HYPERTENSION - New England Journal of Medicine, May 10, 2007
Background: High blood pressure affects 25% of adults throughout the world. It is the major risk for heart disease and causes most of the deaths worldwide. Unexplained high blood pressure (essential idiopathic hypertension) accounts for 95% of high blood pressure.
An imbalance of kidneys and the outside environment occurs. Most studies label sodium as the culprit causing hypertension. By contrast, potassium, the main cation inside cells, has played a minor role. Yet a deficit of potassium plays a critical role. How sodium and potassium interact as the main role in high blood pressure and its heart risks.
High blood pressure is absent in cultures where less than 50 mmol of sodium are consumed. Most high blood pressure occurs when people consume more than 100 mmol. Since most people consume more than 100mmol and have normal pressures this cannot be enough evidence to develop hypertension.
Processed food is high in sodium and low in potassium. Diets of fruit and vegetables are rich in potassium and low in sodium. People eating natural foods have 150 mmol of potassium daily and only 20-40mmol of sodium. Most of us who eat processed foods take in only 30-70 mmol of potassium and up to 100-400 mmol of sodium.
One third of people in industrial nations get hypertension and only one percent of isolated societies. Perhaps it’s not the sodium intake but the low potassium intake.
Results: Restricting potassium in young rats caused a shortage of potassium inside the cells. This triggers cells to gain sodium to keep their tonicity and volume. The pressor effect of potassium deficiency requires consuming a great deal of sodium. When there is a decrease in potassium excretion by 50 mmol the systolic pressure goes up 3.4mm Hg and the diastolic pressure of 1.8mm Hg.
By increasing the potassium intake of hypertensive rats that were fed high sodium diets, the blood pressure dropped. The incidence of stroke, heart enlargement and kidney injury were prevented.
Review of 33 trial studies showed that a supplement of 260 moms daily lowered the systolic pressure by 4.4mm and the diastolic pressure by 1.8mm Hg. Dietary potassium exerts a powerful dose dependent inhibitory effect on sodium sensitivity.
Our kidneys want to save sodium and excrete potassium. This was great for our prehistoric ancestors who consumed a high potassium-rich diet and low sodium diet. But today our modern society is rich in sodium and low in potassium. Our kidneys have failed to adapt to this change.
Despite our excess intake of sodium, the extra-cellular fluid volume does not increase in hypertensive people. Potassium depletion caused intracellular acidosis and stimulating the sympathetic nervous system. Taking potassium has an opposite effect. A high sodium diet increases potassium excretion. Long-term depletion stimulates the renal sodium pump to retain sodium.
EFFECT ON THE WALLS OF ARTERIES
When sodium is retained, a digitalis factor effect is released and a potassium deficit blocks the sodium pump in the smooth muscle cell walls of the arteries. This results in increased sodium concentration and decrease potassium concentration in the intracellular fluid. More sodium inside the cells stimulates a calcium exchanger to drive calcium into the cells. The potassium channels in the cell membrane and depolarize the membranes. This promotes yet more calcium into the cells, which triggers constriction of the smooth muscle of the artery walls.
Increasing the potassium in the diet block artery clotting, and arthrosclerosis of the artery wall. Diuretics decrease the systemic vascular resistance by changing the ionic concentration in the arterial wall. The diuretic activates the potassium channels causing vascular dilatation.
EFFECT ON THE BRAIN
Increasing the sodium in the cerebrospinal fluid raises the blood pressure. These changes alter the sympathetic outflow, which causes changes in blood pressure.
EFFECT ON METABOLISM
Low potassium blocks insulin secretion and glucose intolerance occurs. Insulin triggers vasodilatation in skeletal muscle by releasing nitric oxide.
Diuretics make glucose tolerance worse in type 2 diabetes.
Eating fruits and vegetables high in potassium increases the metabolic rate. Potassium in these foods does not contain chloride. This allows larger cellular entry of potassium in exchange for sodium and has a great antihypertensive effect. Only 12%of dietary sodium chloride is found naturally in food while 80% is the result of food processing. The rest is in adding salt in cooking.
Conclusion: People with hypertension should eat more fruit and vegetables and avoid processed foods. Potassium supplements also help.
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