Recently, I’ve encountered several similar cases.
Children have been taking vitamin D regularly, but when checked outside the hospital, vitamin D is shown to be deficient or insufficient, and doctors prescribe a large dose of vitamin D; some doctors say that a certain brand of vitamin D is not absorbed well and need to be changed to another brand; others say that the liquid form is not absorbed well and need to be changed to granules.
Parents are puzzled. Their children have been taking vitamin D seriously, but they have to believe the results on the test report. So, where does the problem lie?
Why are children still deficient in vitamin D if they have been supplementing?
Sometimes, data can be misleading, and children may not actually be deficient in vitamin D.
To determine whether vitamin D is lacking, the serum 25(OH)D concentration level is measured, which is the most abundant, stable, and longest half-life vitamin D metabolite in the human body. The reference values are shown in the table below:
However, When conducting an inspection, special attention should be paid to the following two points:
1. It is crucial to clearly understand the concentration unit
When interpreting the test report, it is essential to clearly see the unit behind the numbers, in clinical practice, it is often seen that the reference standard of “nmol/L” is used to interpret the numerical value of “μg/L”.
This is also one of the common reasons why different doctors may draw different conclusions from the same results.
2. Peripheral blood data anomalies require venous blood rechecking
The 25(OH)D concentration measured by using capillary blood whole blood testing should not be directly equivalent to the serum 25(OH)D concentration obtained by venous blood collection.
Current research shows that there is a certain correlation between capillary blood and venous blood in the measurement of 25(OH)D concentration, but since capillary blood testing may be affected by blood collection techniques (such as squeezing the local area to dilute the specimen with tissue fluid), small blood volume (a small fluctuation can result in a large error), and the reliability of different laboratory testing methods varies, in clinical practice, it is also common to encounter situations where capillary blood results are abnormal, but when rechecked with venous blood, they are completely normal.
Considering the convenience of capillary blood operation compared to venous blood, and the smaller amount of blood required, as well as the fact that capillary blood results are often lower than venous blood results, capillary blood testing can be used as a preliminary screening, but when the initial screen is abnormal, further venous blood testing is needed for confirmation, and then subsequent treatment decisions should be made based on the confirmation results to avoid misdiagnosis and overtreatment.
It is precisely because of these factors that when parents reported to me that their child was deficient in vitamin D, I further reviewed and found that the child’s vitamin D level was normal, and those claims of “poor absorption” were debunked.
Do children need routine screening for vitamin D?
The answer is not recommended.
Firstly, for children without high-risk factors for vitamin D deficiency, no clinical symptoms and signs, and who have been supplementing vitamin D regularly and adequately, routine testing of 25(OH)D levels is not recommended.
If inaccurate capillary blood vitamin D testing, especially non-standardized testing methods, is used for screening, it may cause unnecessary anxiety and misdiagnosis and mistreatment.
Secondly, for high-risk groups of vitamin D deficiency, a history of the disease can be identified through inquiry, and even if the current evidence is not sufficient to assess the pros and cons of screening asymptomatic vitamin D deficiency, empirical supplementation of vitamin D can still be directly administered to high-risk groups.
For infants <12 months old, a dosage of 2000IU (50μg)/d is recommended for 6-12 weeks, followed by a maintenance dose of at least 400IU (10μg)/d; for children ≥12 months old, a dosage of 2000IU (50μg)/d is recommended for 6-12 weeks, followed by a maintenance dose of 600-1000IU (15-25μg)/d.
Of course, if a deficiency is diagnosed after testing, regular monitoring and supplementation of vitamin D in large doses, followed by regular follow-up monitoring is necessary. Although a single capillary blood 25(OH)D level is not sufficient for diagnosis, regular monitoring using the same standardized method to observe changes in 25(OH)D levels in the body still has reference value.
Follow-up monitoring is recommended every 3-4 months to assess treatment response by measuring serum 25(OH)D levels until an appropriate level is reached, after which monitoring once every 6 months is suggested. Once the serum 25(OH)D level reaches the target level(ie, normal level, 25(OH)D ≥20ng/mL(50nmol/L)), no further monitoring is necessary.
What are the high-risk factors for vitamin D deficiency?
The following situations are recommended for routine supplementation of vitamin D（routine supplementation dosage for children, 400IU per day from a few days after birth to 12 months old, 600IU per day for children 1-18 years old）, there is no need to screen before supplementation or regularly recheck after supplementation.
Pregnant mothers lacking in vitamin D Preterm infants Infants exclusively breastfed Diet lacking sufficient fortified vitamin D Dark skin or insufficient sunlight exposure* Obesity (Vitamin D concentrations are usually lower in obese children, but the clinical significance is unclear)
*Note: Between 10:00-15:00 in spring, summer, and autumn,exposing arms and legs or hands, arms, and face to sunlight for 10-15 minutescan fully synthesize vitamin D in people with light skin. Most individuals with medium skin color (e.g., many South Asians) need up to three times the sun exposure of light-skinned individuals to achieve the same 25(OH)D concentration, while those with very dark skin (e.g., some individuals of African descent) need six to ten times more sun exposure than light-skinned individuals. However, unprotected ultraviolet exposure also increases the risk of sunburn and skin cancer (especially in light-skinned individuals), so it is recommended to prioritize vitamin D supplementation and avoid unprotected sun exposure.
The following situations require regular monitoring of vitamin D levels, follow-up, and supplementation of vitamin D and calcium as prescribed by a doctor.
1. Use of medications affecting vitamin D absorption and metabolism
Such as the use of certain anti-epileptic drugs and antiretroviral drugs for the treatment of HIV infection; corticosteroids; antifungal drugs like ketoconazole.
2. Diseases that may lead to poor absorption of vitamin D
Diseases that impair fat absorption (such as celiac disease, inflammatory bowel disease, pancreatic exocrine insufficiency, such as cystic fibrosis and cholestasis, as well as children after bowel resection or bariatric surgery); diseases affecting the activation of vitamin D (such as liver and kidney diseases); certain genetic diseases that can lead to vitamin D deficiency or resistance (such as 25-hydroxylase deficiency, 1-α-hydroxylase deficiency, hereditary vitamin D resistance).
As mentioned above, calcium supplementation is needed in special circumstances, but do healthy children need it?
Indeed, in clinical practice, it is often seen that children who have adequate milk intake are given calcium supplements while taking vitamin D, and many do so because “screening shows low bone density” and double the supplementation of vitamin D and calcium.
At this time, before supplementing calcium, we might as well review the 3 popular science articles:
It can be seen that many problems in children are not due to calcium deficiency, as long as children have a balanced diet, the calcium in milk and food is enough to meet the nutritional needs of children.
In summary, for the vast majority of healthy children without underlying diseases, routine supplementation of vitamin D is sufficient, and there is no need for routine screening of vitamin D levels in the blood. For children who do not supplement regularly or those with high-risk factors, it is important to choose the appropriate method to verify vitamin D levels and standardize diagnosis, treatment, and follow-up.
When encountering healthy children who supplement vitamin D regularly and have insufficient or deficient vitamin D in capillary blood tests, it is necessary to carefully identify the reliability of the test and the sufficiency of the diagnosis, and especially to pay attention to whether there are underlying diseases that cause poor absorption or metabolic problems of vitamin D.
As the old saying goes, auxiliary tests are just auxiliary and should serve clinical practice, not override it. “To supplement or not to supplement” is not a decision that can be made impulsively, otherwise, it will not only fail to provide help but also cause unnecessary anxiety and financial burden, becoming a stumbling block in the healthy upbringing of children, which is counterproductive.
Do healthy children need to supplement calcium while taking vitamin D?
References
