A banana a day, spinach or donut lettuce might be better to keep the doctor away from me, and a new study confirms the cause-and-effect relationship.
An analysis of Women’s Health Initiative data found an inverse correlation between dietary potassium intake and stroke risk in postmenopausal women.
In addition, among women without hypertension, patients with potassium intake in the highest quartile had a 27% lower risk of ischemic stroke than those with potassium intake in the lowest quartile, writes the journal Stroke.
The researchers noted that only about 3 percent of the women in the analysis reported consuming 4700 mg or more of potassium per day – the USDA nutritional guidelines recommended for most adults.
Women in the WHI cohort without hypertension appeared to derive the most benefit from a high potassium diet.
Hypertensive women with high potassium intake had a lower risk of death but failed to reduce the risk of stroke, suggesting that the benefit of high potassium intake may be greater before the development of hypertension. Therefore, health care providers may wish to emphasize the importance of a potassium-rich diet, especially for postmenopausal women.
Study Overview
Researchers evaluated data from 90,137 participants with WHI aged 50 to 79 years with a mean follow-up of 11 years. All women were free of stroke episodes at the time of enrollment.
Dietary potassium intake averaged 2,611 mg/day. current smokers, as well as non-drinkers, reported lower dietary potassium intake, and women who exercised recreationally two or more times per week had higher dietary potassium intake than those who exercised less or did not exercise.
Stroke rates were 3.1/1000 person-years for all stroke types, 2.24/1000 person-years for ischemic stroke, 0.50/1000 person-years for hemorrhagic stroke, and 11.60/1000 person-years for all-cause death.
Patients with dietary potassium intake in the lowest quartile (potassium <1,925.5 mg) had a higher incidence of all outcomes (stroke) than those in the other quartiles," the researchers wrote. The linear trend in mortality was statistically significant, but the linear curves for the other outcomes did not reach statistical significance."
In unadjusted multivariate models, when researchers evaluated dietary potassium intake quartiles and stroke risk, they found that the risk of all-cause death, all strokes and ischemic strokes was lower and statistically significant in all quartiles of dietary potassium intake than in the lowest quartile (<1,925.5 mg/d).
In fully adjusted models comparing highest and lowest quartile dietary potassium intake, the HR for all-cause mortality was 0.90 (95% CI 0.85-0.95), for all strokes 0.88 (95% CI 0.79-0.98), and for ischemic strokes 0.84 (95% CI 0.74-0.96). There was no association with hemorrhagic stroke.
In the fully adjusted model, the risk of ischemic stroke was 27% lower in the highest quartile of female patients without hypertension than in the lowest quartile (HR 0.73, 95% CI 0.60-0.88) and was not associated with hemorrhagic stroke. Higher potassium intake was associated with lower all-cause mortality in hypertensive patients, but not with lower stroke risk.
Cox analysis showed that high potassium intake was associated with a lower risk of small vessel disease in women without hypertension. Compared with the lowest quartile, the second quartile HR was 0.43, the third quartile HR was 0.60, and the highest quartile HR was 0.67.
The findings suggest that dietary potassium intake prior to developing hypertension may be more effective, and that studies in cell culture and animal models have shown that high potassium levels improve endothelial function and can promote nitric oxide release to improve blood flow, the researchers wrote.
They say that while other studies have shown that higher potassium intake is associated with lower blood pressure, the association between systolic blood pressure and potassium intake in the WHI cohort study was minimal, suggesting that “the beneficial effects of potassium intake in non-hypertensive patients are not mediated by its effects on blood pressure.”
Another reason to eat fruits and vegetables
Fruits and vegetables are good sources of potassium, including dark green vegetables such as spinach and romaine lettuce, sweet potatoes and regular potatoes, winter squash, dried apricots, prunes, citrus fruits, cantaloupe and bananas. The results of the study provide another reason for women to eat fruits and vegetables.
Red and white meat, many fish, and white lentils are also good sources of potassium.
Study limitations include the fact that this was an observational study, excluding the hypothesis of a causal relationship. Potassium intake was also assessed from dietary frequency questionnaires, which tend to overestimate or underestimate true intake.
The investigators did not assess other diets that have potentially important effects on stroke risk.