Vitamin D Benefits, Deficiency, Sources, Dosage and More - Dr. Axe

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Vitamin D Benefits Bones, Immunity, Skin & More


Vitamin D benefits - Dr. Axe

More and more research shows just how important it is for overall health to get enough sun exposure, which is why vitamin D deficiency is a serious issue. One reason is because the sun provides us with vitamin D, an essential nutrient that 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 and brain function.

According to a 2019 review, benefits of vitamin D are thought to include enhanced protection against heart disease, cancer, diabetes and depression, along with infections and viruses.

Unfortunately, so many people — 40 percent to 80 percent of Americans, depending on factors such as race, for example— are lacking in vitamin D. This is why most adults, children, and even infants and breastfed babies are now encouraged to supplement with vitamin D.

What Is Vitamin D?

Vitamin D (also called 25-hydroxyvitamin D) is a fat-soluble vitamin that is present only in small amounts in certain foods. It’s also made in our bodies but only when our skin is exposed to the sun.


It’s considered an “essential” nutrient because the human body cannot make vitamin D on its own without the assistance of food and sunlight.

Calcium and vitamin D are two important micronutrients that work together in the body. 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.

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

  1. 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 converts “previtamin D” and makes it into usable D3.
  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 type our bodies naturally make D3/cholecalciferol. 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.

For the most vitamin D benefits, supplementing with D3 is recommended.

Vitamin D Benefits

What are the benefits of taking vitamin D? Here are some of the ways that maintaining adequate levels can positively impact your 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. Phosphorus, in addition to calcium and other compounds, is needed in order to properly mineralize bone density.

Low vitamin D 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. This 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.

2. Supports the Immune System

Vitamin D is considered an “immune modulator.” 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 T cells, B cells, dendrite cells and macrophages, white blood cells that attack pathogens, to do their jobs properly.

Vitamin D benefits seem capable of helping 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. Additionally, this vitamin is thought to support integrity of the gut lining, protect the mucosal barrier and regulate gut immunity.

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 inflammatory responses and maintain B-lymphocyte homeostasis, vitamin D may also benefit those with autoimmune disorders and other conditions, including:

  • multiple sclerosis
  • rheumatoid arthritis
  • lupus
  • psoriasis
  • 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. Inflammation and obesity can also contribute to type 2 diabetes.

D3 is needed to help stimulate pancreatic β-cells to secrete insulin. According to research, calcium is also 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.

A 2022 study also found that vitamin D supplementation benefited those with prediabetes who had low D levels, however it wasn’t enough to prevent insulin resistance without other measures.

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, colorectal, bladder 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.

It’s believed that vitamin D may 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.

That being said, some studies have found that supplementation alone doesn’t necessarily lower cancer risk.

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 epidemiological and clinical studies indicate 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 may potentially contribute to hypertension, atherosclerosis and cardiac hypertrophy, considering that this vitamin impacts endothelial function and vascular smooth muscle cells. In addition, those with severe deficiencies are more susceptible to developing coronary artery disease, heart failure and atrial fibrillation

We know that humans who are deficient are also more likely to die from coronary heart disease and other heart-related symptoms, but it’s still being investigated whether supplementation might lower complications from heart disease, including when used with or without other interventions.

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. Deficiency seems to put people at a greater risk for depression, seasonal affective disorder, and severe mood problems experienced during PMS, insomnia and anxiety.

One reason this is true is because of vitamin D’s homeostatic, trophic and immunomodulatory effects, meaning its ability to stimulate activity of endocrine glands, support neurotransmitter production, help maintain homeostasis of the nervous system and fight inflammation in the brain. We also know that vitamin D receptors are located in brain areas such as the prefrontal cortex that are known to play a key role in mood regulation.

Low levels of D3 may interfere with activities of the hypothalamic-pituitary-adrenal axis, which can interrupt testosterone and estrogen production, leading to hormonal imbalances that can result in many unwanted symptoms.

7. Helps with Concentration, Learning and Memory

Several studies have shown that vitamin D affects cognitive function in part by reducing oxidative stress. It may be able to affect our ability to make decisions, memorize/retain information and concentrate.

Researchers indicate that people with lower levels may be at greater risk for cognitive decline, and people with lower levels have been found to perform poorly on 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
  • helping to 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. There’s also evidence that normal vitamin D levels may help protect against skin issues such as:

  • lupus erythematosus
  • ichthyosis
  • atopic dermatitis
  • hidradenitis suppurativa
  • acne
  • alopecia areata
  • androgenetic alopecia
  • melanoma
  • non-melanoma skin cancer

9. May Help Older Adults Stay Active

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. Plus, higher levels may help older adults retain normal cognitive function into older age.

10. Aids in Thyroid Function

When levels of vitamin D are low, the thyroid gland seems more susceptible to becoming dysfunctional. Therefore, vitamin D may help with maintenance of normal thyroid function, as well as adrenal and pituitary function, including by helping prevent hyperparathyroidism and hypothyroidism.

Vitamin D benefits - Dr. Axe

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?

  • 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.
  • Certain foods, such as fish, eggs and dairy products, provide some vitamin D
  • 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

The top vitamin D-rich foods include:

  • 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:


  • 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, such as 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, diarrhea and fatigue.


  • Vitamin D is a fat-soluble vitamin that we get mostly from exposing our skin to the sun. Vitamin D benefits include supporting bone metabolism, cardiovascular function, immunity against infections and illnesses, skin health, and cognitive/mental health.
  • To maintain normal levels, 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 and dairy.
  • Supplementing with D3 is another good option for those lacking this nutrient.

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