Do higher levels of fluid intake really help the kidneys?

Posted on November 27, 2011 by Dr. Jonathan

Summary: higher levels of fluid intake do protect against chronic kidney disease.

Chronic kidney disease (CKD) is far more common than generally known. Drinking water in excess of that demanded by thirst has been criticized as a useless effort lacking in benefit. However, a paper published in the journal Nephrology presents evidence that relatively high levels of fluid intake, up to 3.2 liters per day, does in fact protect against chronic kidney disease (CKD). The authors…

“…evaluated the association between fluid and nutrient intake and chronic kidney disease (CKD).”

They gathered data from two studies, calculating intakes of over 40 nutrients, total daily energy intake, and the total content of fluid and drinks, which they correlated to CKD as the primary outcome. What did the data show?

“Participants who had the highest quintile of fluid intake (3.2 L/day) had a significantly lower risk of CKD. These findings were consistent across both study periods, both equations to calculate GFR and both GFR thresholds.”

Increasing fluid intake beyond the amount compelled by thirst has been criticized as mythic folk medicine with no science to justify the practice. The evidence presented in this study suggests that the widespread scourge of chronic kidney disease can be reduced by higher levels of fluid intake. The authors conclude:

“Higher intakes of fluid appear to protect against CKD. CKD may be preventable at a population level with low-cost increased fluid intake.“

3.2 liters is 13.5 cups, a lot of water. It remains to be proven, but I suspect that somewhat lesser amounts also have benefit.

Kidney disease is another reason to prevent metabolic syndrome

Posted on October 26, 2011 by Dr. Jonathan

Summary: the insulin receptor resistance and higher insulin levels of metabolic syndrome are a significant risk factor for kidney disease.

We’ve long known that the kidneys are exquisitely sensitive to damage from higher levels of insulin. A study recently published in the Clinical Journal of the American Society of Nephrology further reveals the contribution metabolic syndrome to chronic kidney disease. Since MetS is on the rise, chronic kidney may too. The authors state:

“Observational studies have reported an association between metabolic syndrome (MetS) and microalbuminuria or proteinuria and chronic kidney disease (CKD) with varying risk estimates. We aimed to systematically review the association between MetS, its components, and development of microalbuminuria or proteinuria and CKD.”

The authors undertook an analysis of eleven studies encompassing 30,146 subjects that reported the development of microalbuminuria or proteinuria and/or CKD in subjects with MetS, with attention to eGFR (estimated glomerular filtration rate, a metric for kidney function). Their data present a clear picture:

“MetS was significantly associated with the development of eGFR <60 ml/min per 1.73 m2 [impaired kidney function]. The strength of this association seemed to increase as the number of components of MetS increased. In patients with MetS, the odds ratios for development of eGFR <60 ml/min per 1.73 m2 for individual components of MetS were: elevated blood pressure 1.61, elevated triglycerides 1.27, low HDL cholesterol 1.23, abdominal obesity 1.19, and impaired fasting glucose 1.14. Three studies reported an increased risk for development of microalbuminuria or overt proteinuria with MetS.”

The ‘take home’ message for clinicians and patients is don’t wait until the onset of type 2 diabetes; bear in mind the authors’ conclusion and take decisive action before delicate kidney tissue is irrevocably lost:

“MetS and its components are associated with the development of eGFR <60 ml/min per 1.73 m2 and microalbuminuria or overt proteinuria.”

Heart rate variability analysis predicts kidney disease

Posted on July 15, 2010 by Dr. Jonathan

Here’s more evidence for the profound value of heart rate variability analysis and the fundamental importance of the regulation of functions throughout the body by the autonomic nervous system. In a study just published in the Journal of the American Society of Nephrology the authors investigated the correlation between HRV and chronic kidney disease (CKD):

“Autonomic imbalance, a feature of both diabetes and hypertension, may contribute to adverse cardiovascular outcomes. In animal models, sympathetic nerve activity contributes to renal damage but the extent to which autonomic dysfunction precedes the development of CKD and ESRD [end-stage renal disease] in humans is unknown.”

They measured a number of parameters of HRV analysis in a population of 13,241 adults for 16 years: and found 199 cases of ESRD and 541 patients of CKD; higher resting heart rate and lower heart rate variability was associated with both.

“Other time and frequency domain measures [of HRV] were similarly and significantly associated with ESRD and CKD-related hospitalizations. These results suggest that autonomic dysfunction may be an important risk factor for ESRD and CKD-related hospitalizations…”

It’s hard to think of a clinical test that is easier to perform yet yields more valuable information on the arousal state and capacity of the body to regulate its functions than the heart rate variability analysis.