Many infants appear to lack vitamin D, which doesn’t necessarily show immediate symptoms but can lead to a weakened immune system that is more predisposed to disease, a new report published in the Archives of Pediatrics and Adolescent Medicine shows.

Researchers from Children’s Hospital Boston led by Dr. Catherine Gordon analyzed 380 children aged from 8 to 24 months and found that 2 out of 5 children had less-than-optimal blood levels of vitamin D, accounting for 40 percent of the children involved in the study. Moreover, 12 percent actually had vitamin D deficiency. About a third of these kids had bone demineralization, a sign of thinner bones when being X-rayed.

According to the report, breastfed babies were more likely to have low levels of vitamin D as “breast milk is the perfect food except it lacks vitamin D,” Gordon said, as quoted by Reuters.

The factors contributing to vitamin D deficiency included: not drinking enough fortified milk, not taking vitamins and being overweight. The report found that only 20 babies involved in the research were exclusively breastfed and only six of those infants had gotten vitamin D supplements. Also, overweight children were found to be predisposed to vitamin D deficiency most probably because the vitamin dissolves into fat. It is known that diabetes which is often associated with obesity is one disease linked to the deficiency.

Dr. Gordon said she was struck by how many children were vitamin D deficient and showing no symptoms. “The silence of what we saw worries me more,” she added.

Many previous studies indicate that vitamin D deficiency plays a significant role in causing seventeen varieties of cancer as well as heart disease, stroke, hypertension, autoimmune diseases, diabetes, depression, chronic pain, osteoarthritis, osteoporosis, muscle weakness, muscle wasting, birth defects and periodontal disease.

Dr. Gordon’s study adds to the growing body of evidence that vitamin D is essential for our body. No further than last month, Canadian researchers found that breast cancer patients with low levels of vitamin D are nearly twice as likely to have the disease spread to other parts of their bodies and are 73 percent more likely to end dying from it.

To prevent vitamin D deficiency in children, since 2003, the American Academy of Pediatrics has recommended vitamin D supplements of 200 international units (IU) per day for all infants who don’t get at least 500 milliliters of vitamin D-fortified formula or milk.

As little as 10 minutes in the sun is also thought to prevent vitamin D deficiency but of course taking care that the children don’t suffer burns. This is the reason why the vitamin is also called the “sunshine vitamin.”