Cassava is not a goitrogen in mice

Area of Science:

• Endocrinology
• Nutritional Science
• Toxicology

Background:

• Cassava consumption is widespread in many regions.
• Concerns exist regarding potential goitrogenic effects of cassava due to its thiocyanate content.
• Previous studies have yielded conflicting results on cassava's impact on thyroid function.

Purpose of the Study:

• To investigate the effects of fresh cassava root consumption on thyroid function in mice.
• To determine if cassava consumption leads to goiter or other thyroid abnormalities.
• To elucidate the mechanisms underlying cassava's influence on thyroid hormone metabolism.

Main Methods:

• Mice were fed fresh cassava root, a low-iodine diet, or a standard Purina diet.
• Thyroid function was assessed by measuring iodine uptake, protein-bound iodine, iodide trapping, and serum/thyroid hormone concentrations.
• Thiocyanate levels in urine and serum were analyzed.
• Hepatic T4 5'-monodeiodination was measured in liver homogenates.

Main Results:

• Cassava consumption resulted in low iodine intake, increased urinary and serum thiocyanate, and weight loss in mice.
• No significant thyroid enlargement (goiter) was observed in mice fed cassava, even when normalized for body weight.
• Thyroid iodine uptake and iodide trapping were similar to low-iodine diet groups.
• Serum thyroxine (T4) and triiodothyronine (T3) levels, as well as thyroidal T4 and T3 content, were reduced in cassava-fed mice.
• Hepatic T3 content and T4 5'-monodeiodination were impaired in mice on the cassava diet.

Conclusions:

• Cassava consumption does not induce goiter in mice.
• The thiocyanate produced from cassava ingestion is insufficient to inhibit thyroid iodide transport or organification.
• The observed effects are likely due to low iodine intake and impaired hepatic T4 metabolism, suggesting cassava itself is not goitrogenic.
• These findings do not support the concept of cassava per se having a goitrogenic action in humans.