may result from the ability of triglycerides to rapidly pass through the small intestine before they are broken down. (Consumer Summary produced by Reliance Medical Information, Inc.)

Analysis, Food and nutrition, Infants (Premature), Premature infants, Fatty acids, Fat, Fats

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