ENDOCRINE EXPLAINED

Vitamin D and Your Child: Do they need Calcium?

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!  Last newsletter, we reviewed the importance of Vitamin D in creating and maintaining a child's bones and teeth.

 

So, if Vitamin D is so important, do we also need calcium? 

 

I'm SO glad you asked! The simple answer is, "Yes!" and I'd even add an "Absolutely!"

True to the intent of the newsletter, let's go back to the basic science, and then translate that into answers.

 

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

 

Vitamin D is critically important for normal development because it helps ensure children absorb enough calcium to form their adult teeth, grow their long bones properly, and gain the bone density they need for the rest of their lives. Because children and adolescents grow so much - especially in their first few years, and again during their pubertal growth spurt - having enough of these important building blocks is necessary for the proper formation of their skeletons throughout their growing years. Indeed, a person's bone density increases only until it peaks in their mid-20's, at which time bones don't typically gain additional density.

 

How do we know that Vitamin D can't create strong bones all by itself?

 

As I discussed in the previous newsletter, Vitamin D was discovered by figuring out it was the substance that heals rickets, a skeletal disease of growing children that causes soft and bent bones, muscle weakness, and even seizures.  BUT, Vitamin D doesn't explain everything about treating rickets. In laboratory experiments, it was only when calcium and phosphorus were added to the liquid surrounding bone cells in cell culture that bone healing was visible. And there are children who have such a lack of calcium in their diets that they develop rickets, too!

 

This explains the main action of Vitamin D, and why it treats rickets: it increases the absorption of calcium and phosphorus from our intestines to increase their concentrations and allow the formation of hydroxyapatite, the crystalline structure in bones that provide their strength. Rickets and soft bones (osteopenia) occur when there's not enough absorption of calcium and phosphorus to make a durable structure, either through insufficient Vitamin D for absorption of calcium, or insufficient calcium intake for Vitamin D to have something to absorb. 

 

So, it's a partnership: a normal Vitamin D level is one that allows the absorption of enough available calcium (and phosphorus) from the intestines to build and rebuild bones.

 

Think of Vitamin D as the general contractor for your bones. 

 

As above, Vitamin D's primary role is to bring building materials to your bones, so they're at hand for any skeletal building. In its second role, Vitamin D begins the process of demolition for skeletal renovation - breaking down a small area of bone that needs to lengthen and strengthen. With the available building blocks of calcium and phosphorus that it already helped absorb, the structure of the bones can gain density and add structural strength and grow through skeletal remodeling.

 

Unfortunately, if there's low calcium, but high Vitamin D, a person can develop weaker bones. It turns out that Vitamin D's demolition work in remodeling the skeleton will take place whether or not there is enough calcium absorbed for the renovation. So, starting high Vitamin D without enough calcium in the diet can worsen bone strength by breaking down bones without having the building material available for rebuilding them.

 

So, in order to have optimal conditions for bone health, we need optimal Vitamin D (described last week as likely a level at least 30, but maybe closer to 50), AND optimal calcium - both for ensuring normal phosphorus levels and to have enough available for  Vitamin D to partner with in its absorption, for the building and remodeling of bones and teeth.

 

Interestingly, the opposite situation, where a child has a diet VERY high in calcium, but has relatively low Vitamin D, the high calcium intake CAN override some Vitamin D deficiency. Although the remodeling may be somewhat less than with higher Vitamin D levels, the bones will still basically grow. 

 

How much calcium does my child need for healthy bones, teeth, and growth?

 

Since rickets and softer bones tend to develop when a child's diet contains less than one serving daily of calcium (about 300 mg). Ideally, 2-4 servings are consumed daily.  Since only a limited amount of calcium is absorbed at one time, it's best to divide multiple calcium servings or supplements over the course of a day. Please refer to the excellent links below for a longer list of foods that are calcium-rich, but here are a few examples, with the caveat that they are ROUGH guides.

 

Dairy - one cup milk, one ounce of cheese, or one cup of yogurt

Greens - 1 cup cooked spinach, 2 cups of chopped broccoli, 5 cups of chopped kale 

Beans - 4 oz. tofu, 2 cup cooked beans

Fish - 3 ounces of canned salmon (with bones), 6 canned sardines

Nondairy milks - one cup of fortified milk

Nuts and Seeds - 3/4 cup almonds, 1 oz sesame seeds

 

Bottom line: Anyone who is taking Vitamin D should be sure to have at least two servings of calcium-rich foods daily, or to take supplements - calcium citrate 500 (with or without food) or calcium carbonate 750 mg daily (best with food) - to make sure calcium is available for a child's healthy skeleton, allowing for its strong formation and timely renovation! 

 

Next newsletter: Does Vitamin D affect health beyond the skeleton?

 

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

 

All my best!

 

SL

 

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

 

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. 

https://www.ucsfhealth.org/education/calcium-content-of-foods

https://my.clevelandclinic.org/health/drugs/16297-increasing-calcium-in-your-diet