A new research suggests that nearly half of US women have at least mild deficiency in the nutrient iodine , and it could impair their fertility . The study findings were published in the journal  Human Reproduction .

Iodine , a mineral that helps regulate metabolism and is found in seafood, iodized salt, dairy products, and some fruits and vegetables.

However, in a study of 467 American women who were trying to get pregnant, those with moderate-to-severe iodine deficiency were 46% less likely to get pregnant during each menstrual cycle than those with sufficient iodine levels.

Researchers led by According To Dr. James Mills of the US National Institute of Child Health and Human Development, Women with even mildly deficient iodine levels had a slightly harder time getting pregnant .

Mills said, "Women who are thinking of becoming pregnant may need more iodine." One fertility expert said the study puts the spotlight on the interplay between nutrition and conception .

"The Western diet has changed in the last few decades and the adoption of vegetarian and vegan diets has led to reduction in dietary iodine ," noted Dr. Tomer Singer, who directs reproductive endocrinology and infertility care at Lenox Hill Hospital in New York City

"Given that diet is the main source of iodine for our patients-seafood, salt, some fruits and vegetables, cranberries and strawberries to name a few-experts advise our patients to take prenatal vitamins, which include iodine, at least three months prior to conception, "Singer explained.  

Indeed, the new research showed that iodine deficiency is common among US women. In the study, about 56% of the women had sufficient levels of iodine, nearly 22% were mildly deficient, about 21% were moderately deficient, and 1.7% were severely deficient.

Mills said, " Iodine requirements increase during pregnancy , and the fetus depends on this mineral to make thyroid hormone and to ensure normal brain development ."

The study was not designed to prove that low iodine levels actually caused infertility . However, if the study findings are confirmed, countries where iodine deficiency is common could take steps to boost iodine intake among women of child bearing age, the researchers suggested in a journal news release.

Singer agreed, and gave some guidance on just how women might achieve healthy iodine levels. "Prenatal vitamins should include 150 micrograms of iodine, as per the American Thyroid Association's 2015 statement, and they should be taken before and during pregnancy , as well as during lactation ," he said.