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CVM GFI #55 Supportive Data for Cat Food Labels Bearing "Reduces Urinary pH Claims: Protocol Development June 1994

Docket Number:
Issued by:
Guidance Issuing Office
Center for Veterinary Medicine

Revised --


Supportive Data for Cat Food Labels Bearing "Reduces Urinary pH" Claims: Guideline in Protocol Development

Guidelines state procedures or practices that may be useful to the persons whom they are directed, but they are not legal requirements. Guidelines represent the agency's position on a procedure or a practice at the time of their issuance. A person may follow the guideline or may choose to follow alternate procedures or practices. If a person chooses to use alternate procedures or practices, that person may wish to discuss the matter further with the agency to prevent the expenditure of money or effort on activities that may later be determined to be unacceptable to FDA. A guideline does not bind the agency, and it does not confer any rights, privileges, or benefits for or on any person. When a guideline states a requirement imposed by statute or regulation, however, the requirement is law and its force and effect are not changed in any way by virtue of its inclusion in the guideline.

William Burkholder, DVM
Center for Veterinary Medicine
June, 1994

Docket No. 94D-0230

Supportive Data for Cat Food Labels Bearing "Reduces Urinary pH" Claims: Guideline in Protocol Development

  1. Test diet formulations should be nutritionally complete and balanced. This should be demonstrated by, at minimum, the successful passage of an adult maintenance feeding trial using current AAFCO protocols. Formulations should be limited to ingredients that are justifiable on a nutritional basis, and amounts of ingredients should be consistent with sound nutritional practices.
  2. Product utility (i.e., the ability of the diet to produce an appropriately acidic urine) should be demonstrated by means of well controlled, scientifically sound studies. At minimum, a concurrent control group of cats fed a non-acidifying diet is needed to allow for meaningful comparisons. To facilitate data collection, cats should be housed individually, not in groups. The control diet may be a commercially available product or an experimental formulation (such as the test diet minus its acidifying components). It should also be nutritionally complete and balanced, preferably determined by previous testing using AAFCO protocols. Adequate numbers of animals in control and test groups, as determined by appropriate statistical methodology, should be used in order to be able to detect statistically significant differences between groups.
  3. Data sufficient to demonstrate product safety are paramount. At minimum, data should include veterinary observations on cat health, as well as measurements of body weight, food consumption, urinalysis (including sediment examination), serum chemistries, blood gases, and mineral balances (Ca, P, Mg, K). Appropriate statistical comparisons should be conducted, using suitable methodology and numbers of animals to confidently (95 %) detect statistically significant (10%) differences, should they exist. Particular attention should be paid to parameters that assess renal and bone function. A necropsy should be performed on any animal that dies during the study, and the findings recorded. The reason for any medical treatment or removal of any animal from the study should be noted.
  4. The length of the studies should be sufficient to assure product safety. At minimum, a six-month study, consistent with the length of time to conduct an AAFCO maintenance feeding trial, is needed. Food consumption and body weight determinations should be measured routinely. Data on other parameters should be collected on at least four occasions during the course of the study, including the beginning and termination of the study.
  5. The submission should include all data generated, and include both data on individual animals and group summaries. Full discussion of product formulation, experimental methodology, statistical methods, and interpretation of findings should be included.
  6. Data on additional parameters and/or longer studies may be required depending on the study findings. It is prudent to keep animals on test and to continue data collection while the six-month data is under review. Aliquots of serum and urine samples should be frozen for possible additional testing.
  7. These key points cannot address all specifics in protocol design. Submission of protocols for review is strongly encouraged. Questions on details of the protocols should be resolved before the study is begun.


Submit Comments

You can submit online or written comments on any guidance at any time (see 21 CFR 10.115(g)(5))

If unable to submit comments online, please mail written comments to:

Dockets Management
Food and Drug Administration
5630 Fishers Lane, Rm 1061
Rockville, MD 20852

All written comments should be identified with this document's docket number: FDA-1994-D-0230.


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