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Among the various vitamins required by the human body, it must be said that Vitamin D is a rather special existence.
Unlike other vitamins that must be ingested orally, when the skin is exposed to ultraviolet rays in sunlight, 7-dehydrocholesterol present in the skin is converted into a precursor of Vitamin D3 through a non-enzymatic pathway. Subsequently, the precursor of Vitamin D3 undergoes temperature-dependent rearrangement to form Vitamin D3.
For the human body, while ultraviolet radiation on the skin does bring the gift of Vitamin D, it also increases the risk of skin cancer . Cumulative sun exposure is the most important environmental factor leading to squamous cell carcinoma of the skin, and intense intermittent sun exposure (such as sunburn, exposure during childhood) is the most significant risk factor for basal cell carcinoma and melanoma.
Therefore, after weighing the pros and cons, it is currently recommended that people actively protect themselves from the sun when outdoors , but as a result, the synthesis rate of Vitamin D in the skin is almost zero, so it is also recommended to actively take oral Vitamin D supplements to ensure a sufficient source of Vitamin D .
Recommended Intake for Different Ages and Conditions
In terms of Vitamin D supplementation, it is recommended that infants start supplementing with Vitamin D as soon as possible after birth, generally:
Breastfed infants under 1 year old are advised to supplement with 400IU of Vitamin D daily; formula-fed babies , the Vitamin D content in the formula can be calculated to determine an individualized supplement amount to achieve a total of 400IU per day.
Children and adults aged 1-18 years and those 70 years and under require a Vitamin D supplement of 600IU/d .
Adults aged 71 and above require a Vitamin D supplement of 800IU/d .
Pregnant and lactating women require a Vitamin D supplement of 600IU/d .
Preterm infants , depending on their birth weight, have different recommended intakes, and a supplementation plan should be established by a doctor.
How to take it for the best effect?
Once a week or once a day?
When it comes to the idea of “having to take medicine every day,” people often have some resistance or concerns, either finding it troublesome or fearing they might forget.
At the same time, because Vitamin D is a fat-soluble vitamin that can be stored in fat, some opinions suggest that one could consume a week’s worth of Vitamin D in one meal, meaning changing from a daily intake to a weekly intake, which would be more convenient.
So, is this approach feasible? To discuss this, we need to start with the functions of Vitamin D.
The functions of Vitamin D are diverse; the most familiar to us is its role in promoting calcium absorption in the intestines. In terms of calcium absorption, Vitamin D is stored as 25-hydroxyvitamin D, which has a half-life of 2-3 weeks , therefore if we only consider bone health, taking Vitamin D once a week can ensure its effectiveness .
However, in recent years, as research on Vitamin D has deepened, it has been discovered that Vitamin D also has an important impact on the immune system, and Vitamin D in the autocrine system acts as a substrate for the production of 1,25-dihydroxyvitamin D, to maintain stable levels of 1,25-dihydroxyvitamin D, a continuous supply of the parent Vitamin D is needed, and the half-life of the parent Vitamin D is only 24 hours, which means, if we consider the immune-boosting effects of Vitamin D, taking Vitamin D orally once a day is a better choice .
Also, if you do plan to take multiple days’ worth of Vitamin D at once, it is necessary to consider the maximum safe daily intake of Vitamin D to avoid overdose(See the following text for the maximum daily dose) .
With meals or on an empty stomach?
Not only that, because Vitamin D is a fat-soluble vitamin, taking it with fatty foods can enhance absorption efficiency, which means, Vitamin D is more effective when taken with meals . As for which meal to take it with, it’s not that critical .
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What if you miss a dose of Vitamin D?
What should you do?
Actually, the approach to handling this situation mainly depends on the degree of the missed dose.
Not a “serious” miss
Generally speaking, if you just occasionally miss 1-2 days, there is no need to make up for it , just remember to take it regularly every day afterwards.
A “serious” miss
But if the degree of the miss is a bit “serious,” such as not taking Vitamin D for several weeks, it is recommended to immediately start resuming regular supplementation of Vitamin D. If you haven’t taken it for several months (or even several years without taking it) it is recommended to check the serum 25(OH)D concentration and adjust the dosage according to the results assessed by a doctor.
Is there a risk of poisoning?
What are the symptoms of Vitamin D poisoning?
Acute Vitamin D poisoning can cause hypercalcemia, with common symptoms including confusion, polyuria, thirst, anorexia, vomiting, and muscle weakness .
Chronic poisoning may cause nephrocalcinosis, demineralization of bones, and pain .
If these symptoms occur, it is necessary to complete blood calcium concentration, serum 25(OH)D concentration, parathyroid hormone, etc. related examinations for assessment.
If you take the recommended dose every day , there is no need to worry about the risk of Vitamin D poisoning.
A small number of infants and young children who take 2000IU of Vitamin D per day , after 2-3 months may show signs of poisoning(this is a more extreme case) .
Children aged 9-18 and adults have a Vitamin D “tolerable upper intake level” of 4000IU/day , but the specific dosage and duration that can cause Vitamin D poisoning vary from person to person and are not entirely certain at present.
What happens if you are deficient in Vitamin D?
Who needs to pay more attention?
Typical Vitamin D deficiency can lead to rickets in children , osteomalacia and osteoporosis in adults , but these typical symptoms are not common. Currently, subclinical Vitamin D deficiency is more common(without obvious clinical symptoms, but blood tests indicate low Vitamin D) .
Compared to children, adults who do not engage in outdoor activities are more likely to experience this situation. Therefore, adult Vitamin D deficiency requires more attention , and it is recommended to include a serum 25(OH)D level test in your next medical check-up , adjust the Vitamin D supplementation plan according to the results, strive for improvement if none is needed, and make changes if there are deficiencies, all for the sake of healthy bones and immune system.
Peer Review Expert Sha Xiaodan
Distinct Pediatrics Doctor, Ph.D. from Shanghai Medical College of Fudan University
References
Content Editor LEE
Disclaimer: The article is intended to provide general health information. For personal medical issues, please consult a doctor. To republish the article, please contact: medicine@distinctclinic.com.
