What? Isn’t it enough to turn on UVB?


It's not that simple. However, if you only want to stop at the primary stage of lighting your reptiles, then there is no need to delve into this issue. But if you want to know what German experts are studying, then vitamin D3 and the synthesis principle are the introductory knowledge you must understand.


To summarize first, we need to remember one sentence: different wavelength bands of ultraviolet rays have different effects on the synthesis of vitamin D.


As long as you remember this sentence, you will master two pieces of information at the same time:


1. It is not only UVB that affects the synthesis of vitamin D.


2. Even within the UVB band, the effects of different bands are different.

Only when you remember this major premise can you continue to delve deeper. Now, we will analyze the synthesis principle of vitamin D3 in detail. Of course, this topic involves biochemistry, organic chemistry, and medical knowledge. It is impossible for me to delve into every principle, but I can integrate the mature conclusions of predecessors to clarify this complex chemical process for you.

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Talking about the synthesis principle, here we have to introduce the vitamin D3 synthesis principle diagram designed by Sarina Wunderlich, a German terrestrial expert and Ph.D. in physics. This diagram may also be annotated for the first time in China (hurry up and follow this account!)

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Feeling messy? Don’t rush out of the article, let me help you summarize the information in the picture:


1. Let’s look at the green vertical main line first.


This line shows the production and conversion process of vitamin D. From top to bottom, they are 7DHC (original vitamin D3), previtamin D3, vitamin D3, calcifediol, and calcitriol.


7DHC (provitamin D3): the “primordial switch” present in the skin. After being exposed to ultraviolet light, it "opens" to produce the next stage compound - provitamin D3.

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Provitamin D3: The heart of this article. Because this compound not only determines the synthesis amount of vitamin D3, but also effectively prevents too much vitamin D3 (too much vitamin D is also harmful), and it is the variable most affected by different bands of ultraviolet rays.

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Vitamin D3: mentioned repeatedly in my videos. It determines the absorption of calcium. Without vitamin D3, calcium cannot be absorbed into our vertebrate bodies.

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Calcidiol: Vitamin D3 is converted into the first form of vitamin D by the liver and circulates mainly in our blood. Its concentration reflects the level of vitamin D in the body and is an important detection indicator for preventing calcium deficiency. Yes, it is already too late to diagnose calcium deficiency when you see bone deformation. To prevent calcium deficiency in the early stage, it is scientific to measure blood calcium concentration.

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Calcitriol: When calcifediol is transported to the kidneys, kidney processing plants convert it into calcitriol. It can accelerate the synthesis of calcium-binding protein, thereby allowing the intestinal absorption of calcium, further increasing blood calcium; it can also promote the intestinal absorption of phosphorus, etc. (phosphorus and calcium are equally important, but daily food has higher phosphorus content and is easier for the body to absorb Phosphorus, so additional calcium supplementation is needed in various ways)

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2. The yellow horizontal line above shows the different products converted into vitamin D by exposure to ultraviolet rays of different bands before synthesis.

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3. The yellow horizontal line below shows the by-products of vitamin D produced after ultraviolet irradiation. These by-products also have a positive impact on health, but this part of the content is not introduced in this article. Everyone can breathe a sigh of relief

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good! I now assume that everyone has understood the synthesis principle of vitamin D, so we now move to the next step: how different bands of ultraviolet rays affect calcium absorption. As mentioned before, provitamin D3 is the key to this issue. So, how is it affected by UV rays?


First of all, we can see that previtamin D3 is produced after receiving UVB irradiation of 290-310nm, which shows that ultraviolet rays in this band are the most effective in the production of this element. And this band happens to be within the range of UVB, so we came to a simple conclusion in the past - UVB is the most effective for synthesizing vitamin D3.


but! UVB is not only 290-310nm, the entire UVB band is 275-320nm. So are the shorter and longer wave UVB parts useless? The problem arises precisely here: UVB at 275-290nm has a stronger effect on the synthesis of pre-vitamin D, but this band is uncommon in nature because the atmosphere will filter it out to a large extent. The synthetic ability of this band is not only very strong, but there is even a risk of overdose and burns to the eyes of reptiles. However, the UVB band produced by some unprofessional lighting manufacturers is exactly within this range, which creates the hidden danger of excessive vitamin D. What's more, some will increase the reading of the UVB tester by adding shorter wave UVC... I can only wish you to go bankrupt soon.


Although this problem can be solved by the distance between the lamps, if you don't have a UVB tester, you can't debug it based on your feeling. Because UVB is completely invisible to the naked eye, a height difference of 10cm may cause significant changes in the data, making it impossible to visually inspect. But if we do not pursue the extreme high-radiation ultraviolet rays in the wild, but choose the relatively safe Ferguson area, this hidden danger can be minimized.

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What about 310-320nm? Is longer wave UVB also useful? it works! This is as useful as an insurance measure!


Looking back at the schematic diagram, we can see that there is a purple line on the provitamin D3, which says "290-335nm", and the arrow is indeed pointing upward. Why is it facing upward? Because the process of synthesizing vitamin D3 is reversible!


We have developed a set of insurance measures with the reptile body to prevent excessive synthesis of vitamin D, that is, through long-wave UVB and part of UVA, pre-vitamin D3 is converted back to original vitamin D3, so that it can no longer synthesize more vitamin D3. Vitamin D3! This band exists in large quantities in nature, so it is difficult for wild animals to develop "hypervitamin D syndrome" by basking in the sun.

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The second problem lies here - many lamp manufacturers have ignored the effects of ultraviolet rays in this band, and the UVB lamps they produce do not contain the long-wavelength part, so that the reptile's body cannot automatically run this "insurance measure". Combined with the above, the combination increases the risk of "vitamin D oversynthesis" caused by artificial light fixtures.


So how do I know which band my lights are on? A spectrometer, the cheapest domestic product, costs more than 10,000 yuan... There are still ways, but you need to learn some new knowledge. Here are two ways I hope you can remember:


1. Remember the Ferguson District Usage Rules


The Ferguson Zone is a set of ultraviolet usage standards tailored for two-person climbers based on the UV Index (UVI). Since last year, some friends and I have been vigorously promoting this part of the content on domestic social platforms (although my updates are very slow, which is a bit of a drag on everyone). But after nearly a year of dissemination, more and more friends have become aware of it. Importance of UV rays. For detailed information, you can read this article: https://www.bilibili.com/read/cv20929457.

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Remember how the Ferguson Zone is used, your animals can adjust the distance between themselves and ultraviolet rays through shelter, distance and distance, which is equivalent to letting them choose a suitable basking position. Rather than leaving them with nowhere to escape, they are forced to stay in the sun when they can't take shelter. If anyone doesn’t want to read the paper, you can leave a message in the comment area and we can interpret it later.

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2. Standby UV tester


UVB products of the same specification produced by different manufacturers may have very different wavelength bands. Some are normal, while others are mixed with harmful short-wave ultraviolet rays. This can be reflected from the UVI index.


In the UVI tester, since the weighting standards of different bands are different, the shorter the wavelength of the UV, the greater the weight, and the more obvious it is reflected in the results. If any manufacturer cuts corners and mixes in some UVC in order to increase the UVB reading, the UVI value will soar above 10.0 - and the reptiles we commonly raise may not require a maximum UVI of more than 5.0. It can be said that 10.0 Consider it a lethal dose.


However, the Solarmeter 6.5R that can measure UVI is not cheap. The domestic price is around 1,800 yuan (although it is already cheap among testers) and it is often out of stock. Then, a UVB tester becomes an effective alternative


Because the response peak of general UVB testers is also between 270-310nm. If the UVB reading is too high, such as more than 50μW/cm2, then an area below 30μW/cm2 needs to be arranged as a transition zone. Usually this can be achieved by increasing the distance between the lamp and the animal, because the shorter the wavelength band, the greater the impact of ultraviolet rays on distance. By increasing the distance, those harmful ultraviolet rays will quickly dissipate in the space or be intercepted by obstructions.

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So without a tester, it's difficult to know what distance is appropriate. Because different manufacturers have different production standards, there may be quality fluctuations in individual products even in the same batch. Rather than trusting a manufacturer you are not familiar with, it is better to prepare a tester to verify its quality at any time.


Now Giant's newly developed UVB tester has been launched online and can be found in the official Taobao store. Not only is the price nearly 6 times lower than Solarmeter, the difference between the two under artificial lights is also very small. Everyone is welcome to visit the store for details. I will introduce a more comprehensive usage evaluation to you in a follow-up video, so stay tuned.

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