Effects of low fat diets varying in P/S ratio on nutrient intakes, fecal excretion, blood chemistry profiles, and fatty acids of adult men.

Twenty-three apparently healthy volunteers aged 35 to 60 years consumed closely monitored self-selected (SS) diets for five weeks followed by two low fat controlled diets (25% energy) for two six-week periods followed by another five-week SS diet. The two low fat diets, fed in a crossover design to one-half of the subjects per controlled diet period, had a polyunsaturated/saturated (P/S) fat ratio of either 0.3 or 1.0. Results are reported for bi-weekly measurements of energy and nutrients; blood profiles and plasma fatty acids; and for end-of-period values for stool characteristics. Blood chemistry profiles differed in the two groups. The low P/S diet produced significant increases not only in cholesterol, but in 16:0, 16:1, and percent saturated fatty acids and decreases in 18:2 and omega 6 fatty acids. The reverse was seen with the high P/S diet. The essential fatty acid (EFA) linoleic acid returned in the poststudy period to prestudy levels (all subjects), but arachidonic acid did not. The explanation for negative correlation between magnesium intake or excretion and percent plasma linoleic acid must await further research.

Moderate changes in linoleate intake do not influence the systemic production of E prostaglandins.

A pilot study was undertaken to determine if moderate changes in linoleate (18:2 omega 6) intake would modulate the prostaglandin E turnover concurrently with, or independently of, changes in the plasma prostaglandin (PG) precursor levels. Four adult male volunteers in good health were fed two controlled diets containing 35% of energy from fat, with either 10 (diet L) or 30 g (diet H) linoleate/day, 30 to 50 g saturated fatty acids/day, and the balance mainly monounsaturated fatty acids. All four subjects were consuming sufficient amounts of polyunsaturates before the study. Protein (13-14%) and carbohydrate (51-53%) contribution to total caloric intake was kept constant. The menu cycle was 7 days, and all diets were calculated to provide adequate amounts of nutrients known to be required by man when data were available. Plasma fatty acids were determined by gas-liquid chromatography, and the turnover of E prostaglandins was assessed by measuring the urinary output of the major metabolite of PGE1 + PGE2 (PGE-M). Whereas we found a clear correlation between 18:2 omega 6 intake and 18:2 omega 6 concentrations in the neutral lipid (P = 0.007) and phosphoglyceride (P = 0.012) fractions of plasma, arachidonate (20:4 omega 6) concentrations in those same plasma fractions did not respond significantly to changes in linoleate intake. Moreover, we could not detect an influence of moderate changes in dietary levels of 18:2 omega 6 on the systemic production of PGE as measured by the daily urinary output of PGE-M.

Variations in plasma fatty acid concentrations during a one-year self-selected dietary intake study.

A group of healthy volunteers, maintaining their usual lifestyle, was monitored as to their nutrient intake for a period of 1 yr. Diet records were kept daily and blood samples were collected at even intervals five times during the year. Plasma fatty acid levels were analyzed to determine any sex, age, or seasonal variations or if the plasma fatty acid levels could be correlated to dietary fat intake. In the population studied, there was a significant (p less than 0.0001) sex by age interaction, but no seasonal effect was observed. No major differences in plasma fatty acids related to diet were found. However, the younger men had the highest linoleic acid intake and the lowest plasma linoleic acid. Plasma linoleic acid levels for males older than 35 yr of age (87.0 +/- 3.1 mg/dl) were significantly greater than for males younger than 36 yr of age (67.9 +/- 1.8 mg/dl). The plasma linoleic acid levels of all the women were intermediate in value to the men but not different from each other (73.8 +/- 1.7 mg/dl for the younger women and 78.7 +/- 1.9 mg/dl for the older women). There was a significant (p less than 0.01) sex effect in the relative percentage of plasma linoleic acid (34.4 +/- 0.4% for the women and 32.4 +/- 0.6% for the men), but no age or seasonal effect was observed.

Effect of dietary fat on the fluidity of platelet membranes.

Dietary fat type was reflected in the phospholipid fatty acid composition of the plasma membrane of rabbit platelets and apparently controlled the fluidity of these membranes. Rabbits were maintained for 6 months on diets that varied in stearic and polyunsaturated fatty acids and thus had different potentials for thrombosis. Microviscosities at 37 C, calculated from the arisotropy of fluorescence from the probe 1,6-diphenyl-1,3,5-hexatriene, were 3.5, 3.4, 2.8 and 2.2 poise for platelet membranes isolated from rabbits whose only source of dietary fat was cocoa butter, milkfat, coconut oil, or corn oil, respectively. The relative findings of the membrane isolates were correlated with the polyunsaturated fatty acid contents of the membrane phospholipids.

N-Acetylprocainamide levels in patients with end-stage renal failure.

Serum concentrations of procainamide (PA) and N-acetylprocainamide (NAPA) were measured by fluorometry in subjects with normal renal function (n = 4) and in patients with end-stage renal failure (n = 3) after administration of 6.5 mg/kg of PA-HCl orally. Two subjects with normal renal function were rapid isonicotinic acid hydrazide (INH) acetylators and two were slow acetylators. The rapid acetylators had higher peak serum levels of NAPA (1.80 mug/ml) than the slow acetylators (0.40 mug/ml). Peak serum levels of PA were essentially identical in both. The half-life (T1/2) of PA was shorter, 2.5 hr, in the rapid acetylators than in the slow, 4.1 hr. The slope of the terminal portion of the blood time curve for NAPA was steeper (-0.087) for slow acetylators than for rapid (-0.078). These apparent differences between rapid and slow acetylators are not conclusive in themselves but tend to support the differences in acetylation previously reported. In the absence of renal function, the serum levels of PA were higher and the T1/2 prolonged. The serum levels of NAPA rose slowly and reached peak levels of 2 to 3 mug/ml and declined only with hemodialysis. In 3 patients measurable levels of NAPA were still present 78 hr (0.62 mug/ml), 94 hr (0.36 mug/ml), and 124 hr (0.70 mug/ml) after the single oral dose of PA. Clearance of NAPA during clinical hemodialysis was 48 +/- 10 cc/min compared to 75 +/- 12 ml/min for PA.