Iodine is a trace element that is naturally present in some foods which is added to some types of salt, and is available as a dietary supplement. Iodine is the key component for the thyroid hormones thyroxine (T4) and triiodothyronine (T3). These hormones control the body's metabolism and many other important functions. The body also needs thyroid hormones for proper bone and brain development during pregnancy and infants. Foods like Seaweed, Fish, shellfish, Table salts labeled “iodized” Dairy (milk, cheese, yogurt) Eggs. Chicken etc. are rich in iodine. Similarly, Iodine deficiency leads to Cretinism, Goiter, Hashimoto's Thyroiditis, Congenital Hypothyroidism, Postpartum Thyroiditis. Moreover, its over intake leads to Graves' Disease, Toxic Adenoma etc.
Historically, Nepal struggled with endemic goiter, often regarded as a sign of beauty. The reliance on Tibetan rock salt led to widespread iodine deficiency and cretinism in northern regions. In 1970, recognizing the severity of iodine deficiency disorder (IDD), Nepal established the first IDD control program. The successful implementation of iodized salt reduced iodine deficiency from 55% in 1965 to 0.4% in 2007. However, this achievement created a new challenge - the rising prevalence of thyroid disorders due to iodine over intake.
Hyperthyroidism has become a hidden serious health problem in Nepal. WHO recommends that sodium consumption be reduced to < 2 g/day in adults and < 2 g/day in children relative to their age.( SEA-Nut 193,WHO nd) About 150 mcg is the daily requirement of the iodine in our human body. Nepal National Micronutrient Status Survey 2016, also revealed the median urinary iodine concentration among school age children to have increased from 144 to 314 μg/L between 1998 and 2016 which is above 300 μg/L (excess) while it's in “adequate” range in pregnant women and ‘more than adequate’ in women of childbearing age. Iodine intake was found higher in the central and western parts of the country and the Terai region. The mean iodine content for all salt samples was found as 44.1 ppm, and 67.5% samples had more than 40 ppm, well above the expected level at the retail (30 ppm) and household (15 ppm) levels. However, there is no national level epidemiological study regarding iodine deficiency but there is hospital based data and studies. One study from seven places in five districts of Nepal found the prevalence of thyroid disorders in general population to be 4.32%; twice more common in females and among them, 72.41% had subclinical hypothyroidism, 13.7% primary hypothyroidism and 13.7% hyperthyroidism. Another hospital based study showed 35.3% people with thyroid dysfunction with the prevalence of overt hyperthyroidism, subclinical hyperthyroidism, to be 2.5%, 2.4%, respectively. A hospital in eastern Nepal also revealed the prevalence of thyroid disorder at 39.3% among which 4.04% had overt hyperthyroidism. A study from tertiary level hospital in far western Nepal showed the prevalence of total hyperthyroidism as 24.8% including both overt hyperthyroidism (14.9%) and subclinical hyperthyroidism (9.9%). Similarly, 34.4% of school children in eastern Nepal had excess urinary iodine concentration above the WHO recommended levels and 88% of the household salt samples tested were found to have high iodine concentration.
The over intake of iodine has a severe effect on human beings. Excessive iodine intake during childhood can lead to thyroid dysfunction, manifesting as either hyperthyroidism (overactive thyroid) or hypothyroidism (underactive thyroid). Thyroid imbalances can interfere with normal growth and development. Similarly, Pregnant women who consume excessive iodine may put their unborn child at risk of developmental issues, including thyroid dysfunction and cognitive impairment. High iodine levels in children can adversely affect cognitive development, leading to lower IQ scores and impaired cognitive functions. Iodine over intake in pregnant women has been associated with an increased risk of pregnancy complications, including preterm birth and low birth weight. And also high iodine levels in expectant mothers may negatively affect the neurological development of the fetus, potentially leading to cognitive and developmental issues in the child later in life. Similarly, prolonged over intake of iodine can cause the enlargement of the thyroid gland, resulting in a condition known as a goiter. However, iodine deficiency is a more common cause of goiter, excessive iodine can also trigger its development. Additionally, some studies have suggested that high iodine intake may increase the risk of autoimmune thyroiditis (Hashimoto's disease) in susceptible individuals. This condition involves the immune system attacking the thyroid gland, leading to inflammation and potential thyroid dysfunction. Not only that, high iodine intake has been associated with adverse effects on the cardiovascular system, such as irregular heartbeat and an increased risk of hypertension. Moreover, Iodine overload can have implications for kidney function, leading to decreased kidney function and potential renal impairment.
Similarly, to overcome this ongoing burning issue several valuable steps should be taken. The Nepal government should conduct a comprehensive survey to determine the prevalence of iodine over intake in different regions of Nepal. Gather data on iodine consumption patterns, particularly from iodized salt, as well as from other dietary sources. Moreover, conduction of a systematic review of existing studies to evaluate the health consequences associated with iodine over intake, with a focus on thyroid-related disorders and other adverse effects should be effectively done. Likewise, the government should start a survey for identification of sociodemographic and dietary factors associated with higher iodine intake, such as age, gender, socioeconomic status, and consumption patterns. There must be proper engagement with relevant government agencies, international organizations, NGOs, healthcare professionals, and community leaders to develop and implement a cohesive approach to address iodine over intake. Not only that, Investigation on regional variations in iodine intake and over intake rates to tailor intervention strategies according to the specific needs of different areas. Furthermore, clear and informative food labeling regulations to indicate the iodine content in food products should be implemented. This will enable consumers to make informed choices and avoid excessive iodine intake. Launching targeted public awareness campaigns to educate the population about the importance of iodine in the diet and the risks of both iodine deficiency and excess. These campaigns can inform people about the recommended daily intake of iodine and the potential health consequences of consuming too much iodine.
While iodine is essential for human health, over intake can lead to significant health challenges. Nepal must act swiftly to tackle the issue of iodine over intake. By implementing preventive measures and raising awareness, we can protect the physical and mental well-being of present and future generations.