Along with vitamin D’s crucial role in bone health, it also has many benefits you may not know about — from reducing inflammation to regulating the immune system and preventing dementia. Despite being called the “sunshine vitamin,” not everyone can get enough from the sun alone, and supplementation may be necessary.
Vitamin D plays an important role in promoting bone health, regulating immune system function and mood disturbances, among other benefits.
The time it takes to feel better after taking Vitamin D varies based on factors such as your current vitamin D levels, dosage, and health status.
To determine vitamin D deficiency, your healthcare provider will request a blood test. Common symptoms include weakness/fatigue, bone pain, mood changes, and impaired immune function.
If you lack sun exposure, are an older adult or obese, have dark skin, a poor diet, or have certain health conditions, you are at an increased risk of vitamin D deficiency.
If you're taking vitamin D supplements or considering it, you may what to know how long it takes to notice the benefits. In this article, we'll provide practical information about vitamin D and when you can expect to see the positive effects of this vital nutrient.
What does vitamin D do?
Vitamin D is essential for maintaining overall health and well-being. The lack of this nutrient can lead to various health problems that supplementation may prevent or treat.
Some functions of vitamin D include:
- Bone health. Vitamin D plays a crucial role in promoting calcium absorption to increase bone mineral density, which is important for maintaining strong bones, preventing bone loss, or improving soft bones. A deficiency in vitamin D can lead to conditions like rickets in children and osteoporosis in adults.
- Inflammation. Vitamin D is known to regulate inflammation. It can reduce the release of pro-inflammatory cytokines and promote the production of anti-inflammatory molecules. Research shows that vitamin D deficiency promotes an increase of the inflammatory molecule in the blood called CRP (C-reactive protein).
- Immune function. Vitamin D is essential for regulating immune system function and can help prevent infections and diseases. Low vitamin D levels have been linked to an increased risk of autoimmune disorders and susceptibility to infection.
- Asthma. Clinical trial also supports vitamin D supplementation to reduce the severity of asthma and improve symptoms.
- Mood and anxiety disorders. Some research suggests vitamin D may have an impact on mood, with low levels linked to depression and other mood disorders. Low levels of vitamin D have been linked to depression and mood disorders, and supplementation with vitamin D may regulate mood disturbances and reduce symptoms of anxiety and depression.
- Postpartum depression. Women with low levels of vitamin D during pregnancy are at an increased risk of developing postpartum depression. Adequate vitamin D levels during pregnancy may help reduce the risk.
- Insulin Levels. Vitamin D plays a role in regulating insulin levels and may help improve insulin sensitivity and pancreas beta cell function.
- Diabetes. Vitamin D helps regulate blood sugar levels and can also reduce the risk of adults with pre-diabetes from developing type 2 diabetes.
- Cancer prevention. A Harvard-initiated clinical trial found that vitamin D3 supplementation reduced the development of advanced cancer among adults without a baseline diagnosis. Other data suggest vitamin D may play a role in reducing the risk of certain types of cancer, including breast, prostate, and colon cancer.
- Cognitive function. Adequate vitamin D levels may be important for maintaining cognitive function and reducing the risk of cognitive decline and dementia.
How much vitamin D do I need per day?
The recommended daily vitamin D intake can vary depending on age, sex, and overall health status.
Here are the current U.S. recommended daily intakes, by international units (IU), of vitamin D according to the National Institutes of Health (NIH).
|Birth: 0–12 months old||10 mcg (400 IU)||10 mcg (400 IU)||-||-|
|Children: 1–13 y/o||15 mcg (600 IU)||15 mcg (600 IU)||-||-|
|Teens: 14–18 y/o||15 mcg (600 IU)||15 mcg (600 IU)||15 mcg (600 IU)||15 mcg (600 IU)|
|Adults: 19–50 y/o||15 mcg (600 IU)||15 mcg (600 IU)||15 mcg (600 IU)||15 mcg (600 IU)|
|Older adults: 51–70 y/o||15 mcg (600 IU)||15 mcg (600 IU)||-||-|
|Elderly: >70 y/o||20 mcg (800 IU)||20 mcg (800 IU)||-||-|
How long does it take for vitamin D to work?
The time it takes for vitamin D to work depends on several factors, such as current vitamin D levels, dosage, and the reason for taking it.
If someone has a severe vitamin D deficiency, it may take several weeks of regular supplementation before they start to see symptom improvement. Someone with mild to moderate deficiency may notice improvement within a few weeks.
Taking vitamin D supplements for at least 8–12 weeks is recommended to see a significant increase in vitamin D blood levels. However, it's important to note vitamin D supplements are not a quick fix.
Some clinical trials found that, depending on the conditions being treated and other relevant factors, short-term supplementation of several weeks may not be enough to improve health, so consistency is key. Regular supplementation is necessary to maintain adequate vitamin D levels in the body.
It's important to talk to a healthcare professional about the appropriate vitamin D supplement dose and how long it may take to see improvement.
How to know if you are vitamin D deficient
A blood test will measure your serum vitamin D levels. A serum 25-hydroxyvitamin D (25(OH)D) level of less than 20 ng/mL (50 nmol/L) is indicative of vitamin D deficiency.
However, some common signs and symptoms can suggest a vitamin D deficiency, including:
- Weakness and fatigue
- Muscle and bone/joint pain
- Impaired wound healing
- Dental/gum problems
- Hair loss
- Mood changes
- Impaired immune function
- Slow-healing fractures
It's important to note that these symptoms can also be caused by other health conditions, so a blood test is the most reliable way to confirm vitamin D deficiency. If you suspect you may be vitamin D deficient, consult a healthcare professional for advice on testing and supplementation.
Who’s at risk for vitamin D deficiency?
Several risk factors can predispose an individual to vitamin D deficiency, including:
- Lack of exposure to sunlight. The skin produces vitamin D when exposed to sunlight. People who don't spend much time outdoors or live in areas with little sunlight may not get enough vitamin D from the sun.
- Aging. Older adults have a reduced ability to produce vitamin D in the skin and may not consume enough from their diet.
- Dark skin. Melanin, the pigment that gives skin its color, reduces its ability to produce vitamin D in response to sunlight. This means those with darker skin may require more prolonged sun exposure to produce the same amount of vitamin D as those with lighter skin.
- Obesity. Vitamin D is stored in fat tissue, which can decrease the amount of vitamin D available to the body. Obese individuals may require higher doses of supplements to maintain adequate levels.
- Poor diet. Vitamin D is found naturally in few foods, and people who follow a vegan or vegetarian diet may not get enough vitamin D.
- Certain health conditions. People with certain medical conditions, such as Crohn's disease, cystic fibrosis, and celiac disease, may have difficulty absorbing vitamin D and require higher doses of supplements.
What foods have vitamin D?
Vitamin D is present in very few foods naturally, but some foods are fortified with vitamin D. Here are some examples of foods that contain vitamin D:
- Fatty fish. Salmon, tuna, mackerel, and sardines are rich in vitamin D.
- Egg yolks. Egg yolks contain small amounts of vitamin D.
- Mushrooms. Some mushrooms, such as shiitake, are exposed to UV light to increase their vitamin D content.
- Fortified foods. Foods such as milk, orange juice, cereal, and yogurt are often fortified with vitamin D.
The amount of vitamin D in these foods can vary, depending on the brand and the specific type of food, so it's important to check the nutrition label to determine how much vitamin D is in a serving. It can be difficult to get enough vitamin D from food alone, and many people may need to take supplements to ensure they are getting enough.
Vitamin D vs. D3: What’s the difference?
Vitamin D and D3 are related compounds, but they are not the same.
Vitamin D is the collective term for a group of fat-soluble vitamins that mainly includes two forms:
- Vitamin D2 (ergocalciferol) — primarily found in mushrooms or plant sources.
- Vitamin D3 (cholecalciferol) — synthesized in our skin when it is exposed to sunlight but is also found in animal products.
Additionally, both can be obtained from fortified foods and dietary supplements, but vitamin D3 is generally preferred due to its higher potency, absorbability, half-life, and effectiveness: vitamin D3 is the most effective form of vitamin D for raising blood levels and providing the best health benefits.
How long does it take for vitamins to work?
Most vitamins show effects within a few days to weeks of consistent supplementation, although this can vary depending on factors such as the type of vitamin, the individual's health status, and the dosage.
How long does it take for vitamin D3 to work?
The effects of vitamin D3 supplementation can vary depending on the individual's initial vitamin D levels and the dosage of the supplement, but some studies have reported noticeable changes in vitamin D status within a few weeks to months of regular supplementation.
How long does it take to restore vitamin D levels?
The time it takes to restore vitamin D levels can vary depending on the severity of the deficiency, supplement dosage, and the individual's ability to absorb vitamin D. However, some studies suggest that it may take several months of regular supplementation to restore vitamin D levels to normal.
- Frontiers in Medicine. Effect of Vitamin D Supplementation on Bone Mineral Density in Rheumatoid Arthritis Patients With Osteoporosis.
- International Journal of Epidemiology. Vitamin D deficiency and C-reactive protein: a bidirectional Mendelian randomization study.
- European Respiratory Journal. Evaluation of vitamin D in bronchial asthma and the effect of vitamin D supplementation on asthma severity and control: A randomised control trial.
- Journal of Investigative Medicine. Vitamin D and the Immune System.
- Current Nutrition Reports. Is Vitamin D Important in Anxiety or Depression? What Is the Truth?
Show all references
- Critical Reviews in Food Science and Nutrition. Postpartum depression and vitamin D: A systematic review.
- European Journal of Endocrinology. Effects of 6-month vitamin D supplementation on insulin sensitivity and secretion: a randomised, placebo-controlled trial.
- Annals of Internal Medicine. Vitamin D and Risk for Type 2 Diabetes in People With Prediabetes: A Systematic Review and Meta-analysis of Individual Participant Data From 3 Randomized Clinical Trials.
- JAMA Netw Open. Effect of Vitamin D3 Supplements on Development of Advanced Cancer A Secondary Analysis of the VITAL Randomized Clinical Trial.
- PNAS. Vitamin D prevents cognitive decline and enhances hippocampal synaptic function in aging rats.