Sodium excretion and blood pressure of West and East Finns

FINDIET 2007 Survey: energy and nutrient intakes

Objective

The National FINDIET surveys are carried out every 5 years to monitor dietary habits and nutrient intake of the adult Finnish population. The latest survey was carried out in 2007.

Design

Cross-sectional population-based study. Dietary assessment was carried out using 48 h recall interviews. A picture book of food portions was used to estimate portion sizes and the national Food Composition Database Fineli® to calculate nutrient intakes.

Setting

A representative sample taken in five regions in Finland.

Subjects

A total of 730 men and 846 women aged 24–64 years.

Results

The percentage contribution of fat to the total energy intake was 33 % in men and 31 % in women. The respective percentages for SFA in men and women were 13 % and 12 %, respectively, and 0·4 % for trans fatty acids in both genders. The average intakes of folate, vitamin D and fibre fell below the recommended levels, whereas the average salt intake was somewhat higher than the recommendations. Women’s diet was higher in protein, dietary fibre and sucrose compared to that of men.

Conclusions

According to the FINDIET 2007 Survey, the dietary habits of the adult Finnish population have headed in a positive direction overall. However, although the quality of the fats consumed has continued to improve, and the intake of salt has decreased, they still do not meet the recommended levels of intake. Similarly, the average intakes of folate and vitamin D continue to fall below the recommendations. There is also a need to increase fibre intake and to cut down the intake of sucrose.

Comparison of energy and nutrient intakes in women with high and low blood pressure levels

The present study found no link between the intake of energy and various nutrients, on the one hand, and high or low blood pressure (BP) in women, on the other. Sixty women not on treatment for hypertension were selected from a defined population and examined, applying the duplicate portion technique, with respect to the relationships between BP and the intake of energy and nutrients. They were selected from above the 95th percentile for BP (group A) and from below the 30th (group B). The two groups were age-matched. The food sampling comprised six days, divided into three periods of two consecutive days within a period of four weeks. Twenty-four hour urine specimens were collected in each period and on two other occasions. The mean values for intake of energy, fat, protein, carbohydrates, minerals and electrolytes did not differ between the two groups despite the large differences in BP and obesity. The mean values for urinary excretion of minerals, electrolytes and nitrogen (calculated as crude protein) did not differ between groups. The present findings for the effect of salt on BP do not justify restriction of the salt intake as a means for decreasing BP in the population.

Labelling the salt content in foods: a useful tool in reducing sodium intake in Finland

Objective

To estimate the impact of choosing food products labelled either as low or high in salt on salt intake in the Finnish adult population.

Setting and subjects

The National FINDIET 2002 survey with 48-hour recalls from 2007 subjects aged 25–64 years. Sodium intake was calculated based on the Fineli® food composition database including the sodium content of natural and processed foods as well as the salt content of recipes. The distribution of salt intake was calculated in different ways: the present situation; assuming that all breads, cheeses, processed meat and fish, breakfast cereals and fat spreads consumed would be either ‘lightly salted’ or ‘heavily salted’ based on the current labelling practice; and, in addition, assuming that all foods would be prepared with 50% less or more salt.

Results

Excluding underreporters, the mean salt intake would be reduced by 1.8 g in men and by 1.0 g in women if the entire population were to choose lightly salted products and further by 2.5 and 1.8 g, respectively, if also salt used in cooking were halved. Choosing heavily salted products would increase salt intake by 2.1 g in men and by 1.4 g in women. In the worst scenarios, salt intake would be further increased by 2.3 g in men and by 1.6 g in women.

Conclusions

These calculations show that the potential impact of labelling and giving consumers the possibility to choose products with less salt is of public health importance. In addition, strategies to reduce the salt content of all food groups are needed.

Part III. Can we turn back the clock or modify the adverse dynamics? Programme and policy issues

A global health transition is currently underway. The burden of non-communicable diseases (NCDs) is increasing rapidly in the developing world, very much as a result of changes in lifestyles. In addition to changes in tobacco use and physical activity, major changes are taking place in diets, contributing greatly to the growing epidemic of NCD. Thus, a huge global public health challenge is how to influence the trends in diet and nutrition for effective global NCD prevention.

The health transition took place rapidly in Finland after World War II and mortality from cardiovascular disease (CVD) was exceptionally high. The North Karelia Project was launched in 1972 as a community-based, and later as a national, programme to influence diet and other lifestyles that are crucial in the prevention of CVD. The intervention had a strong theory base and it employed comprehensive strategies. Broad community organisation and the strong participation of people were the key elements. Evaluation has shown how the diet (particularly fat consumption) has changed and how these changes have led to a major reduction in population serum cholesterol and blood pressure levels. It has also shown how ischaemic heart disease mortality in a working-age population has declined by 73% in North Karelia and by 65% in the whole country from 1971 to 1995.

Although Finland is an industrialised country, North Karelia was rural, of rather low socio-economic level and with many social problems in the 1970s and 1980s. The project was based on low-cost intervention activities, where people's participation and community organisations played a key role. Comprehensive interventions in the community were eventually supported by national activities – from expert guidelines and media activities to industry collaboration and policy. Similar principles for nutrition intervention programmes could be used in developing countries, obviously tailored to the local conditions. This paper discusses the experiences of the North Karelia Project in the light of needs from the less-industrialised countries and makes some general recommendations.

Sodium in the Finnish diet: 20-year trends in urinary sodium excretion among the adult population

OBJECTIVE

High sodium intake increases the risk of cardiovascular diseases and may also be associated with higher rates of stomach cancer, asthma disorders and infections. In Finland, cross-sectional population surveys to monitor cardiovascular risk factors have been carried out since the 1970s. The main aim of this paper is to present trends in urinary sodium and potassium excretion from 1979 to 2002.

DESIGN

Cross-sectional population surveys on cardiovascular risk factors.

SETTING

Surveys were carried out in Finland in 1979, 1982, 1987 and 2002 in four geographical areas: North Karelia, the Kuopio area, Southwestern Finland and the Helsinki area.

SUBJECTS

For each survey a random sample stratified by age and sex was drawn from the population register. In this analysis, participants of urine collection subsamples aged 25-64 years (n = 4648) were included.

INTERVENTIONS

A 24-h urinary collection was carried out in subsamples (n = 2218-2487) in connection with population risk factor surveys. Urinary sodium and potassium concentrations were analyzed in the same laboratory throughout, using a flame photometer in 1979, 1982 and 1987 and an ion-selective electrode in 2002.

RESULTS

Between 1979 and 2002 urinary sodium excretion in Finland decreased from over 220 to less than 170 mmol/day among men and from nearly 180 to less than 130 mmol/day among women. Although potassium excretion decreased somewhat as well, the decrease in sodium-potassium molar ratio was also significant.

CONCLUSIONS

The 24-h urinary sodium excretion in Finland has decreased significantly during the last 20 years. However, excretion levels are still considerably higher than recommendations. A further decrease in sodium intake remains a goal for the Finnish food industry and consumers.

SPONSORSHIP

All surveys were funded by the National Public Health Institute in Finland.

Sodium Intake and Cardiac Sympatho-Vagal Balance in Young Men with High Blood Pressure

We have previously reported that a high sodium intake increases sleep-time blood pressure (BP) in young men. However, there are cases in which this relation does not apply. To account for them, we investigated the relation between sodium intake and cardiac sympatho-vagal balance (SVB) in young men with high BP. Sodium intake was estimated from the amount of urinary sodium excretion over 1 week. Twenty-four-hour (24-h) urinary sodium excretion (Salt24), 24-h ambulatory BP and ECG were obtained on the last day of the observation period. As an index of sodium intake, the expression In(Salt24/Cr24) (Cr24, 24-h urinary creatinine excretion) was used. From power-spectral analysis of ECG-RR intervals during sleep, we obtained the LF/HF ratio between the low-frequency component (LF) and the high frequency component (HF) and used it as an index of SVB. The subjects were male medical students divided into a normal BP group (N-group; n=103) and a high BP group (H-group; n=26, 24-h BP>125/75 mmHg). Mean In(Salt24/Cr24) and LF/HF in the H-group were significantly higher than those in the N-group (LF/HF: 1.86+/-0.44 [SD] vs. 1.37+/-0.30, p<0.001). The calculated discriminant function (D) for the H-group and N-group was D=1.6x + 5y - 11, where x is In(Salt24/Cr24) and y is LF/HF. This formula (D) resulted in high discriminant predictive accuracy (82%) between the groups. If D=0 (the value of the cut-off line determining separation of the groups), the relation y=-0.32x + 2.2 (negative relation between y and x) was obtained. These results suggest that excessive sodium intake in combination with accentuated SVB (LF/HF) increases BP in young men.

Relation between sodium intake and blood pressure during sleep in young men

In the past, cross-sectional studies of small groups have not always shown a significant relation between habitual sodium intake and blood pressure (BP). This study examined the relation between 24-h urinary sodium excretion (Salt24, g/day) and BP during sleep in young subjects. The subjects were 132 medical students (93 males, 39 females) aged 21 to 26 years, with no renal disorder. Urine was collected for 24 h, and sodium (Na), chloride (Cl), and creatinine (Cr) excretion were measured. The 24-h urinary Cr excretion (Cr24) was compared with the Cr24 estimated from lean body mass as a guide to ensure accurate collection of 24-h urine. The natural logarithm [ln (Salt24/Cr24)] was taken as an index of sodium intake. On the same day, a portable multi-biomedical recorder (TM2425) was used to measure 24-h systolic BP (SBP)/diastolic BP (DBP). Daytime BP was calculated as the average of waking-time BP, and sleep BP was taken as statistical base BP (minimum BP) during nighttime sleep. No correlation was observed between ln (Salt24/Cr24) and daytime BP. The correlation coefficient with sleep SBP, on the other hand, was 0.34 (p<0.05) in the male group and 0.54 (p<0.01) in the male high-BP group (24-h BP>127/75 mmHg, n=28). No relation of this kind was observed in the female group. In conclusion, despite the small number of subjects, the present cross-sectional study revealed a significant positive correlation between sodium intake and sleep SBP in young men with high BP.

Risk factors and 25 year risk of coronary heart disease in a male population with a high incidence of the disease: the Finnish cohorts of the seven countries study

OBJECTIVE

To assess the efficacy of high serum cholesterol concentration, raised blood pressure, and smoking as predictors of coronary heart disease.

DESIGN

Prospective cohort study of middle aged men conducted over 25 years.

SETTING

Finish components of an ongoing international study (seven countries study).

PARTICIPANTS

1520 Men who at age 40-59 in 1959 were free of clinically evident heart disease.

INTERVENTIONS

At each follow up visit a detailed medical examination including resting electrocardiography was performed, blood pressure and serum total cholesterol concentration were measured, and smoking was assessed.

MEASUREMENTS AND MAIN RESULTS

825 Deaths (54% of participants) occurred during follow up, of which 335 were due to coronary heart disease. The hazard ratio for death from coronary heart disease with respect to risk factors at entry were: for serum cholesterol concentrations above 8.4 mmol/l v below 5.2 mmol/l, 2.68 (95% confidence interval 1.62 to 4.42); for systolic blood pressure in the highest quintile v that in the lowest quintile, 2.46 (1.72 to 3.50); and for smoking 10 or more cigarettes daily v never smoking, 1.95 (1.36 to 2.79). The hazard ratios with respect to cholesterol concentrations and blood pressure remained constant during follow up but the ratio with respect to smoking diminished, mainly owing to men giving up the habit. The estimated conditional probability of a 50 year old man dying of coronary heart disease in the next 25 years ranged from 12% among those with the most favourable risk factor profile to 75% among those with the least favourable profile.

CONCLUSIONS

High risk factor levels (as determined in this study) in middle aged men may greatly increase the absolute probability of death from coronary heart disease when the period of study is relevant to the human life span.

The association between blood pressure, age, and dietary sodium and potassium: a population study

We examined the relationship between blood pressure and dietary sodium and potassium intake estimated from 24 hr diet recall in a population of 584 men and 718 women 30 to 79 years old in Southern California. In men, but not women, age-adjusted systolic and diastolic blood pressure correlated significantly with dietary sodium intake. In both men and women, age-adjusted diastolic blood pressure significantly inversely correlated with dietary potassium intake. Age-adjusted systolic and diastolic blood pressure correlated significantly with the dietary sodium/potassium ratio in each sex; correlations were better for the ratio than for either sodium or potassium alone. The relationship was apparent over the whole range of blood pressure and dietary intake. A marked age gradient was apparent in men, the regression slope for blood pressure vs sodium/potassium ratio increasing with increasing age, suggesting increasing sensitivity to dietary sodium/potassium ratio with age. Adjusting for intake of other dietary variables, including calories, protein, carbohydrate, saturated fat, alcohol, calcium, and fiber, did not alter the relationships; adjusting for body mass index reduced the strength of the association in women but not in men. These results support the hypothesis that dietary sodium and potassium are related to blood pressure within a population.

Management of hypertension in high school students by using new salt titrator tape

In a blood pressure screening program involving 6589 high school students, 180 male (4.7%) and 17 female (0.6%) students were identified as borderline hypertensive. The 174 hypertensive male adolescents studied further showed pathophysiological features such as a significantly higher frequency of obesity, higher 24-hour urinary sodium excretion, higher hematocrit value, higher sodium and lower potassium concentration in red blood cells, and higher ouabain-sensitive sodium efflux compared with the control group (231 male students; p less than 0.05). When used alone, the ordinary 10-week period of counseling about a low salt diet failed to significantly reduce the blood pressure of hypertensive students. However, when education and counseling efforts were combined with self-monitoring of salt (chloride) excretion in overnight urine samples using a new salt titrator tape developed in our laboratory, 24-hour urinary sodium excretion, weight, and blood pressure decreased significantly over 10 weeks (mean reduction: 52 mEq/day for 24-hour urinary sodium excretion, 1.7 kg for weight, 12/7 mm Hg for blood pressure). These results indicate that blood pressure of borderline hypertensive adolescents could be effectively reduced with this nonpharmacological method of dietary education. Such systematic management might be of importance for the prevention of essential hypertension.

Is calcium more important than sodium in the pathogenesis of essential hypertension?

The hypothesis that abnormalities of calcium homeostasis at both an organ and cellular level are a primary factor in the pathogenesis of human and experimental hypertension forms the basis of this review. The rapidly expanding data base relating disordered calcium metabolism to altered vascular smooth muscle function and increased peripheral vascular resistance is summarized and integrated with the observations that reduced dietary calcium intake is the most consistent nutritional correlate of hypertension in the United States. The role of sodium and sodium chloride in pathogenesis of hypertension is reassessed in the light of new data from epidemiological clinical research, experimental models, and cell physiology investigations. The data supporting the thesis that the effects of sodium or chloride or both on blood pressure may represent, in selected situations, secondary influences mediated through induced changes in calcium homeostasis are presented. The interface between these nutritional factors and the normal regulation of vascular smooth muscle is discussed, providing a theoretical framework in which to assess the current information and to formulate the necessary future research.

Salting of food--a function of hole size and location of shakers

The establishment of an association between hypertension and the level of sodium in the diet has focused interest in many countries on the amount of salt added to food, with estimates of intake in western countries being in the range 6-14 g per person per day. As a result, many health authorities have advocated a decrease in salt consumption by the population in general, a common suggestion for achieving a meaningful reduction being to limit the amount of salt used at the table. It is generally assumed that salting habits are influenced by taste preference as shaped by socio-cultural determinants. However, from our observations of the rate of discretionary salt usage of over 1,900 people (mainly adults) consuming main meals in public institutions in Sydney, Australia, were suggest that salting is strongly influenced by the physical factor of mode of presentation of salt to the consumer, particularly the hole size of the salt shaker, and is not influenced by demographic variables.

Human nutrition and blood pressure regulation: an integrated approach

This review highlights the complex interactions that constitute the disciplines of nutrition and cardiovascular physiology. Nutritional factors have long been considered as critical in the pathogenesis of human hypertension. Theoretical and established contributions of various nutrients to blood pressure regulation are presented. A brief historical perspective of sodium's dominance in this area is provided. "Accepted" principles of nutrient interaction are then applied to cardiovascular research. First, the interrelationships among all macronutrients and diet composition, nutrient absorption, renal elimination, and ultimate bioavailability to the vascular tissue are assessed. An analysis of dietary recall data from human studies is provided to illustrate such nutrient interaction. Second, associated factors that influence nutrition are considered in relation to both human and animal investigations of blood pressure regulation. Finally, the development and interpretation of future studies are assessed in light of these principles. Examples from both the human and animal investigations of blood pressure regulation. Finally, the development and interpretation of future studies are assessed in light of these principles. Examples from both the human and animal literature are provided to show why it is necessary to incorporate fully the established principles of nutrition into our current concepts of the pathogenesis of hypertension. Future progress in terms of nutrition, food, and health will be dependent upon such an integrated approach.

Nutrition and gastric cancer

Gastric cancer (Gc) is generally conceived as having a multifactorial origin. Different genetic factors, soil, nutritional and socioeconomic factors have all been mentioned in the literature as possible causes. Further research on the causation of Gc has, in fact, been hampered by the large number of hypotheses. A strong geographic association between gastric cancer and stroke mortality was found by chance in 1964; this association could be spurious, but the quantitative analysis of the data showed similar relationships both between countries and within countries (e.g., in countries as different as the US and Japan), a very unlikely situation if due to chance. The same quantitative relationship was maintained using multiple regression analysis of stroke mortality. All this was observed for each sex separately and for both sexes combined. The working hypothesis was set forth in 1965 that salt intake was the predominant linking factor for both types of mortality. Stroke would then be influenced by the relationship between salt and blood pressure; Gc would result from the delaying and caustic properties of a hypertonic stomach content. The latter condition could produce atrophic gastritis, a common problem in Japan, Chile and Columbia. Atrophic gastritis favors the synthesis of endogenous nitrites and, henceforth, of nitroso-carcinogens. The salt hypothesis can give an explanation for the geographical and time behavior of Gc and stroke mortality and for the socioeconomic gradient of both diseases. Gc mortality can also be used to provide a rough estimate of the salt intake in a given country and year. The hypothesis was tested in Belgium through a deliberate attempt to lower the salt intake of the population. The observed decreases in Gc and stroke mortality were consistent with the measured decrease in salt excretion. Further research is urgently needed through the monitoring of 24-hour salt and creatinine excretion in different countries and over many years.

Sodium and potassium excretion in a sample of normotensive and hypertensive persons in eastern Finland

A 24-hour urine collection was carried out during a cardiovascular survey in eastern Finland. The study population comprised 148 hypertensive subjects in a random sample of the middle-aged population and 86 normotensive controls. The mean sodium excretion was 197 mmol/24h in both normotensive and hypertensive men, 179 mmol/24h in normotensive women, and 174 mmol/24h in hypertensive women. There were no significant differences in potassium excretion rate or in sodium: potassium molar ratio between the normotensive and the hypertensive among either men or women. There was no statistically significant correlation between blood pressure level and sodium or potassium excretion or sodium: potassium molar ratio. One in four of the subjects reported that they usually added salt to their food before tasting it. The results of this study show that the average level of salt intake in a Finnish population is high, and so is the sodium: potassium molar ratio. Although there was no correlation between sodium excretion and blood pressure levels, it is known that in this population the average blood pressure level is high and cardiovascular disease extremely frequent.

Sodium and potassium intake and blood pressure

Sodium and potassium intakes were increased in normotensive volunteers to assess the effects on their blood pressures. An approximately threefold increase in sodium intake for eight days had no effect on the blood pressures of seven volunteers, while a two-stage increase in potassium intake, by about 40% for eight days and a further 55% for 14 days, had no effect on the blood pressures of 21 volunteers. Renal electrolyte excretions and the blood pressures of all 28 subjects showed no statistically significant correlations between either sodium or potassium excretion and blood pressure. A weak negative correlation was found between the sodium: potassium ratio and systolic pressure. The small reductions in sodium intake and increases in potassium intake that might be achieved through propaganda and changes in food processing are unlikely to lower mean blood pressure in Western societies.