What Vitamin D Dosage is Best?
Thatâ€™s because your skin makes vitamin D when it is exposed to sunlight (1).
Getting enough vitamin D is important for optimal health. It helps maintain strong and healthy bones, aids your immune system and may help protect against many harmful conditions (2, 3).
Despite its importance, roughly 42% of people in the US have a vitamin D deficiency. This number rises to a staggering 82.1% of black people and 69.2% of Hispanic people (4).
There are several other groups of people that have higher vitamin D needs because of their age, where they live and certain medical conditions.
This article will help you discover how much vitamin D you need daily.
What Is Vitamin D and Why Is It Important?
Vitamin D belongs to the family of fat-soluble vitamins, which include vitamins A, D, E and K. These vitamins are absorbed well with fat and are stored in the liver and fatty tissues.
There are two main forms of vitamin D in the diet:
- Vitamin D2 (ergocalciferol): Found in plant foods like mushrooms.
- Vitamin D3 (cholecalciferol): Found in animal foods like salmon, cod and egg yolks.
However, sunlight is the best natural source of vitamin D3. The UV rays from sunlight convert cholesterol in your skin into vitamin D3 (1).
Before your body can use dietary vitamin D, it must be â€œactivatedâ€ through a series of steps (5).
First, the liver converts dietary vitamin D into the storage form of vitamin D. This is the form that is measured in blood tests. Later, the storage form is converted by the kidneys to the active form of vitamin D thatâ€™s used by the body (5).
Interestingly, D3 is twice as effective at raising blood levels of vitamin D as vitamin D2 (6).
The main role of vitamin D in the body is to manage blood levels of calcium and phosphorus. These minerals are important for healthy bones (7).
Research also shows that vitamin D aids your immune system and may reduce your risk of heart disease and certain cancers (8).
A low blood level of vitamin D is linked to a greater risk of fractures and falls, heart disease, multiple sclerosis, several cancers and even death (9, 10, 11).
Summary: There are two main forms of vitamin D in the diet: D2 and D3. D3 is twice as effective at raising blood levels of vitamin D, which is linked to a variety of health benefits.
How Much Vitamin D Do You Need for Optimal Health?
In the US, current guidelines suggest that consuming 400â€“800 IU (10â€“20 mcg) of vitamin D should meet the needs of 97â€“98% of all healthy people (12).
However, many experts believe the guidelines are far too low (13.
Your vitamin D needs depend on a variety of factors. These include your age, skin color, current blood vitamin D levels, location, sun exposure and more.
To reach blood levels linked to better health outcomes, many studies have shown that you need to consume more vitamin D than the guidelines recommend (14, 15, 16).
For instance, an analysis of five studies examined the link between vitamin D blood levels and colorectal cancer (15).
Scientists found that people with the highest blood levels of vitamin D (over 33 ng/ml or 82.4 nmol/l) had a 50% lower risk of colorectal cancer than people with the lowest levels of vitamin D (less than 12 ng/ml or 30 nmol/l).
Research also shows that consuming 1,000 IU (25 mcg) daily would help 50% of people reach a vitamin D blood level of 33 ng/ml (82.4 nmol/l). Consuming 2,000 IU (50 mcg) daily would help nearly everyone reach a blood level of 33 ng/ml (82.4 nmol/l) (15, 17, 18).
Another analysis of seventeen studies with over 300,000 people looked at the link between vitamin D intake and heart disease. Scientists found that taking 1,000 IU (25 mcg) of vitamin D daily reduced heart disease risk by 10% (16).
Based on current research, it seems that consuming 1,000â€“4,000 IU (25â€“100 mcg) of vitamin D daily should be ideal for most people to reach healthy vitamin D blood levels.
However, donâ€™t consume more than 4,000 IU of vitamin D without your doctorâ€™s permission. It exceeds the safe upper limits of intake and is not linked to more health benefits (12).
Summary: Consuming 400â€“800 IU (10â€“20 mcg) of vitamin D should meet the needs of 97â€“98% of healthy people. However, several studies show that taking more than this is linked to greater health benefits.
How Do You Know If You Have a Vitamin D Deficiency?
A vitamin D deficiency can only be discovered through blood tests that measure levels of storage vitamin D, known as 25(OH)D.
According to the Institute of Medicine (IOM), the following values determine your vitamin D status (19):
- Deficient: Levels less than 12 ng/ml (30 nmol/l).
- Insufficient: Levels between 12â€“20 ng/ml (30â€“50 nmol/l).
- Sufficient: Levels between 20â€“50 ng/ml (50â€“125 nmol/ l).
- High: Levels greater than 50 ng/ml (125 nmol/l).
The IOM also states that a blood value of over 20 ng/ml (50 nmol/l) should meet the vitamin D needs of 97â€“98% of healthy people (20).
However, several studies have found that a blood level of 30 ng/ml (75 nmol/l) could be even better for preventing fractures, falls and certain cancers (3, 21, 22).
Summary: Blood tests are the only way to know if you are vitamin D deficient. Healthy people should aim for blood levels over 20 ng/ml (50 nmol/l). Some studies find that a blood level over 30 ng/ml is better for preventing falls, fractures and some cancers.
Some People Need More Vitamin D
There are certain groups of people who need more dietary vitamin D than others.
These include older people, those with darker skin, people who live far from the equator and those with certain medical conditions.
There are many reasons why people need to consume more vitamin D with age.
For starters, your skin gets thinner as you grow older. This makes it harder for your skin to make vitamin D3 when it is exposed to sunlight (24).
Older people also often spend more time indoors. This means they get less exposure to sunlight, which is the best way to naturally boost vitamin D levels.
Additionally, your bones become more fragile with age. Maintaining adequate blood levels of vitamin D can help preserve bone mass with age and may protect against fractures (25, 26).
Older people should aim for a blood level of 30 ng/ml, as research shows it may be better for maintaining optimal bone health. This can be achieved by consuming 1,000â€“2,000 IU (25â€“50 mcg) of vitamin D daily (3, 17, 18).
People With Darker Skin
Research shows that people with darker skin are more prone to vitamin D deficiency (27, 28, 29).
This is because they have more melanin in their skin â€” a pigment that helps determine skin color. Melanin helps protect the skin from the sunâ€™s ultraviolet (UV) rays (30).
However, it also reduces the bodyâ€™s ability to make vitamin D3 from the skin, which can make you prone to deficiency (31).
People with darker skin can benefit from consuming 1,000â€“2,000 IU (25â€“50 mcg) of vitamin D daily, especially during winter months (32).
Those Who Live Farther Away From the Equator
Countries close to the equator get plenty of sunlight all year round. Conversely, countries farther away from the equator get less sunlight all year round.
This can cause low blood vitamin D levels, especially during winter months when there is even less sunlight.
If you live far from the equator, then you need to get more vitamin D from your diet and supplements. Many experts believe that people in these countries should consume at least 1,000 IU (25 mcg) daily (13).
People With Medical Conditions That Reduce Fat Absorption
Because vitamin D is fat-soluble, it relies on the gutâ€™s ability to absorb fat from the diet.
Thus, people who have medical conditions that reduce fat absorption are prone to vitamin D deficiencies. These include inflammatory bowel disease (Crohnâ€™s disease and Ulcerative colitis), liver disease and also people who have had bariatric surgery (20, 34).
People with the above conditions are often advised to take vitamin D supplements in an amount prescribed by their doctors (34).
Summary: Those who need the most vitamin D are older people, people with darker skin, those who live farther from the equator and people who canâ€™t absorb fat properly.
Can You Take Too Much Vitamin D?
While it is possible to take too much vitamin D, toxicity is very rare.
In fact, you would need to take extremely high doses of 50,000 IU (1,250 mcg) or more for a long period of time (35).
Itâ€™s also worth noting that it is impossible to overdose on vitamin D from sunlight (36).
Although 4,000 IU (100 mcg) is set as the maximum amount of vitamin D you can take safely, several studies have shown that taking up to 10,000 IU (250 mcg) daily wonâ€™t cause side effects (37, 38).
That said, taking more than 4,000 IU may provide no extra benefit. Your best bet is to take 1,000 (25 mcg) to 4,000 IU (100 mcg) daily.
Summary: Although it is possible to take too much vitamin D, toxicity is rare, even above the safe upper limit of 4,000 IU. That said, consuming more than this amount may provide no extra benefit.
The Bottom Line
Getting enough vitamin D from sunlight and foods is necessary for optimal health.
It helps maintain healthy bones, aids your immune system and may reduce the risk of many harmful diseases. Yet despite its importance, many people donâ€™t get enough vitamin D.
In addition, older people, people with darker skin, those who live farther away from the equator and people who canâ€™t absorb fat properly have higher dietary vitamin D needs.
The current recommendations suggest consuming 400â€“800 IU (10â€“20 mcg) of vitamin D per day.
However, people who need more vitamin D can safely consume 1,000â€“4,000 IU (25â€“ 100 mcg) daily. Consuming more than this is not advised, as it is not linked to any extra health benefits.