Iodine deficiency, a public health problem solved decades ago, may be returning due to changes in eating habits, according to new findings from McMaster University researchers.
The scientists measured iodine levels in urine samples collected from 800 adults in Vancouver, Hamilton, Ottawa and Quebec.
“Iodine is an essential micronutrient that is relevant to fertility, cognitive development, and immune health,” explains Philip Britz-McKibbin, a professor in the Department of Chemistry and Chemical Biology and lead author of a new study that analyzes levels of iodine in some adults. Canadian communities.
Iodine plays a key role in many health functions, as it is necessary for the synthesis of the hormone thyroxine, especially during pregnancy and for child development. Approximately one billion people worldwide are iodine deficient and it is the leading preventable cause of irreversible cognitive impairment in children.
The results, recently published in the journal Nutrients, showed a striking regional variation in iodine status across Canada.
While residents in Hamilton and Ottawa showed sufficient iodine levels, those in Vancouver and Quebec City were more often deficient in iodine and showed higher exposure to iodine uptake inhibitors, which prevent iodine uptake by part of the body.
“That’s a double whammy,” Britz-McKibbin says. “If you have a low dietary intake of iodine and are also exposed to ubiquitous environmental iodine uptake inhibitors such as nitrate and thiocyanate, you have an even higher risk of iodine deficiency. These regional variations in the risk of iodine deficiency among Canadians have not been reported before “.
The team identified three main sources of iodine: iodine supplements, prescribed thyroxine hormone, and diet.
Iodine is found in very few foods, and the best natural source is algae, says Britz-McKibbin. It is also found in seafood, expressly iodized table salt and in dairy products, by chance.
“Most dairy iodine comes from sanitation practices. Iodine-based antiseptics are typically used in cow’s teats between milking and filtration to the milk supply,” he explains. Differences in these practices cause the iodine content of milk and dairy products to vary significantly between regions.
Severe iodine deficiency rarely occurs in Canada. Goat, a swelling of the thyroid gland in the neck caused by severe iodine deficiency, is not often seen, but the subclinical effects of moderate and mild iodine deficiency are still worrisome.
“A major public health success story has been the prevention of iodine deficiency disorders that cause goiter with the introduction of iodized table salt,” says Britz-McKibbin. Recent trends in eating and cooking, however, 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 could make them run out of iodine.
People also don’t cook at home as much as before and eat more processed foods, which may be rich in salt but not necessarily iodized salt.
Meanwhile, public health messages suggesting that people reduce their sodium intake may be limiting another source of iodine in their diet.
“Reducing salt to extremely low levels can lead to iodine deficiencies, and therefore public health policies aimed at reducing salt should take into account these unwanted harms,” says Salim Yusuf, co-author of the study who is the executive director of Population Health Research. Distinguished institute and university professor of medicine at McMaster.
Britz-McKibbin says a greater understanding of iodine is needed, which could come from more regular testing of iodine levels, as excessive iodine intake can also contribute to adverse health effects.
“Periodic monitoring would allow us to obtain an assessment of a population’s iodine nutritional status and public health could change its guidelines based on this information,” he says, noting that Denmark, Australia and New Zealand have begun to enrich the bread with iodized salt. .
“With changes in people’s diets, it may be time to rethink how to improve iodine intake, perhaps strengthening certain staple foods or beverages that ensure most people would ingest adequate levels for optimal health.” .