Several large epidemiological studies have suggested that increased potassium intake is associated with decreased risk of brain infarction (‘stroke’).
A prospective study in more than 43,000 men followed for eight years found that men with the highest dietary potassium intake (median intake, 4,300 mg/day) were only 62% as likely to have a stroke as those with the lowest potassium intake (median intake, 2,400 mg/day) (4).
However, a similar prospective study in more than 85,000 women followed for 14 years found a much more modest association between potassium intake and the risk of stroke (5).
Another large study that followed more than 9,000 people for an average of 16 years found that higher potassium intake was related to lower risk of stroke only in black men and men with hypertension (6). However, black men and women reported significantly lower potassium intakes than white men and women (1,606 mg/day vs. 2,178 mg/day). More recent data from the same population indicate that those with potassium intakes higher than 1,352 mg/day were only 72% as likely to have a stroke as those with potassium intakes lower than 1,352 mg/day (7).
A prospective study in 5,600 men and women older than 65 years found that low potassium intake was associated with a significantly increased incidence of stroke in individuals not taking diuretics (8).
Taken together, the epidemiological data suggest that a modest increase in intake of rich sources of dietary potassium could significantly reduce the risk of stroke, especially in individuals with hypertension and/or relatively low potassium intakes.
Osteoporosis
At least four cross-sectional studies have reported significant positive associations between dietary potassium intake and bone mineral density (BMD) in populations of women before, during, and after menopause, as well as in elderly men (9, 10, 11). The average dietary potassium intakes of the study participants ranged from about 3,000 to 3,400 mg/day, while the highest potassium intakes exceeded 6,000 mg/day and the lowest intakes ranged from 1,400 to 1,600 mg/day.
Potassium-rich foods, such as fruits and vegetables, are also rich in precursors to ‘bicarbonate ions’, which buffer acids in the body, to maintain a certain ‘pH’ (acidic or alkaline). The modern Western diet tends to be relatively low in sources of alkali (fruits and vegetables) and high in sources of acid (fish, meats, and cheeses). When the quantity of bicarbonate ions is insufficient to maintain normal pH, the body is capable of mobilizing alkaline calcium salts from bone in order to neutralize acids consumed in the diet and generated by metabolism (12). Increased consumption of fruits and vegetables reduces the net acid content of the diet and may preserve calcium in bones, which might otherwise be mobilized to maintain normal pH, resulting in bone loss (13). Support for this theory was provided by some studies (13, 14, 15).
Kidney stones
Abnormally high urinary calcium (‘hypercalciuria’) increases the risk of developing kidney stones. In individuals with a history of developing calcium-containing kidney stones, increased dietary acid load was significantly associated with increased urinary calcium excretion (16). Increasing dietary potassium (and alkali) intake by increasing fruit and vegetable intake or by taking potassium bicarbonate supplements has been found to decrease urinary calcium excretion. Additionally, potassium deprivation has been found to increase urinary calcium excretion (17, 18).
A large prospective study of more than 45,000 men followed for four years found that men whose potassium intake averaged more than 4,042 mg/day were only half as likely to develop symptomatic kidney stones as men whose intake averaged less than 2,895 mg/day (19). A similar study that followed more than 90,000 women over a period of 12 years found that women with the highest potassium intake (averaging 3,458 mg/day) were only 65% as likely to develop symptomatic kidney stones as women with the lowest potassium intake (averaging 2,703 mg/day) (20).