Dietary protein and soluble fiber reduce ambulatory blood pressure in treated hypertensives

Effects of fiber intake on the blood pressure, lipids, and heart rate in Goto Kakizaki rats

OBJECTIVE

The prevalence of hypertension in individuals with diabetes mellitus is higher than that in individuals without diabetes mellitus. High fiber intake decreases blood glucose and lipids levels. This study investigated the effects of cereal fiber intake on systolic and diastolic blood pressures in a rat model of type 2 diabetes mellitus.

METHODS

Thirty male Goto Kakizaki rats were randomly assigned to one of three groups. Each group was fed a barley diet, a white rice diet, or cornstarch diet. The rats were pair fed for 16 wk. Systolic and diastolic blood pressures were measured once every 4 wk by the photoelectric oscillometric tail-cuff method without anesthesia.

RESULTS

The barley diet significantly decreased systolic blood pressure from week 12 and decreased the plasma levels of total cholesterol, triacylglycerol, and low-density lipoprotein cholesterol. There were significant positive correlations between plasma lipids levels and systolic blood pressure.

CONCLUSIONS

High fiber intake has beneficial effects on systolic blood pressure and blood lipids levels and suggests that fiber intake should be increased in individuals who have diabetes mellitus to prevent complications.

Long-term effects of advice to consume a high-protein, low-fat diet, rather than a conventional weight-loss diet, in obese adults with type 2 diabetes: one-year follow-up of a randomised trial

AIMS/HYPOTHESIS

This study compared the long-term weight loss and health outcomes at 1-year follow-up, after a 12-week intensive intervention consisting of two low-fat, weight-loss diets, which differed in protein content.

METHODS

We randomly assigned 66 obese patients (BMI: 27-40 kg/m2) with type 2 diabetes to either a low-protein (15% protein, 55% carbohydrate) or high-protein diet (30% protein, 40% carbohydrate) for 8 weeks of energy restriction (approximately 6.7 MJ/day) and 4 weeks of energy balance. Subjects were asked to maintain the same dietary pattern for a further 12 months of follow-up.

RESULTS

The study was completed by 38 of the subjects, with equal dropouts in each group. At Week 64, weight reductions against baseline were -2.2+/-1.1 kg (low protein) and -3.7+/-1.0 kg (high protein), p<0.01, with no diet effect. Fat mass was not different from baseline in either group. At Week 12, both diets reduced systolic and diastolic blood pressure by 6 and 3 mm Hg respectively, but blood pressure increased more with weight regain during follow-up in the low-protein group (p< or =0.04). At Week 64, both diets significantly increased HDL cholesterol and lowered C-reactive protein concentrations. There was no difference in the urinary urea : creatinine ratio at baseline between the two groups, but this ratio increased at Week 12 (in the high-protein group only, p<0.001, diet effect), remaining stable during follow-up in both diets.

CONCLUSIONS/INTERPRETATION

A high-protein weight-reduction diet may in the long term have a more favourable cardiovascular risk profile than a low-protein diet with similar weight reduction in people with type 2 diabetes.

Dietary fiber and coronary disease: does the evidence support an association?

Large, prospective, epidemiologic studies show a protective effect of dietary fiber against coronary heart disease (CHD) and form the basis for new recommendations from the National Academy of Science for fiber intake (38 and 25 g/d for young men and women, respectively, based on an intake of 14 g of fiber per 1000 kcal). Mechanisms by which fibers may protect against CHD include lowering blood cholesterol (soluble fibers), attenuating blood triglyceride levels (mostly soluble fibers), decreasing hypertension (all fibers), and normalizing postprandial blood glucose levels (all fibers). An important consideration in making diet recommendations to protect against CHD is that the total amount of fiber from fiber-containing foods is important, and individuals should not just be counseled to focus on soluble fiber.

Lifestyles of older adults: can we influence cardiovascular risk in older adults?

Influences of lifestyle habits on cardiovascular disease risk among older adults are not well established. The authors present evidence from the Cardiovascular Health Study that dietary, physical activity, and smoking habits assessed late in life are associated with cardiovascular disease risk among adults aged 65 years or older. Persons consuming fatty fish twice per week had a 47% lower risk of coronary death compared with those who consumed fatty fish less than once per month, while cereal fiber intake (about two whole-grain bread slices per day) was associated with a 14% lower risk of myocardial infarction or stroke. Modest alcohol intake (1-6 drinks per week) predicted the fewest subclinical cerebrovascular abnormalities. Compared with little activity, moderate and high leisure-time activity predicted 28% and 44% lower mortality, respectively, while compared with nonexercisers, low, moderate, and high exercise intensity predicted 30%, 37%, and 53% more years of healthy life, respectively. Former and current smokers had 25% and 44% fewer years of healthy life than those who never smoked; lifetime smoking (pack-years) predicted higher mortality. Clinical practice and public health implications, gaps in knowledge, and future research directions are summarized.

Primary prevention of essential hypertension

The best approach to the primary prevention of hypertension is a combination of lifestyle changes: weight loss in overweight persons; increased physical activity; moderation of alcohol intake; and consumption of a diet that is higher in fruits, vegetables, and low-fat dairy products and lower in sodium content than the average American diet (Table 3). Recent randomized controlled trials have demonstrated that these lifestyle changes can be sustained over long periods of time (more than 3 years) and can have blood pressure-lowering effects as large as those seen in drug studies. Hypertension is an important preventable risk factor for cardiovascular disease, the leading cause of mortality in the United States. To achieve the Healthy People 2010 goal of reducing the proportion of adults with hypertension from 28% to 16%, concerted efforts must be directed toward primary prevention strategies. Lifestyle modifications including weight loss, increased physical activity, and dietary changes in individuals have been shown to reduce the incidence of hypertension and should be recommended for all persons and especially those with prehypertension. In addition, timely adoption of prevention strategies to reduce the incidence of hypertension and its subsequent complications in the general population may interrupt the costly cycle of hypertension and prevent the reductions in quality of life associated with this chronic disease.

Divergent effects of soy protein diet on the expression of adipocytokines

Adipose tissue secretes various bioactive molecules called adipocytokines. Dysregulation of adipocytokines plays an important role in the development of atherosclerotic vascular diseases. Consumption of vegetable protein reduces the risks of atherosclerotic vascular diseases. Here, we investigated the effects of 10-day dietary soy protein isolate (SPI) on the regulation of adipocytokines in Wistar rats. No significant difference in body weight was observed between SPI and Casein (animal protein) group. Expression of adipose PAI-1 was lower and expression and plasma concentration of adiponectin were higher in SPI than Casein group. Triglyceride content was lower and fatty acid synthase mRNA level in adipose tissue was lower in SPI than Casein group. Although SREBP-1 mRNA expression was decreased in the liver of SPI group, adipose SREBP and PPARgamma mRNA levels remained unchanged. Our data suggest that dietary SPI alters the gene expressions in adipose tissue and has beneficial effects on the expression of adipocytokines.

The effects of protein intake on blood pressure and cardiovascular disease

PURPOSE OF REVIEW

Investigators, especially those from western countries, have commonly assumed that there is either no association or a direct association of protein intake with elevated blood pressure and atherosclerosis. In contrast, recent observational studies and clinical trials have suggested that increased protein intake, particularly protein from plant sources, might actually reduce blood pressure and prevent cardiovascular disease.

RECENT FINDINGS

In epidemiological studies, an increased intake of protein has been associated with lower blood pressure and an attenuated increase in blood pressure over time. Furthermore, such studies also suggest that the beneficial effects of increased protein intake result from an increased consumption of protein from plant rather than animal sources. In several predominantly small trials, an increased intake of soy protein lowered blood pressure. With respect to clinical outcomes, reports from large cohort studies suggest that increased protein intake is associated with a reduced risk of ischemic heart disease and perhaps intraparenchymal hemorrhage. In other reports, a higher protein intake is one characteristic of a dietary pattern associated with a reduced risk of ischemic heart disease. The mechanisms by which protein could exert its beneficial effects include an increased intake of biologically active amino acids, peptides, or highly correlated nutrients.

SUMMARY

Recent evidence suggests that an increased intake of protein, particularly plant protein, may lower blood pressure and reduce the risk of cardiovascular disease. However, the data are not sufficiently compelling to advocate an increased consumption of protein.

Pressor responsiveness to angiotensin in soy-fed spontaneously hypertensive rats

Dietary soy may attenuate the development of arterial hypertension. In addition, some soy-containing foods exhibit angiotensin-converting enzyme (ACE) inhibitory properties. Accordingly, we tested the hypothesis that ACE inhibition contributes to the antihypertensive effect of dietary soy. Mean arterial blood pressure (MAP) was recorded from conscious spontaneously hypertensive rats (SHR) at least 24 h after the implantation of catheters. Cumulative dose-response curves to intravenous angiotensin I (AI) (5-100 ng x kg(-1) x min(-1)) and angiotensin II (AII) (1-20 ng x kg(-1) x min(-1)) were constructed for male, sham-operated female, and ovariectomized female (OVX) SHR that were maintained on either casein or soy diets. The soy diet was associated with a significant reduction in baseline MAP in the OVX SHR (approximately 20 mmHg, 1 mmHg = 133.322 Pa). AI and AII infusions caused graded increases in MAP in all groups. However, there was no significant attenuation of the pressor responses to AI in the soy-fed SHR. Conversely, we observed a significant rightward displacement of the AII dose-response curves in the soy-fed sham-operated and OVX SHR. We conclude that ACE inhibition does not account for the antihypertensive effect of dietary soy in mature SHR.

Role of automated measurements in understanding lifestyle effects on blood pressure

Ambulatory measurements are increasingly used to evaluate the effects of different aspects of lifestyle on blood pressure. Such measurements provide greater statistical power than casual measurements and are particularly useful for assessing diurnal variations, 24-hour load and variability, and both acute and sustained effects of common behaviours. Concomitant heart rate and biochemical and genetic measurements can provide clues as to the mechanisms underlying the effects of lifestyle on blood pressure in different target populations. The information obtained is proving helpful in evaluating actions and interactions of smoking, alcohol, physical activity, caffeine consumption, various types of psychological stress, obesity, and dietary habits.