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J T Knuiman

Publications and source records attributed to J T Knuiman.

14 recordsLinked to original sources
PubMed1989

Lecithin intake and serum cholesterol.

To find out whether the consumption of lecithin has a more beneficial effect on serum cholesterol than does the consumption of equivalent amounts of polyunsaturated oils, we scrutinized 24 studies on the effect of supplementary lecithin intakes ranging from 1 to 54 mg/d. Most of the studies lacked an appropriate control group, had a small sample size, or had changes in intake of other foods because of increased energy intake from lecithin. In only four trials were attempts made to balance fatty acid intakes of control and experimental groups. There is no evidence for a specific effect of lecithin on serum cholesterol independent of its linoleic acid content or secondary changes in food intake. The observed lecithin-induced hypocholesterolemic effects found in various studies were artifacts caused by the design and the manner of data analysis, were mediated by other dietary changes, or were due to the linoleic acid present in lecithin.

Cholesterol↗
PubMed1988

Differences in individual responsiveness of serum cholesterol to fat-modified diets in man.

In the period 1963-1974, 82 monks and 48 nuns from five Dutch and Belgian Trappist monasteries each participated in two or more out of nine different trials designed to test the effect of 58 different fat-modified diets on serum cholesterol. We analysed these data to quantify the extent to which healthy, normolipaemic subjects differ in the responsiveness of their serum cholesterol to a change in dietary fatty acid composition. Statistically significant between-person variance components (SD2p) were found in the serum cholesterol responses for the whole group (SD2p = [0.20 mmol l-1]2), for the men (SD2p = [0.24 mmol l-1]2) and for those women who participated in three or more trials (SD2p = [0.14 mmol l-1]2). The between-person variation (expressed as SD) was on average only half as large as the within-person variation in response when the same subject was challenged repeatedly. It is concluded that medically significant differences in responsiveness to fat-modified diets exist in both men and women. However, few subjects fail entirely to respond to a change in dietary fatty acid composition. In addition, the large within-subject variability makes it difficult to identify hypo- and hyperresponders.

Adult↗
PubMed1988

Blood pressure and excretion of sodium, potassium, calcium and magnesium in 8- and 9-year old boys from 19 European centres.

We have measured systolic and diastolic blood pressure and excretions of sodium, potassium, calcium and magnesium in groups of about 50 8- and 9-year-old boys from 19 European centres using standardized methods for the measurement of blood pressure and collection of urine, and by carrying out all analyses in one laboratory. Weight, height, pulse rate and environmental temperature were also studied. Mean systolic blood pressure ranged from 91 to 105 mm Hg and diastolic blood pressure from 51 to 66 mm Hg. Mean 24-h excretion of sodium was between 91 and 146 mmol/d, that of potassium between 29 and 60 mmol/d, that of calcium between 1.5 and 2.6 mmol/d and that of magnesium between 2.7 and 4.2 mmol/d. Mean sodium excretion tended to be lower and potassium excretion tended to be higher in the boys from the north-western parts of Europe. Relations between either systolic or diastolic blood pressure and electrolyte excretions were generally weak or absent. Most remarkable is that only the association between mean diastolic blood pressure and 24-h magnesium excretion (partial regression coefficient (b +/- s.e., -5.04 +/- 2.08 mm Hg/mmol/d) was statistically significant after adjusting for differences in creatinine excretion and environmental temperature. Mean systolic blood pressure was not significantly related with any of the variables measured. The partial regression coefficient (b +/- s.e.) for diastolic blood pressure on weight was 0.186 +/- 0.062 mm Hg/kg, on height 0.165 +/- 0.056 mm Hg/cm, on pulse rate 0.364 +/- 0.100 mm Hg/beats per min and on outside temperature -0.25 +/- 0.07 mm Hg/degrees C.

Blood Pressure↗
PubMed1988

Multiple overnight urine collections may be used for estimating the excretion of electrolytes and creatinine.

We studied the excretion of sodium, potassium, calcium, magnesium, and creatinine in overnight and 24-h urines collected over a period of seven consecutive days from 28 Dutch boys, ages eight and nine years. The correlation coefficients for the relation between true mean overnight and true mean 24-h excretion ranged between 0.94 and 1.00 for sodium, calcium, magnesium, and creatinine and was equal to 0.61 for potassium. Generally the within-person coefficients of variation for overnight excretions (range, 33-52%) were greater than for 24-h excretions (range 16-35%). We conclude that overnight collections may replace 24-h collections in the case of young boys, but that generally more overnight than 24-h urine specimens are required to achieve a similar degree of precision. The exact number of urine specimens required varies with the aims of the study.

Calcium↗
PubMed1988

Congruence of individual responsiveness to dietary cholesterol and to saturated fat in humans.

Previous experiments have shown that differences between humans in the response of serum cholesterol to dietary cholesterol are at least partly reproducible and stable over a prolonged period. In this study it was investigated whether enhanced sensitivity to dietary cholesterol and saturated fat go together. The subjects had also participated in three or four experiments dealing with the reproducibility of the effect on blood cholesterol of either adding cholesterol to the diet in normal subjects (NORM-EGG group; n = 23) or of cessation of egg consumption in subjects with a high habitual egg intake (HAB-EGG group; n = 24). In the present experiment the NORM-EGG subjects were fed a mixed natural diet providing 21% of energy as polyunsaturated and 11% as saturated fat (P/S2 ratio, 1.9) for 3 weeks, and one providing 5% of energy as polyunsaturated fat and 23% as saturated fat (P/S ratio, 0.2) for the next 3 weeks. The HAB-EGG group was fed the same diets in reverse order. The serum cholesterol concentrations were higher on the low P/S diet than on the high P/S diet (on average 23% in normal subjects and 16% in habitual egg eaters). The correlation coefficient between each subject's serum cholesterol response to fatty acids and his or her average response to dietary cholesterol in the dietary cholesterol experiments was 0.62 for the normal subjects (P less than 0.01) and 0.15 for the HAB-EGG group. We conclude that modest differences in responsiveness of serum cholesterol to dietary saturated fat do exist in humans, and that, in people of normal cholesterol intake, responsiveness to dietary cholesterol and to saturated fat tend to go together.

Adult↗
PubMed1987

Importance of time interval between repeated measurements of total or high-density lipoprotein cholesterol when estimating an individual's baseline concentrations.

We studied intra-individual variation in total and high-density lipoprotein (HDL) cholesterol in healthy volunteers (22 men and 19 women, ages 19 to 62 years) on controlled natural diets. The within-person coefficient of variation (CV) depended on the interval between blood samples, increasing from about 2% to 3% for measurements made 24 h apart to 4% to 5% for measurements made at four-day intervals or longer. We conclude that within-subject fluctuations in total and HDL cholesterol have a time constant of several days. Multiple measurements are generally needed to decide whether an asymptomatic subject exceeds a certain concentration of total or HDL cholesterol; we recommend that such measurements be made at least four days apart.

Adult↗
PubMed1987

Within-person variation in daily dietary intake of boys from Finland, the Netherlands, Italy, the Philippines and Ghana.

We have studied the within-person variation in daily dietary intake of energy, protein, fat, carbohydrate, cholesterol, saturated and polyunsaturated fatty acids in 8- and 9-year-old boys from five countries, using record and recall methods of dietary assessment. The average within-person coefficients of variation ranged from 19 to 31 per cent of the mean intake of energy, protein and carbohydrate; from 43 to 77 per cent of the mean intake of cholesterol, from 28 to 50 per cent of the mean intake of saturated fatty acids, and from 37 to 105 per cent of the mean intake of polyunsaturated fatty acids. Some of this variation may have been due to differences in the methods used to assess dietary intake. The day of the week on which food intake is estimated can also influence the number of measurements required to estimate precisely an individual's intake of energy or specific nutrients. From the results of this study it can be shown that it is not always justified to assume that every person in a population has the same within-person variance. This may lead to an underestimation of the number of measurements needed to estimate individual intakes. The results of this study are useful in the planning of dietary surveys when decisions are to be made about methods of data collection, sample size and length of the study, and also in the analysis and interpretation of the results of dietary surveys.

Child↗
PubMed1987

The relative validity of reports of food intake of Dutch and Finnish boys aged 8 and 9 years.

Two studies were carried out to assess the relative validity of the techniques used in measuring the food intake during school lunch or home dinner of 30 Finnish and 68 Dutch boys aged 8 and 9 years. For each of the 30 Finnish boys, duplicate portions of three lunches provided to the boys were collected by a non-participating observer. Nutrient intakes were calculated with the use of a food composition table, and the results were compared with those from the records that were kept by the boys' mothers. For each of the 68 Dutch boys, duplicate portions of the hot meal, taken at home, were collected and analyzed chemically. The results were compared with those from the records that were kept by the boys' mothers. The mean values for the absolute intakes of energy and nutrients for the boys from both Finland and The Netherlands as reported by the boys themselves or their mothers were generally higher (15% to 35%) than those measured by chemical analysis of a duplicate portion or calculated from a weighed portion as collected by a non-participating observer. However, the results for the relative proportions of energy generally showed closer agreement (range of difference, +11% to -15%). The authors found in this study that collection of duplicate portions of food resulted in lower (3% to 15%) recorded food intakes in comparison with measurements recorded for meals consumed on other days.

Child↗
PubMed1986

A multi-centre study on completeness of urine collection in 11 European centres. I. Some problems with the use of creatinine and 4-aminobenzoic acid as markers of the completeness of collection.

We have studied the completeness of urine collections in 11 European centres. The completeness of collection was examined by questioning the participants, by calculating the ratio of observed to expected creatinine, and by measuring the recovery of p-aminobenzoic acid (PABA) in the urine after administration of a 240 mg dose. The ratio of observed to expected creatinine is a fairly insensitive measure of undercollection. People who report that their collection is incomplete are likely to have collected incompletely to a considerable degree. It was concluded that the use of PABA in epidemiological studies is still questionable; overcollection cannot be detected by using PABA, and it appeared that people sometimes forget or refuse to take the capsules. It is also suggested that differences in the meal-time patterns between countries may interfere with the PABA recovery test.

4-Aminobenzoic Acid↗
PubMed1986

A multi-centre study on within-person variability in the urinary excretion of sodium, potassium, calcium, magnesium and creatinine in 8 European centres.

We have studied the within-person variability in the excretion of sodium, potassium, calcium, magnesium and creatinine in 20-60-year old men and women from 8 European centres. Only the data from people who reported that their collections were complete were entered in the analysis. The within-person coefficients of variation for the electrolytes ranged from 28 to 38 and that for creatinine from 21 to 24. The corresponding number of days required to estimate the excretion of electrolytes and creatinine to within 20 per cent of the habitual excretion (95 per cent confidence interval) varied between 4 for creatinine in men to 14 for magnesium in both men and women. The results of this study demonstrate once more that creatinine is unsuitable as a marker of completeness of urine collection for the individual.

Adult↗
PubMedDate not supplied

Total cholesterol and high density lipoprotein cholesterol levels in populations differing in fat and carbohydrate intake.

This paper reviews epidemiological studies on the relationship between diet and high density lipoproteins (HDL), with emphasis on the authors' studies of boys and men from different countries and with different dietary habits. Sera were collected from boys (ages 7 to 9 years) and men (ages 33 to 48 years) in 20 countries, and these were analyzed in one standardized laboratory. In boys, total and HDL cholesterol changed in parallel, from low values in populations in developing countries with low-fat, high-carbohydrate diets to high values in affluent populations. The correlation between HDL and total cholesterol was 0.90 (n = 16 populations). A similar trend was seen in groups of vegetarian and omnivorous boys within one region. Detailed analyses of individual diets of boys in five countries showed a negative relation between carbohydrate intake and HDL cholesterol both for group means (r = -0.99, n = 5) and for individual boys within one country (r = -0.26 to 0.04, n = 109 to 133 boys per country). In these boys, differences in obesity and physical activity were slight, and unrelated to differences in HDL. Total cholesterol rose with saturated fat intake (r = 0.87 for five population means; r = 0.07 to 0.26 within population groups). In adult men, total and HDL cholesterol also tended to rise simultaneously with affluence. However, the relation was much weaker (r = 0.60, n = 13 population groups).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗