Gertjan Schaafsma

Calcium excretion, apparent calcium absorption and calcium balance in young and elderly subjects: influence of protein intake.

The present study was conducted to investigate the effect of dietary protein on urinary Ca excretion, apparent Ca absorption and Ca balance in young and elderly subjects. Young adults (n 29) and elderly persons (n 26) consumed diets containing 12% (diet A) and 21% (diet B) of total energy as protein for 3 weeks according to a randomized crossover design. Results showed no differences between the two age groups with respect to the interaction between protein intake and Ca excretion (both in urine and in faeces), apparent Ca absorption and Ca balance. Therefore analyses were done for both age groups separately and also for the whole group. In elderly persons and in the whole group the Ca excretion in faeces (as a percentage of Ca intake) was lower during the higher protein intake (elderly: diet A, 106 (SEM 7)%; diet B, 86 (SEM 7)%; P = 0.018; whole group: diet A, 99 (SEM 4)%; diet B, 84 (SEM 4)%; P = 0.003). In young adults faecal Ca excretion tended to be lower when they consumed diet B (diet A: 94 (SEM 5)%; diet B: 83 (SEM 6)%; P = 0.093). Relative urinary Ca excretion was greater during the higher protein intake in young adults and in the whole group while relative urinary Ca excretion was not different in the elderly (diet A: 15 (SEM 1)%, 14 (SEM 1)%, 15 (SEM 1)%; diet B: 16 (SEM 1)%, 16 (SEM 1)%, 17 (SEM 2)% for the whole group, the young and elderly subjects respectively, P = 0.019; P = 0.016; P = 0.243). The resulting Ca balance was not influenced by the amount of protein in the diet in young adults. Values for the elderly and for the whole group showed that the Ca balance during diet A was significantly more negative compared with Ca balance during diet B, despite the higher urinary Ca excretion during diet B. It can be concluded that increasing the protein intake from 12 to 21% of total energy intake had no negative effect on Ca balance.

Moderate Alcohol Consumption and Changes in Postprandial Lipoproteins of Premenopausal and Postmenopausal Women: A Diet-Controlled, Randomized Intervention Study

Moderate alcohol consumption is associated with a reduced risk of coronary heart disease. Earlier studies in men have shown that moderate alcohol consumption affects lipoprotein metabolism and hemostasis. In this diet-controlled, randomized, crossover trial, we investigated the effect on lipoprotein metabolism of moderate consumption of red wine or red grape juice with evening dinner for 3 weeks in premenopausal women using oral contraceptives and in postmenopausal women. After 3 weeks, blood samples were collected 1 hour before dinner up to 19 hours after starting dinner at 2-hour or 4-hour intervals. Plasma triglyceride concentrations and very low density lipoprotein (VLDL) triglyceride levels peaked 3 hours after dinner with wine in both premenopausal and postmenopausal women. After wine consumption, the overall high-density lipoprotein (HDL) cholesterol level was increased in postmenopausal women (mean increase 0.17 mmol/L, or 12%, p = 0.03), and the plasma low-density lipoprotein (LDL) cholesterol level was reduced in premenopausal women (mean reduction 0.35 mmol/L, or 12%, p = 0.01) as compared with grape juice consumption. The findings suggest that postprandial lipoprotein metabolism after moderate alcohol consumption differs between oral contraceptive-using premenopausal women and postmenopausal women. The response of postmenopausal women to alcohol resembled the response found in earlier studies in men.

Advantages and limitations of the protein digestibility-corrected amino acid score (PDCAAS) as a method for evaluating protein quality in human diets

PDCAAS is a widely used assay for evaluating protein quality. It is a chemical score, which is derived from the ratio between the first limiting amino acid in a test protein and the corresponding amino acid in a reference amino acid pattern and corrected for true faecal N digestibility. Chemical scores exceeding 100 % are truncated to 100 %. The advantages of the PDCAAS are its simplicity and direct relationship to human protein requirements. The limitations are as follows: the reference pattern is based on the minimum amino acid requirements for tissue growth and maintenance and does not necessarily reflect the optimum intake. Truncated PDCAAS of high-quality proteins do not give any information about the power of these proteins to compensate, as a supplement, for low levels of dietary essential amino acids in low-quality proteins. It is likely that faecal N digestibility does not take into account the loss from the colon of indispensable amino acids that were not absorbed in the ileum. Anti-nutritional factors, such as lectins and trypsin inhibitors, in several plant protein sources can cause heightened endogenous losses of amino acids, an issue which is particularly relevant in animal feedstuffs. The assumption that amino acid supplementation can completely restore biological efficiency of the protein source is incorrect since the kinetics of digestion and absorption between supplemented free amino acids and amino acids present in dietary proteins, are different.

Kinetics of Homocysteine Metabolism After Moderate Alcohol Consumption

BACKGROUND Moderate alcohol consumption is associated with a decreased risk of cardiovascular disease. Because plasma homocysteine (tHcy) is considered an independent risk factor for cardiovascular disease and associated with alcohol consumption, the authors investigated the effect of moderate alcohol consumption on kinetics of plasma tHcy concentration, vitamin B status, and other parameters involved in tHcy metabolism. METHODS Ten healthy men and nine healthy postmenopausal women (aged 45-65 years) participated in a randomized, diet-controlled, crossover trial. They consumed beer or alcohol-free beer (men: 4 units/day; women: 3 units/day) during 3 weeks, separated by a 1-week washout. On days 5, 10, 15, and 20 of each period, fasting blood samples were taken. RESULTS Plasma tHcy (microM) and S-adenosyl methionine/S-adenosyl homocysteine ratio were not affected by consumption of beer or alcohol-free beer (p = 0.33 and p = 0.14, respectively). Plasma pyridoxal-5-phosphate (microg/liter) increased during consumption of beer (+11.0%), whereas it decreased during consumption of alcohol-free beer (-34.0%; p = 0.042). Changes over time of plasma vitamin B6 (microg/liter) were similar to changes in plasma pyridoxal-5-phosphate (p = 0.10). Serum vitamin B12 was higher (p < 0.001) after 3 weeks consumption of alcohol-free beer (382.8 +/- 23.7 pg/liter) as compared with beer consumption (327.5 +/- 22.2 pg/liter). Changes in serum methionine, cysteine, cystathionine, and plasma folate were not different between beer-drinking and alcohol-free beer-drinking periods. CONCLUSIONS This study shows that moderate alcohol consumption does not affect plasma tHcy concentrations or S-adenosyl methionine/S-adenosyl homocysteine ratio. However, it does increase plasma vitamin B6 and decrease serum vitamin B12.

Food Matrix Effects on Bioaccessibility of β‑Carotene Can be Measured in an in Vitro Gastrointestinal Model

Since the food matrix determines β-carotene availability for intestinal absorption, food matrix effects on the bioaccessibility of β-carotene from two diets were investigated in vitro and compared with in vivo data. The “mixed diet” consisted of β-carotene-rich vegetables, and the “oil diet” contained β-carotene-low vegetables with supplemental β-carotene. The application of extrinsically labeled β-carotene was also investigated. The bioaccessibility of β-carotene was 28 μg/100 μg β-carotene from the mixed diet and 53 μg/100 μg β-carotene from the oil diet. This ratio of 1.9:1 was consistent with in vivo data, where the apparent absorption was 1.9-fold higher in the oil diet than in the mixed diet. The labeled β-carotene was not equally distributed over time. In conclusion, the food matrix effects on bioaccessibility of β-carotene could be measured using an in vitro model and were consistent with in vivo data. The application of extrinsically labeled β-carotene was not confirmed.

Postprandial ghrelin responses are associated with the intermeal interval in time-blinded normal weight men, but not in obese men.

OBJECTIVE To investigate the relation between ghrelin responses and meal initiation and the effects of BMI and energy status on this. DESIGN The experiment had a randomised, cross-over design. SETTING AND SUBJECTS Nine normal-weight (age: 33.2+/-4.8 y, BMI: 23.2+/-0.5 kg/m2) and eleven obese (age: 40.8+/- 4.7 y, BMI: 33.2+/-0.8 kg/m2) healthy men were recruited from a pool of volunteers and by advertisements. INTERVENTIONS Subjects followed a three-day energy restrictive and a three-day energy balanced diet separated by one month. Each diet was followed by a time-blinded (overnight) stay at the research facility. Subjects received a breakfast (preload) and were instructed to ask for lunch when they felt hungry. Ghrelin, insulin, glucose, free fatty acids, appetite, IMI and energy intake during lunch were assessed. RESULTS Postprandial decreases in ghrelin (r=-0.54; p<0.05) and the AUC of the ghrelin response (r=-0.57, p=0.01) were associated with the intermeal interval, independent of diet, but in normal weight subjects only. Lunch request was preceded by an increase in ghrelin, reaching at least 93% of fasting values. These preprandial increases in ghrelin were correlated with IMI, after energy restriction only. Ghrelin concentrations but not changes in ghrelin were correlated with appetite. CONCLUSION Meal-related changes in ghrelin are correlated with the IMI in normal weight subjects only, independent of diet. Ghrelin concentrations may need to reach a certain threshold level before the next meal is initiated.

Moderate alcohol consumption and fibrinolytic factors of pre- and postmenopausal women

Moderate alcohol consumption is associated with a reduced risk of coronary heart disease. Earlier studies in men have shown that moderate alcohol consumption affects lipoprotein metabolism and haemostasis. In this diet-controlled, randomized, cross-over trial we investigated the effect of moderate consumption of red wine or red grape juice with evening dinner for 3 weeks on fibrinolytic factors in premenopausal women using oral contraceptives and in postmenopausal women. After 3 weeks blood samples were collected from both pre- and postmenopausals between 1 hour before dinner up to 15 hours after starting dinner, at 2 or 4 hour intervals. In premenopausal women using oral contraceptives moderate alcohol consumption had little effect on the fibrinolytic factors. In postmenopausals fibrinolytic activity decreased directly after alcohol consumption, as plasma plasminogen activator inhibitor (PAI) activity increased to 23.1 IU/mL (or 339%, p = 0.0004) and plasma tissue-type plasminogen activator (tPA) activity decreased to 0.90 IU/mol (or 62%, p = 0.0009). As a result of this decreased fibrinolytic activity plasma plasmin antiplasmin (PAP) complex level was decreased to 148 μg/L (or 34%, p = 0.04). The following morning the fibrinolytic activity was increased, as plasma tPA activity increased to 0.44 IU/mol (or 69%, p = 0.04). Probably alcohol transcriptionally upregulated tPA gene expression, but effects on clearance cannot be ruled out. The response of fibrinolytic activity in postmenopausal women after moderate alcohol consumption appears similar to the response described earlier for middle-aged men.