Vitamin D is absolutely essential for good health.
Also known as the sun's vitamin, it is produced on the skin when exposed to sunlight.
Despite this, vitamin D deficiency is one of the most common nutrient deficiencies in the world.
Up to 42% of the adult population in the US UU You have low levels of vitamin D, which can cause health problems (1, 2, 3, 4, 5).
Vitamin D is particularly important for bone health and the function of the immune system.
This article discusses the amount of vitamin D you need.
What is vitamin D?
Vitamin D is a fat-soluble vitamin that works like a steroid hormone in the body.
There are two forms of vitamin D in the diet:
- Vitamin D2 (ergocalciferol): It is found in some mushrooms.
- Vitamin D3 (cholecalciferol): It is found in fatty fish, fish liver oil and egg yolks.
D3 is the most powerful of the two types and raises levels of vitamin D in the blood almost twice as much as D2 (6, 7).
Large amounts of vitamin D can also be produced in the skin when exposed to UV rays from sunlight. Any excess of vitamin D is stored in your body's fat for later use.
Each cell in your body has a vitamin D receptor. This vitamin participates in many processes, such as bone health, the function of the immune system and protection against cancer (8, 9, 10, 11).
Bottom line: Vitamin D works like a steroid hormone in your body. There are two forms in the diet, D2 and D3. It can also occur on the skin when exposed to sunlight.
How common is vitamin D deficiency?
Vitamin D deficiency is a problem throughout the world.
However, it is especially common in young women, babies, the elderly, and people with dark skin (12, 13).
About 42% of the population of the United States is deficient in vitamin D. However, this rate increases to 82% in black people and 70% in Hispanics (5).
If you have access to strong sun throughout the year, occasional sun exposure may be enough to meet your vitamin D requirements.
However, if you live far north or south of the equator, your vitamin D levels may fluctuate depending on the season. The levels can go down during the winter months, due to lack of sufficient sunlight (14, 15, 16).
In that case, you should rely on your diet (or supplements) for vitamin D, as well as on vitamin D that is stored in body fat during the summer (15).
In adults, a vitamin D deficiency can (17, 18, 19):
- It causes muscle weakness.
- Intensify bone loss.
- Increase the risk of fractures.
In children, a severe vitamin D deficiency can cause growth retardation, as well as rickets, a disease where the bones become soft.
In addition, vitamin D deficiency has been linked to several cancers, type 1 diabetes, multiple sclerosis, high blood pressure and thyroid problems (17, 20).
Bottom line: Vitamin D deficiency is very common throughout the world, but occurs at higher rates in specific populations. A deficiency of vitamin D is related to several health problems.
How much vitamin D should he take?
The amount of vitamin D you need depends on many factors. These include age, race, latitude, season, sun exposure, clothing and more.
The recommendations of the US Institute of Medicine UU They suggest that an average daily intake of 400-800 IU, or 10-20 micrograms, It is suitable for 97.5% of individuals (21, 22).
However, some studies have shown that the daily intake should be greater than that if it is not exposed to the sun.
Depending on who you ask, blood levels above 20 ng / ml or 30 ng / ml are considered "sufficient". A study in healthy adults showed that a daily intake of 1120-1680 IU was needed to maintain sufficient blood levels (23).
In the same study, people with vitamin D deficiency needed 5000 IU to reach levels in the blood above 30 ng / ml.
Studies in postmenopausal women with vitamin D levels below 20 ng / ml found that intake of 800 to 2000 IU elevated blood levels above 20 ng / ml. However, higher doses were needed to reach 30 ng / ml (24, 25).
People who are overweight or obese may also need higher amounts of vitamin D (26, 27).
After all, a daily intake of vitamin D 1000-4000 IU, or 25-100 micrograms, It should be enough to ensure optimal levels in the blood in most people.
4000 IU is the safe upper limit according to the Institute of Medicine (IOM). Be sure not to take more than that without consulting a health professional.
Bottom line: Vitamin D intake is recommended at 400-800 IU / day, or 10-20 micrograms. However, some studies suggest that a higher daily intake of 1000-4000 IU (25-100 micrograms) is needed to maintain optimal blood levels.
What are the optimal blood levels of vitamin D?
Blood levels of vitamin D are evaluated by measuring 25 (OH) D in the blood, which is the storage form of vitamin D in the body (28).
However, there has been some debate about the definition of optimal blood levels.
The Institute of Medicine (IOM) and the Nordic Nutrition Council base their recommendations on the following blood levels (18, 21):
- Enough: 25 (OH) D greater than 20 ng / ml (50 nmol / l).
- Insufficient: 25 (OH) D less than 20 ng / ml (50 nmol / l).
- Deficient: 25 (OH) D less than 12 ng / ml (25 nmol / l).
These organizations claim that blood levels of more than 20 ng / ml meet the vitamin D requirements of more than 97.5% of the population.
An IOM committee found no higher blood levels associated with any additional health benefits (21).
However, other experts, including the Endocrine Society, recommend targeting higher blood levels that are closer to 30 ng / ml (75 nmol / l) (17, 29, 30, 31).
Bottom line: Vitamin D levels are generally considered sufficient when they are above 20 ng / ml (50 nmol / l). However, some experts claim that blood levels above 30 ng / ml (75 nmol / l) are optimal.
What are the main sources of vitamin D?
You can get vitamin D from:
- Solar exposition.
- Foods that contain vitamin D.
The intake of vitamin D is generally quite low, since very few foods contain significant amounts (32).
Foods that contain vitamin D include fatty fish such as salmon, as well as fish liver oils.
Egg yolks also contain small amounts, and in some countries milk and cereals are enriched with vitamin D (33).
However, supplements are also widely available, and they are safe and effective.
Bottom line: The main sources of vitamin D are sunlight, fatty fish, egg yolks, fish liver oils, fortified foods and supplements.
Can we get enough vitamin D from the sun alone?
Sun exposure in summer is the best way to get enough vitamin D.
However, the amount of sunlight needed varies.
Older people and those with dark skin produce less vitamin D in the skin.
The geographical location and the season are very important, because vitamin D can not be produced throughout the year in countries that are far from the equator.
Even though the sun shines, it is not necessarily strong enough to produce vitamin D.
Here are some facts about the production of vitamin D in the sun:
- In more than 70 countries that are located north of 35 ° N, vitamin D is not produced during the winter months (34, 35).
- Further north, in countries such as Norway (69 ° N), vitamin D is not produced from October to March (36).
- Factors such as clothing, weather, pollution, the use of sunscreen, weight and genetics can also affect the body's ability to produce vitamin D.
In strong sun conditions, exposing arms and legs for 5 to 30 minutes between 10 a.m. and 3 p.m. is usually sufficient to meet the daily requirements of most light-skinned people. People with darker skin may need a little more time (22).
One study showed that prolonged exposure to the sun during the summer was sufficient to guarantee excellent levels of vitamin D during the winter, independently of the intake of vitamin D (37).
However, if you live far from the equator, you should probably consume supplements or foods that contain vitamin D.
Bottom line: Vitamin D requirements can be met only with the sun during the summer. During the winter, and for those who live far from the equator, supplements may be necessary.
How much is too much?
The information on overdose of vitamin D is obsolete and the toxicity is extremely rare.
It is associated with dangerously high amounts of calcium and phosphates in the blood, along with low levels of parathyroid hormone.
This is usually only seen in people who have accidentally or intentionally taken extremely high doses of vitamin D for long periods of time, such as 50,000 to 1 million IU / day for months (38, 39).
The highest level of safe ingestion is set at 4000 IU, or 100 micrograms, per day.
However, it has not been shown that up to 10,000 IU per day causes harm to healthy people (21).
That said, very few people really need more than 4000 IU per day (40).
A study of 17 thousand people who took variable doses of vitamin D, up to 20,000 IU / day, showed no signs of toxicity. Their blood levels were even lower than the upper-normal range, which is 100 ng / ml or 250 nmol / l (26).
Also, an overdose of vitamin D from sunlight is not possible.
Keep in mind that although large doses are unlikely to cause harm or toxicity, they may be completely unnecessary.
Bottom line: The recommended upper intake level of vitamin D is 4000 IU / day. However, it has been shown that higher doses are safe in some studies.
Bring the message home
Vitamin D is essential for bone health and many other aspects of health.
A deficiency is incredibly common and can have serious consequences for the health of many people.
If you are thinking about adding more vitamin D to your diet, consider the following factors:
- If you live somewhere where there is sun throughout the year, you may not need more vitamin D while making sure you get enough sun.
- If you do not have access to the sun, then Vitamin D3 supplements of 1000-4000 IU. (25-100 micrograms) should be enough for most people.
- The only way to know if really need Taking a vitamin D supplement is having your blood levels measured.
At the end of the day, vitamin D is very important. Correcting a deficiency is simple, cheap and can have immense health benefits.
Read this for more information on vitamin D: Vitamin D 101 – Detailed guide for beginners.
Reference: https: //www.healthline.com/nutrition/how-much-vitamin-d-to-take