Vitamin D for Kids: What Parents Need to Know

This post was originally posted February 2015 and was updated in May 2020

Lisa’s family lived on the beach, so she made sure her kids had on factor 50 sunscreen before she went outside.

She was surprised to discover her 12-year-old daughter diagnosed with vitamin D deficiency after experiencing pain and weakness in her legs following hip surgery.

“We live right by the beach so Tyler was outside with her friends every day last summer,” her mom said in an article on the Daily Mail. “I’ve always been very careful with her and her brother, and nagged them to wear hats and sunscreen when it’s hot. I thought I was doing the right thing.” 

Stories like these are on the upswing in recent years. That’s because, with few foods containing vitamin D, the sun is the main source. Yet with recommendations to wear sunscreen and stay out of the sun, many children are not getting enough of the sunshine vitamin.

After having my first child, I delved into the research on vitamin D and development. Not only did I take vitamin D during my second pregnancy, but I was also ready to supplement my daughter as an infant.

Yet my daughter’s pediatrician never mentioned vitamin D and studies showed few supplement their babies.

I believe every parent needs to know why vitamin D is important for growth and development. And an important part is understanding vitamin D’s complicated history.

Vitamin D and Rickets

In the 1600s, the industrial revolution made its way to Northern Europe. This brought tall buildings, air pollution, and a disease never seen before: rickets.

Rickets is a bone disease resulting in defective bone mineralization, usually brought on by vitamin D deficiency. Children with rickets show skeletal abnormities such as bowed legs, softening of the skull, and frontal bossing (prominent forehead). They also have impaired growth and developmental delays.

Left untreated, rickets can result in death. And for more than 200 years the cause of this terrible disease remained unknown.

In the early 1800s, clues about what might help came to light. For instance, experts began to notice that children who lived in the inner city had a higher incidence of rickets than those living in rural areas. Later, children exposed to a mercury arc lamp showed improvements in rickets.

By the turn of the 20^th century, 80-90% of children living in Northern Europe and Northeastern United states had rickets. During the time period between 1910 and 1961, 13,807 rickets-related deaths occurred with 8387 of them being in children less than one-year-old.

By 1921, doctors discovered rickets could be cured by direct sunlight and cod liver oil. Yet they noticed that dark-skin children needed more sunlight to both treat and prevent rickets.

Soon vitamin D deficiency was found to be at the cause and correcting it the cure of rickets.

Fortification and a comeback

The discovery of vitamin D led to its widespread fortification in Europe and the United States in the 1930s and 40s. Not only in milk but in soda, custard, bread, cereals, and even beer. One advertising for beer said: “if you want to keep sunny energy all winter long drink vitamin D fortified Schlitz beer.”

In 1931, the United States government established an agency, the Department of Labor, whose main goal was to promote sensible sun exposure to prevent rickets. Within a few years of fortification and guidance on sun exposure, rickets was eradicated.

In the 1950s there was an outbreak of hypercalcemia in England – which included infants with heart problems and elfin faces – which led to the removal of fortification in Great Britain. Investigators believed it was due to vitamin D toxicity. This ban spread across Europe.

It is now believed that these infants had a rare disease called Williams syndrome, which produces hypersensitivity to vitamin D. Despite this setback, rickets was thought of as a disease of the past.

Yet in the 1970s, rickets began to be reported again. Health experts believe this had to do with a resurgence of breastfeeding. That’s because formula is fortified with vitamin D, but breastmilk is low (15-35IU per liter). Out of several hundred children with rickets, many had been long-term breastfeeders.

There also was a growing awareness that UV rays from the sun can lead to skin cancer. In 1998, the National Council on Skin Cancer Prevention was formed, and a major report set in motion the regular use of sunscreen and reduced time in the sun. During the 90s, UV blockers were added to sunscreen. The SPF number on sunscreen began to increase and by 2009, only 6% had SPF below 5.

In 2003, the American Academy of Pediatrics recommended breastfed infants be supplemented with 200IU the first couple of months after being born. In 2008, it increased to 400IU changing to the first couple of days after birth.

Rickets prevention and treatment had come full circle. Four hundred IU was the same amount of vitamin D in a teaspoon of cod liver oil. But the support for supplementation was nothing like it was in the past. See guidance from the US government in 1938 recommending cod liver oil and regular “sun baths” for infants.

Research shows that in the US during two time points, 2009 and 2016, only 30% of formula-fed babies met the recommendations, and only 20% of breastfeeding babies did. No changes occurred between 2009 and 2016.

21^st Century Vitamin D Discoveries

Now it’s well known that vitamin D helps the body maintain the right balance of calcium and phosphorus. Without adequate vitamin D, not enough calcium can be deposited into bones to keep them strong and healthy.

But vitamin D isn’t just about bone health anymore. Over the last two decades, researchers have found many different conditions associated with low vitamin D levels from heart disease to diabetes to autoimmune diseases.

The reason for this has to do with another discovery: most body cells have a vitamin D receptor. This means vitamin D plays a role in many of the body’s functions. Discussing all of these is beyond the scope of this post so we’ll focus on health concerns for developing infants and children.

Let’s start with the brain. Studies reveal that children with autism and ADHD have lower levels of vitamin D than those without those conditions. According to one study, children with autism had lower levels of vitamin D at 3 months gestation, birth, and at age 8 compared to their siblings without autism.

One study found subjects with ADHD had lower vitamin D levels than the control group and supplementation improved symptoms of ADHD such as impulsivity and inattention. A meta-analysis showed supplementing with vitamin D had a small but significant impact on ADHD scores.

There are also vitamin D receptors on the lung. Children with asthma tend to have lower vitamin D levels. In one study, more than half had deficient and insufficient levels of vitamin D. According to a Cochrane Review, taking vitamin D along with asthma medication, can reduce the severity of asthma attacks.

Vitamin D receptors are found on the pancreas B-cells that produce insulin. Research shows a relationship between the development of type 1 diabetes and low levels of vitamin D. In one review, supplementation with vitamin D early in life was associated with a reduced risk of type 1 diabetes.

There are vitamin D receptors in the stomach and the large and small intestine. Having an anti-inflammatory immune response, vitamin D may help to decrease the risk of food allergies and inflammatory bowel disease.

According to the American Academy of Allergy and Immunology (AAAAI), children living further away from the equator (resulting in less ultraviolet rays) have higher rates of food allergy. Plus, there’s 6 times the risk of epinephrine autoinjector prescriptions and peanut allergy.

On their website AAAAI state:

Research using direct measures of vitamin D from blood samples have also shown an association between low vitamin D and increased risk of allergic sensitization in children and adolescents and food allergy in infants. In this Australian study, infants with low vitamin D were more likely to have egg or peanut allergy and were more likely to have multiple allergies compared to infants with normal vitamin D levels.

These health effects are not like rickets where vitamin D deficiency is the known cause and cure. For example, a child with normal vitamin D wouldn’t get rickets, but they could still be diagnosed with ADHD or asthma. It’s more likely that vitamin D plays a role along with other factors like genes.

Yet we can take this evidence, along with the known risk of low vitamin D in post-industrious societies, and make sure we are all getting enough.

Vitamin D Status of Infants and Children

One of the confusing parts of vitamin D deficiency is the lack of consensus on optimal blood levels.

In 2010, the Institute of Medicine recommended a baseline target of at >20ng/ml (that’s nanograms per milliliter) for bone health. This is often used in studies with inadequacy or “at risk for inadequacy” considered 13-19ng/ml and deficiency <12ng/ml.

Other studies use higher levels such as the Endocrine Society’s >30ng/ml for optimal. Inadequacy is 20-29ng/ml, deficiency <20ng for deficiency, and severe deficiency <12ng/ml. A review in Advances in Experimental Medicine and Biology points to ideal levels of at least 30ng/ml to benefit from positive health outcomes.

Because the vitamin D status during pregnancy affects baby’s levels it’s important to start there. In a sample of low-risk pregnant women, it was found that 30% had levels >30 ng/ml, 47% between 20-29 ng/ml, and 22% were <20 ng/ml.

At 4 months of age, 40% of un-supplemented breastfed babies had levels <20ng/ml.

In the 2011-2014 National Health and Examination Survey (NHANES), 6.6% of one-to-five-year-olds had levels <12ng/ml and .5% between 12-19ng/ml, 1.4% of six-to-eleven-year-old’s had levels <12ng/ml and 12.3 % between 12-19ng/ml. And 4.8% of 12-to-19-year-old’s had levels <12ng/ml and 22.7% between 12-19ng/ml.

There was no data for those over 30ng/ml. But according to the 2001-2004 NHANES about 61% of children had levels between 15-29ng/ml.

What we know is that non-Hispanic blacks, Asians and Mexican Americans have significantly lower vitamin D levels than Non-Hispanic whites. Those who supplement are also are more likely to have higher vitamin D levels.

In short, most pregnant women, infants, and children do not have vitamin D levels >30ng/ml.

Vitamin D Sources

Vitamin D can come from three places: diet, supplements, and sun exposure. For infants under one, the recommended amount of vitamin D from the diet is 400IU and for older children (>1), pregnant women, and adults its 600IU. This jumps to 800IU at age 65.

One a child is born, the AAP recommends breastfed babies, and those partially breastfed, be supplemented with 400IU after birth. But the US is lagging behind other countries.

As children get older you want to consider what they are getting from their diet. The chart below shows key food sources of vitamin D. Not included is infant formula which is fortified with vitamin D, breast milk which contains 35IU per liter and fortified foods that have a range of vitamin D per serving (see this link for complete list).

It would take about 4 ounces of salmon (every day), 11 ounces of tuna, 6 glasses of milk and 12 eggs to meet the 600IU recommendations using food.

What about the sun? If you follow recommendations to prevent skin cancer, you will wear sunscreen that blocks out most of the UV rays. But doing so 100% of the time is hotly debated as some experts believe regular sunshine without burning (15 minutes max) 2-3 times per week is beneficial.

See this post for how much you can expect to get from the sun depdending skin type and ultraviolet index

Here’s where it gets tricky. Not all people make the same amount of vitamin D from the sun. Those who have dark skin, use sunscreen, are over 50, and live in Northern or highly polluted climates make less.

The time of the year (and day) also matters as UV rays exposure is highest from April to October between the hours of 11 am and 3 pm. So even with regular sun exposure, there’s no guarantee it’s keeping vitamin D levels up year-round.

Based on what we know, it just makes sense to supplement with vitamin D. In fact, the AAP also says that children that can’t get the recommended amount from diet consider supplementation.

Deficiency increases the amount of vitamin D required. And according to the Endocrine Society, children need 1000IU to keep levels above 30ng/ml in children and adults need 1500-2000IU. This is especially true in the winter

The figure below can help you decide what is right for your child.

Safety and type of vitamin D supplement

Most health professionals recommend vitamin D3 supplements. I love Carlson’s drops and use them with my son but now my daughter takes a pill.

Instead of the 400IU I used their first year, my son gets the 1000IU drops about 5 times a week. My 13-year old non-milk drinking daughter takes 2000IU every other day. My husband and I take about 2000IU daily to keep our levels above 30ng/ml.

In the summer, we all supplement less due to increased sun exposure.

Unless under the supervision of a doctor, it’s best not to exceed the safe upper limit set by the IOM. This is 1000IU for infants up to 6 months old, 1500IU for infants 6-12 months old, 3000IU for children 4 to 8 years old, and 4000IU for those 9 years and older.

Many worry vitamin D is toxic because it’s a fat-soluble vitamin. Yet research shows toxicity doesn’t occur until blood levels reach about 150ng/ml. Out of 15,000 cases of vitamin-D overdoses reported to Poison Control over a 15 year period after 2000, only 3 developed toxicity, and no one died.

Vitamin D awareness

History teaches us what happens when we do nothing to ensure we are getting adequate vitamin D. For most of human history, people received more than their share of vitamin D from the sun. And this helped get them through winter.

Now that we no longer live this way, it’s time everyone is aware of vitamin D.

Does your family take vitamin D supplements?

For more on nutrients needed for children of all ages, check out Maryann’s book Fearless Feeding: How to Raise Healthy Eaters from. High Chair to High School