PubMed Health⌕ Search

Biomedical subjects

E Menden

Publications and source records attributed to E Menden.

11 recordsLinked to original sources
PubMed1994

[The effect of tryptophan on the regulation of food intake in normal and overweight persons].

The neurotransmitter serotonin significantly contributes to the regulation of food intake and appetite behaviour. The cerebral serotonin synthesis depends on the availability of the precursor tryptophan. To examine how diets with different carbohydrate, protein and tryptophan content affect food preferences and the mood, healthy obese and non-obese male adults consumed the following isocaloric diets at breakfast: standard diet (60% carbohydrate), protein-rich diet (35% carbohydrate, 40% protein), carbohydrate-rich diet (80% carbohydrate), tryptophan supplemented diet (standard diet + 1.5 g tryptophan). The plasma concentration of tryptophan (TRP) and large neutral amino acids (LNAA) is determined by their uptake with the diet. In obese and non-obese adults the TRP/LNAA-quotient rose significantly by upto 0.40 to 0.57, following the tryptophan supplemented breakfast. The protein-rich diet reduced the TRP/LNAA-quotient. The preference of protein-rich food after the consumption of carbohydrate-rich diets (60-80% carbohydrate) was diagnosable with the non-obese person and not with the obese person. No obvious connection was detected between nutrient preferences and plasma TRP/LNAA-quotient. There was no influence of the plasma TRP/LNAA-quotient after meals with different nutrient relation on mood. Therefore it is concluded that different carbohydrate and protein content and also additional tryptophan supplementation of single meals is not able to modify the brain serotonin synthesis and release in healthy people in a kind that serotonin induced behaviour would be changed, at least on a short time basis.

Adult↗
PubMed1988

[The effect of long-term increased protein administration on mineral metabolism and kidney function in the rat. I. Renal and enteral excretion of calcium, magnesium, phosphorus, sulfate and acid].

The influence of continuous imbalanced high protein intake on the metabolism of minerals (calcium, magnesium, phosphorus) and renal function was the subject of a long-term experiment with rats. In the first part of the study particular attention was directed to the contribution of protein-induced endogenous acid production and renal excretion of hydrogen ions and sulphate to the development of hypercalciuria. For 61 weeks 200 male Wistar rats in eight groups were fed isocaloric diets, whose protein contents were increased from 13 to 26 and 40 J% at the expense of carbohydrate intake. The fat content of the diets was 40 J%. In two groups with 13 and 26 J% protein the effect of different kinds of animal protein was also studied, replacing casein by beef. Mineral contents were kept constant in these diets. To examine the excretion mechanisms of calcium and phosphorus especially under conditions of excessive protein intake, the ratio of calcium to phosphorus was varied in three diets with 40 J% protein by increasing both minerals alternatively or together from 0.6 to 1.2%. An increase in dietary protein content from 13 to 26 or 40 J% produced a sustained hypercalciuria and also hypermagnesiuria over a period of more than 400 days (after 58 weeks: 3.3, 5.9, and 6.8 mg calcium/day; 2.2, 3.3, and 3.4 mg magnesium/day; p less than or equal to 0.05). No adaptation to high protein intake occurred. Hypermagnesiuria, which equally hasn't been described before as a result of high protein intake, was accompanied by a reduced fecal excretion of magnesium. With increased protein intake (casein and beef) hypercalciuria and also hypermagnesiuria were positively correlated with an increased formation and renal excretion of hydrogen ions and sulphate, which resulted from protein catabolism. The dietary protein source influenced the extent of hypercalciuria, irrespective of a constant phosphorus intake. Although leading to equal increases in renal total acid and sulphate excretion, beef as the main protein source caused a lower calciuria than casein. High phosphorus intake caused the highest total acid excretion of all groups, but resulted in a reduced hypercalciuria and hypermagnesiuria and counteracted the influence of an increased protein intake.

Acid-Base Equilibrium↗
PubMed1988

[The effect of long-term increased protein administration on mineral metabolism and kidney function in the rat. II. Kidney function and bone mineralization].

In the Federal Republic of Germany the average daily protein intake exceeds the Recommended Dietary Allowances for adults (0.8 g protein/kg body weight) by about 100%. On the other hand calcium intake is below the recommendations for certain age groups. Protein-induced hypercalciuria involves the risk of depletion of skeletal calcium stores, especially for older people who have a decreased absorption capacity for calcium. As a result of our study we postulate, that an altered renal function probably is one inducing factor of hypercalciuria. While urea excretion and serum urea concentration increased with an elevated dietary protein content from 13 to 26 or 40 J%, glomerular filtration rate remained unchanged. Fractional tubular reabsorption of calcium was significantly reduced by about 3% with increased endogenous acid production and renal excretion of hydrogen ions (first part of the study), which were accompanying a higher protein intake of 40 J% compared to 13 J% protein in the control group. Increasing the phosphorus content of the diet improved the reabsorption of calcium and magnesium. The kidneys of rats fed diets high in protein and phosphorus were hypertrophied. Histology of the kidneys showed signs of glomerulonephrosis. While the calcium content of the femora was slightly reduced with a higher protein intake of 40 compared to 13 J%, the magnesium content was increased (after 61 weeks: calcium from 261.4 to 257.1 mg/g dry fat-free wt [p less than or equal to 0.05]; magnesium from 3.2 to 3.5 mg/g dry fat-free wt [p less than or equal to 0.001]). Calcium and magnesium metabolism depends not only on the level of protein intake, but also on its interrelation with the dietary phosphorus content. With continuous high protein intake higher intakes for calcium, phosphorus and magnesium should be recommended, especially for older people.

Animals↗
PubMed1982

[Long-term effects of various levels of dietary proteins as well as starch and sucrose as dietary carbohydrates on lipoprotein metabolism in the rat].

UNLABELLED: The repeatedly reported effect of proteins on lipoprotein metabolism leaves the question if this is caused mainly by the amount of amino acid composition of the protein itself, by the accompanying fat of cholesterol content, or by the contemporary predominant kind of carbohydrate in the diet. The conducted experiments with male rats, feeding them in 6 groups of 20 animals for one year semipurified, cholesterol-free diets with constantly 40 (J-)% fat in all diets, 13% (I), 20% (II, III, IV) or 40% (V, VI) protein and complementary carbohydrates (50% starch, 50% sucrose). III received sucrose only, IV starch only. VI was given additionally 0.8% arginine (arg). Rats on 40% protein exhibited higher total plasma cholesterol levels in comparison to 13% protein, HDL values were nearly identical in I, II, III, IV, and increased in V and VI. LDL was increased in V, compared to all other groups. CONCLUSION: The level of dietary protein alone may influence amount and distribution of lipoproteins in rats. LDL may be decreased by addition of arg, HDL remains unchanged. The type of carbohydrate had no influence on HDL or LDL on conditions of our experiment, whereas earlier experiments showed elevation of LDL values with sucrose in comparison to starch if cholesterol was present in the diet.

Animals↗
PubMed1976

[A reducing diet with a high proportion of bread].

10 female and 10 male moderately obese persons, pursuing their usual activities, received a reduction diet for 4 weeks, in which 46% of the calories were supplied by rye bread. In percent of calories the diet consisted of 60% carbohydrates, 20% fat and 20% protein. The total intake of calories corresponded to 60% of the caloric requirement. Weight losses ranged from 1.8 to 10.7 kg; the mean was 6.0 kg. Serum cholesterol values tended to decrease by 15% on the average, triglyceride values decreased by 38%. All subjects declared to be satiated during the entire 4 week period. No significant differences between the influence of crumb and crust on weight reduction could be observed.

Adult↗