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Biomedical subjects

F J Kok

Publications and source records attributed to F J Kok.

At least 19 recordsLinked to original sources
PubMed2006

Phytate intake and molar ratios of phytate to zinc, iron and calcium in the diets of people in China.

OBJECTIVE: To assess the phytate intake and molar ratios of phytate to calcium, iron and zinc in the diets of people in China. DESIGN: 2002 China Nationwide Nutrition and Health Survey is a cross-sectional nationwide representative survey on nutrition and health. The information on dietary intakes was collected using consecutive 3 days 24 h recall by trained interviewers. SUBJECTS: The data of 68 962 residents aged 2-101 years old from 132 counties were analyzed. RESULTS: The median daily dietary intake of phytate, calcium, iron and zinc were 1186, 338.1, 21.2 and 10.6 mg, respectively. Urban residents consumed less phytate (781 vs 1342 mg/day), more calcium (374.5 vs 324.1 mg/day) and comparable amounts of iron (21.1 vs 21.2 mg/day) and zinc (10.6 vs 10.6 mg/day) than their rural counterparts. A wide variation in phytate intake among residents from six areas was found, ranging from 648 to 1433 mg/day. The median molar ratios of phytate to calcium, iron, zinc and phytate x calcium/zinc were 0.22, 4.88, 11.1 and 89.0, respectively, with a large variation between urban and rural areas. The phytate:zinc molar ratios ranged from 6.2 to 14.2, whereas the phytate x calcium/zinc molar ratios were from 63.7 to 107.2. The proportion of subjects with ratios above the critical values of phytate to iron, phytate to calcium, phytate to zinc and phytate x calcium/zinc were 95.4, 43.7, 23.1 and 8.7%, respectively. All the phytate/mineral ratios of rural residents were higher than that of their urban counterparts. CONCLUSIONS: The dietary phytate intake of people in China was higher than those in Western developed countries and lower than those in developing countries. Phytate may impair the bioavailability of iron, calcium and zinc in the diets of people in China.

Adolescent↗
PubMed2006

Blood pressure response to calcium supplementation: a meta-analysis of randomized controlled trials.

Calcium plays a role in blood pressure (BP) regulation, but the importance of supplemental calcium intake for the prevention of hypertension is still debated. We conducted a meta-analysis of randomized controlled trials to determine the effect of calcium supplementation on BP. A systematic search for randomized trials of calcium supplementation and BP in non-pregnant subjects was performed in Medline from 1966 to June 2003. Seventy-one trials were identified, 40 of which met the criteria for meta-analysis (total of 2492 subjects). Two persons independently extracted data from original publications on changes in calcium intake and BP. In addition, data were collected on subjects' characteristics, that is, age, gender, initial BP and initial calcium intake. A random effects model was used to obtain the effect of calcium supplementation on BP, overall and in predefined population subgroups. Calcium supplementation (mean daily dose: 1200 mg) reduced systolic BP by -1.86 mm Hg (95% confidence interval: -2.91 to -0.81) and diastolic BP by -0.99 mm Hg (-1.61 to -0.37). In people with a relatively low calcium intake (< or =800 mg per day) somewhat larger BP estimates were obtained, that is, -2.63 (-4.03 to -1.24) for systolic BP and -1.30 (-2.13 to -0.47) for diastolic BP. Our study suggests that an adequate intake of calcium should be recommended for the prevention of hypertension. More research on BP in people with calcium-deficient diets is warranted.

Adolescent↗
PubMed2006

Fasting leptin and appetite responses induced by a 4-day 65%-energy-restricted diet.

OBJECTIVE: Animal studies show that the leptin decline after acute severe caloric restriction is a peripheral signal to increase food intake. However, most human studies have failed to observe such a relationship. We studied the acute effects of severe caloric restriction on the association between serum leptin concentrations and subjective appetite. SUBJECTS: A total of 44 healthy adult men (aged: 43 +/- 5 years; BMI: 27.3 +/- 3.2 kg/m(2)). MEASUREMENTS: Fasting serum leptin concentrations and self-perceived appetite levels were measured during a 4-day diet containing 36% of the estimated energy requirements. Appetite levels were assessed with a 10-point Likert scale, reflecting hunger, fullness, desire to eat, prospective consumption and total appetite. RESULTS: After the 4-day energy deficit, fasting leptin concentrations decreased by 39.4% (95% CI: -43.6; -34.9%). This decline was associated with an increase in fasting hunger (r = -0.42; P < 0.01), desire to eat (r = -0.39; P < 0.05) and total appetite (r = -0.38; P < 0.05). Furthermore, the association between fasting leptin concentrations and fasting appetite levels became stronger during the energy restriction period (for total appetite: day 0 r = -0.15, P = 0.32; day 2 r = -0.31, P =< 0.05; day 4 r = -0.41, P < 0.01). CONCLUSIONS: The acute proportional reduction in fasting leptin after 4-day energy restriction is associated with an increase in self-perceived appetite. Additionally, the inverse association between proportional fasting leptin concentrations and self-perceived appetite response becomes stronger as energy restriction is prolonged. These findings suggest that leptin has an instrumental role in restoring energy balance in humans through the expression of appetite.

Adult↗
PubMed2006

Impact of promotion of mango and liver as sources of vitamin A for young children: a pilot study in Burkina Faso.

OBJECTIVE: To assess the effectiveness of a behaviour change approach, with or without financial support, in improving vitamin A (VA) intake and serum retinol concentration through mango and liver consumption by children. DESIGN: A parallel design (no control area) was used to assess changes in VA intake and serum retinol over a 15-week period. SETTING AND SUBJECTS: A pilot study was implemented in the Department of Kokologho, a rural area in central west Burkina Faso. One hundred and fifty children aged 2-3 years were randomly selected and assigned to two treatment groups: PA$$ (promotional activities and financial support) and PA (promotional activities). RESULTS: The intervention significantly increased (P < 0.001) total VA intake by 56% in PA$$ and by 50% in PA. VA intake from liver increased significantly (P < 0.001) from 12.7 +/- 23.5 to 155.3 +/- 56.3 microg retinol activity equivalents (RAE) in PA$$ and from 21.6 +/- 29.7 to 135.3 +/- 44.9 microg RAE in PA. Changes in VA intake from liver were significantly higher (P = 0.004) in PA$$ compared with PA. Mean serum retinol concentration increased significantly by 26% (P < 0.001) in PA$$ and 30% (P < 0.001) in PA. Changes in serum retinol concentration (0.13 micromol l(-1) in PA$$ vs. 0.17 micromol l(-1) and in PA) did not differ significantly (P = 0.455) between groups over the intervention. CONCLUSION: Promotional activities on mango and liver intake effectively increased VA intake and serum retinol concentrations. Although an additional beneficial effect of financial support on liver intake was observed, this did not translate into a further increase in serum retinol concentration.

Burkina Faso↗
PubMed2006

Faecal SIgA secretion in infants fed on pre- or probiotic infant formula.

Secretory immunoglobulin A (SIgA) plays an important role in the defence of the gastrointestinal tract. The level of faecal SIgA antibody is associated with increased neutralization and clearance of viruses. Formula-fed infants who lack the transfer of protective maternal SIgA from breast milk may benefit from strategies to support maturation of humoral immunity and endogenous production of SIgA. We aimed at studying the effects of standard, prebiotic and probiotic infant formulas on the faecal SIgA levels. At birth, infants of whom the mother had decided not to breastfeed were allocated to one of three formula groups in a randomized, double-blind fashion. Nineteen infants received standard infant formula; 19 received prebiotic formula containing a specific mixture of 0.6 g galacto-oligosaccharides (GOS)/fructo-oligosaccharides (FOS)/100 ml formula and 19 received probiotic formula containing 6.0 x 10(9) cfu Bifidobacterium animalis/100 ml formula. Faecal samples were taken on postnatal day 5, day 10, wk 4 and every 4 wk thereafter until wk 32. SIgA in faeces was determined by an enzyme-linked immunosorbent assay. During the intervention, infants fed on prebiotic formula showed a trend towards higher faecal SIgA levels compared with the standard formula-fed infants reaching statistical significance at the age of 16 wk. In contrast, infants fed on the probiotic formula showed a highly variable faecal SIgA concentration with no statistically significant differences compared with the standard formula group. Formula-fed infants may benefit from infant formulas containing a prebiotic mixture of GOS and FOS because of the observed clear tendency to increase faecal SIgA secretion. Adding viable B. animalis strain Bb-12 to infant formula did not reveal any sign for such a trend.

Breast Feeding↗
PubMed2005

Netherlands research programme weight gain prevention (NHF-NRG): rationale, objectives and strategies.

OBJECTIVE: To outline the rationale, objectives and strategies used in a systematically designed research programmme to study specific weight gain-inducing behaviours, their social-psychological as well as environmental determinants, and the effects of interventions aimed at the prevention of weight gain. DESIGN: The evidence for potential behavioural determinants and strategies to prevent weight gain was reviewed, and the methods applied within the Netherlands Research programme weight gain prevention (NHF-NRG) project were described. The project is designed according to the Intervention Mapping protocol. SETTING: The Netherlands. SUBJECTS: The main target groups are (a) adolescents (12-16 y) in secondary school, (b) young adults (20-40 y) at the workplace and (c) recently retired people (55-65 y) at home. INTERVENTIONS: Each intervention includes an individual component, in which computer-tailored information is provided. Additionally, interventions are aimed at changing environmental components. RESULTS: The short-term results of this project can be expected by the beginning of 2005. Guidelines for nationwide weight gain prevention, based on this research programme, will become available in 2007. CONCLUSIONS: Based on the few interventions that were evaluated to date, no robust conclusions can be drawn regarding the effectiveness of obesity prevention. The systematic and multidisciplinary design of the NHF-NRG programme enables the identification of potentially effective methods and strategies for the prevention of weight gain.

Adolescent↗
PubMed2005

Public health impact of community-based nutrition and lifestyle interventions.

Community-based interventions have increasingly received attention since researchers and public health professionals have come to acknowledge the importance of an environment that makes the healthy choice the easy choice. All stakeholders including the target community are involved to achieve changes in legislation, in people's social and physical context, and in individual characteristics that support healthy diets and other lifestyles. Some early large-scale community-based heart health interventions showed promising results. The Stanford Five City Project, for example, showed net improvements in knowledge of coronary heart disease risk factors of approximately 12%. Net declines in smoking prevalence (14%), cholesterol (2%), and systolic (3%) and diastolic (5%) blood pressure were also observed. Most later studies did not replicate these findings and it was therefore suggested that community-based interventions, which require substantial commitment and resources, may be less effective than approaches targeting high-risk groups. We present the rationale and theories for community-based interventions, and then elaborate on the methodological challenges in the design and the outcome and process evaluation of community-based interventions. We provide an overview of some of the evidence on the effectiveness of community-based heart health interventions and conclude with the perspectives for community-based interventions in future research and practice.

Community Networks↗
PubMed2005

Impact of dietary and lifestyle factors on the prevalence of hypertension in Western populations.

The impact of dietary and lifestyle factors on the prevalence of hypertension was quantified for Finland, Italy, The Netherlands, UK and USA. For this purpose, we combined data of blood pressure (BP) and risk factors distributions in these five countries with BP estimates from randomized controlled trials of dietary and lifestyle factors to obtain population attributable risk percentages (PAR%) for hypertension. Overweight made a substantial contribution to hypertension (PAR%: 11-17%), as was the case for excessive sodium intake (9-17%), low potassium intake (4-17%), physical inactivity (5-13%), and low intake of fish oil (3-16%). PAR% were smaller for low calcium intake (2-8%), low magnesium intake (4-8%), excessive coffee consumption (1-9%) and excessive alcohol intake (2-3%). We conclude that diet and lifestyle have a major impact on hypertension in Western societies. The relative significance of different risk factors varies among populations, which is important for preventive strategies.

Blood Pressure↗
PubMed2003

Leptin and insulin responses to a four-day energy-deficient diet in men with different weight history.

OBJECTIVE: To assess the leptin responses to a 4-day energy-restricted diet in men with different weight history; high retrospective weight gain was expected to be associated with a small decline in leptin. DESIGN: Changes in fasting leptin and insulin were measured during a 4-day controlled intervention, in which men with high retrospective weight gain and men who had stable weight consumed 35% of their estimated energy needs. SUBJECTS: A total of 44 healthy men (age: 31-52 y, BMI: 22.7-39.8 kg/m(2)) were recruited from a cohort study: 22 men who had gained weight (weight change >1 kg/y) and 22 men whose weight had remained stable (weight change +/-0.3 kg/y) between the first (1987-1991) and the second measurement (1993-1997) of the cohort study. The intervention study was carried out in 2001. RESULTS: After intervention, changes in fasting leptin levels were similar for both groups of retrospective weight gain: -2.2 microlU/ml (95% CI: -2.8; -1.7) and -2.4 microlU/ml (95% CI: -3.2; -1.7) respectively (P=0.69). Proportional changes in fasting leptin levels were different: -43.3% (95% CI: -47.8; -38.4) in the participants whose weight had remained stable (n=22) and -35.2% (95% CI: -42.4; -27.1) in those who had gained weight (n=22)(P<0.05). Analyses in a subgroup of men (n=18), in which the contrast in weight history was more pronounced than in the total group, did not show this difference. A higher proportional decrease in insulin levels was seen in men whose weight remained stable than in those who had gained weight: -35.4% (95% CI: -46.9; -21.3) and -12.8% (95% CI: -28.1; 5.7), respectively. The proportional decrease in leptin was positively associated with the proportional decrease in insulin (r=0.52; P<0.05). The decrease in leptin was positively associated with preintervention body weight (r=0.36; P<0.05), BMI (r=0.44; P<0.05), and waist-circumference (r=0.46; P<0.05). CONCLUSION: Although we found that the 4-day energy restriction had a smaller effect on the decrease in leptin in men with retrospective weight gain, our study does not show convincing evidence that men who gained weight are less leptin responsive to changes in energy balance than those who were weight stable.

Adult↗
PubMed2003

Blood pressure response to changes in sodium and potassium intake: a metaregression analysis of randomised trials.

The objective of the study was to assess the blood pressure response to changes in sodium and potassium intake and examine effect modification by age, gender, blood pressure, body weight and habitual sodium and potassium intake. Randomised trials of sodium reduction or potassium supplementation and blood pressure were identified through reference lists of systematic reviews and an additional MEDLINE search (January 1995-March 2001). A total of 40 sodium trials and 27 potassium trials in adults with a minimum duration of 2 weeks were selected for analysis. Data on changes in electrolyte intake and blood pressure during intervention were collected, as well as data on mean age, gender, body weight, initial electrolyte intake and initial blood pressure of the trial populations. Blood pressure effects of changes in electrolyte intake were assessed by weighted metaregression analysis, overall and in strata of trial population characteristics. Analyses were repeated with adjustment for potential confounders. Sodium reduction (median: -77 mmol/24 h) was associated with a change of -2.54 mmHg (95% CI: -3.16, -1.92) in systolic blood pressure and -1.96 mmHg (-2.41, -1.51) in diastolic blood pressure. Corresponding values for increased potassium intake (median: 44 mmol/24 h) were -2.42 mmHg (-3.75, -1.08) and -1.57 mmHg (-2.65, -0.50). Blood pressure response was larger in hypertensives than normotensives, both for sodium (systolic: -5.24 vs -1.26 mmHg, P < 0.001; diastolic: -3.69 vs -1.14 mmHg, P < 0.001) and potassium (systolic: -3.51 vs -0.97 mmHg, P=0.089; diastolic: -2.51 vs -0.34 mmHg, P=0.074). In conclusion, reduced intake of sodium and increased intake of potassium could make an important contribution to the prevention of hypertension, especially in populations with elevated blood pressure.

Blood Pressure↗
PubMed2003

Myocardial infarction risk in relation to zinc concentration in toenails.

Zn is an essential mineral. The role of Zn in atherosclerosis is not clear. Epidemiological studies, which have reported contradictory results, are limited by the use of serum Zn levels as a marker of intake. We assessed the association of toenail Zn, which integrates dietary Zn intake over 3 to 12 months, with the risk of a first myocardial infarction. Toenail Zn concentrations were determined by neutron activation analysis in the European multi-centre case-control study on antioxidants, myocardial infarction and breast cancer. This multi-centre case-control study included 684 cases and 724 controls from eight European countries and Israel. Toenail Zn levels of controls (adjusted for age and study centre) were positively associated with age, alpha-tocopherol and Se, but not with additional dietary variables or with classical risk factors for CHD. Average toenail Zn was 106.0 mg/kg in cases (95 % CI 103.1, 108.9) and 107.5 mg/kg in controls (95 % CI 104.5, 110.7). After controlling for cardiovascular risk factors and for centre, the adjusted odds ratios of myocardial infarction for quintiles 2-5 of toenail Zn with respect to the first quintile were 0.97 (95 % CI 0.59, 1.58), 1.15 (95 % CI 0.72, 1.85), 0.91 (95 % CI 0.56, 1.50), and 0.85 (95 % CI 0.52, 1.39). The P for trend was 0.45. In conclusion toenail Zn levels (reflecting long-term dietary intake) were not significantly associated with acute myocardial infarction.

Adipose Tissue↗
PubMed2002

Meat consumption and meat preparation in relation to colorectal adenomas among sporadic and HNPCC family patients in The Netherlands.

Meat consumption and meat preparation methods are thought to be associated with the risk of sporadic colorectal cancer, and possibly adenomas. As the same somatic mutations occur in sporadic adenomas and hereditary non-polyposis colorectal cancer (HNPCC)-related adenomas, similar exogenous factors may play a role in the development of both types of adenoma. In a case control study among 57 sporadic colorectal adenoma cases and 62 adenoma cases from HNPCC families (and 148 adenoma-free controls) from the Netherlands, we examined whether meat consumption and preparation are similarly associated with sporadic and suspected HNPCC colorectal adenomas. Frequency of meat consumption was not significantly associated with adenoma risk in our population of sporadic and HNPCC family cases and controls (Odds Ratios (OR) for high versus low consumption were 1.0 and 0.6, respectively). Interestingly, consumption of red meat and specific preparation methods (i.e., "not adding any water" and " closed lid with most meat types") slightly, but non-significantly, increased the risk of adenomas in the sporadic group only (OR, 95% Confidence Interval (CI): 4.1, 0.7-23.0, 2.0, 0.6-6.5 and 2.6, 0.9-7.2, respectively). This is the first study to examine possible differences or similarities in risk factors for sporadic and HNPCC colorectal carcinogenesis. Our results do not provide support for meat consumption as a risk factor for adenoma formation in HNPCC family members. Some characteristics of habitual meat preparation in the Netherlands may, however, increase the risk of sporadic adenomas.

Adenoma↗
PubMed2002

Physical exercise or micronutrient supplementation for the wellbeing of the frail elderly? A randomised controlled trial.

OBJECTIVE: To examine the effects of 17 weeks of physical exercise and micronutrient supplementation on the psychological wellbeing of 139 independently living, frail, elderly subjects (inactive, body mass index < or =25 or experiencing weight loss). METHODS: Participants (mean (SD) age 78.5 (5.7)) were randomly assigned to: (a) comprehensive, moderate intensity, group exercise; (b) daily micronutrient enriched foods (25-100% recommended daily amount); (c) both; (d) neither. A social programme and identical regular foods were offered as attention control and placebo. RESULTS: At baseline, moderate to low but significant correlations were found between general wellbeing scores and physical fitness (r = 0.28), functional performance (r = 0.37), and blood concentrations of pyridoxine (r = 0.20), folate (r = 0.25), and vitamin D (r = 0.23) (all p values < or =0.02), but not with physical activity levels and other blood vitamin concentrations. General wellbeing score and self rated health were not responsive to 17 weeks of exercise or nutritional intervention. CONCLUSION: Psychological wellbeing in frail elderly people was not responsive to 17 weeks of intervention with exercise and/or micronutrient enriched foods. The moderate but significant correlations between wellbeing and physical fitness and several blood vitamin concentrations at baseline suggest that changes in wellbeing may occur after long term interventions.

Activities of Daily Living↗
PubMed2001

Cohort analysis of fruit and vegetable consumption and lung cancer mortality in European men.

Our aim was to examine the relationship between fruit and vegetable consumption and lung cancer mortality in a cohort of European males. Around 1970, dietary intake of Finnish, Italian and Dutch middle-aged men was assessed using a cross-check dietary history. Complete baseline information was available for 3,108 men, of whom 1,578 were baseline smokers. We used Cox proportional hazard analyses to calculate risk estimates for the consumption in country-specific tertiles on lung cancer in smokers. During 25 years of follow-up, 149 lung cancer deaths occurred in the smokers. Fruit consumption was inversely associated with lung cancer mortality among smokers; compared with the lowest, adjusted RRs for the intermediate and highest tertiles were 0.56 (0.37-0.84) and 0.69 (0.46-1.02), p-trend 0.05. Only in the Dutch cohort was this association statistically significant [adjusted relative risks (RRs) 1.00, 0.33 (0.16-0.70) and 0.35 (0.16-0.74), p-trend 0.004]. In Finland lung cancer risk was lower with higher fruit intake but not significantly, whereas in Italy no association was observed. Stratifying on cigarette smoking intensity (non, light and heavy) revealed an inverse association in the heavy smokers only [adjusted RRs (95% confidence intervals [CI]) 1; 0.47 (0.26-0.84); 0.40 (0.20-0.78)). Vegetable consumption was not related to lung cancer risk in smokers. However, analyses stratified on cigarette smoking intensity gave some indication for a lower lung cancer risk with higher intake. In conclusion, in this prospective analysis among European smoking men, fruit intake was inversely related to lung cancer mortality. This association was confined to heavy cigarette smokers.

Adult↗
PubMed2001

Association between trans fatty acid intake and 10-year risk of coronary heart disease in the Zutphen Elderly Study: a prospective population-based study.

BACKGROUND: Evidence on the relation between trans fatty acid intake and coronary heart disease is limited. We investigated this relation in a Dutch population with a fairly high trans fatty acid intake, including trans fatty acids from partly hydrogenated fish oils. METHODS: We prospectively studied 667 men of the Zutphen Elderly Study aged 64-84 years and free of coronary heart disease at baseline. We used dietary surveys to establish the participants' food consumption patterns. Information on risk factors and diet was obtained in 1985, 1990, and 1995. After 10 years of follow-up from 1985-95, there were 98 cases of fatal or non-fatal coronary heart disease. FINDINGS: Between 1985 and 1995, average trans fatty acid intake decreased from 4.3% to 1.9% of energy. After adjustment for age, body mass index, smoking, and dietary covariates, trans fatty acid intake at baseline was positively associated with the 10-year risk of coronary heart disease. The relative risk for a difference of 2% of energy in trans fatty acid intake at baseline was 1.28 (95% CI 1.01-1.61). INTERPRETATION: A high intake of trans fatty acids (all types of isomers) contributes to the risk of coronary heart disease. The substantial decrease in trans fatty acid intake, mainly due to industrial lowering of trans contents in Dutch edible fats, could therefore have had a large public-health impact.

Aged↗