China will change its requirement that all salt nationwide be iodized and instead set different standards for different regions, The Beijing News reported Thursday.

The new rules aim to take a more “scientific and precise” approach toward iodine requirements, adjusting dosages based on environmental and dietary factors, according to a draft regulation a bureau under the National Health Commission has submitted for public feedback until June 15.

Iodine is essential to humans, who generally consume it through food and water. The thyroid gland, located in the neck, takes iodine and converts it into thyroid hormones. Consuming either too much or too little iodine can cause severe metabolic problems — from goiters, elevated heart rate, and high blood pressure to low metabolism and general listlessness.

In 1991, the World Health Organization estimated that around 20 percent of the world’s population lived in areas where iodine supply was insufficient. After publishing these findings, the organization began promoting iodized salt as a safe and economic way of supplementing an otherwise iodine-deficient diet. Beginning in 1994, China became one of the now 18 Asian countries to make iodized salt compulsory, setting a baseline concentration of 50 milligrams of iodine per kilogram of salt — with no upper limit.

Recent studies, however, have shown that between 1997 and 2011, Chinese people consumed too much iodine — and, more importantly, indicated that excessive iodine consumption can lead to thyroid-related illnesses. For example, the rate of thyroid nodules, or abnormal growths in the thyroid gland, rose from less than 5 percent in 1999 to 20 percent in 2017, according to a study by Teng Weiping, an endocrinology expert at China Medical University in the northeastern city of Shenyang.

Apart from the risk of excessive iodine intake from salt, a 2005 research paper found that nearly 31 million Chinese people — including communities in Shandong, Anhui, Henan, and Shanxi provinces — are at risk of thyroid problems from naturally high iodine levels in their drinking water.

When Hu Bei’s father developed a thyroid nodule, her doctors advised her to consume less iodine as a precautionary measure. “I stopped eating iodized salt years ago,” the Shanghai resident told Sixth Tone. And Yang Dan, a Beijing resident with a thyroid nodule, told Sixth Tone that she consumes noniodized salt whenever she can find it. In parts of China where iodine intake from water or seafood is high, vendors can apply for special permits to sell noniodized salt.

Several people from Zhejiang — a coastal province just south of Shanghai — told Sixth Tone that they don’t consume iodized salt because they believe they get all the iodine they need from fresh seafood.

Zhang Wanqi, a nutrition expert at Tianjin Medical University, told Sixth Tone that while China’s booming logistics industry and advances in quality-of-life standards have to some extent bridged the gap between coastal and inland diets, iodine intake still varies widely across the country due to dietary habits, water iodine levels, and each individual’s physical needs.

The new regulation would allow iodine-sufficient provinces to sell noniodized salt and encourage provincial governments to set concentration standards for iodized salt that take local factors such as drinking water and a seafood-heavy diets into consideration. The regulation also proposes that local governments publicize where residents can buy noniodized salt.

According to Zhang, the government should be deliberate in setting the new standards. “The policymakers should set [iodine concentrations] by taking geographical and physiological differences into account,” he said, adding that online surveys or apps could be used to assess iodine intake and then provide a customized range users could then choose to follow.

Zhang also suggested targeting specific demographics: Pregnant women, for example, need more iodine to keep their babies healthy. Apart from iodized salt, they can get the iodine they need through dietary supplements — which are not yet a common option in China, especially in rural areas.

This is not the first time the Chinese government has considered amending its saline standards. In 1996, policymakers set a maximum iodine concentration of 60 milligrams per kilogram of salt, and then in 2000 set the average recommended concentration at 35 milligrams.

Whether to make iodized salt compulsory has long been a contentious issue worldwide. India, one of the first Asian countries to do so in the 1960s, lifted its ban on noniodized salt in 2000, only to reinstitute it five years later. Yet many of the country’s doctors and health experts have opposed the ban, arguing that iodine deficiency is no longer a major concern.

For now, at least, noniodized salt remains strictly regulated in China, where selling unauthorized or mislabeled salt can lead to detention or a fine of up to 30,000 yuan ($4,700).

Editor: David Paulk.

(Header image: A woman shovels salt in Gaotai County, Gansu province, Sept. 6, 2016. Wang Jiang/VCG)