Journal Scan: Feeding a limited-iodine diet to healthy cats may not have adverse effects


In multicat homes, keeping a healthy cat from eating a hyperthyroid cats food can be a struggle. Is it hurting the healthy cat to eat this food long term?

Hyperthyroidism is a common disease in cats, with anywhere from 6% to 10% of cats over the age of 10 expected to suffer from the disease in the course of their lifetime. Many treatment options are available to treat hyperthyroidism, including thyroidectomy, radioactive iodine therapy and medical management using methimazole. However, no treatment is perfect for every cat.

More recently, medical management using a limited-iodine diet has become available. To be effective, cats must eat the limited-iodine diet only, with no other sources of iodine in their diet. This became problematic for multicat households as it was not known whether feeding the limited-iodine diet exclusively to normal cats would cause health problems.

What they did

Thirty healthy cats aged 2-5 years were enrolled in the study and then randomly assigned to the limited-iodine diet group or a conventional diet group. Baseline samples were obtained for a complete blood count, serum chemistry profile, urinalysis and thyroid hormone concentrations. Ultrasound measurements of the height of the thyroid gland were also obtained. Cats were then fed the diet of their assigned group, and blood samples and measurements were taken at six, 12, 18 and 24 months during the trial.

What they found

No significant abnormalities or clinically relevant differences were detected between the two groups.

Take-home points

Based on this study, it appears that a limited-iodine diet may be safe and healthy to feed to non-hyperthyroid cats on a regular basis. The authors caution that while the findings were significant, the study does have limitations. First, the study looked only at healthy middle-age cats, so the findings may not correlate well with senior/geriatric cats or cats with concurrent diseases. Second, the study time frame was two years, and it's possible that effects of feeding a limited-iodine diet may be observed over a longer period.

Paetau-Robinson I, Melendez LD, Forrester SD, et al. Comparison of health parameters in normal cats fed a limited iodine prescription food vs a conventional diet. J Feline Med Surg 2018;20(2):142-148.

Link to abstract:

Dr. Michael Nappier is assistant professor of community practice in the Department of Small Animal Clinical Sciences at the Virginia-Maryland College of Veterinary Medicine in Blacksburg, Virginia.

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