Compared with White adults, Non-Hispanic Black adults are at an elevated risk of
developing cardiovascular disease (CVD) and end-stage chronic kidney disease (CKD) two of
the leading causes of mortality in the United States (U.S.). Inadequate hydration status
is associated with all-cause mortality and several risk factors for CVD and CKD including
obesity, insulin resistance, hypertension, and metabolic syndrome. Prior data demonstrate
Black American individuals are more likely to be hypohydrated (i.e., inadequately
hydrated) when compared with White individuals. One study in emerging adults (18-25 years
old) indicates that Black adults are more likely to be hypohydrated compared with White
adults when assessed using gold-standard 24-hour urine collections. Socioeconomic factors
influence hydration practices. For example, there are well-justified increased
perceptions of unsafe tap water among racial and ethnic minorities. Indeed, the recent
Flint, Michigan, and Jackson, Mississippi water crises have raised public awareness over
these environmental injustices and ways to increase safe drinking water availability and
access. However, there remains a critical need for empirical studies on 1) strategies to
address racial disparities in hydration and resultant health consequences; and 2) the
role socioeconomic factors in contributing to hydration.
Importantly, hypohydration is associated with increased production of arginine
vasopressin (AVP), a peptide hormone produced in the hypothalamus that influences body
water balance via anti-diuretic effects. Plasma copeptin is an established surrogate
marker of circulating AVP concentration. Plasma copeptin is associated with incident type
2 diabetes, metabolic syndrome, the progression of CKD, and CVD. Some, but not all,
studies have demonstrated racial differences in circulating AVP/copeptin. Further, prior
studies that aimed at increasing water resulted in reductions in copeptin and
improvements in cardiometabolic health. For example, in a cohort with high plasma
copeptin, increased water intake also reduced fasting plasma glucose. In a cohort of
adults with overweight and obesity, increased water or low-calorie beverage intake
reduced fasting plasma glucose and contributed to modest weight loss. Lastly, over 90% of
adults do not meet recommendations for potassium intake. Importantly, potassium improves
blood pressure (BP), particularly in Black adults, who tend to consume less potassium and
have higher BP. Yet, there remains a knowledge gap regarding whether hydration
intervention(s) inclusive of water (with or without) potassium could attenuate racial
disparities in hydration status and circulating AVP/copeptin. Therefore, the
investigators are seeking to test the investigators' central hypothesis that water with a
potassium supplement (2000mg/day) will improve hydration and cardiovascular health in
White adults (n = 20, 10 females, 10 males), and to a greater extent in young Black
Adults (n = 20, 10 females, 10 males). The investigators will utilize three complementary
specific aims to address the investigators' hypotheses:
Aim 1: Determine whether water with potassium supplementation improves hydration status
and reduces circulating copeptin. The investigators hypothesize that water and potassium
supplementation will improve hydration and renal biomarkers, including increased urine
volume, and reduced urine specific gravity, urine osmolality, and plasma copeptin.
Aim 2: Determine whether water with potassium supplementation improves BP and vascular
health. The investigators hypothesize that water and potassium supplementation will
reduce resting laboratory BP and ambulatory BP (awake, asleep, and nocturnal BP dipping),
and reduce arterial stiffness assessed via pulse wave velocity.
Aim 3: Determine whether socioeconomic factors are associated with hydration perceptions,
knowledge, and practices. The investigators hypothesize that area deprivation index (ADI,
i.e., more deprivation) will be associated with hydration perceptions (e.g., greater
distrust of tap water) and inadequate hydration assessed by self-reported fluid intake
and urine-specific gravity.
In summary, a knowledge gap remains in determining the underlying reasons for the
consistently reported racial differences in hydration. To restate, the purpose of this
study is to determine 1) whether prescribing water with potassium supplementation is
efficacious at improving hydration and reducing plasma copeptin in Black and White
adults; 2) whether improving hydration with supplemental potassium improves BP and
vascular function in young Black and White adults; 3) Another area of innovation in the
investigators' proposal is determining whether area deprivation index (ADI, i.e., more
deprivation) is associated with and 3a) beliefs and practices around hydration and 3b)
hydration status. 4) We also seek to determine whether the intervention leads to greater
improvements in Black adults who are more likely to be underhydrated.
