In Mild Kidney Disease, Dietary Restriction May Be The Best Way To Reduce Phosphate's Negative Effects On The Heart

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In Mild Kidney Disease, Dietary Restriction May Be The Best Way To
Reduce Phosphate's Negative Effects On The Heart
22 Apr 2013

High phosphate levels in the blood carry increased heart-related
risks, but taking a drug that targets phosphate does not improve
cardiovascular measures in patients with mild kidney disease,
according to a study appearing in an upcoming issue of the Journal of
the American Society of Nephrology (JASN). The findings suggest that,
at least for now, reducing dietary intake of phosphate may be the best
way for these patients to reduce the mineral's effects on the heart.

Higher blood levels of phosphate, even in the normal range, are linked
with an increased risk of dying from heart-related causes. This was
first demonstrated in patients with chronic kidney disease (CKD) and
subsequently in the general population. Researchers have suggested a
number of possible explanations, including phosphate's ability to
promote calcification and stiffening of blood vessels and its
potential to cause structural changes in the heart, such as increased
wall thickness.

To see if lowering phosphate levels in the blood may help lower
cardiovascular risks, Charles Ferro, MBChB, MD, Colin Chue, MBChB
(University Hospitals Birmingham NHS Foundation Trust and the
University of Birmingham, in England), and their colleagues designed a
double-blind, randomized, placebo-controlled trial of 120 patients
with early stage CKD that tested the effects of the phosphate binder
sevelamer carbonate, which is approved only for patients with kidney
failure. The researchers looked to see if the drug might reduce heart
muscle thickness and decrease markers of blood vessel stiffness after
40 weeks of treatment.

"We hoped that by asking a very motivated group of patients with early
stage chronic kidney disease to take phosphate binders with every
meal, we would be able to reduce the amount of phosphate absorbed from
the diet," explained Dr. Ferro.

At the end of the study, the investigators found no differences in any
of the measures of cardiovascular structure and function between the
groups. However, only 56% of patients took more than 80% of the study
medication. When the sub-group of patients with more than 80%
compliance was analyzed separately, the group taking sevelamer
excreted significantly smaller amounts of phosphate in their urine
compared with those taking placebo. The sevelamer group also had
reduced levels of a hormone called FGF-23, which is critical for
maintaining phosphate balance but is also toxic to the cardiovascular
system. No changes were noted in any of the measures of cardiovascular
structure, though.

"It would appear that for now it would be better to lower the amount
of phosphate in the diet rather than rely on pharmacological
interventions," said Dr. Ferro. Foods with large amounts of added
phosphate are processed meat, ham, sausages, canned fish, baked goods,
cola drinks, and other soft drinks. "Fast food and ready-to-eat
processed foods are the main contributors to today's rising dietary
consumption of phosphate," Dr. Ferro noted. He suggested that a
comprehensive public education effort that explains the harmful
effects of high phosphate intake and provides clear labeling of the
phosphate content of food could help limit the damage done by this
newly recognized cardiovascular risk factor.

In an accompanying editorial, Rajiv Agarwal, MD (Indiana University
School of Medicine) noted that the study "should not serve as a death
knell to investigations on phosphorus in progressive CKD, but should
instead serve as a crčche for future investigations on the value of
phosphorus reduction in preventing cardiovascular disease and CKD
progression."
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References:

Study co-authors include Jonathan Townend, MBChB, MD, William Moody,
MBChB, Daniel Zehnder, MD, PhD, Nadezhda Wall, MBChB, Lorraine Harper,
MBChB, PhD, Nicola Edwards, MBBS, PhD, and Richard Steeds, MBBS, MD.

Disclosures: This study was funded by an unrestricted grant from
Genzyme Corporation. Genzyme Corporation provided the study drug
sevelamer carbonate and matching placebo. Genzyme Corporation had no
role in study design or data analysis and interpretation. Dr. Ferro
and Dr. Chue have received lecture and advisory board fees from
Genzyme Corporation.

The article, entitled "Cardiovascular Effects of Sevelamer in Stage 3
CKD," appeared online at http://jasn.asnjournals.org/ on April 18,
2013, doi: 10.1681/ASN.2012070719.

The editorial, entitled "What Can We Learn from Null Randomized
Controlled Trials?" appeared online at http://jasn.asnjournals.org/ on
April 18, 2013, doi: 10.1681/ASN.2013030295.

American Society of Nephrology


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MLA
American Society of Nephrology. "In Mild Kidney Disease, Dietary
Restriction May Be The Best Way To Reduce Phosphate's Negative Effects
On The Heart." Medical News Today. MediLexicon, Intl., 22 Apr. 2013.
Web.
24 Apr. 2013. <http://www.medicalnewstoday.com/releases/259349.php>
APA
American Society of Nephrology. (2013, April 22). "In Mild Kidney
Disease, Dietary Restriction May Be The Best Way To Reduce Phosphate's
Negative Effects On The Heart." Medical News Today. Retrieved from
http://www.medicalnewstoday.com/releases/259349.php.
Please note: If no author information is provided, the source is cited
instead.