Recent research studies have shown that ( ).

参考解析：

根据题干关键词recent research可以定位至第四段…it measured the relationship between urinary sodium excretion—a direct measure of salt consumption—and blood pressure.可知选项B：尿液中盐排泄是测量盐摄入量的手段，正确。选项A：盐摄入会导致中风，根据stroke定位至第五段And hypertension is a risk factor for two of the biggest killers in this country: coronary heart disease and stroke.可知中风只是高血压会引起的疾病之一，并不是盐摄入会导致中风；选项C：高血压会引起盐摄入量增加，属于本末倒置，错误；选项D：尿液中钠排泄越多，高血压的几率越高，根据第四段末句…the lowest sodium excretion also have the lowest blood pressures.可知文中只是说尿液中钠排泄量最少，其血压也是最低，但是并不能推出选项D的内容。故本题正确答案选B。