Reviewing the evidence on low iodine diets for thyroid cancer patients undergoing radioiodine treatment

It is still unclear whether a low iodine diet improves treatment success rates for thyroid cancer, according to a systematic review of the evidence published in Clinical Endocrinology. Researchers from the Nutrition Theme of the National Institute of Health and Care Research Bristol Biomedical Research Centre (NIHR Bristol BRC) reviewed studies on the subject. None of the studies they found on success of radioiodine treatment following a low iodine diet were considered high quality, meaning no firm conclusions can be drawn.

Radioiodine treatment is used to destroy any remaining thyroid tissue following cancer surgery. Radioactive iodine is used in the process. Debate remains around whether a low iodine diet ahead of treatment improves its success, with different treatment centres giving varying advice to patients.

This review aimed to look at the evidence for the impact on treatment success while understanding the impact on patients of adopting a low iodine diet. They found 59 studies to answer these questions. This is the first time that the wellbeing of patients on a low iodine diet has been systematically reviewed. It was also supported by researchers from the NIHR Applied Research Collaboration West (NIHR ARC West).

Whilst it remains unclear whether a low iodine diet improves treatment success rates, the review showed that the diet does lead to lower iodine levels, but that following such a diet is challenging for many patients. The main challenges were a negative impact on psychological health, being overly restrictive, confusion and difficulty for some groups of people.

Georgia Herbert, Senior Research Associate at NIHR Bristol BRC, said:

“The jury is still out on the question of the effectiveness of low iodine diets for patients undergoing radioactive treatment for thyroid cancer. However, we did demonstrate that this type of diet can be a challenge for patients who are already undergoing stressful cancer treatment. We need well designed studies to answer the question of whether restricting iodine in the diet ahead of radioiodine treatment is helpful or not.”