ENDOCRINE EXPLAINED

Vitamin D and Your Child: Bone Health

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Vitamin D has been touted as the cure to, well basically, everything: osteoporosis, infertility, diabetes and insulin resistance, autoimmune disease, depression and inflammation - even COVID! 

 

So, what do we know about Vitamin D and children?

 

I'm SO glad you asked! True to the intent of the newsletter, let's go back to the basic science, and then translate that into answers.

 

It all started with rickets.

 

Rickets is a bone condition where children have soft, bent and weak bones, and can have muscle spasms and seizures, too. It became very, very common in cities in the 1800's.  Eventually, it was discovered that children were cured of rickets by either taking cod liver oil, or by spending time in the sun. The substance in cod liver oil was named Vitamin "D", since it was the fourth Vitamin - "vitamine" being the new word for a substance other than fat, protein, or carbohydrate necessary for a child to thrive - with the first three vitamins appropriately named "A", "B", and "C". Sunlight was later found to transform pre-vitamin D into Vitamin D within the children's skin. With the industrial revolution and movement of populations into cities, clouds of pollution from factories and coal fires blocked the sun's rays. Because city children no longer had enough exposure to sunlight the way they had in the countryside, the vast majority of children living in cities were affected with rickets.

 

Vitamin D allows our bodies to absorb calcium and phosphorus from the foods we eat.

 

Vitamin D is critically important for the normal development of our children's bones and teeth because In childhood and adolescence, enough Vitamin D helps ensure children have enough calcium to form their adult teeth, grow properly and gain the bone density they’ll need for the rest of their lives.

During summer, or year-round south of the 37th parallel - an imaginary line crossing the United States, just south of Virginia, Missouri, Colorado and Central California - sunshine allows skin to produce as much Vitamin D as it needs, shutting off production when it has enough. It's likely that 10-20 minutes of daily sunshine with a child's head, hands, and legs exposed is enough for their basic Vitamin D requirement, and on balance, keeps us at low risk for skin cancers.

 

But, if you live in the United States north of the 37th parallel, as I do, the sun's wavelength that reaches us between October and April doesn't allow us to make Vitamin D even if all our skin is exposed!  Many of us also spend much of our lives indoors, or don't expose much skin, or have darker skin, or use sunscreen daily, all of which limit the wavelength needed to produce Vitamin D. As a result, Vitamin D in food and supplements is important for children to have normal levels and to thrive. 

 

How much Vitamin D do we need?

 

We need to take in enough to supply us with a level in their blood to absorb the calcium from our food, to make it available to our bones. We know that microscopic changes are seen in children's bones with a blood level of Vitamin D below 30 (ng/ml), but as long as there is enough calcium in the diet, 20 is the usual cut-off for deficiency, with 20-29 considered "insufficient".

 

Does your child need a supplement? Maybe, maybe not - but if we give a relatively small supplement, it should be safe to do so.

 

If your child loves the following foods, they may have normal Vitamin D levels. The best food sources are fatty fish and fortified dairy, and mushrooms (especially shitake). Fatty fish include salmon, tuna, and mackerel, which many children don’t eat regularly. They provide somewhere about 600-1000 IU per 3.5 oz serving. Fortified dairy or dairy substitute products, like almond, soy, or oat milk, usually provide 100 IU/cup. And if you can get your child to swallow cod liver oil, you’re set! 

 

On the other hand, if your child doesn't love fish, or have at least 4 servings of fortified dairy daily, then a supplement is appropriate and reasonable insurance for bone health. According to the US guidelines, infants should take a supplement of 400 IU, unless they drink at least 32 ounces of formula per day, and older children ages 1 year old and up should take 600 IU. This amount should be enough to avoid rickets. The Endocrine Society guidelines recommend even higher levels: that children and adults should take 1000-2000 IU daily. Vitamins D2 and D3 are both possibilities in the Vitamin aisle, but in the last few years it became clear that D3 is a better for bones.

 

The degree of Vitamin D deficiency, a child's age, body type, BMI, and health factors each contributes to an individual recommendation of the amount of daily Vitamin D to support a child's optimal health and growth. if the level is low, they need more. If a child carries extra weight, then they also need  more, because Vitamin D is a fat-soluble vitamin - meaning it is easily absorbed into fat cells - so more Vitamin D is needed for blood levels to be sufficient. Other children who need more are those who don’t digest well, so they don’t absorb the Vitamin D that they eat. These are children with inflammatory bowel disease, celiac disease, or cystic fibrosis - they need more, too.

 

Unfortunately, it is possible and dangerous to have a Vitamin D level that is too high, so it is wise to be cautious in our recommendations. I often recommend supplementing up to Vitamin D3 2000 IU daily for my patients. If a child's Vitamin D level is very low, I'll recommend a dose higher than 2000 IU daily, but recheck the level to make sure I'm recommending enough to raise the low level, and ensure I'm not giving too much. If a child is taking more than 2000 IU daily for any extended period of time, it should be under medical supervision, with a blood level checked to make sure it isn’t too high, and urine checked for kidney stones, with the recommended dose of Vitamin D supplementation adjusted appropriately.

 

I hope this was interesting and useful. Please see the sources below for further reading:

 

Next newsletter: My child takes a Vitamin D supplement. Do they need calcium, too?

 

I'd love to hear your feedback! Please send suggestions to: EndocrineExplainedNewsletter@gmail.com. I read every email I receive.

 

All my best!

 

SL

 

Botelho J, Machado V, Proença L, Delgado AS, Mendes JJ. Vitamin D Deficiency and Oral Health: A Comprehensive Review. Nutrients. 2020;12(5):1471. Published 2020 May 19. doi:10.3390/nu12051471

Bouillon R, Marcocci C, Carmeliet G, et al. Skeletal and Extraskeletal Actions of Vitamin D: Current Evidence and Outstanding Questions. Endocr Rev. 2019;40(4):1109-1151.

Charoenngam N, Shirvani A, Holick MF. Vitamin D for skeletal and non-skeletal health: What we should know.  J Clin Orthop Trauma. 2019 Nov-Dec;10(6):1082-1093. 

Deluca HF. History of the discovery of vitamin D and its active metabolites. Bonekey Rep. 2014;3:479.

A dose of vitamin D history. Nat Struct Mol Biol 9, 77 (2002).

NIH fact sheet for non-health professionals: https://ods.od.nih.gov/factsheets/VitaminD-Consumer/

NIH fact sheet for health professionals: https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/