Vitamin D is important, not only good for bones, but also helps strengthen muscles, and can reduce the severity and frequency of respiratory diseases, immune system diseases, as well as reduce the incidence of cancer tumors, and reduce mortality from all causes (Medicine referred to as all-cause mortality).

Vitamin D deficiency is common in the population, especially in the elderly.

　　Why are we prone to vitamin D deficiency

　　Inadequate sun exposure such as working indoors, covering your clothes or using a sunshade (also called physical sun protection) when going out, using sunscreen externally, sun exposure through clothing or glass, and not getting enough sun during periods of time;

　　Some chronic diseases include malabsorption, obesity, liver and kidney insufficiency, etc.;

　　Drugs antiepileptic drugs, antiretroviral drugs, rifampicin, glucocorticoids, etc.;

　　Older people are older than 70 years old, and the skin produces only 30% of the vitamin D of young people with the same light.

　　Best time to bask in the sun

　　Because only 10% of the vitamin D in our body is provided by exogenous food. Foods rich in vitamin D include fish liver, egg yolk, milk, green vegetables, and fungi; while 90% are endogenous and exposed to ultraviolet light. The skin is synthetic, so sunlight is important, and it is important that the sun shines directly on the skin.

We know that an SPF-8 sunscreen can reduce the skin's production of vitamin D by 92%; an SPF-15 sunscreen can reduce it by 99%.

　　When is the best time to bask in the sun?

The shadow principle can be applied: when your own shadow is longer than your height, the UV rays are already very weak and the skin cannot synthesize vitamin D, so the recommended sun exposure time is 2 hours before and after noon, half an hour a day.

In summer, the time period and sun exposure time can be adjusted appropriately.

　　Reasonable vitamin D supplementation is not easy to cause poisoning

　　How can I know if I am vitamin D deficient?

In fact, it is very simple. As long as blood is drawn for testing, it is currently available in all major hospitals.

　　In the case of not being able to meet the sun exposure, we can choose the way of oral vitamin D supplementation.

For the elderly without gastrointestinal absorption dysfunction, oral vitamin D supplementation is preferred.

If there is absorption dysfunction, intramuscular injection of vitamin D is required, and the interval depends on the dose used.

When supplementing vitamin D, the dose can be 2000-5000IU per day, and after supplementation, 1000IU per day can be maintained.

　　There are also some adverse consequences of vitamin D supplementation, including kidney calcification and urinary stones.

Vitamin D is fat-soluble, and there is a risk of accumulation of poisoning, but if it is not used in large quantities for a long time, poisoning generally does not occur.

It can be determined by measuring blood vitamin D levels and monitoring urinary calcium levels.

A 24-hour urinary calcium level of less than 300 mg is safe.

　　It's worth noting that this article is for regular vitamin D supplementation.

Active vitamin D is a treatment drug for osteoporosis, and the common ones are calcitriol and alfacalcidol.

Taking active vitamin D does not supplement the lack of vitamin D in the body, nor does it bring the same benefits as vitamin D in terms of breathing, immunity, and tumors.

　　Text/Li Xinping (Beijing Jishuitan Hospital)