A great many studies show that high potassium foods prevent hypertension, strokes, cardiovascular disease, and osteoporosis. There are other diseases for which it has long been suspected that a high potassium foods diet would reduce the prevalence of the disease. One of these is type 2 diabetes. A recent study (1) has become the first prospective long-term study showing an association between a diet high in sodium and diabetes.
Another First For Finland
This study was done in Finland. Finland was the source of the first extensive nation-wide study showing a reduction in strokes and hypertension from an improved potassium sodium ratio in the diet. We discussed this work here.
In this recent study there was an 18 year follow-up of over 1900 people. The researchers were able to show an association of a high intake of sodium and diabetes. They did multiple statistical adjustments to try to adjust for any other possible underlying associations. They adjusted for the confounders of body mass index (BMI), obesity, physical activity, and hypertension. In all cases, the association persisted independently. The researchers felt that the association between a high intake of sodium and diabetes was independent of these other factors.
The 24-hour urinary potassium excretion rose from 68 to 94 in those that had the lowest amount of sodium to those who had the highest amount of sodium intake. The exact potassium sodium ratio cannot be calculated from the data. But the sodium level rose by a much higher percentage. Thus the potassium sodium ratio was much worse in the high sodium group.
The body mass index (BMI) rose from 26 to 29 in the lowest to highest sodium intake groups. Although the BMI did not seem to rise much, the percentage of obese subjects in the high sodium group rose quite a bit. The percentage of obese people rose from 13% in the lowest group to 33% in the highest sodium group.
The blood pressure average did not rise very much between the lowest and highest sodium groups. The systolic pressure only rose from 144 systolic to 145. The diastolic only rose from 86 to 88. Nonetheless, there was a big difference in the number of people who were hypertensive in these groups. The group with the lowest sodium intake had a 36% incidence of hypertension. But the group with the highest intake had an incidence of hypertension of 45%.
There also were differences in the daily consumption of vegetables and fruit between groups. The daily consumption of vegetables went from 21% in the group with the lowest blood pressure down to 15% in the group with the highest blood pressure. The daily consumption of fruits went from 29% down to 22% in these same groups.
When the researchers looked at the association between the intake of sodium and diabetes, they used several models to try to adjust for other possible factors. In the first model they only adjusted for age, gender and the year that the person entered the study. In this model they compared the lowest three groups with the highest salt intake group. They found that members of the highest group had diabetes 2.84 times as often as the members of the lowest three groups.
The researchers adjusted for age, gender, study year, education, physical activity, smoking, alcohol, coffee, vegetable and fruit consumption, sausage consumption, bread consumption and saturated fat consumption. They found the risk for diabetes was 3 times as much for the highest salt consuming group as it was for the lowest three groups.
When the researchers also adjusted for systolic blood pressure and hypertension treatment, they found the ratio to be 2.8. Then the researchers adjusted for all the mentioned factors and also included body mass index (BMI). With this final adjustment, they found the risk of diabetes had only a twofold increase in the high salt group.
Conclusions About Sodium And Diabetes
The authors concluded that a high sodium intake does predict an increased risk of type 2 diabetes. Of course the confounding effects of other dietary factors cannot be fully excluded. And because the Finnish population has a relatively uniform dietary consumption, the study does not include a large range of some of these other dietary factors, such as fruit and vegetable consumption. This means that with a greater variation, sodium consumption may be shown to be dependent on these other dietary factors.
The authors also emphasized that it is important to investigate the physiological mechanisms behind this association. Some of this basic science work has been done previously by several researchers, including Dr. Richard Moore. He was among the first to show the effect of insulin on the sodium potassium ATPase pump, and how this affects sugar metabolism and diabetes. At present, more of this type of research is being done, as well as genetic and molecular studies on the association of sodium and diabetes.
This study and other similar studies are finding associations of a diet low in potassium and high in sodium with several diseases beyond those most commonly mentioned. When combined with basic science studies to show the mechanism of how the potassium sodium ratio leads to a specific disease, these diseases will have the kind of strong evidence now present for hypertension, strokes and cardiovascular disease.
1. Urinary sodium and potassium excretion and the risk of type 2 diabetes: a prospective study in Finland. Hu G, Jousilahti P, Peltonen M, Lindström J, Tuomilehto J. Diabetologia. 2005 Aug;48(8):1477-83. Epub 2005 Jun 22.