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Recently, the prestigious medical journal The New England Journal of Medicine (NEJM) published the results of a major study:
In a generally healthy middle-aged and elderly population, high-dose (2000IU/d)vitamin D3 supplementation did not significantly reduce the risk of fractures.
Many people will ask: Mr. Gu, haven’t you always suggested daily vitamin D supplementation? This… shall we continue to eat?
I have finished reading the research paper. As for whether to take vitamin D or not, I still insist on the point of view:
Too long to read
Vitamin D is very important, and people with insufficient sun exposure, regardless of age, can take supplements in winter and spring, unless they get very high levels of vitamin D from formula milk and fortified foods. There is no harm in supplementing with vitamin D every day except for the money.
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Vitamin D is important,
But the role of supplements is controversial
Vitamin D is an indispensable nutrient for the human body, and its important functions are basically familiar to everyone.
The main physiological role of vitamin D and its metabolites is to promote the absorption of calcium and phosphorus in the intestine, inhibit the release of parathyroid hormone, maintain normal levels of blood calcium and phosphorus, and thus ensure bone health and normal neuromuscular function [1].
How much vitamin D do we need?
Serum 25OHD is the most abundant form of vitamin D in the body and can reflect the nutritional level of vitamin D in the human body, so it is recognized as the most reasonable indicator to reflect the vitamin D status of the human body.
Image from reference [1]
It is generally accepted that serum 25-hydroxyvitamin D(25 OHD)levels>30 ng/mL(75 nmol/L), To maximize bone and calcium metabolism and muscle function.
When it is below this level, it is vitamin insufficiency and deficiency (the following is a looser standard):
Vitamin D deficiency: Serum 25OHD level 20-30ng/ml (50-75 nmol/L)
Vitamin D deficiency: Serum 25OHD levels
Severe vitamin D deficiency: serum 25OHD levels
In 2011, the Institute of Medicine (IOM) recommended that adults get 600-800 IU of vitamin D daily through meals, corresponding to total serum 25-hydroxyvitamin D levels At least 20 ng/mL can be achieved to meet the bone health needs of 97.5% of the population.
Other societies and organizations recommend that adults consume at least 800-2000 IU of vitamin D per day, resulting in a serum 25-hydroxyvitamin D level of at least 30ng/mL. level [2].
Will vitamin D supplements work?
Inadequate or deficient vitamin D can affect bone health, with fractures being the most serious consequence.
However, the results of vitamin D supplements to prevent fractures have been inconsistent, with some saying they are beneficial, some don’t, and others It is even believed that high doses may increase the risk of fractures [2].
There is also a lack of large randomized controlled trials to assess the role of vitamin D supplementation in preventing fracture risk.
The VITAL study published this time is a large randomized controlled trial evaluating the effects of high-dose (2000IU/d) vitamin D3 supplementation and n-3 fatty acids (1 g/d) on the The effect of primary prevention of cancer and cardiovascular disease in the middle-aged and elderly population in the United States (men ≥50 years old, women ≥55 years old).
Researchers conducted a secondary analysis based on this study to try to find an association between vitamin D3 supplementation and the risk of fractures.
Image from reference [2]
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What does the study say?
The study covered 25,871 middle-aged and older adults in the United States, of whom 50.6% were women and 20.2% were black (both women and blacks are at high risk for vitamin D insufficiency or deficiency). With a median follow-up of 5.3 years, the results showed:
Does not prevent or increase fracture risk
Vitamin D3 supplementation did not significantly improve subjects’ overall, nonvertebral, and hip fracture risk compared with placebo.
A – total fracture, B – vertebral fracture, C – hip fracture. Placebo – Placebo, Vitamin D – Vitamin D. ｜ Picture from reference [2]
Nor there was no evidence that participants with serum 25-hydroxyvitamin D ≥50 ng/ml had an increased risk of fracture.
Improving bone health and related metrics
While vitamin D3 supplementation will not prevent fractures, vitamin D supplementation is not entirely ineffective and does improve bone health:
Mean serum 25-hydroxyvitamin D levelsincreased from 29.2ng/ml in the vitamin D group in
participants who provided blood samples for both years strong> to 41.2 ng/ml, while the placebo group decreased slightly from 30.0 ng/ml to 29.4 ng/ml.
Many previous studies have shown that 800IU of vitamin D supplementation per day is not effective in increasing vitamin D levels, and this study proves that daily high-dose (2000IU) vitamin D supplementation is meaningful for increasing human vitamin D levels. .
In participants with serum 25-hydroxyvitamin D levels below the median at baseline, vitamin D3 supplementation slightly improved spine and total hip bone mineral density.
The
vitamin D group mean parathyroid hormone levelsreduced from 40.8 ng/ml to 37.2 ng/ml.
When blood calcium decreases, it stimulates the secretion of parathyroid hormone, acts on osteocytes and osteoclasts, absorbs bone calcium and releases it into the blood; when blood calcium increases, it inhibits its secretion.
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Are you still taking vitamin D supplements?
Depends on one’s vitamin D status, but vitamin D is insufficient for most people in our country and lack of status.
Study subjects had better vitamin D status
In discussing the findings of the study, the researchers also noted that,Conclusions (which do not prevent fractures) not applicable to the elderly population with severe vitamin D deficiency, low bone mass, osteoporosis, and elderly care institutions.
Because the effect of vitamin D and placebo on fracture events was compared, the study subjects were generally healthy people, not vitamin D deficient or Deficiency, osteoporosis patients, because it is neither feasible nor against medical ethics.
So the study participants were generally good in vitamin D status, with a mean baseline level of 25-hydroxyvitamin D at the start of the trial of 30.7±10.0 ng/ ml, only 12.9% were below 20 ng/ml and 2.4% were below 12 ng/ml.
By contrast…
Vitamin D nutritional status in the world is not good
From a real-world perspective, the nutritional status of vitamin D around the world is not very good.
Vitamin D insufficiency or deficiency is fairly common worldwide, accounting for 50%-80% of the general population[1], even in the United States Vitamin D deficiency also exists in 41.6% [3].
In China, surveys in cities at different latitudes show that vitamin D insufficiency or deficiency is widespread in the population. A cross-sectional study of 1436 healthy people in five major cities in my country found that the average level of serum 25-hydroxyvitamin D was only 19.87±8.14 μg/L, of which serum 25-hydroxyvitamin D was sufficient ( > 30 ng/ml) Only 11.7%, vitamin D insufficiency (20~30 ng/ml) and deficiency (31. 3%and 57. 0%[1].
Also, Chinalow bone mass and osteoporosis are more serious.
According to the data of the first Chinese resident osteoporosis epidemiological survey in my country in 2018, osteoporosis has become an important health problem for people over 50 years old in my country. The problem of osteoporosis is particularly serious in women. The prevalence is about 2-5 times higher than that in men.
Image data from reference [4]
At the same time, there are a large number of people with low bone mass, which are at high risk of osteoporosis. Among the middle-aged people aged 40-49, the proportion of people with low bone mass is nearly 1/3, and the proportion of people over 50 years old is as high as 46.4%.
Image data from reference [4]
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Vitamin D supplementation recommendations for the average person
Would you like to have your vitamin D levels checked?
Seeing the above, many people may have decided to go to the hospital to check serum 25-hydroxyvitamin D.
Don’t be in such a hurry, see if you’re a special and at-risk group before making a decision.
Although vitamin D insufficiency or deficiency is common in populations worldwide, general screening of serum 25-hydroxyvitamin D levels in the population is not advocated , screening is only recommended for those who are at risk of vitamin D deficiency and need to maintain a reasonable vitamin D nutritional status.
In addition to diseases or the use of certain drugs, some special populations should also pay attention to screening serum 25-hydroxyvitamin D levels, such as pregnancy and breastfeeding women, older adults with falls and history of nontraumatic fractures, and obese children and adults, >Crowds that lack sunlight. See the chart below for more details.
Image from reference [1]
How should vitamin D be “supplemented”?
The most cost-effective way to prevent vitamin D insufficiency or deficiency is to increase sunlight exposure.
Image from reference [1]
Make it up early
Vitamin D is an important endocrine hormone that regulates bone growth and development. Synthesis and intake of sufficient vitamin D during adolescence can promote bone building and mineralization, and help obtain higher of peak bone mass.
In adulthood, adequate vitamin D can help maintain positive calcium balance, reduce bone turnover imbalances and accelerate bone loss.
The occurrence of osteoporosis depends on the peak bone mass obtained at a young age and the rate of bone loss in middle and old age.
Therefore, ensure adequate intake of vitamin D from children and adolescents, and supplement in adulthood, middle-aged and old age Vitamin D still makes sense.
Sunbathe
Encourage everyone to get outside when the weather is nice, so you can by the way get a vitamin D supplement .
Although the appropriate way to bask in the sun can be either short-term direct exposure, or long-term exposure under shaded conditions. However, the American Academy of Dermatology states that vitamin D should not be obtained through unprotected UV exposure[5].
No matter how you choose, it is recommended to do sunscreen on the face and eyes, and try to sun the skin of the limbs. First, the skin of the limbs is more efficient in producing vitamin D, Second, even if the skin in these parts has some photoaging, people don’t pay much attention…
Perfect time
First, it has to be sunny.
Outdoor
When outdoor activities on sunny days, try to use umbrellas or shade under dense trees, which can not only achieve a certain degree of sun protection, but also supplement vitamin D. The only problem is that it takes time relatively long…
Spring and Autumn: Before 10 am and after 14 pm are better.
Summer: Better after 16:00 pm.
Indoor
Spring, summer and autumn: The intensity of ultraviolet rays from 10:00 to 14:00 is more suitable for indoor sunbathing.
Winter: It also makes sense to sunbathe indoors through the glass, especially for the elderly and infants who are inconvenient for outdoor activities.
A suitable length of time
No sun exposure for more than 0.5 hours at noon in spring.
Summer noon should not exceed 0.2h.
No more than 0.9h at noon in autumn. [6]
Eat foods rich in vitamin D
Few foods are rich in vitamin D, one of the few nutrients that the body needs to be fully met through dietary intake.
The best sources of vitamin D3 are fatty fish (salmon, swordfish, sardines, etc.) and cod liver oil, found in egg yolks, cheese, beef liver, and some mushrooms Also contains small amounts of vitamin D.
And then there are vitamin D-fortified foods, such as vitamin D-fortified dairy products, soy milk, and cereals[7].
Theory is difficult to “fit” into reality
However, real life is often less than ideal. There are many factors that affect vitamin D levels, such as age, skin color, obesity, clothing habits, sun protection, dietary habits, air pollution, season, geographic latitude, altitude , sunshine duration, and drugs and diseases that affect vitamin metabolism.
Modern social lifestyle has greatly reduced the time spent living and working outdoors.
season, latitude, and altitude vary widely in UV exposure time and intensity, Air pollution not only affects the duration and intensity of UV exposure, but also reduces time spent outdoors.
And with age, the amount of vitamin D synthesized in the skin decreases significantly, and the skin’s ability to synthesize vitamin D with the same degree of sun exposure is only young 30%[1] of people.
These all make it unrealistic to get vitamin D entirely from sun exposure. And generally speaking, most people don’t get more than 150 IU of vitamin D from food sources a day.
Taking vitamin supplements is a more convenient and efficient way~
Vitamin D is relatively safe, if you take it every day, then you can eat 400 IU (you can increase to 600 IU over 65 years old), and supplement your routine like this Regular doses of vitamin D generally do not require monitoring of serum and urinary calcium.
Of course, if there is already a deficiency or problems such as osteoporosis, please follow the doctor’s advice for the specific treatment dosage.
Finally, in addition to ensuring adequate nutrition, continuous exercise, especially resistance training is also very important, which can help us “store” muscle and bone mass in advance, Prevent fractures.
References
[1] Xia Weibo, Zhang Zhenlin, Lin Hua, Jin Xiaolan, Yu Wei, Fu Qin. Consensus on the clinical application of vitamin D and its analogs[J]. Chinese Osteoporosis and Bone Mineral Diseases Magazine, 2018, 11(01):1-19.
[2] Supplemental Vitamin D and Incident Fractures in Midlife and Older Adults, New England Journal of Medicine (2022). DOI: 10.1056/NEJMoa2202106
[3] Forrest KY, Stuhldreher WL. Prevalence and correlates of vitamin D deficiency in US adults. Nutr Res. 2011 Jan;31(1):48-54. doi: 10.1016/j .nutres.2010.12.001. PMID: 21310306.
[4] The National Health Commission released the results of the epidemiological survey on osteoporosis in China https:https://www.chinacdc.cn/gsywlswxx_9498/crbs/201812/t20181217_198289.html< /p>
[5] https:https://www.aad.org/Forms/Policies/Uploads/PS/PS-Vitamin%20D.pdf
[6] Wu Mei, Zhang Wei. UV radiation intensity in different seasons and exposure modes in Beijing[J]. Health Research, 2011,40(02):233-235.DOI :10.19813/j.cnki.weishengyanjiu.2011.02.031.
[7] Vitamin D. Retrieve from 2022.8.3. https:https://www.hsph.harvard.edu/nutritionsource/vitamin-d/