A growing number of young women are at risk of giving birth to children with disabling neurological conditions due to low iodine intake.
Dietary changes, including an increasing trend toward avoidance of bread and iodized salt, as well as reduced intake of iodized animal products may contribute to lower iodine levels.
A small pilot study conducted by the University of South Australia (UniSA) identified potential health risks by comparing iodine levels in 31 vegetarian/plant-based participants and 26 omnivores.
Urine samples showed iodine readings of 44 ug/L in the plant-based group compared to levels of 64 ug/L in meat eaters. Neither group came close to the World Health Organization’s recommended 100 grams per liter.
Participants in both groups who chose pink or Himalayan salt instead of iodized salt had severely deficient iodine levels, averaging 23 ug/L.
Results are published International Journal of Environmental Research and Public Health.
While the research was conducted in South Australia, it builds on evidence from a 2017 US study that found nearly two billion people worldwide were iodine deficient, with 50 million experiencing clinical side effects.
UniSA research dietitian Jane Whitbread says adequate iodine is essential for fetal intellectual development.
“Mild to moderate iodine deficiency has been shown to affect language development, memory and mental processing speed,” says Ms Whitbread.
“During pregnancy, the need for iodine increases and a 150mcg supplement is recommended before conception and during pregnancy. Unfortunately, most women do not take iodine supplements before conception. It is especially important to get enough iodine during the reproductive years.”
Dietary sources of iodine include fortified bread, iodized salt, seafood including seaweed, eggs, and dairy products.
Concerns about the link between poor iodine status and impaired neurological conditions in newborns prompted the mandatory strengthening of non-organic bread with iodized salt in Australia in 2009.
It has since been reported that women who eat 100 grams of iodine-fortified bread per day (about three slices) are five times more likely to meet their iodine intake than women who do not consume as much. The average amount of bread consumed by women in this study was one slice of bread.
A growing preference for Himalayan salt over iodized table salt could also be problematic, Ms Whitbread said. A quarter of women in the study reported using pink salt that contained a negligible level of iodine.
Another problem is that plant-based milk has low levels of iodine and is currently not fortified with this nutrient.
Neither group met the Estimated Average Requirement (EAR) for calcium.
The vegetarian/plant-based group also did not reach recommended levels for selenium and B12 without supplementation, but their dietary intakes of iron, magnesium, vitamin C, folate and fiber were higher than those eating meat. This reflects the inclusion of iron-rich soy products, whole foods, legumes and green vegetables in their diet.
The researchers recommend that both new salt and plant milk be fortified with iodine, as well as campaigns to increase awareness of the importance of iodine in the diet, especially for women in their reproductive years.
They also called for a larger study sample to determine the iodine status of Australian women.