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Vitamin D is completely different than most other vitamins.
实际上，这是一种类固醇激素，当您的皮肤暴露在阳光下时产生的类固醇激素。
For this reason, vitamin D is often referred to as “the sunshine vitamin.”
However, sun exposure rarely provides adequate vitamin D, making it necessary to obtain it from supplements or your diet.
Yet, only a handful of foods contain significant amounts of this crucial vitamin, and deficiency is very common (
In fact, around 41.6% of the U.S. population is deficient (
This article explains everything you need to know about vitamin D.
维生素D是fat-soluble vitamin, meaning that it dissolves in fats and oils and can be stored in your body for a long time.
Two main dietary forms exist (
- Vitamin D3 (cholecalciferol).在某些动物食品中发现，例如脂肪鱼和egg yolks.
- 维生素D2（Ergocalciferol）。Found in some plants, mushrooms, and yeasts.
在这两种情况下，D3（胆固醇）似乎几乎是维生素D的血液水平与D2（Ergocalciferol）的有效有效的两倍（
SUMMARY维生素D是fat-soluble vitamin that your body can store for long periods of time. Of the two main forms — D2 and D3 — the latter is more effective at raising vitamin D levels in your blood.
Vitamin D needs to undergo two conversion steps to become active (
首先，它在肝脏中转换为钙二醇，即25（OH）D。这是维生素的储存形式。
Second, it is converted to calcitriol, or 1,25(OH)2D, mostly in your kidneys. This is the active, steroid-hormone form of vitamin D.
骨化三醇与维生素D受体（VDR）相互作用，该受体几乎在您体内的每个细胞中都发现（
当维生素D的活性形式与该受体结合时，它打开或关闭基因，导致细胞的变化。这类似于大多数其他类固醇激素的工作方式（
Vitamin D affects various cells related tobone health. For example, it promotes the absorption of calcium and phosphorus from your gut (
但是科学家最近发现，它在其他健康领域也扮演着角色，例如免疫功能和保护癌症(15）。
SUMMARY维生素D转化为钙二醇，钙二酚，维生素的储存形式，然后将其转化为钙化类固醇形式。钙三醇与细胞内的维生素D受体结合，打开或关闭基因。
当暴露于紫外线B（UVB）射线时，您的皮肤中的胆固醇D可以由维生素D产生the sun(
If you live in an area with abundant sunshine, you can probably get all the vitamin D you need by sunbathing a few times per week.
请记住you need to expose a large part of your body. If you’re only exposing your face and hands, you will produce much less vitamin D.
Also, if you stay behind glass or use sunscreen, you will produce less vitamin D — or none at all (
However, you should make sure to use sunscreen when staying in the sun for extended periods. Sunshine is healthy, but sunburns can cause prematureskin agingand raise your risk of skin cancer (18,
如果你呆在阳光下很长一段时间,缺点ider going without sunscreen for the first 10–30 minutes — depending on your sensitivity to sunlight — then applying it before you start to burn.
As vitamin D gets stored in your body for weeks or months at a time, you may only need occasional sunshine to keep your blood levels adequate.
That said, if you live in an area without adequate sunlight, getting vitamin D from foods or supplements is absolutely essential — especially during winter.
SUMMARY阳光是获得维生素D的有效方法，但防晒霜会阻止其产量。尽管安全地晒日光浴可以帮助您获得足够的水平，但许多人在一年中大部分时间都无法获得阳光。
这是一些最好的食物来源的维生素D3含量（
| Food | Amount | % RDI |
| Cod liver oil, 1 tablespoon (15 ml) | 1,360 IU / 34 MCG | 227％ |
| Salmon, cooked, 3 ounces (85 grams) | 447 IU / 11 mcg | 75％ |
| Tuna, canned in water, 3 ounces (85 grams) | 154 IU / 4 mcg | 26% |
| Beef liver, cooked, 3 ounces (85 grams) | 42 IU / 1 mcg | 7％ |
| 1 large whole egg (D is found in yolk) | 41 IU / 1 MCG | 7％ |
| 1 sardine, canned in oil, drained | 23 IU / 0.6 mcg | 4% |
虽然胖鱼喜欢salmon, mackerel, swordfish, trout, tuna, and sardines are decent sources, you would have to eat them almost every day to get enough.
维生素D的唯一优质饮食来源是鱼肝油（例如鳕鱼肝油），其中一汤匙（15毫升）中的参考每日摄入量（RDI）的两倍以上。
请记住dairy productsand cereals are often fortified with vitamin D (
Some rare mushrooms also harbor vitamin D, and egg yolks contain small amounts.
SUMMARYCod liver oil is the single best source of vitamin D3. Fatty fish is also a good source, but you have to eat it frequently to get enough.
Vitamin D deficiency is one of the most common nutrient deficiencies.
有些人的风险比其他人更大。在美国，尽管少数群体的情况差得多，但总人口的41.6％分别不足，有82.1％和69.2％的人不足（
Additionally, older adults are at a much greater risk of being deficient (
那些患有某些疾病的人也很可能会缺乏。一项研究表明，经历心脏病发作的人中有96％的维生素D低（
总体而言，维生素D缺乏症是一种无声的流行病。这symptomsare usually subtle and may take years or decades to surface.
维生素D缺乏症的最著名症状是Rickets，这是发展中国家儿童常见的骨骼疾病。
Rickets has been mostly eliminated from Western countries because of the fortification of some foods with vitamin D (
Deficiency is also linked to osteoporosis, reduced mineral density, and increased risk of falls and fractures in older adults (25）。
此外，研究表明，维生素D水平低的人患心脏病的风险要大得多，diabetes(types 1 and 2), cancer, dementia, and autoimmune diseases like multiple sclerosis (
Finally, vitamin D deficiency is linked to a reduced life expectancy (
That said, it’s unclear whether deficiency contributes to these diseases or whether people with low levels are just more likely to get them.
SUMMARYVitamin D deficiency is associated with a variety of health issues, as well as reduced life expectancy.
Here are some potential benefits of vitamin D:
- Reduced risk of osteoporosis, falls, and fractures.Higher doses of vitamin D can help prevent osteoporosis, falls, and fractures in older adults (
30 ）。 - 更好的力量。维生素D可以增加上肢和下肢的身体强度（
31 ）。 - Cancer prevention.Vitamin D may help prevent cancer. One study noted that 1,100 IU per day — alongside calcium — reduced cancer risk by 60% (
32 ,33 ）。 - 抑郁症管理。Studies show that vitamin D may ease symptoms in people with clinical depression (
34 ）。 - Reduced risk of type 1 diabetes.一项针对婴儿每天2,000 iU的维生素D与1型糖尿病风险降低78％的研究（
35 ）。 - 改善死亡率。一些研究表明，维生素D降低了人们在研究期间死亡的风险，表明这可能会帮助您live longer(
36 ,37 ）。
However, many of these results are preliminary. According to a recent review, more evidence is necessary to confirm many of these benefits (
SUMMARY研究表明，维生素D可能与癌症，骨骼健康，心理健康和自身免疫性疾病有关。但是，需要更多的研究。
知道你的唯一途径are deficient — and thusneed to supplement— is by having your blood levels measured.
您的医疗保健提供者将测量维生素D的储存形式，即被称为Calcifediol。12 ng/mL以下的任何物体都被认为不足，而超过20 ng/ml的任何东西都被认为是足够的。
维生素D的RDI如下（
- 400 IU (10 mcg):infants, 0–12 months
- 600 IU（15 MCG）：children and adults, 1–70 years old
- 800 IU (20 mcg):older adults andpregnantor breastfeeding women
Although adequacy is measured at 20 ng/ml, many health experts believe that people should aim for blood levels higher than 30 ng/ml for optimal health and disease prevention (
此外，许多人认为，推荐的摄入量太低了，人们需要更多才能达到最佳血液水平（
According to the U.S. National Academy of Medicine, the safe upper limit is 4,000 IU (100 mcg) per day (
Vitamin D3 supplements appear to be more effective at raising vitamin D levels than D2 supplements. D3 capsules are available in most supermarkets and health food stores, as well asonline.
SUMMARY这RDI for vitamin D is 400 IU (10 mcg) for infants, 600 IU (15 mcg) for children and adults, and 800 IU (20 mcg) for older adults and pregnant or breastfeeding women.
It’s important to keep in mind that nutrients usually don’t work in isolation.
Many of them depend on one another, and increased intake of one nutrient may increase your need for another.
Some researchers claim that fat-soluble vitamins work together and that it’s crucial to optimize your vitamin A and K intake while supplementing with vitamin D3 (
This is especially important for维生素K2, another fat-soluble vitamin that most people don’t get enough of (
Magnesium- 现代饮食中经常缺乏的另一个重要矿物质 - 对于维生素D功能也可能很重要（
SUMMARYEvidence suggests that vitamin D works with magnesium and vitamins A and K to promote health.
It is a myth that it is easy tooverdose在维生素D上
Vitamin D toxicity is very rare and only happens if you take very high doses for extended periods (
这main symptoms of toxicity include confusion, lack of concentration,睡意, depression, vomiting, abdominal pain, constipation, and high blood pressure (
SUMMARYVitamin D toxicity is very rare. The symptoms include confusion, drowsiness, depression, constipation, and high blood pressure.
维生素D是fat-soluble vitamin important for bone health.
For those low in this nutrient, increasing intake may also reduce depression and improve strength.
Your skin produces vitamin D when exposed to sunlight. Foods like fatty fish, fish oil, and liver also contain vitamin D — as well as certain fortified foods and supplements.
Deficiency is fairly common due to limited sunlight exposure and a small selection of rich dietary sources.
如果您不花太多时间在阳光下而很少吃脂肪鱼，请考虑补充。
Getting enough vitamin D can go a long way to boosting your health.
