Excessive vitamin D accelerates bone loss instead!

Edited and written by Yimaitong, please do not reprint without authorization.

Introduction: Vitamin D, also known as "sunshine vitamin", can promote calcium absorption.
It and the calcium pair of CPs have become the "golden partner" on the road to fracture prevention and can be said to be inseparable.

However, it is not that the more VD is supplemented, the better.
Studies have shown that excessive supplementation of VD can accelerate bone loss.

So, what dosage of VD will be beneficial to bone health? Professor Xie Zhongjian: "Look at this indicator.
"
 VD deficiency brings many harms 1.
VD in the human body is mainly derived from its own synthesis.
Vitamin D is a fat-soluble vitamin necessary to maintain life.
It is a steroid derivative, also known as "anti-rickets vitamin" or "sunshine vitamin".

 80%-90% of vitamin D in the human body comes from self-synthesis (vitamin D is synthesized in epidermal cells under the sun's ultraviolet rays), and 10%-20% comes from ordinary vitamin D in food [ordinary vitamin D passes through the liver and kidneys Metabolism is activated to 1,25(OH)2D to have biological activity], such as ingesting wild marine fish with more fat.

Therefore, if the human epidermis lacks sufficient ultraviolet radiation, vitamin D deficiency will easily occur.

 Figure 1 Vitamin D metabolism pathway (source: "Consensus on the clinical application of vitamin D and its analogues") 2.
VD deficiency brings multiple harms In the early stage of VD deficiency, due to the compensation of increased secretion of parathyroid hormone (PTH), There will be no decrease in the synthesis of 1,25(OH)2D temporarily, so that the intestinal calcium absorption capacity can still be maintained in a normal state, without bone mineralization obstacles, but due to increased PTH secretion, bone absorption will increase accordingly , There is bone loss.

 With the further aggravation of vitamin D deficiency, although the compensatory secretion of PTH is increased, the synthesis of 1,25(OH)2D will eventually decrease, resulting in decreased intestinal calcium absorption, resulting in bone mineralization disorders, and vitamin D deficiency occurs in children.
Rickets, vitamin D-deficiency osteomalacia occurs in adults.

 Too much too much-excessive vitamin D supplementation will accelerate bone loss! A five-year large study (VITAL study) involving 25,875 elderly people showed that compared with placebo, oral intake of 2000IU vitamin D per day does not prevent bone loss.

 Studies have also reported that 331 people aged 55-70 were supplemented with 3 different doses of vitamin D.
The total bone density decreased by 1.
4% in the 400IU group daily and 2.
6% in the 4000IU group daily.
, The daily consumption of 10000IU group decreased by 3.
6%.

In other words, compared with supplementing small doses of vitamin D, supplementing large doses of vitamin D makes bone loss faster.

 The reason is that? The main function of 1,25(OH)2D is to promote the absorption of intestinal calcium, thereby maintaining the stability of blood calcium.

The effect of 1,25(OH)2D on bones is mainly played by promoting intestinal calcium absorption.

 ➤When intestinal calcium absorption is sufficient, 1,25(OH)2D promotes bone mineralization and can stabilize blood calcium; ➤When intestinal calcium absorption is insufficient, 1,25(OH)2D promotes bone absorption.
The bone calcium is released into the blood to maintain the stability of blood calcium.

In addition, too high 1,25(OH)2D can also stimulate bone resorption.

 Therefore, maintaining an appropriate level of 1,25(OH)2D is very important for bones.
Too low or too high is not good for bones, and at the same time, enough calcium is required.

 So, what dose of vitamin D supplementation is beneficial to bone health? Serum 25(OH)D level was used as the evaluation standard.

 Fracture is the end point of osteoporosis, and prevention of fracture is our ultimate goal of vitamin D supplementation.

Studies have shown that the relationship between human serum 25(OH)D levels and the risk of falls and fractures may present a "U"-shaped curve.
Too low or too high levels may increase the risk of falls and fractures.

Therefore, from the perspective of fracture prevention, before deciding how much to supplement, it is necessary to assess the patient's serum 25(OH)D level.

 Diagnostic criteria for vitamin deficiency: ➤Vitamin D deficiency: serum 25(OH)D concentration <20ng/ml; ➤Vitamin D deficiency: serum 25(OH)D concentration 20-30ng/ml.

Therefore, vitamin D supplementation should make the patient's serum 25(OH)D concentration> 30ng/ml, but at the same time, Professor Xie Zhongjian mentioned in a related article: the vitamin D dose should not be too large, when the serum 25(OH)D concentration exceeds 40 ng/ml.
-45ng/ml, it may gradually lose its beneficial effects on bones and muscles.

1.
The general population can determine the individualized supplemental dose based on the baseline level of serum 25(OH)D.

For patients who are receiving anti-osteoporosis treatment, maintain the serum 25(OH)D concentration above 30ng/ml to ensure that the anti-osteoporosis drugs exert their due curative effect.

However, if the supplement dose is too large and the serum 25(OH)D concentration exceeds 40-45ng/ml, it may gradually lose its beneficial effects on bones and muscles.

 Table 1 Recommendations for vitamin D supplementation in high-risk groups of vitamin D deficiency (source: "Consensus on the clinical application of vitamin D and its analogues") 2.
Postmenopausal women The average level of serum 25(OH)D in postmenopausal women in my country-22.
2ng in summer /ml, 13.
2ng/ml in winter.

Generally in the state of vitamin D deficiency or deficiency, it is recommended to take 800-2000IU of vitamin D3 daily or intramuscular injection of 400,000-600,000 units of vitamin D2 for 4-6 months, which can increase serum 25(OH)D by 10ng/ ml, make the serum 25(OH)D level reach 20ng/ml or even 30ng/ml to maintain bone and muscle health.

 3.
The elderly group Vitamin D deficiency is more common in the elderly group and is closely related to senile diseases.

In my country, 70%-90% of elderly people aged> 60 years have serum 25 (OH) D levels <50 nmol/L.
As the age increases, vitamin D deficiency becomes more serious, and the proportion of people aged 80-89 years with vitamin D deficiency is higher than that 90%.

 ➤It is recommended that the elderly routinely supplement vitamin D 600-1000U/d; ➤It is recommended that elderly patients with osteoporosis supplement vitamin D 800-1000U/d, which can effectively prevent and treat osteoporosis and reduce fractures; ➤Recommend vitamin D supplementation for elderly patients with fractures 800-1000 U/d, can increase bone density, reduce bone loss, and reduce the risk of recurring fractures; ➤ It is recommended that elderly patients with sarcopenia supplement with vitamin D 600-800 U/d, which can improve the muscle mass of patients with sarcopenia and reduce falls and Fracture risk.

 In terms of drug selection, active vitamin D is preferred.

 4.
Chronic kidney disease patients The proportion of people with chronic kidney disease (CKD) who are inadequate or lacking in vitamin D is higher than that of the general population.
It is recommended to supplement vitamin D to achieve a serum 25(OH)D level> 30ng/ml.

 It is recommended to choose ordinary vitamin D, and vitamin D3 is the first choice, and it is recommended to use continuous oral administration.
According to the age of CKD patients, the vitamin D dose should be prescribed and the maximum tolerated dose should be avoided.
See Table 1.

 ➤Why is it not recommended to use active vitamin D preparations? The main consideration is that it has a short half-life, cannot accumulate in the body, and cannot supplement the lack of vitamin D in the body; ➤Why is it recommended to use continuous oral administration? Because the annual reserve administration method of intramuscular injection or oral vitamin D has been proved to be ineffective or increase the risk of poisoning; to treat osteoporosis and prevent fractures, intermittent high-dose vitamin D administration is ineffective and increases the risk of fractures.

 References: [1] Xie Zhongjian.
How much vitamin D do I need to supplement to maintain bone health? [J].
Chinese Journal of Endocrinology and Metabolism.
October 2020, Vol.
36, No.
10.
[2] Chinese Medical Doctor Association of Nephrology Physicians Branch Vitamin D Practice Program Expert Collaboration Group.
Vitamin D and its analogues in patients with chronic kidney disease Applied Chinese Practice Plan (2019 Edition) [J].
Chinese Journal of Internal Medicine.
Vol.
59, Issue 2, February 2020.
[3] China Geriatric Healthcare Medical Research Association Aging Health Service and Standardization Branch, "Chinese Geriatric Healthcare Medicine" Journal Editorial Committee.
Consensus on the norms of vitamin D supplementation for the elderly[J].
China Geriatric Healthcare.
2019 Vol.
17 No.
4.
[4]Chinese Medical Association Osteoporosis and Bone Mineral Disease Branch.
Vitamin D and Consensus on the clinical application of its analogues[J].
Chinese Journal of Osteoporosis and Bone Mineral Diseases.
Volume 11, Issue 1, January 2018.