Beware! Vitamin D overdose may lead to poisoning! Learn how to supplement correctly in one article →

The sunshine in late autumn this year was so elusive that there was no sign of it showing up for several days in a row. I couldn't help but think of the words my parents used to teach me when I was a child:
Get more sun exposure to supplement vitamin D!

As my parents kept nagging, I began to wonder:
Why do people need to supplement vitamin D?
01

What is vitamin D?

We are all familiar with the term vitamin D, but most people are not very clear about what it is.
Vitamin D is a steroid derivative and a substance necessary for maintaining normal physiological functions of the body.
Although the human body's demand is very small, it plays an important role in regulating material metabolism.
There are many types of vitamin D, including vitamin D1, D2, D3, D4 and D5. Among them, vitamin D2 and vitamin D3 are most closely related to human health.
Vitamin D2 comes from plants. When the body digests food, the vitamin D2 in it will combine with fat, be absorbed in the small intestine, and enter the human blood circulation.
02

The relationship between vitamin D and inflammation

Human beings have been studying and exploring vitamins since the late 19th century, and it has a history of more than a hundred years. People have discovered many functions of vitamin D - anti-rickets, anti-osteomalacia, cancer prevention, diabetes prevention, improvement of schizophrenia, etc.
Recently, there have been new advances in human understanding of vitamin D.
In May this year, scientists from the Cancer Research Institute of the University of South Australia and other institutions pointed out in a paper published in the International Journal of Epidemiology that vitamin D and chronic inflammation are closely related.

Image source: International Journal of Epidemiology
The researchers recruited more than half a million volunteers aged between 37 and 73 through the UK Biobank.
After screening out the impact of the volunteers' British ancestry, the researchers conducted a statistical analysis of 300,000 samples.

Image source: International Journal of Epidemiology
The researchers chose C-reactive protein (CRP) as an indicator to determine the body's inflammation level.
The statistical conclusion is shown in the figure above. As the level of 25-hydroxyvitamin D (25 (OH) D) in the serum of volunteers increased, the proportion of C-reactive protein decreased rapidly.

The data in brackets are standard values, the data in red circles represent vitamin D content, and the last set of data is CRP content. Image source: International Journal of Epidemiology

Combined with the data from the blank control group, it was found that when the vitamin D level reached the normal level of normal people, further increasing the vitamin D content had little effect on the C-reactive protein ratio.
Through this trend of change, researchers tell us two pieces of information:

1. When vitamin D is deficient, taking vitamin D can lower the C-reactive protein ratio and reduce inflammation.
2. For people who are already deficient in vitamin D, taking vitamin D can effectively reduce inflammation and have certain benefits to their health; however, there is no obvious benefit for ordinary people with normal vitamin D levels to take vitamin D.
   Moreover, excessive vitamin D can lead to vitamin D poisoning , which in turn causes an increase in blood calcium, resulting in symptoms such as anorexia, irritability, convulsions, frequent urination, and arrhythmia, which harm the human body.
   It will also over-suppress inflammation and cause adverse consequences.
   03

What are the consequences of ignoring inflammation?

Inflammation is one of the diseases that torment us the most. For example, some people suffer from rhinitis and wish they could carry ten packs of tissues every day. But in fact, the existence of inflammation is not only to torture humans, but also to defend against microbial infection.
When a part of the body becomes infected, the body launches an indiscriminate attack on that area, which we see as “inflammation.”

If inflammation is ignored, the microbial infection may further expand, followed by inducing vascular damage, serious body lesions, and even long-term chronic inflammation can induce cancer.
Therefore, we must treat inflammation with caution and moderation, and accurately and specifically identify the causes of inflammation.
04

What foods contain vitamin D

Richer in content?

Putting aside special vitamin supplement pills, scientists in Chinese academic electronic journals have listed several foods rich in vitamin D - salmon and tuna are ranked first.
Most fish contain a certain amount of vitamin D, but these two types of fish are particularly rich in vitamin D.

Secondly, there is formula milk , which can be fortified with vitamin D; in addition, some plants contain ergosterol, which can be converted into vitamin D2 under ultraviolet light, which is beneficial for human intake of vitamin D.
Through today's understanding, we know that everything has two sides - indispensable, but too much is as bad as too little.
The general public may not have much knowledge of medicine, but they need to have a scientific concept - to pay attention to all diseases and medicines, while ensuring moderation.

Review｜Li Nannan Director of Hunan Science Writers Association, Deputy Director of Research and Publicity Department of Hunan Science and Technology Association, Second-level Researcher, Chinese Science Writer (Medical Field)

Source: Beijing Science Center