Monovalent and divalent cations in hypertension.

The relationship of four cations (sodium, potassium, calcium, magnesium) to hypertension is reviewed. It seems reasonable to advise some reduction in sodium intake, and an initial goal of a mean intake of 120 mmole per day for men and 90-100 mmole per day for women is suggested. Some increase in potassium intake may well be justifiable but is better achieved through potassium-containing foods than by any artificial supplements. The data for calcium and magnesium are not sufficiently strong to warrant any recommendation for a change in intake at present.

Iodide excretion in a salt-restriction trial.

Twenty-four hour urinary iodide excretion was measured twice, with a four month interval, in 133 individuals who were in a 12-month salt-restriction study in an area where iodine-deficiency goitre was once common and where most household salt is iodised. Half the subjects were salt restricted; their mean 24 h sodium excretion after eight months was 89 mmol for men and 73 mmol for women. Iodide excretion correlated with sodium excretion in the whole group on each occasion. After eight months mean 24 h iodide excretion in the salt-restricted group (men 1.3 SD 0.6 mumol, women 1.1 SD 0.4 mumol) was lower (p less than 0.01) than that in the control group (men 1.8 SD 0.8 mumol, women 1.7 SD 0.8 mumol), but was reasonable in terms of recommended dietary allowances (1.2 mumol, 150 mg). Mean iodide content of local milk was 1.3 mumol/l. Any salt that is used in the home should continue to be iodised. However, it has become unnecessary in this population to use salt (ie, iodised salt) simply in order to avoid iodine deficiency, so long as other foodstuffs continue to contain iodine as at present. As the other sources of iodine may be subject to change, the adequacy of intake of iodine from these sources should be monitored from time to time in samples of the population.

Evidence against a circulating ouabain-like transport inhibitor as a cause of increased red cell sodium in essential hypertension.

Red cell sodium and potassium concentrations, and total ouabain-sensitive and ouabain-insensitive first order red constants for sodium efflux, were measured in 15 patients (11 female, 4 male) with essential hypertension (162 +/- 14/99 +/- 7 (s.d. mmHg) and 15 normotensive control subjects (117 +/- 17/64 +/- 10 mmHg) individually matched for age (45.8 +/- 10 versus 45.7 +/- 10 years, respectively, sex, weight (68.6 +/- 16.1 versus 64.7 +/- 11.2 kg) and blood group. To test for possible plasma inhibitors of sodium transport in hypertension, total efflux rate constants were measured in red cells incubated in two plasma samples, from either the same or the complementary (paired) subjects, respectively. Intracellular sodium was significantly increased in patients (11.8 +/- 3.45 versus 8.75 +/- 2.48 mmols/l of red cell water; P = 0.023). Intracellular potassium and total and ouabain-sensitive sodium efflux rate constants, were similar in both groups. Sodium efflux was similar when cells were incubated in the homologous and complementary plasma samples. Ouabain-insensitive rate constants were decreased in the patients (0.16 +/- 0.08 versus 0.20 +/- 0.05 h-1) but the difference was of borderline significance (P = 0.059). These results confirm the presence of abnormal intracellular sodium concentrations and membrane transport in essential hypertension but are not consistent with the suggestion that the abnormalities are due to a circulating sodium transport inhibitor.

Selenium and risk factors for cardiovascular disease in New Zealand.

Blood selenium (Se) concentrations and glutathione peroxidase (GSHPX) activities were measured in 118 men (39 +/- SD 15 yr) and 112 women (42 +/- 16 yr) randomly selected from the total respondents (1192) to health survey in Milton, a low soil-selenium area in Otago. GSHPx activities were marginally lower for men (11.9 +/- 3.2 units/g Hb) than for women (12.9 +/- 3.8 units/g Hb). Blood, erythrocyte and plasma selenium concentrations were about the same for both sexes and means for all subjects (61 +/- 15; 73 +/- 19; 49 +/- 12 ng Se/ml) were almost identical with a control group of Otago blood donors. No differences in blood levels could be associated with smoking, use of oral contraceptives, arthritis and/or rheumatism, or anti-hypertensive drugs. No relationship was found for the men or women between any of the parameters of selenium status and any of the parameters of risk factors for cardiovascular disease measured in the health survey: age, Quetelet's index, total skinfolds, systolic and diastolic pressure, pulse rate, plasma lipids and lipoprotein lipid concentrations. Moreover no relationship was found for the subgroups (36% group) of men and of women with plasma selenium below 45 ng Se/ml. This study indicates that if selenium is important it does not operate through the risk factors of cardiovascular disease as presently understood.

Licorice consumption among high school students.

A survey was carried out of licorice intake among 603 4th and 5th form pupils of two Dunedin high schools. Licorice was eaten on a regular (weekly) basis by 29 percent of the girls and 17 percent of the boys. At least 200 g (of black licorice confectionery) was eaten weekly by 5.9 percent of the girls and 4.9 percent of the boys; at least 500 g was eaten weekly by 1.8 percent of the girls and I percent of the boys. The intake reported by two pupils exceeded 1000 g per week.