Vitamin D is needed for immune function, bone health, cellular growth, and more. Unfortunately, more than 1 billion people worldwide are deficient in this important nutrient.
Vitamin D can be taken at any time of day, and most of these supplements should be taken with fat-containing meals or snacks to ensure optimal absorption.
For example, one study in 50 older adults found that vitamin D absorption was 32% greater in those who took a vitamin D supplement with a fat-containing meal compared with those who took it with a fat-free meal (17Trusted Source).
However, some vitamin D supplements aren’t affected by what you eat. For example, one animal study found that oil-based and microsomal vitamin D supplements — vitamin D encapsulated in fatty acid spheres — can be taken without food (18Trusted Source, 19Trusted Source).
It’s important to note that vitamin D activation depends on having adequate levels of magnesium. Therefore, to maintain healthy vitamin D levels, make sure you’re also getting enough magnesium (20).
Also, keep in mind that certain fat-soluble vitamins, including vitamin E, may affect vitamin D absorption. On the other hand, taking vitamin K alongside vitamin D may benefit bone mineral density (21Trusted Source, 22Trusted Source).
Vitamin D has multiple roles in the body. It assists in:
- promoting healthy bones and teeth
- supporting immune, brain, and nervous system health
- regulating insulin levels and supporting diabetes management
- supporting lung function and cardiovascular health
- influencing the expression of genes involved in cancer development
Read on to find out about these roles in more detail:
1. Healthy bones
Vitamin D plays a significant roleTrusted Source in the regulation of calcium and maintenance of phosphorus levels in the blood. These factors are vital for maintaining healthy bones.
People need vitamin D to allow the intestines to stimulate and absorb calcium and reclaim calcium that the kidneys would otherwise excrete.
Vitamin D deficiency in children can cause rickets, which leads to a severely bowlegged appearance due to the softening of the bones.
Similarly, in adults, vitamin D deficiency manifests as osteomalaciaTrusted Source, or softening of the bones. Osteomalacia results in poor bone density and muscular weakness.
A vitamin D deficiency can also present as osteoporosis, for which over 53 million people in the United States either seek treatment or face an increased risk.
2. Reduced risk of flu
A 2018 reviewTrusted Source of existing research suggested that some studies had found that vitamin D had a protective effect against the influenza virus.
However, the authors also looked at other studies where vitamin D did not have this effect on flu and flu risk.
Further research is, therefore, necessary to confirm the protective effect of vitamin D on the flu.
3. Healthy infants
Vitamin D deficiency has links to high blood pressure in children. One 2018 study found a possible connection between low vitamin D levels and stiffness in the arterial walls of children.
The American Academy of Allergy Asthma and Immunology (AAAAI) suggest that evidence points to a connection between low vitamin D exposure and an increased risk of allergic sensitization.
An example of this is children who live closer to the equator and have lower rates of admission to hospital for allergies plus fewer prescriptions of epinephrine autoinjectors. They are also less likely to have a peanut allergy.
The AAAAI also highlight an Australian study of egg intakeTrusted Source. Eggs are a common early source of vitamin D. The children who started eating eggs after 6 months were more likely to develop food allergies than children who started between 4–6 months of age.
Furthermore, vitamin D may enhance the anti-inflammatory effects of glucocorticoids. This benefit makes it potentially useful as a supportive therapyTrusted Source for people with steroid resistant asthma.
4. Healthy pregnancy
A 2019 reviewTrusted Source suggests that pregnant women who are deficient in vitamin D may have a greater risk of developing preeclampsia and giving birth preterm.
Doctors also associate poor vitamin D status with gestational diabetes and bacterial vaginosis in pregnant women.
It is also important to note that in a 2013 studyTrusted Source, researchers associated high vitamin D levels during pregnancy with an increased risk of food allergy in the child during the first 2 years of life.
For more in-depth resources about vitamins, minerals, and supplements, visit our dedicated hub.
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Although the body can create vitamin D, a deficiency can occur for many reasons.
Skin type: Darker skin, for example, and sunscreen, reduce the body’s ability to absorb the ultraviolet radiation B (UVB) rays from the sun. Absorbing sunlight is essential for the skin to produce vitamin D.
Sunscreen: A sunscreen with a sun protection factor (SPF) of 30 can reduce the body’s ability to synthesize the vitamin by 95% or moreTrusted Source. Covering the skin with clothing can inhibit vitamin D production also.
Geographical location: People who live in northern latitudes or areas of high pollution, work night shifts, or are homebound should aim to consume vitamin D from food sources whenever possible.
Breastfeeding: Infants who exclusively breastfeed need a vitamin D supplement, especially if they have dark skin or have minimal sun exposure. The American Academy of Pediatrics recommend that all breastfed infants receive 400 international unitsTrusted Source (IU) per day of oral vitamin D.
Supplement drops for babies are available online.
Although people can take vitamin D supplements, it is best to obtain any vitamins or minerals through natural sources wherever possible.
Read more on vitamin D deficiency.
Symptoms of vitamin D deficiency may include:
- regular sickness or infection
- bone and back pain
- low mood
- impaired wound healing
- hair loss
- muscle pain
If Vitamin D deficiency continues for long periods, it may result in complicationsTrusted Source, such as:
- cardiovascular conditions
- autoimmune problems
- neurological diseases
- pregnancy complications
- certain cancers, especially breast, prostate, and colon.
Getting sufficient sunlight is the best way to help the body produce enough vitamin D. Plentiful food sources of vitamin D include:
- fatty fish, such as salmon, mackerel, and tuna
- egg yolks
- beef liver
- fortified milk
- fortified cereals and juices
Here, learn how to get more vitamin D from the sun.
People can measure vitamin D intake in micrograms (mcg) or international units (IU). One microgram of vitamin D is equal to 40 IU.
The recommended daily intakesTrusted Source of vitamin D are as follows:
- Infants 0–12 months: 400 IU (10 mcg).
- Children 1–18 years: 600 IU (15 mcg).
- Adults up to 70 years: 600 IU (15 mcg).
- Adults over 70 years: 800 IU (20 mcg).
- Pregnant or lactating women: 600 IU (15 mcg).
Sensible sun exposure on bare skin for 5–10 minutes, 2–3 times per week, allows most people to produce sufficient vitamin D. However, vitamin D breaks down quite quickly, meaning that stores can run low, especially in winter.
The upper limit that healthcare professionals recommend for vitamin D is 4,000 IU per dayTrusted Source for an adult. However, the National Institutes of Health (NIH) say that vitamin D toxicity is unlikely at intakes under 10,000 IU per day.
Excessive consumption of vitamin D can lead to over calcification of bones and the hardening of blood vessels, kidney, lung, and heart tissues.
The most common symptoms of excessive vitamin D include headache and nausea. However, too much vitamin D can also lead to the following:
- loss of appetite
- dry mouth
- a metallic taste
Excess vitamin D usually occurs from taking too many supplements. It is best to get vitamin D from natural sources.
If someone is taking supplements, they should choose their brand carefully, as the FDA do not monitor the safety or purity of supplements.
There is a selection of vitamin D supplements available for purchase online.
It is the total diet and eating pattern that is most important in disease prevention and good health. It is better to eat a diet with a variety of nutrients than to concentrate on one nutrient as the key to good health.
When Is the Best Time to Take Vitamin D? Morning or Night?
Vitamin D is an incredibly important vitamin, but it’s found in very few foods and is hard to obtain through diet alone.
As a large percentage of the world population is at risk of deficiency, vitamin D is one of the most common nutritional supplements.
However, many factors can influence its effectiveness, including when and how you take your daily dose.
This article explores the best time to take vitamin D to maximize its absorption and effectiveness.
Vitamin D stands out from other vitamins because it’s considered a hormone and is produced by your skin as a result of sunlight exposure (1Trusted Source).
Getting enough vitamin D is essential for your health, as studies indicate it may play a role in immune function, bone health, cancer prevention and more (2Trusted Source, 3Trusted Source, 4Trusted Source).
However, vitamin D occurs in very few food sources — making it difficult to meet your needs if you’re not getting regular sun exposure.
For older adults and people who have darker skin, are overweight or live in areas where sunlight is limited, the risk of deficiency is even higher (5Trusted Source).
Around 42% of adults in the US are deficient in this key vitamin (6Trusted Source).
Supplementing is an easy and effective way to meet your vitamin D needs, especially if you’re at risk of deficiency.
SUMMARYThough vitamin D is produced by your skin in response to sunlight exposure, it’s found naturally in very few foods. Supplementing with vitamin D is an effective way to meet your needs and prevent deficiency.
Vitamin D is a fat-soluble vitamin, meaning that it does not dissolve in water and is absorbed best in your bloodstream when paired with high-fat foods.
For this reason, it’s recommended to take vitamin D supplements with a meal to enhance absorption.
According to one study in 17 people, taking vitamin D with the largest meal of the day increased vitamin D blood levels by about 50% after just 2–3 months (7Trusted Source).
In another study in 50 older adults, consuming vitamin D alongside a fat-heavy meal increased vitamin D blood levels by 32% after 12 hours compared to a fat-free meal (8Trusted Source).
Avocados, nuts, seeds, full-fat dairy products and eggs are nutritious sources of fat that help boost your vitamin D absorption.
SUMMARYStudies indicate that having vitamin D with a large meal or source of fat can significantly increase absorption.
Many people prefer to take supplements such as vitamin D first thing in the morning.
Not only is it often more convenient, but it’s also easier to remember your vitamins in the morning than later in the day.
This is especially true if you’re taking multiple supplements, as it can be challenging to stagger supplements or medications throughout the day.
For this reason, it may be best to get in the habit of taking your vitamin D supplement with a healthy breakfast.
Using a pillbox, setting an alarm or storing your supplements near your dining table are a few simple strategies to remind you to take your vitamin D.
SUMMARYSome people may find that taking vitamin D first thing in the morning is more convenient and easier to remember than taking it later on.
Research links vitamin D levels to sleep quality.
In fact, several studies associate low levels of vitamin D in your blood to a higher risk of sleep disturbances, poorer sleep quality and reduced sleep duration (9Trusted Source, 10Trusted Source, 11Trusted Source).
Conversely, one small study suggested that higher blood levels of vitamin D may be linked to lower levels of melatonin — the hormone responsible for regulating your sleep cycle — in people with multiple sclerosis (12Trusted Source).
Some anecdotal reports claim that taking vitamin D at night can negatively influence sleep quality by interfering with melatonin production.
However, scientific research to determine how supplementing with vitamin D at night may affect sleep is currently unavailable.
Until studies exist, it may be best to simply experiment and find what works best for you.
SUMMARYVitamin D deficiency may negatively impact sleep quality. Some anecdotal reports assert that supplementing with vitamin D at nighttime may interfere with sleep, but scientific data to that effect is unavailable.
Taking vitamin D with a meal can enhance its absorption and increase blood levels more efficiently.
However, there’s limited research on whether taking it at night or in the morning may be more effective.
The most important steps are to fit vitamin D into your routine and take it consistently to ensure maximum effectiveness.
Try taking it alongside breakfast or with a bedtime snack — as long as it doesn’t interfere with your sleep.
The key is to find what works for you and stick with it to ensure you’re meeting your vitamin D needs.
SUMMARYTaking vitamin D with a meal can increase its absorption, but studies on specific timing are limited. For best results, experiment with different schedules to find what works for you.
Supplements can be an effective way to boost your blood levels of vitamin D, which is crucial to your health.
Taking vitamin D with food can enhance its effectiveness, as it’s fat-soluble.
While the best timing has not been established, scientific data to confirm anecdotal reports that supplementing at night may interfere with sleep is unavailable.
Current research suggests you can fit vitamin D into your routine whenever you prefer.