Controlling dietary acid intake by increasing consumption of fruits and vegetables could help improve kidney health, according to three new studies from the US and Japan.
The studies were presented at the ASN Kidney Week 2013 held at the Georgia World Congress Centre in Atlanta from 5 November 2013 to 10 November 2013.
A diet rich in wheat flour and animal protein produces an acidic environment in the body that worsens with age as kidney function declines. This acid load can be detrimental to a variety of tissues and processes. Research suggests that consuming more fruits and vegetables — which are highly alkaline — may help counteract these effects.
Kidney health preserved by consuming more fruits and vegetables
One of the three studies, conducted at the Texas A and M University College of Medicine investigated whether consuming fruits and vegetables can protect the kidney health of individual with hypertensive nephropathy, a condition in which damage to the kidneys occurs due to high blood pressure. The study was led by Nimrit Goraya, MD.
In this study, 23 patients received extra dietary fruits and vegetables, 23 patients received an oral alkaline medication, and 25 patients received nothing. One year later, kidney injury progressed in patients who had received no intervention, but kidney health was preserved in those receiving fruits and vegetables or oral alkaline medication.
High diet acidity increased kidney function decline
Another study from the Tokyo Kyosai Hospital in Japan, investigated the role of dietary acid levels in chronic kidney disease (CKD) progression.
The retrospective study, which was led by Eiichiro Kanda, MD, PhD, analysed data from 249 CKD patients in Japan. High acid levels were linked with accelerated kidney function decline, and patients with elevated acid levels had an increased risk of CKD progression compared with patients with low acid levels. Researchers said the findings suggest that monitoring and control of dietary acid levels are necessary for the prevention of CKD progression.
Detrimental effect of high dietary acid differs with ethnicity
The third study, from the John Hopkins University School of Medicine, investigated whether the effect of dietary acid risk of kidney failure differed by race in a group of 159 non-Hispanic black and 760 non-Hispanic white CKD patients who had an annual household income below 300 per cent of the federal poverty line.
The study, which was led by Deidra Crews, MD, FASN, examined data from participants in the 1999-2004 National Health and Nutrition Examination Survey.
Overall, 12.4 per cent of participants (38.3 per cent whites and 61.7 per cent blacks) developed kidney failure during an average of 6.4 years of follow up. Black participants had higher acid levels than white participants. They also had a three-fold higher risk of developing kidney failure compared with white participants after adjusting for factors such as age, sex and caloric intake. Increased acid levels were more strongly associated with kidney failure among black participants than among white participants.
Researchers said the findings indicate that among CKD patients with low socioeconomic status, the detrimental effect of high dietary acid levels on progression to kidney failure appears to be greater for black people than for white people.
Deidra C. Crews is a consultant for The Boston Consulting Group and receives honoraria from the National Institute on Aging and National Institutes of Health. Hal Morgenstern is a consultant for the Arbor Research for Collaborative Health. Rajiv Saran receives research funding from the Renal Research Institute, Forest Research Institute, and Arbor Research Collaborative for Health; and honoraria from Otsuka. Neil R. Powe receives honoraria from ABIM, ASN, Robert Wood Johnson Foundation, Vanderbilt University, Commonwealth Fund, Informed Medical Decision Making Foundation. The authors report funding from the Department of Defense.