Dietary fat and blood pressure

Relationship of dietary linoleic acid to blood pressure. The International Study of Macro-Micronutrients and Blood Pressure Study [corrected]

Findings from observational and interventional studies on the relationship of dietary linoleic acid, the main dietary polyunsaturated fatty acid, with blood pressure have been inconsistent. The International Study of Macro-Micronutrients and Blood Pressure is an international cross-sectional epidemiological study of 4680 men and women ages 40 to 59 years from 17 population samples in China, Japan, United Kingdom, and United States. We report associations of linoleic acid intake of individuals with their blood pressure. Nutrient intake data were based on 4 in-depth multipass 24-hour dietary recalls per person and 2 timed 24-hour urine collections per person. Systolic and diastolic blood pressures were measured 8 times at 4 visits. With several models to control for possible confounders (dietary or other), linear regression analyses showed a nonsignificant inverse relationship of linoleic acid intake (percent kilocalories) to systolic and diastolic blood pressure for all of the participants. When analyzed for 2238 "nonintervened" individuals (not on a special diet, not consuming nutritional supplements, no diagnosed cardiovascular disease or diabetes, and not taking medication for high blood pressure, cardiovascular disease, or diabetes), the relationship was stronger. With adjustment for 14 variables, estimated systolic/diastolic blood pressure differences with 2-SD higher linoleic acid intake (3.77% kcal) were -1.42/-0.91 mm Hg (P<0.05 for both) for nonintervened participants. For total polyunsaturated fatty acid intake, blood pressure differences were -1.42/-0.98 mm Hg (P<0.05 for both) with 2 SD higher intake (4.04% kcal). Dietary linoleic acid intake may contribute to prevention and control of adverse blood pressure levels in general populations.

Hypertension is related to the degradation of dietary frying oils

BACKGROUND

The family kitchen resembles an uncontrolled laboratory experiment, and some discrepancies in the relation between the risk of hypertension and dietary fat may be partly due to the manipulation to which the fats were subjected.

OBJECTIVE

We investigated whether deterioration in the quality of the cooking oils in the family household contributes to the risk of high blood pressure.

DESIGN

The study was cross-sectional. Anthropometric measurements were obtained for 1226 persons aged 18-65 y who were selected randomly from the municipal census of Pizarra, Spain. An oral-glucose-tolerance test was given to 1020 of these persons. Samples of the cooking oil being used were taken from the kitchens of a random subset of 538 persons. The concentrations of polar compounds and polymers were used as markers of the deterioration of the oils. The strength of association between variables was measured by calculating the odds ratio from logistic models.

RESULTS

Hypertension was strongly associated with obesity and was influenced by sex, diabetes, and age. The presence of excess polar compounds in the cooking oil and the use of sunflower oil were related to the risk of hypertension, whereas the concentration of monounsaturated fatty acids in the serum phospholipids was negatively related to this risk. These associations remained after inclusion in the models of age, sex, obesity, and the presence of carbohydrate metabolism disorder.

CONCLUSIONS

The risk of hypertension is positively and independently associated with the intake of cooking oil polar compounds and inversely related to blood concentrations of monounsaturated fatty acids.

Blood pressure among the Inuit (Eskimo) populations in the Arctic

AIMS

Studies of blood pressure among various Inuit (Eskimo) populations in the Arctic have given inconsistent results. Most studies reported lower blood pressure among the Inuit as compared with the predominantly white national populations. This has been attributed to traditional subsistence practices and lifestyle. This study compared the blood pressure among the major Inuit population groups with other populations and examined the associations with factors like age, gender, obesity and smoking.

METHODS

The study comprised four Inuit populations from Alaska, Canada, and Greenland with participation rates ranging from 51% to 73%. In a cross-sectional design, 2,509 randomly selected adults from 31 villages were examined. Blood pressure, anthropometric measurements, smoking, and medication were recorded.

RESULTS

Mean systolic blood pressures ranged from 116 to 124 mm Hg among men and 110 to 118 among women in the four populations. Mean diastolic blood pressures ranged from 75 to 78 mm Hg among men and from 71 to 73 among women. Systolic blood pressure increased with age. Male gender, obesity, being a non-smoker, and being on anti-hypertensive treatment were associated with high systolic and diastolic blood pressure. Adjusted for age, body mass index, smoking, and anti-hypertensive treatment, blood pressure differed among the populations (p </= 0.001). Mean systolic blood pressure was low among the Inuit compared with most European populations of the INTERSALT study, but higher than in several Asian populations and the Amazonian Indians.

CONCLUSIONS

Inuit blood pressures rank intermediate on a global scale but low in comparison with most European populations. The Inuit population is not homogeneous, and this is reflected in blood pressure differences among the four regional subgroups. The role of the traditional diet, a rural lifestyle with a low level of psychosocial stress, and genetics must be further explored.

Increased blood pressure later in life may be associated with perinatal n-3 fatty acid deficiency

Hypertension is a major risk factor for cardiovascular and cerebrovascular disease. Previous work in both animals and humans with high blood pressure has demonstrated the antihypertensive effects of n-3 polyunsaturated fatty acids (PUFA), although it is not known whether these nutrients are effective in preventing hypertension. The predominant n-3 PUFA in the mammalian nervous system, docosahexaenoic acid (DHA), is deposited into synaptic membranes at a high rate during the perinatal period, and recent observations indicate that the perinatal environment is important for the normal development of blood pressure control. This study investigated the importance of perinatal n-3 PUFA supply in the control of blood pressure in adult Sprague-Dawley rats. Pregnant rat dams were fed semisynthetic diets that were either deficient in (DEF) or supplemented with (CON) n-3 PUFA. Offspring were fed the same diets as their mothers until 9 wk; then, half of the rats from each group were crossed over to the opposite diet creating four groups, i.e., CON-CON; CON-DEF; DEF-DEF, DEF-CON. Mean arterial blood pressures (MAP) were measured directly, at 33 wk of age, by cannulation of the femoral artery. The phospholipid fatty acid profile of the hypothalamic region was determined by capillary gas-liquid chromatography. The tissue phospholipid fatty acid profile reflected the diet that the rats were consuming at the time of testing. Both groups receiving DEF after 9 wk of age (i.e., DEF-DEF and CON-DEF) had similar profiles with a reduction in DHA levels of 30%, compared with rats receiving CON (i.e., CON-CON and DEF-CON). DEF-DEF rats had significantly raised MAP compared with all other groups, with differences as great as 17 mm Hg. DEF-CON rats had raised MAP compared with CON-CON rats, and DEF-DEF rats had higher MAP than CON-DEF rats, despite the fact that their respective fatty acid profiles were not different. These findings indicate that inadequate levels of DHA in the perinatal period are associated with altered blood pressure control in later life. The way in which these long-term effects are produced remains to be elucidated.

Higher blood pressure among Inuit migrants in Denmark than among the Inuit in Greenland

STUDY OBJECTIVE

Previous studies of blood pressure among the Inuit have given inconsistent results and studies comparing Inuit migrants with those living in traditional Inuit areas are absent. The purpose of the study was to compare the blood pressure of the Inuit in Greenland with that of Inuit migrants in Denmark.

DESIGN

Questionnaire, interview, and clinical examination in a cross sectional random population sample.

SETTING

A population based survey among Inuit in Greenland and Inuit migrants in Denmark.

PARTICIPANTS

2046 Inuit aged >/or =18, 61% of the sample.

MAIN RESULTS

Age and gender adjusted blood pressures were 117/72 mm Hg in Greenland and 127/81 mm Hg among the migrants (p<0.001). In both populations, blood pressure increased with age and body mass index, and was higher among men and non-smokers. In Greenland, blood pressure increased with the level of school education. The associations with Inuit heritage, alcohol, diet, and physical activity were not significant. The difference between the two populations persisted after adjusting for age, gender, body mass index, education, and smoking. Among those who had completed high school, there was no difference between the systolic blood pressure of the two populations while the difference for diastolic blood pressure was much less than for those with less education.

CONCLUSIONS

Blood pressure was lower among the Inuit in Greenland than among the Inuit migrants in Denmark but the difference was absent (systolic pressure) or reduced (diastolic pressure) among the better educated. The results suggest that the blood pressure of the Inuit, especially Inuit men, may be responsive to factors related to the modern Western way of life.

Effect of different high-fat diets on the myocardium stereology and blood pressure in rats

The effect of three high-fat diets containing 29% canola oil (CA), lard plus egg yolk (LE) or canola oil, lard and egg yolk (CA+LE) in male Wistar rats was investigated over a period of 6 months. We analyzed the myocardium, composed of cardiomyocytes and interstitium, which is made up of connective tissue and blood vessels. Volume density of cardiomyocyte (Vv[m]), volume density of blood vessels (Vv[v]), and volume density of connective tissue (Vv[ct]) were the stereological parameters determined. The rats of the LE group had a significantly higher heart mass/body mass ratio than those of the CA group. The blood pressure of the LE group was significantly higher than that of the other groups. In the CA group, the Vv[m] was significantly higher and the Vv[ct] was significantly lower than in the other groups. The myocardium of both the LE and CA+LE groups showed a significant reduction of Vv[m] and a compensatory increase of the Vv[ct]. These findings were less pronounced in the CA+LE group, in which the Vv[v] was found to be significantly higher than in the CA group. Comparing three high-fat diets, the data suggest that the diet canola oil had a major beneficial effect, preserving the myocardial structure and the blood pressure in rats.

Blood pressure, ventricular volume and number of cardiomyocyte nuclei in rats fed for 12 months on diets differing in fat composition

Blood pressure (BP), body mass (BM), ventricular volume (V[vent]) and the number of ventricular cardiomyocyte nuclei (N[vcn]) were analysed in rats fed different dietary fats. A total of 20 Wistar male rats were studied from 21 days old to 12 months of age and divided in the groups: soybean oil (S), canola oil (CA), lard and egg yolk (LE) and canola oil+lard and egg yolk (CA+LE). The diets had the same basal diet that included cornstarch, casein, maize, egg white and mineral and vitamin mixtures. At the moment of the sacrifice, the LE group had the greatest BP and V[vent] which was significantly higher than the other groups, and the S group had the greatest BM. The myocardial structure was apparently normal in the S and CA groups while it showed areas of diffuse interstitial fibrosis and hypertrophied cardiomyocytes in the LE group, and intramyocardial coronaries with thick tunica media and little interstitial fibrosis in CA+LE group. The N[vcn] was significantly higher in the CA group and it was lower in the LE group. These results suggest that the different dietary fats affect the myocardial structure, and the canola oil diet reduces the cardiomyocyte loss in the old rats.

Dietary factors in the pathogenesis and treatment of hypertension

Data accumulated from epidemiological observations, intervention trials and studies on experimental animals provide a growing body of evidence of the influence of various dietary components on blood pressure. Dietary sodium, usually taken in the form of sodium chloride (common salt), is positively associated with blood pressure, and in many hypertensive patients reduction in sodium intake lowers blood pressure. On the other hand, in certain patients potassium, calcium and magnesium may be protective electrolytes against hypertension. Dietary fats, especially n-3 polyunsaturated fatty acids, may also influence blood pressure, whereas the possible role of other macronutrients, such as proteins and carbohydrates, or vitamins in the regulation of blood pressure is less well understood. Occasional ingestion of coffee transiently increases blood pressure, but the effects of habitual coffee consumption are controversial. Excessive use of alcohol on a regular basis has been associated with elevated blood pressure. It has also been shown in case reports that large amounts of liquorice lead to the development of hypertension. Thus, with appropriate dietary modifications, it is possible to prevent the development of high blood pressure and to treat hypertensive patients with fewer drugs and with lower doses. In some patients antihypertensive medication may not be at all necessary.