Iodine deficiency may be making a comeback due to changing eating habits in Canadian communities

Iodine deficiency, a public health problem solved decades ago, may be making a comeback as a result of changing eating habits, according to new findings from researchers at McMaster University.

Scientists measured iodine levels in urine samples collected from 800 adults in Vancouver, Hamilton, Ottawa and Quebec City.

“Iodine is an essential micronutrient relevant to fertility, cognitive development and immune system health,” explains Philip Britz-McKibbin, a professor in the Department of Chemistry and Chemical Biology and lead author of a new study looking at iodine levels. in adults in some Canadian communities.

Iodine plays a key role in many health functions as it is needed for the synthesis of the thyroxine hormone, especially during pregnancy and child development. About a billion people around the world are deficient in iodine and it is the leading preventable cause of irreversible cognitive impairment in children.

The results, recently published in the journal nutrients, showed surprising regional variation in iodine status across Canada.

While residents of Hamilton and Ottawa showed adequate iodine levels, those from Vancouver and Quebec City were more likely to be iodine deficient and had higher exposure to iodine uptake inhibitors, which inhibit the body’s absorption of iodine.

“That’s a double whammy,” Britz-McKibbin says. “If you have a low dietary iodine intake and are also exposed to ubiquitous environmental iodine uptake inhibitors such as nitrate and thiocyanate, you have an even greater risk of iodine deficiency. Such regional variations in iodine deficiency risk in Canadians have not been previously reported.”

The team identified three main sources of iodine: iodine supplements, prescription thyroxine hormone and diet.

Iodine is found in very few foods, with the best natural source being seaweed, Britz-McKibbin says. It is also coincidentally found in seafood, intentionally iodized table salt and in dairy.

“Most of the iodine in dairy comes from sanitation facilities. Iodine-based disinfectants are typically used on the cows’ teats between milking and leaks into the milk supply,” he explains. Differences in these practices mean that the iodine content of milk and dairy products differs significantly between regions.

Severe iodine deficiency is rare in Canada. Goiter, a swelling of the thyroid gland in the neck caused by severe iodine deficiency, is not commonly seen, but the subclinical effects of moderate and mild iodine deficiency are still of concern.

“A major public health success story is the prevention of goiter-causing iodine deficiency disorders with the introduction of iodized table salt,” says Britz-McKibbin. However, recent trends in food and cooking are changing the effectiveness of universal salt iodization programs. For example, more people follow vegetarian and vegan diets or use non-iodized salt products, which means they can lack iodine.

People also don’t cook as much at home as they used to and they eat more processed foods, which may have a lot of salt, but not necessarily iodized salt.

Meanwhile, public health reports suggesting that people reduce their sodium intake may limit another source of dietary iodine.

“Reducing salt to extremely low levels can lead to iodine deficiencies, which is why public health policies aimed at salt reduction need to take this unintended harm into account,” said Salim Yusuf, a study co-author and executive director of Population Health. Research Institute and Distinguished University Professor of Medicine at McMaster.

Britz-McKibbin says greater understanding of iodine is needed, which could come from more regular testing of iodine levels, as excessive iodine intake may also contribute to adverse health effects

“Regular monitoring would allow us to get an assessment of the iodine nutritional status of a population, and public health could change their guidelines based on that information,” he says, pointing out that Denmark, Australia and New Zealand have started bread. to be enriched with iodized salt.

“With changes in people’s diets, it may be time to rethink how to improve iodine intake, perhaps by fortifying certain staple foods or drinks that would ensure most people get adequate levels for optimal health.”

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