Upping vitamin D intake during pregnancy can significantly help the health of the child's teeth long after birth, according to a new study.

Danish researchers started their work in 2009, when more than 300 women were given high doses of vitamin D once they reached 24 weeks of pregnancy. More than 300 other women were given placebo pills. All of the women were told to continue with the normal amounts of vitamin D they had already been taking.

Once the children born to those women turned six, they underwent comprehensive dental exams to determine how the treatment had affected their tooth health.

The researchers found that children whose mothers had taken the extra doses of vitamin D were 50 per cent less likely than the others to have issues such as discolouration and enamel breakdown.

"The risk of enamel defects … was lower in the offspring of mothers who received high-dose vitamin D supplementation during pregnancy compared with standard dose," reads the resulting study, which was published Monday in JAMA Pediatrics.

Enamel defects can also cause teeth to break more easily and leave children with tooth pain.

Based on those findings, the researchers recommend that pregnant women use vitamin D supplements to boost their child's dental health.

Danish health authorities advise that pregnant women take 400 international units (IU) of vitamin D per day. All women in the study used that much as a baseline, while the women who received the supplements got an extra 2,400 IU per day.

Health Canada's recommendation is that pregnant women, like all people between the ages of nine and 70, should take at least 600 IU of vitamin D per day and should not take more than 4,000 IU daily.

The researchers also explored whether vitamin D levels during pregnancy affected a child's experience with caries – decayed, missing or filled surfaces in their teeth – but were not able to find any connection there.

The same women were also subjects in a 2017 study that found that their high doses of vitamin D consumption also reduced their children's risk of developing asthma and recurrent wheezing.