In spontaneously hypertensive (SHR) and normotensive (WKY) rats fed different diets, blood pressure (BP) increased significantly in both strains when the carbohydrate (CHO) source was from refined rather than from natural ingredients. This BP increase was observed whether sucrose, glucose, or starch was the principal CHO. Urinary excretion of norepinephrine, dopamine, and, to some extent, epinephrine also increased, while myocardial concentrations were unaffected. Despite a comparable elevation of catecholamine excretion in both SHR and WKY rats fed high amounts of refined CHO, the BP increases were greater in the former. The strain differences were explained by the known dissimilar response of their blood vessels to catecholamines. The results suggest that BP elevation after high CHO ingestion is mediated via increased catecholamine production and/or release, thus implying a neurogenic mechanism.

No abstract

SummaryIt is generally accepted that ingestion of sucrose in large quantities elevates blood pressure (BP). Less certain is whether starch and other refined carbohydrates (CHO) have similar effects. Using spontaneously hypertensive rats (SHR) and normotensive control rats (WKY), we show that glucose, fructose, and starch fed to rats either in solution or in dry form elevate BP to a similar degree as sucrose. The changes in BP brought on by various refined CHO were greater in SHR than in WKY. The elevations did not consistently correlate with differences in body weight, amount of dry matter or fluid intake, the quantities of sodium and potassium ingested, or to changes in the various blood chemistries examined. We conclude that other refined CHO (glucose, fructose, and starch) like sucrose raise BP significantly. This effect on BP is rapid (within days) and reversible, at least to some extent.Key Words: carbohydrates, effects on blood pressure, spontaneously hypertensive rats, effect of CHO, macronutrients Excess ingestion of sucrose, a disaccharide of glucose and fructose, elevates blood pressure (BP) in rats [1]. However, it is uncertain whether simple carbohydrates (CHO) other than sucrose cause similar BP increases. Because previous studies have been inconsistent, glucose, fructose, and starch individually cannot be conclusively implicated in a BP response. For example, Hall and Hall [2] found that addition of glucose to a saline drinking solution elevates BP but was significantly less hypertensive than the combination of sucrose plus saline. Honey, which is composed of fructose, did not elevate BP when added to saline. Beebe

Ammonium excretion was investigated in spontaneously hypertensive rats (SHR) and normotensive control rats (WKY) ingesting different diets. SHR and WKY on low protein-high sucrose diets surprisingly showed the same ammonium excretion as rats ingesting a higher protein-lower sucrose diet. This was unexpected, because ammonium excretion correlates positively with protein intake. The relatively high ammonium excretion despite low protein intake (approximately 40% of control) was not associated with acidosis, hypokalemia, hypocalcemia, and/or hypomagnesemia. In a follow-up study, where diets were high in refined carbohydrates (sucrose, glucose, and starch) but more equal in protein content compared with a diet high in carbohydrates of a more complex form (grains), ammonium excretion increased significantly. When we examined the factors known to influence ammonium excretion, the only significant positive correlations found were between norepinephrine, epinephrine, dopamine, and ammonium excretion. These correlations still remained significant when only the data from the rats on the diets high in refined carbohydrates, i.e., rats on the same dietary intake of minerals and proteins, were compared. In vitro, we corroborated that catecholamines significantly increased ammoniagenesis from kidney slices. Our data show that diets high in refined carbohydrates augment both ammonium and catecholamine excretion and suggest that these two events may be interrelated.