More and more research shows just how important it is for overall health to get enough sun exposure — one reason being because the sun provides us with vitamin D. This is important because vitamin D benefits the body in so many ways.

What does vitamin D do exactly? Research indicates that this so-called “sunshine vitamin” impacts not only your bones and skeletal structure, but also immune function, blood pressure, mood, brain function and your body’s overall ability to protect against a range of illnesses.

According to a 2019 review, benefits of vitamin D are thought to include support for bone health and immunity, as well as resistance against chronic conditions, including heart disease, cancer, diabetes and depression — along with infections and viruses.

Given all of these vitamin D benefits, it’s unfortunate that so many people (at least 40 percent to 80 percent of Americans, depending on race, for example) are lacking in this essential vitamin.

It’s estimated that up to 95 percent of most people’s vitamin D comes from casual sunlight exposure. However, because many people today don’t spend time in the sun each day, or regularly consume foods that provide enough vitamin D (which is hard to do), most adults — and children too, even infants and breastfed babies — are now encouraged to supplement with vitamin D.

What Is Vitamin D?

Vitamin D (also times called 25-hydroxyvitanim D) is a fat-soluble vitamin that is present only in small amounts in certain foods, and it’s made in our bodies only when our skin is exposed to the sun. It’s considered an “essential” nutrientbecause the human body cannot make it on its own, without the assistance of food and sunlight.

Calcium and vitamin D are two important micronutrients that work together in the body to support overall health. The complex vitamin D and calcium relationship is especially crucial when it comes to bone metabolism, as both are integral to maintaining the strength of the skeleton.

Together they support heart health and a number of other bodily systems.

Here’s an overview of how vitamin D is made and what it does in the body:

  1. Humans evolved to spend time outdoors in the sun. The body converts sunshine into chemicals that are then used by the body. In particular, when UV-B sunshine rays land on the skin, a substance in the skin called 7-dehydrocholesterol is literally converted into vitamin D3(the more active form).
  2. 7-dehydrocholesterol or the cholesterol in our skin — which is very similar to cholesterol itself — converts “previtamin D” and makes it into usable D3, which is sometimes also called provitamin D.
  3. Previtamin D first travels through the kidneys and liver in the bloodstream and then is converted into calcitriol.
  4. Vitamin D actually becomes a hormone within the body, particularly a secosteroid hormone.

Vitamin D2 vs. Vitamin D3:

There are two types of vitamin D supplements: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). The precursor to vitamin D is found in both plant and animal products, but animal-derived products of vitamin D3 are thought to be more absorbable and beneficial.

Why? Well, manmade D vitamin is made one of two ways: D2 is created by irradiating yeast and other molds (known as vegetarian vitamin D2) or by irradiating animal oils and cholesterol, creating vitamin D3.

The type our bodies naturally make is called cholecalciferol, which is vitamin D3. The body is able to convert some D2 to be used for body functions but prefers and is able to use D3 much more effectively.

Unfortunately, most vitamin D-fortified foods and dietary supplements mostly contain ergocalciferol, a type of D2, which is neither as absorbable nor convertible by the body into what it needs.

D3 from animal products (specifically from the cholesterol within these products) is closest to what sunlight naturally produces in humans when the skin works to convert UV light. Vitamin D3 is therefore the more active form and thought to be converted up to 500 times faster than D2.

D3 has been estimated to be four times more effective in humans.

Vitamin D Benefits

What are the benefits of taking vitamin D? Here are some of the ways that maintaining adequate levels of vitamin D supports overall health:

1. Contributes to Bone Health

Vitamin D plays a role in calcium absorption into the bones. Calcitriol (converted D vitamin) works with the parathyroid hormone to maintain calcium levels.

Additionally, it has an effect on other important vitamins and minerals that contribute to both health, including magnesium, vitamin K and phosphorus. Vitamin D is partially responsible for maintaining phosphorus levels in the blood, and since it affects calcium’s ability to bind to proteins, it’s believed that it’s also linked to vitamin K.

Low levels can result in the softening of your bones, which is called osteomalacia, or a bone abnormality called rickets. Additionally, a deficiency increases your risk for developing osteoporosis and experiencing fractures or broken bones.

Studies have shown that vitamin D benefits bone health when taken in doses of 800–5,000 international units per day, which can improve musculoskeletal health by naturally slowing aging of the skeletal structure and reducing the rate of fractures and falls in older adults that are over 65.

Older adults with adequate vitamin D levels are more likely to be active, have improved muscle strength, and are less prone to falls and injuries.

When levels are low, the parathyroid becomes overactive. This is known as hyperparathyroidism and results in drops in phosphorus.

Phosphorus, in addition to calcium and other compounds, is needed in order to properly mineralize bone density.

2. Supports the Immune System

Exposure to UV light causes changes inside the human body, including an increase in vitamin D levels. Our immune cells contain receptors for vitamin D, and it’s been shown vitamin D benefits overall immune function in several ways, including by preventing prolonged or excessive inflammatory responses.

Emerging research shows that this vitamin helps with healthy cell replication and may play a role in protecting against the development of autoimmune conditions, infections, viruses and less serious illnesses like common colds and the flu. There’s evidence that humans need enough D in order for macrophages, white blood cells that attack pathogens, to do their job properly.

Vitamin D benefits seem capable of helping to strengthen the immune system by decreasing the ability of some viruses to replicate and grow. It’s been shown to enhance the expression of an enzyme called ACE2, which is believed to have the ability to protect against acute lung injury.

A 2020 study found that average vitamin D levels among residents of 20 different European countries correlated with the incidence of at least one serious acute respiratory infection. Higher D levels among older adults were associated with reduced rates of deadly infections, while low serum concentrations of vitamin D were linked to higher susceptibility.

Because it can help control inflammation, it may also benefit those with chronic diseases and autoimmune disorders, including:

  • multiple sclerosis
  • rheumatoid arthritis
  • irritable bowel syndrome and other digestive disorders
  • high blood pressure

3. Helps Manage Blood Sugar Levels and Can Prevent Diabetes

Diabetes symptoms result from a lack of insulin or inadequate insulin secretion following increases in insulin resistance. According to research conducted at the London School of Medicine and Dentistry, calcium is necessary for insulin secretion, and vitamin D benefits promote calcium absorption and utilization, therefore contributing to the regulation of insulin secretion.

According to a 2015 study published in Current Diabetes Reviews, vitamin D replacement has beneficial effects on all aspects of type 2 diabetes, including the incidence, control and complications of the disease. There is also mounting evidence linking low vitamin D levels to diabetes.

4. May Help Protect Against Cancer

According to research published in Frontiers in Endocrinology, D vitamin plays a role in factors that influence tumor growth, cell differentiation and apoptosis. Vitamin D deficiency symptoms have been correlated with increased risks for cancer development, especially breast, colon and prostate cancers.

Researchers have found that increased sunlight exposure and circulating levels of vitamin D are associated with the reduced occurrence and mortality in many types of cancer.

Research shows that it can affect the risk of breast, colon and ovarian cancers possibly due to its role in the cell life cycle or its ability to block excess estrogen. According to research published in the American Journal of Clinical Nutrition, improving vitamin D and calcium nutritional status substantially reduces the risk of cancer in postmenopausal women.

Another 2018 study helps solidify these breast cancer findings as researchers found postmenopausal women with 60 ng/mL or more of 25-hydroxyvitamin D, the main form of vitamin D in the blood, had one-fifth the risk of breast cancer compared to those with under 20 ng/mL.

5. Helps Fight Heart Disease

Vitamin D benefits heart health by helping with maintenance of normal blood pressure and inflammation levels.

A growing number of research points to the fact that low vitamin D levels are linked to increased risks for cardiovascular disease since it’s involved in regulating blood pressure, cholesterol levels and inflammation.

Animal studies have shown that the disruption of vitamin D signaling can contribute to hypertension, atherosclerosis and cardiac hypertrophy. We know that humans who are deficient are more likely to die from coronary heart disease and other heart-related symptoms, according to research from the Vanderbilt University Medical Center.

6. Facilitates Hormone Regulation and Can Help Improve Your Mood

Because it acts like a hormone within our bodies and affects brain function, vitamin D deficiency has been linked to an increased risk for mood disorders, including depression, seasonal affective disorder and severe mood problems experienced during PMS, insomnia and anxiety.

Low levels can also interfere with proper testosterone and estrogen production, leading to imbalances that can result in many unwanted symptoms.

7. Helps with Concentration, Learning and Memory

Several studies have shown that vitamin D also affects our ability to make decisions, concentrate and retain information. Researchers indicate that people with lower levels perform poorlyon standardized exams, may have poor decision-making skills, and have difficulty with tasks that require focus and attention.

Additionally, some research has shown a correlation between low levels of vitamin D and an increased risk for developing schizophrenia and multiple sclerosis.

8. Supports Skin Health

Why is vitamin D good for your skin? Some of the ways that vitamin D benefits skin include by supporting your immune system, controlling inflammation, and helping aid in skin cell growth, repair and metabolism.

Adequate levels may even help prevent skin aging and also reduce redness, dryness and other symptoms caused by eczema and psoriasis.

Deficiency Signs/Causes

What happens when your vitamin D is low? Research tells us that vitamin D deficiency symptoms can include:

  • Fatigue
  • Osteoporosis or bone fractures
  • Susceptibility to infectious diseases
  • Higher risk for cardiovascular disease and high blood pressure
  • Higher risk for certain types of cancer
  • Autoimmune diseases
  • Depression
  • Insomnia
  • Arthritis
  • Higher risk for diabetes
  • Asthma
  • Chronic pain
  • Skin issues, such as psoriasis
  • Developmental problems in infants and children

Causes of vitamin D deficiency, and risk factors that make a low status in this vitamin more likely, include:

  • Lack of sunlight exposure.
  • Frequent use of sunscreen, which reduces your body’s ability to make vitamin D.
  • Underlying health conditions, such as obesity, type 2 diabetes, insulin resistance and hypertension, which seem to increases a person’s risk.
  • Having darker skin; a high percentage of African-Americans, Hispanics and Asians living in the United States are believed to suffer from vitamin D insufficiency.
  • Being over the age of 70.
  • Certain occupations that limit outdoor time, including being a shift worker, health care worker and indoor worker.
  • Being a nursing home resident or hospitalized patient.
  • Having celiac disease, Crohn’s disease or cystic fibrosis that interferes with absorption and processing of vitamin D in the intestines, kidneys or liver.
  • Breast-fed infants are also at risk for vitamin D deficiency, which is why supplementing is recommended.

How can I increase my vitamin D level?

Certain foods such as fish, eggs and dairy products provide some vitamin D, but exposure to sunlight is still the best way to maintain a normal status.

A general recommendation is to get about 10 to 15 minutes of direct sunlight daily, without wearing sunscreen, if you are fair- to medium-toned. If you have dark skin, you likely need more time in the sun to make enough vitamin D, about 40 minutes daily.

Taking a vitamin D supplement can also be helpful for many people, especially in the winter months and for those who can’t spend time outside most days.

Foods with Vitamin D

What foods are high in vitamin D? The top vitamin D-rich foodsinclude:

  • Cod liver oil (take about one tablespoon daily)
  • Halibut
  • Carp fish
  • Mackerel
  • Eel
  • Wild-caught salmon
  • Whitefish
  • Swordfish
  • Rainbow trout
  • Sardines
  • Tuna
  • Pastured eggs
  • Beef liver
  • Raw milk
  • Caviar
  • Fortified milk and dairy products
  • Fortified milk alternatives, such as nut-based milks
  • Maitake and portobello mushrooms (when exposed to UV light)

How Much Do You Need? (Dosage)

How much vitamin D should you take each day to take advantage of vitamin D benefits? Below is the USDA’s official recommendation to obtain vitamin D benefits:

Children:

  • 1–3 years: 600 IU (15 mcg/day)
  • 4–8 years: 600 IU (15 mcg/day)

Older Children and Adults:

  • 9–70 years: 600 IU (15 mcg/day)
  • Adults over 70 years: 800 IU (20 mcg/day)
  • Pregnant and breastfeeding: 600 IU (15 mcg/day)

Some health experts believe that higher doses may be even more protective and beneficial.

Recommendations for children go as high as 35 units per pound/day, or about 2,500 units/day for children ages 5 to 10. Recommendations for adults (including pregnant women) go as high as 5,000 units/day.

To get the best vitamin D3 supplement, look for a fermented, food-based source of D3 (preferably fermented with a healthy bacteria, such as L. bulgaricus).

Risks and Side Effects

Can you take too much vitamin D? “Vitamin D toxicity” (when you’ve taken too much vitamin D) is thought to be very rare, but it can occur when someone takes high doses of supplements.

Vitamin D toxicity can potentially develop if someone takes more than 300,000 IU in a 24-hour period or more than 10,000 IU of vitamin D per day for months.

When someone’s blood level becomes abnormally high, vitamin D side effects can include symptoms of hypercalcemia, or high blood calcium levels, such as:

  • digestive issues like vomiting, nausea and stomach pain
  • diarrhea
  • fatigue
  • excessive thirst
  • frequent urination

If you choose to take vitamin D supplements, be sure to stick to a dosage that is within the recommended range. Do not take more unless you’re monitored by a health care provider and instructed to take more.

While supplements are necessary and beneficial in many cases, it’s ideal to get the amount of D vitamin you need directly from sunlight.

Some people are more likely to experience side effects of too much vitamin D — therefore taking supplements is not always recommended, especially in high doses.

Vitamin D supplements should not be taken by anyone who takes these prescription drugs, unless a health care provider recommends otherwise:

  • Steroids
  • Epilepsy drugs, such as phenobarbital and phenytoin
  • The weight loss medication Orlistat
  • Cholestyramine
  • Corticosteroids, such as prednisone
  • Diabetes medicines
  • Blood pressure drugs
  • Seizure medicines, such as phenobarbital and Dilantin (phenytoin)
  • Calcium supplements and antacids

If you have a health conditions such as inflammatory bowel disease, liver or kidney disease, or hypercalcemia, then you should not supplement with vitamin D without being monitored by your doctor.

Conclusion

  • Vitamin D is a fat-soluble vitamin that we get mostly from exposing our skin to the sun. Vitamin D benefits overall health in many ways, such as by supporting bone metabolism, cardiovascular function, immunity against infections and illnesses, skin health, and cognitive/mental health.
  • Vitamin D deficiency is believed to be very common because many people today don’t spend enough time in the sun, due to factors like working indoors or wearing sunblock.
  • The best way to maintain normal levels is to expose your skin to sunlight for 10 to 20 minutes per day. You can also safely increase your vitamin D level by eating vitamin D-rich foods, such as fish, cod liver oil, eggs, dairy products, liver and some mushrooms, to obtain vitamin D benefits.
  • Supplementing is a good option for many people, especially the elderly, infants, people who have malabsorption issues, and those who spend most of their time indoors. To obtain these vitamin D benefits, adults need at least 600 to 800 IU per day (or ideally even more) and children need at least 600 IU.