One hundred and fifty‐one foods were analysed for phytanic acid and 57 foods for free phytol. Foods analysed included examples from all major food groups, beverages and confectionery. No significant amount of phytanic acid was found in any food of purely vegetable origin. The sources of phytanic acid in the UK diet were confirmed to be foods derived from ruminant animals and fish. They include beef, lamb and products containing the milk fats of cows, sheep and goats. All fish were found to contain phytanic acid roughly in proportion to their fat content. Domestic and commercial fat blends containing animal fats (chiefly hydrogenated fish oils) and baked goods made from these fats contained phytanic acid: pure vegetable fat blends and foods containing them did not. Free phytol was found in small amounts in a variety of foods but not in sufficient quantity to warrant the exclusion of any one item from the diet of patients with Refsum's disease.

Previous studies have shown that amino acid (AA) residues are absorbed more rapidly from di- tripeptides than from free AA. In the present study, an intestinal perfusion technique has been used in normal human subjects to compare absorption of AA residues and total alpha-amino nitrogen (N) from 4 partial enzymic hydrolysates of protein (50--80% of the N contents present as small peptides) and their respective equimolar free AA mixtures. alpha-Amino N absorption was greater from 2 casein hydrolytes and a lactalbumin hydrolysate than from the respective free AA mixtures but similar to that from a fish protein hydrolysate and its AA mixture. The considerable variation in absorption of individual AA residues from the AA mixtures was much reduced when the protein hydrolysates were perfused, as a number of AA which were poorly absorbed from the AA mixtures were absorbed to a greater extent from the protein hydrolysates. The casein and lactalbumin hydrolysates had a stimulatory effect on jejunal absorption of water and electrolytes. In contrast, the fish protein hydrolysate appeared to cause a mean net secretion of fluid and electrolytes. The findings indicate that when absorption is limited by diminished luminal hydrolysis or absorptive capacity, serious consideration might be given to using partial enzymic hydrolysates of whole protein rather than free AA mixtures as the N source in "elemental" diets. Care should be taken, however, in ensuring that the preparation of choice does not promote a net secretion of fluid and electrolytes for such a property could have a deleterious effect in the clinical setting.

No abstract

1. The characteristics of intestinal transport and hydrolysis of carnosine (8-alanyl-Lhistidine) have been studied in rings of everted hamster jejunum in uitro.2. During incubation with carnosine, large amounts of intact peptide appeared in the intestinal wall, accompanied by small amounts of the constituent amino acids in the free form. Although there was some extracellular hydrolysis, the free amino acids appearing in the intestinal wall were almost entirely derived from intracellular hydrolysis of the peptide. Incubation in L-alanyl-L-histidine resulted in uptake of the constituent amino acids in the free form without appearance of intact peptide in the intestinal wall.3. Total uptake of B-alanine (both peptide-bound and free) and total uptake of histidine were greater from a low concentration (1 pmol/ml) of carnosine than uptake of these amino acids from the equivalent amino acid mixture. At a high concentration of carnosine (20 pmol/ml), total uptake of 8-alanine was greater from the peptide than from the equivalent amino acid mixture but total uptake of histidine was less. At this concentration, total uptake of p-alanine plus total uptake of histidine from the peptide was approximately the same as from the amino acid mixture.4. Uptake of carnosine by jejunal rings was the result of a saturable process (Kt 9-4 pmol/ml, V,,,. 2.7 pmol g-' initial wet wt. min-l). Intact carnosine was concentrated in the intestinal wall, the concentration ratio between intracellular fluid and incubation medium being up to 3-4/1. Uptake of carnosine was reduced by anoxia, metabolic inhibitors and replacement of medium Na+ . Na+-dependent active transport was shown to be involved in uptake of carnosine by hamster jejunum in vitro.

1. Glycylsarcosine, a peptide which is slowly hydrolysed by the intestine, is transported into the jejunal mucosal cells of the hamster by an active Na+-dependent process.2. Uptake of glycylsarcosine is inhibited by L-methionyl-L-methionine but not by L-methionine, suggesting that L-methionyl-L-methionine and glycylsarcosine share an uptake mechanism which is independent of that for free methionine, and that Lmethionyl-L-methionine may also enter the cells.