Longitudinal study of soy food intake and blood pressure among middle-aged and elderly Chinese women

BACKGROUND: Several small-scale clinical trials have suggested a potential beneficial effect of short-term soy consumption on blood pressure (BP). Data are scanty on long-term effects of the usual intake of soy foods on BP in general populations. OBJECTIVE: Our aim was to examine the association between usual intake of soy foods and BP. DESIGN: The usual intake of soy foods was assessed at baseline, and BP was measured 2-3 y after the baseline survey among 45 694 participants of the Shanghai Women's Health Study aged 40-70 y who had no history of hypertension, diabetes, or cardiovascular disease at recruitment. Multiple regression models were used to estimate mean differences in BP associated with various intakes of soy foods. RESULTS: Soy protein intake was inversely associated with both systolic BP (P for trend = 0.01) and diastolic BP (P for trend = 0.009) after adjustment for age, body mass index, and lifestyle and other dietary factors. The adjusted mean systolic BP was 1.9 mm Hg lower (95% CI: -3.0, -0.8 mm Hg) and the diastolic BP was 0.9 mm Hg lower (-1.6, -0.2 mm Hg) in women who consumed > or =25 g soy protein/d than in women consuming <2.5 g/d. The inverse associations became stronger with increasing age (P for interaction < 0.05 for both BPs). Among women >60 y old, the corresponding differences were -4.9 mm Hg (95% CI: -8.0, -1.9 mm Hg) for systolic BP and -2.2 mm Hg (95% CI: -3.8, -0.6 mm Hg) for diastolic BP. CONCLUSION: Usual intake of soy foods was inversely associated with both systolic and diastolic BPs, particularly among elderly women.     

The relationship between antioxidant nutrient intake and cataracts in older people

This study investigated the relationship between the intake of antioxidant nutrients and the suffering of cataracts in 177 institutionalized elderly people (61 men and 116 women) aged > or = 65 years. Dietary intake was monitored for 7 consecutive days using a "precise individual weighing" method. Subjects, who during their earlier years were exposed by their work to sunlight, had a greater risk of suffering cataracts (OR = 3.2; CI: 1.1-9.3, P < 0.05) than those who worked indoors. A relationship was found between increased vitamin C intake and a reduced prevalence of cataracts (i.e., when comparing those above P95 for vitamin C intake with those below P5; (OR = 0.08; CI: 0.01-0.75, P 0.05). Among subjects with cataracts, 12.1% had vitamin C intakes of < 61 mg/day (P10) and only 2.2% had intakes of > 183 mg/day (P95) (p < 0.01). Subjects who consumed > 3290 microg/day (P95) of lutein were less likely to have cataracts (OR = 0.086; CI: 0.007-1.084; p < 0.05) than those whose consumption was < 256 microg/day (P5). In men, high intakes of zeaxanthin seemed to provide a protective effect against the problem (OR = 0.96; CI: 0.91-0.99; p < 0.05). The results suggest an association exists between exposure to sunlight and the development of cataracts, and that vitamin C, lutein, and zeaxanthin offer some protection against this disorder.     

Oat consumption does not affect resting casual and ambulatory 24-h arterial blood pressure in men with high-normal blood pressure to stage I hypertension

The results of epidemiologic studies suggest that increased intake of dietary fiber is associated with lower levels of arterial blood pressure (BP). However, there is little information available addressing the possibility that increased oat consumption may reduce arterial BP in individuals with elevated arterial BP. To test this hypothesis, middle-aged and older men (n = 36; body mass index, 25-35 kg/m(2); aged 50-75 y) with elevated BP (systolic BP 130-159 mmHg and/or diastolic BP 85-99 mmHg) were randomly assigned to consume an additional 14 g/d of dietary fiber in the form of oat (5.5 g beta-glucan, n = 18) or wheat cereals (no beta-glucan, n = 18) for 12 wk. Casual resting arterial BP was measured at baseline and after 4, 8 and 12 wk of intervention. The 24-h ambulatory arterial BP was measured at baseline and after 12 wk of intervention. There were no differences in casual resting or 24-h ambulatory BP at baseline in the two groups. Casual systolic BP (SBP) did not change as a result of the 12-wk intervention in the oat (138 plus minus 2 vs. 135 plus minus 3 mmHg) or wheat (142 plus minus 2 vs. 140 plus minus 3 mmHg) groups, respectively (all P > 0.05). Casual diastolic BP (DBP) also did not change in the oat (89 plus minus 2 vs. 88 plus minus 2 mmHg) or wheat (90 plus minus 2 vs. 91 plus minus 2 mmHg) group during this period (all P > 0.05). Further, 24-h, daytime and nighttime SBP and DBP did not decrease with the intervention. Therefore, the results of the present study suggest that any cardioprotective benefit of regular oat consumption may not be conferred via an arterial BP-lowering effect.     

Randomised, controlled, cross-over trial of soy protein with isoflavones on blood pressure and arterial function in hypertensive subjects

OBJECTIVE: To examine the effects of dietary soy/isoflavones on 24 hr blood pressure profiles and arterial function [systemic arterial compliance (SAC), pulse wave velocity (PWV) and brachial arterial flow mediated vasodilation (FMD)] compared to non legume-based plant protein without isoflavones, in hypertensive subjects. DESIGN: In a 6 month double-blind, placebo controlled, cross-over trial, 41 hypertensive subjects (26 men, 15 postmenopausal women), 30-75 years, received soy cereal (40 g soy protein, 118 mg isoflavones) and gluten placebo cereal, each for 3 months. RESULTS: Thirty-eight subjects completed protocol with results expressed as mean or mean change (+/-SEM) with each intervention. Soy increased urinary isoflavones (daidzein: 8-fold; genistein: 8-fold; equol: 9-fold; ODMA: 18-fold) with no change during gluten placebo. There was no difference in the change in individual 24 hr ambulatory BP parameters (SBP: 2 +/- 2 vs -1 +/- 1 mmHg, p = 0.21; DBP: 1 +/- 1 vs -1 +/- 1 mmHg, p = 0.06) central BP (cSBP: -4 +/- 2 vs 0 +/- 2 mmHg, p = 0.2) or the change in arterial function (FMD: 0.3 +/- 0.5 vs -0.2 +/- 0.5%, p = NS; SAC: 0.02 +/- 0.02 vs -0.02 +/- 0.02 U/mmHg, p = NS; PWV central: -0.2 +/- 0.2 vs 0.0 +/- 0.2 m/sec, p = NS; PWV peripheral: 0.01 +/- 0.3 vs -0.4 +/- 0.4 m/sec, p = NS) noted between interventions. Analysis of the area under curve of 24 hr BP outputs demonstrated that soy protein compared to gluten protein resulted in higher 24 hr systolic BP by 2.3 mmHg (p = 0.003), a higher daytime systolic BP by 3.4 mmHg (p = 0.0002) and a higher daytime diastolic BP by 1.4 mmHg (p = 0.008). Overall 24 hr diastolic BP, night systolic BP and night diastolic BP were not significantly different between groups. Furthermore, soy protein compared to gluten protein resulted in higher 24 hr heart rates by 3.5 bpm (p < 0.0001). CONCLUSIONS: In hypertensive subjects, compared to gluten placebo, soy dietary supplementation containing isoflavones had no effect on arterial function, on average 24 hr ambulatory blood pressure parameters or central blood pressure in men and women with hypertension. Area under the curve of 24 hr profiles demonstrated that daytime BP was higher after soy compared to gluten.     

PPAR-α agonism improves whole body and muscle mitochondrial fat oxidation, but does not alter intracellular fat concentrations in burn trauma children in a randomized controlled trial

Background

Dietary calcium intake and the renin angiotensin system (RAS) regulate blood pressure (BP) by modulating calcium homeostasis. Despite similar BP regulatory effects, the influence of dietary calcium intake alone and combined with RAS polymorphisms on the BP response following acute aerobic exercise (i.e., postexercise hypotension) has not been studied. Thus, we examined the effect of dietary calcium intake and selected RAS polymorphisms on postexercise hypotension.

Methods

Subjects were men (n = 50, 43.8 ± 1.3 yr) with high BP (145.3 ± 1.5/85.9 ± 1.1 mm Hg). They completed three experiments: non-exercise control and two cycle bouts at 40% and 60% of maximal oxygen consumption (VO₂max). Subjects provided 3 d food records on five protocol-specific occasions. Dietary calcium intake was averaged and categorized as low (<880 mg/d = LowCa) or high (≥ 880 mg/d = HighCa). RAS polymorphisms (angiotensin converting enzyme insertion/deletion, ACE I/D; angiotensin II type 1 receptor, AT₁R A/C) were analyzed with molecular methods. Genotypes were reduced from three to two: ACE II/ID and ACE DD; or AT₁R AA and AT₁R CC/AC. Repeated measure ANCOVA tested if BP differed among experiments, dietary calcium intake level and RAS polymorphisms.

Results

Systolic BP (SBP) decreased 6 mm Hg after 40% and 60% VO₂max compared to non-exercise control for 10 h with LowCa (p < 0.01), but not with HighCa (p ≥ 0.05). Under these conditions, diastolic BP (DBP) did not differ between dietary calcium intake levels (p ≥ 0.05). With LowCa, SBP decreased after 60% VO₂max versus non-exercise control for 10 h among ACE II/ID (6 mm Hg) and AT₁R AA (8 mm Hg); and by 8 mm Hg after 40% VO₂max among ACE DD and AT₁R CC/CA (p < 0.01). With HighCa, SBP (8 mm Hg) and DBP (4 mm Hg) decreased after 60% VO₂max compared to non-exercise control for 10 h (p < 0.05), but not after 40% VO₂max (p ≥ 0.05).

Conclusion

SBP decreased after exercise compared to non-exercise control among men with low but not high dietary calcium intake. Dietary calcium intake interacted with the ACE I/D and AT₁R A/C polymorphisms to further modulate postexercise hypotension. Interactions among dietary calcium intake, exercise intensity and RAS polymorphisms account for some of the variability in the BP response to exercise.     

A population-based dietary intervention trial in a high-risk area for stomach cancer and stroke: changes in intakes and related biomarkers

BACKGROUND: Dietary intervention is one of the important fields in cancer and cardiovascular disease prevention. The Hiraka Dietary Intervention Study is a community-based randomized cross-over trial designed to develop an effective dietary modification tool and system in an area with high mortality of stomach cancer and stroke. METHODS: The subjects were 550 healthy volunteers and were randomized into two groups with tailored dietary education to decrease sodium intake and to increase vitamin C and carotene intakes either in the first year (intervention group) or in the second year (control group). Dietary changes were assessed using a validated self-administered diet history questionnaire, fasting blood samples, and 48-hour urine samples, which were obtained before and after the one year period. RESULTS: During the first year, changes differed significantly between the intervention and control group for both dietary sodium intake (-384 and +255 mg/day, intervention and control respectively, p < 0.001) and urinary sodium excretion (-1003 and -84 mg/day, p < 0.001). Although favorable net changes were also observed in dietary carotene (+418 and +220 mug/day, p < 0.05) and vitamin C (+13 and +2 mg/day, p < 0.05), the serum level differences were modest (+13 and -25 mg/L, p = 0.09 for carotene, +0.1 and -0.5 mg/L, p = 0.07 for ascorbic acid). CONCLUSION: The present dietary intervention strategy effectively decreased sodium and increased carotene and vitamin C intakes, although the former was more distinct.     

Effect of five-year supplementation of vitamin C on serum vitamin C concentration and consumption of vegetables and fruits in middle-aged Japanese: a randomized controlled trial

OBJECTIVE: This study was aimed at evaluating the effect of long-term vitamin C supplementation on serum and dietary vitamin C and identifying the factors associated with change in serum concentration. METHODS: A total of 439 subjects with atrophic gastritis initially participated in a randomized clinical trial using vitamin C and beta-carotene to prevent gastric cancer. We originally randomized the participants into four treatment groups using a 2x2 factorial design, whereby 0 or 15 mg/day beta-carotene and 50 or 500 mg/day vitamin C were administered in a double-blind manner. The beta-carotene component was terminated early after a mean treatment duration of four months. Before and upon early termination of beta-carotene supplementation, 134 subjects dropped out this trial, while 120 and 124 subjects took the vitamin C supplement at either 50 mg or 500 mg daily for five years. RESULTS: Changes in serum vitamin C were significantly higher in the high-dose group (38.5% increase, 95% CI = 27.0-49.9) than in the low-dose group (13.0% increase, 5.1-20.9) or in the dropout group (3.3% increase, -2.1-8.6) after five-year supplementation. The serum vitamin C at baseline was negatively associated with changes in serum vitamin C (p < 0.0001), while high-dose (p < 0.0001) and low-dose (p < 0.05) supplementation and female gender (p < 0.001) were positively associated. Dietary intake of vitamin C in the supplementation group was almost identical before and after five-year supplementation of vitamin C (2.31 mg/day decrease, 95% CI = -15.3-10.7), while a 17.7 mg/day decrease (95% CI = -44.2-8.86) was observed in the drop-out group. CONCLUSION: Five-year vitamin C supplementation induces a remarkable increase in serum vitamin C concentration, and our intervention program appears to have no effect on dietary vitamin C intake.     

The impact of vitamins and/or mineral supplementation on blood pressure in type 2 diabetes

OBJECTIVE: The present study designed to assess the effect of Mg+Zn, vitamin C+E, and combination of these micronutrients on blood pressure in type 2 diabetic patients. MATERIALS AND METHODS: In a randomized, double-blind, placebo controlled clinical trial, 69 type 2 diabetic patients were randomly divided into four groups, each group receiving one of the following daily supplement for three months; group M: 200 mg Mg and 30 mg Zn (n = 16), group V: 200 mg vitamin C and 150 mg vitamin E (n = 18), group MV: minerals plus vitamins (n = 17), group P: placebo (n = 18). Blood pressure was measured at the beginning and at the end of the trial. Treatment effects were analyzed by general linear modeling. RESULTS: Results indicate that after three months of supplementation levels of systolic, diastolic and mean blood pressure decreased significantly in the MV group by 8 mmHg (122 +/- 16 vs. 130 +/- 19 mmHg), 6 mmHg (77 +/- 9 vs. 83 +/- 11 mmHg), and 7 mmHg (92 +/- 9 vs. 99 +/- 13 mmHg), respectively (p < 0.05). Also combination of vitamin and mineral supplementation had significantly effects in increasing serum potassium (p < 0.05) and in decreasing serum malondialdehyde (p < 0.05). There was no significant change in the levels of these parameters in the other three groups. CONCLUSION: The results of the present study indicated that in type 2 diabetic patients a combination of vitamins and minerals, rather than vitamin C and E or Mg and Zn, might decrease blood pressure.     

Dietary vitamin C and bone mineral density in postmenopausal women in Washington State, USA.

STUDY OBJECTIVE: To examine the relationship between dietary vitamin C and hip bone mineral density (BMD) in postmenopausal women. DESIGN: This was a cross sectional study using retrospective diet and vitamin supplement data. SETTING: The Seattle area of Washington State. PARTICIPANTS: Screenees for a clinical trial of a drug to prevent osteoporotic fractures; 1892 women aged 55-80 years who had hip bone densitometry and osteoporosis risk factor information. MAIN RESULTS: Mean energy adjusted dietary intake of vitamin C was 113 mg/day; including supplement use, mean intake was 407 mg/day. There were no differences in BMD according to diet-only vitamin C intake or combined dietary and supplemental vitamin C intake. Longer duration of vitamin C supplement use was associated with higher BMD in women who had not used oestrogen replacement therapy (trend p = 0.02) and among women aged 55-64 years (trend p = 0.01). Women aged 55-64 years who used vitamin C supplements for > or = 10 years had a higher BMD than non-users aged 55-64 years (multivariate adjusted mean BMD 0.699 (0.017) g/cm2 versus 0.655 (0.007) g/cm2, p = 0.02). Benefits were not evident in older age groups or in women who had used oestrogen in the past. Frequent intake of foods rich in vitamin C was not associated with BMD. CONCLUSION: There was no evidence that vitamin C from the diet was associated with BMD, although long term use of vitamin C supplements was associated with a higher BMD in the early postmenopausal years and among never users of oestrogen.     

Plasma-Saturating intakes of vitamin C confer maximal antioxidant protection to plasma.

OBJECTIVE: Supplemental vitamin C has been shown to reduce oxidative damage in vivo, yet the dose-response relationship between vitamin C intake and antioxidant protection is not known. This report examined blood indicators of oxidative stress in subjects consuming graded doses of vitamin C, from 75 to 2,000 mg/day. METHODS: Ten healthy, non-smoking men and women (26.1 +/- 2.1 years) were recruited from a campus population. During the ten-week study, subjects limited fruit and vegetable consumption (< or = 3 servings/day) and consumed a multivitamin and mineral pill daily. Beginning at week 3, subjects ingested either a vitamin C (n = 8) or placebo (n = 2) capsule, which were identical in appearance and taste. The content of the vitamin C capsule increased every two weeks (from 250 mg at weeks 3-4 to 500 mg, 1,000 mg. and 2,000 mg at weeks 5-6. 7-8. 9-10, respectively). Fasting blood samples were collected at two-week intervals and analyzed for vitamin C, total lipid hydroperoxides and Heinz bodies in packed erythrocytes incubated 24 hours at 37 degrees. RESULTS: Plasma vitamin C rose 55% in vitamin C-supplemented subjects by the end of the ten-week treatment (p < 0.05), and measures of oxidative stress decreased 60% to 90% (8.1 +/- 0.6 to 3.5 +/- 0.4 nmol/mL and 69.1 +/- 7.8% to 6.7 +/- 6.0% for total lipid hydroperoxides and Heinz bodies, respectively). Significant decreases in markers of oxidative stress were noted at the 500 mg, 1,000 mg and 2,000 mg dosages versus placebo. Antioxidant protection was similar at the 1,000 mg and 2,000 mg dosage. CONCLUSIONS: These data indicate that the antioxidant protection afforded by short-term vitamin C supplementation is maximal at the 500-1,000 mg dosage range.     

Relation of vegetable, fruit, and meat intake to 7-year blood pressure change in middle-aged men: the Chicago Western Electric Study

Information is sparse on the role of foods in long-term blood pressure (BP) change. The investigators examined relations of food intake to BP change in a prospective cohort study of 1,710 employed men in Chicago, Illinois, initially aged 41-57 years. In 1958 and 1959, BP was measured and nutrient intake assessed by comprehensive interview. In 1959, intake of 26 specific food groups was also assessed. BP was remeasured annually through 1966. The generalized estimating equation method was used to analyze relations of food group intakes to average annual BP change, adjusting for age, weight at each year, alcohol consumption, calories, and other foods. Average systolic blood pressure (SBP)/diastolic blood pressure (DBP) increase was 1.9/0.3 mmHg per year. The SBP of men who consumed 14-42 cups of vegetables a month (0.5-1.5 cups/day) versus <14 cups a month (<0.5 cups/day) was estimated to rise 2.8 mmHg less in 7 years (p < 0.01). The SBP of men who consumed 14-42 cups of fruit a month versus <14 cups a month was estimated to increase 2.2 mmHg less in 7 years (p < 0.05). Beef-veal-lamb and poultry intakes were related directly to a greater SBP/DBP increase (p < 0.05). These results support the concept that diets higher in fruits and vegetables and lower in meats (except fish) may reduce the risk of developing high BP.     

Calcium intake and blood pressure in elderly women.

The authors studied the relative importance of calcium intake as a correlate of blood pressure in a cross-sectional analysis of 6,517 nonblack women aged > or = 65 years from Portland, Oregon; Minneapolis, Minnesota; Baltimore, Maryland; and the Monongahela Valley near Pittsburgh, Pennsylvania, who enrolled in the Study of Osteoporotic Fractures in 1986. Dietary calcium intake was measured by using a modified food frequency questionnaire. There were weak associations between total calcium intake and blood pressure, such that each 1,000 mg/day increase in calcium intake was associated with a 1.5 mmHg decrease in systolic blood pressure (95% confidence interval -2.2 to -0.8, p < 0.0001) and a 0.5 mmHg decrease in diastolic pressure (95% confidence interval -0.8 to -0.20, p < 0.004). After adjustment for confounding variables, total calcium intake continued to have a weak inverse association only with diastolic blood pressure. The multivariate models revealed several stronger independent risk factors for blood pressure, including age, body mass index, alcohol consumption, and level of education (all p < 0.01). The small size of the inverse association between calcium intake and blood pressure limits its biological importance in this population of elderly women.     

Relationship between autonomic neuropathy, 24-hr blood pressure and retinopathy in normoalbuminuric and normotensive type 1 diabetic patients

In order to investigate factors related to the development of retinopathy in 122 normotensive and normoalbuminuric patients 24 hr-blood pressure (BP) measurement and autonomic tests based on standard, vector and spectral analysis of heart rate variation (HRV) were performed. Retinopathy was found in 47 patients with significantly longer duration of diabetes and prevalence of autonomic neuropathy (9.5 +/- 5.5; 59.6%) in comparison with 75 patients without retinopathy (5.29 +/- 4.9; 16%), (p < 0.05). Patients were matched according to age, gender, HbA1c and 24-hr urinary albumin excretion rate. Maximal night systolic, mean night and day diastolic BPs were significantly higher in patients with retinopathy (118.94 +/- 11; 62.94 +/- 8.1; 74.3 +/- 7.2 mmHg) as compared to patients without it (115.03 +/- 8.9; 59.65 +/- 7.1; 71.75 +/- 5.7) (p = 0.03). Maximal night systolic BP was inversely related to power high frequency (HF; r = -0.28, p = 0.05) and deep breathing CV (r = -0.23, p = 0.02). Mean night diastolic BP was inversely related to power mid frequency (r = -0.21, p = 0.03), HF (r = -0.32, p = 0.005), CV deep breathing (r = -0.27, p = 0.005) and mean circular resultant deep breathing (r = -0.24, p = 0.003); mean day diastolic BP to power HF (r = -0.22, p = 0.02). In multiple regression analysis retinopathy was associated with the duration of diabetes (beta = 0.53) and autonomic neuropathy (beta = 0.28) (p < 0.001). Autonomic neuropathy was related to BP elevation and retinopathy in normotensive and normoalbuminuric Type 1 diabetic patients.     

The association of intakes of vitamin D and calcium with blood pressure among women

Blood pressure and its relationship to nutritional factors, particularly intakes of calcium and vitamin D, were evaluated among 86 women, aged 20-35 yr, and 222 women, aged 55-80 yr, who were not using diuretics. Observations were based on a study of bone density among women in two communities which included blood pressure determinations, a food frequency estimate of calcium intake, a 24-h dietary recall and an extensive supplement use history. There was no significant relationship between estimated current dietary calcium consumption and blood pressure in either age group. However, in younger women, there was a significant inverse relationship between estimated dietary intake of vitamin D and systolic blood pressure which remained significant (p = 0.0016) after adjusting for age, Quetelet index, alcohol consumption and calcium intake. Older women whose consumption of both vitamin D and calcium was less than the Recommended Dietary Allowance, 400 IU/day and 800 mg/day respectively, had a significantly higher systolic blood pressure (p = 0.0371) than their counterparts whose estimated intake met the RDA for at least one of the two nutrients. Vitamin D may be related to blood pressure through its regulation of calcium absorption from the gut or its interaction with parathyroid hormone in maintaining plasma calcium homeostasis.     

Anthropometric and nutritional assessment in Italian elderly subjects

The aims of this anthropometric study on 486 non-institutionalized subjects aged 60 and over were to assess the body mass index (BMI), to evaluate possible sex and age-linked differences of BMI and to find whether there were any correlations with systolic and diastolic blood pressure. To this end, the subjects were divided into three age groups: A: 60-69 years, B: 70-79 years and C: > or =80 years old. The results showed a high prevalence (74%) of overweight or clearly obese subjects (BMI >25.1 for men and BMI > 23.9 for women) (70% male and 77% female). Both the BMI and diastolic blood pressure showed a decreasing trend in the three age groups and were significantly correlated in the total population (p < 0.001). A dietary investigation using a 24-hour recall method, repeated on three separate days, was carried out on a subsample of 90 subjects, selected at random from the total population. They underwent in-depth anthropometric assessment (BMI, four skinfolds, mid-arm, waist and hip circumferences, midarm muscle and fat areas, body fat percent). The trend of the anthropometric assessment reflected that of the total population. Total energy intake in both sexes did not significantly differ from the Italian RDA (Recommended Dietary Allowance). As regards the three macronutrients, no significant differences in protein and carbohydrate intakes were found between the sexes. However, in the females, fat intake was over the Italian DRA (30%) and below it in the males. Calcium intake was lower than the Italian RDA (1,000 mg/day) in most males (77%) and females (89%). However, iron and vitamin intakes were adequate in most subjects. As regards age-linked differences, there were non significant changes in the percentage of energy intake from proteins of the males whereas this decreased with age and was significantly different (p < 0.05) in the females. No significant differences were found in the percentage of energy intake from carbohydrates and fats.     

Caffeine consumption and blood pressure: an epidemiological study

A cross-sectional survey of 5147 Australians attending a health screening clinic was conducted to determine if there was an association between habitual consumption of caffeine, or particular caffeine-containing beverages, and blood pressure. The average caffeine consumption of the study population was 240 mg/day. Caffeine consumption within the last three hours was found to be associated with significantly higher mean systolic and diastolic blood pressure in both sexes after controlling for age, adiposity, first degree relatives with hypertension, serum cholesterol level, alcohol consumption and tobacco smoking. Mean systolic and diastolic blood pressures differed significantly by 4 mmHg and 2 mmHg respectively for both males and females between those who had consumed caffeine within the last three hours and those who had not consumed it within the last nine hours (p less than 0.01). Average caffeine consumption per day was not associated with blood pressure in either sex after controlling for time since caffeine consumption. Logistic regression analysis was used to estimate the relative risk of high blood pressure (treated and untreated) for the groups consuming and not consuming caffeine in the last three hours. This relative risk was significantly greater than unity in females only (p less than 0.05). After controlling for time since caffeine consumption, caffeine consumption per day was not associated with significantly increased risk of high blood pressure.     

Randomized Trial on the Effects of Dietary Potassium on Blood Pressure and Serum Potassium Levels in Adults with Chronic Kidney Disease

In the general population, an increased potassium (K) intake lowers blood pressure (BP). The effects of K have not been well-studied in individuals with chronic kidney disease (CKD). This randomized feeding trial with a 2-period crossover design compared the effects of diets containing 100 and 40 mmol K/day on BP in 29 adults with stage 3 CKD and treated or untreated systolic BP (SBP) 120–159 mmHg and diastolic BP (DBP) <100 mmHg. The primary outcome was 24 h ambulatory systolic BP. The higher-versus lower-K diet had no significant effect on 24 h SBP (−2.12 mm Hg; p = 0.16) and DBP (−0.70 mm Hg; p = 0.44). Corresponding differences in clinic BP were −4.21 mm Hg for SBP (p = 0.054) and −0.08 mm Hg for DBP (p = 0.94). On the higher-K diet, mean serum K increased by 0.21 mmol/L (p = 0.003) compared to the lower-K diet; two participants had confirmed hyperkalemia (serum K ≥ 5.5 mmol/L). In conclusion, a higher dietary intake of K did not lower 24 h SBP, while clinic SBP reduction was of borderline statistical significance. Additional trials are warranted to understand the health effects of increased K intake in individuals with CKD.     

An inverse relationship between serum vitamin C and blood pressure in a Japanese community

To examine the relationship between serum vitamin C concentration and blood pressure level, a cross-sectional study was conducted. The subjects were 919 men and 1,266 women aged 40 years and over in a Japanese provincial city, Shibata, Niigata Prefecture. The mean and standard deviation of systolic blood pressure (SBP) were 134.0 +/- 20.0 mmHg for men and 128.3 +/- 20.8 mmHg for women, and those of diastolic blood pressure (DBP) were 81.0 +/- 11.7 mmHg and 75.8 +/- 11.4 mmHg, respectively. The mean and standard deviation of serum vitamin C were 42.5 +/- 18.6 mumol/L for men and 56.8 +/- 16.5 mumol/L for women. SBP and DBP were both inversely correlated with serum vitamin C concentration. The means of SBP or DBP were calculated for quartiles of serum vitamin C, and the significant inverse relationship was observed in any sex and age group. The inverse association persisted after adjustment for possible confounders: body mass index, serum total cholesterol, alcohol consumption, smoking, physical activity, antihypertensive medication, and dietary intake of salt, calcium, and potassium. Serum vitamin C appeared to be inversely related with both SBP and DBP in this Japanese population, although further intervention and experimental studies were required to establish the cause-effect relationship.     

Daily calcium intake and its relation to blood pressure, blood lipids, and oxidative stress biomarkers in hypertensive and normotensive subjects

Several studies revealed that low calcium intake is related to high prevalence of cardiovascular diseases such as hypertension. The prevalence of hypertension is high in Koreans along with their low dietary calcium consumption. Thus, the aim of this study was to evaluate the status of calcium intake between the hypertension and normotension groups and to investigate the correlation between dietary calcium intake and blood pressure, blood lipid parameters, and blood/urine oxidative stress indices. A total of 166 adult subjects participated in this study and were assigned to one of two study groups: a hypertension group (n = 83) who had 140 mmHg or higher in systolic blood pressure (SBP) or 90 mmHg or higher in diastolic blood pressure (DBP), and an age- and sex-matched normotension group (n = 83, 120 mmHg or less SBP and 80 mmHg or less DBP). The hypertension group consumed 360.5 mg calcium per day, which was lower than that of the normotension group (429.9 mg) but not showing significant difference. In the hypertension group, DBP had a significant negative correlation with plant calcium (P < 0.01) after adjusting for age, gender, body mass index (BMI), and energy intake. In the normotension group, total calcium and animal calcium intake were significantly and positively correlated with serum triglycerides. No significant relationship was found between calcium intake and blood/urine oxidative stress indices in both groups. Overall, these data suggest reconsideration of food sources for calcium consumption in management of the blood pressure or blood lipid profiles in both hypertensive and normotensive subjects.     

Oral calcium and blood pressure: a controlled intervention trial

In a double-blind, placebo-controlled trial with 58 normotensive female students, the effect of oral-calcium supplementation (1500 mg Ca++/day for 6 wk) on diastolic and systolic blood pressure was studied while students were consuming a low-calcium diet (500 mg Ca++/day) by restricting the intake of dairy products. Results show that, in both the calcium- and placebo-supplemented groups, blood pressure values decreased slightly and no effect of oral-calcium supplementation on blood pressure could be demonstrated. In addition, at baseline neither systolic nor diastolic blood pressure correlated with habitual calcium intake. Diastolic but not systolic blood pressure correlated significantly with body mass index (r = 0.31, p = 0.01). It is concluded that oral-calcium supplementation for 6 wk does not influence blood pressure in young, healthy normotensive females consuming low-calcium diet.