You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Outcome", "Participant", "Intervention"].

Please return the output as a JSON object of the format: {"Participant" : ["patients with COPD", ...], "Intervention" : ["Atenolol", ...], "Outcome" : ["blood pressure", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Effects of sodium and potassium supplementation on blood pressure and arterial stiffness : a fully controlled dietary intervention study . We performed a randomised , placebo-controlled , crossover study to examine the effects of sodium and potassium supplementation on blood pressure ( BP ) and arterial stiffness in untreated ( pre ) hypertensive individuals . During the study , subjects were on a fully controlled diet that was relatively low in sodium and potassium . After a 1-week run-in period , subjects received capsules with supplemental sodium ( 3 g d ( -1 ) , equals 7.6 g d ( -1 ) of salt ) , supplemental potassium ( 3 g d ( -1 ) ) or placebo , for 4 weeks each , in random order . Fasting office BP , 24-h ambulatory BP and measures of arterial stiffness were assessed at baseline and every 4 weeks . Of 37 randomized subjects , 36 completed the study . They had a mean pre-treatment BP of 145/81 mm Hg and 69 % had systolic BP ⩾140 mm Hg . Sodium excretion was increased by 98 mmol per 24 h and potassium excretion by 63 mmol per 24 h during active interventions , compared with placebo . During sodium supplementation , office BP was significantly increased by 7.5/3.3 mm Hg , 24-h BP by 7.5/2.7 mm Hg and central BP by 8.5/3.6 mm Hg . During potassium supplementation , 24-h BP was significantly reduced by 3.9/1.6 mm Hg and central pulse pressure by 2.9 mm Hg . Pulse wave velocity and augmentation index were not significantly affected by sodium or potassium supplementation . In conclusion , increasing the intake of sodium caused a substantial increase in BP in subjects with untreated elevated BP . Increased potassium intake , on top of a relatively low-sodium diet , had a beneficial effect on BP . Arterial stiffness did not materially change during 4-week interventions with sodium or potassium .
{"Intervention": ["supplemental potassium", "placebo", "sodium and potassium supplementation", "sodium"], "Outcome": ["intake", "increased", "pre-treatment", "blood pressure and arterial stiffness :", "measures of arterial", "blood pressure ( BP ) and arterial stiffness"], "Participant": ["blood pressure ( BP )", "blood pressure", "untreated ( pre ) hypertensive individuals", "37", "36", "arterial stiffness", "arterial stiffness :", "sodium caused a substantial increase"]}