Fact checked by Aimee McNew for Accuracy
Vitamin D, the “sunshine vitamin,” is one of the few vitamins that it’s hard to obtain fully from food sources. Yet it is a critical nutrient for many aspects of health: skeletal, hormone, mental, neurological, immune, and more.
Without enough vitamin D, the body is at risk for many diseases and disorders. Many people don’t have high enough levels to be protective.
Learning how to optimize levels through sun exposure and supplementation is an important part of wellness.
However, since vitamin D is a fat-soluble nutrient, it can become toxic, so it is vital to understand how to safely supplement.
What Is Vitamin D?
Vitamin D is one of several essential nutrients, vital for protecting well-being. Unlike most, it’s very hard to obtain high enough levels from food alone.
Because you can get vitamin D from sun exposure, it is also referred to as a pro-hormone because it is synthesized in the body in response to a chemical reaction. (source)
Vitamin D has many essential benefits. The top 10 that are backed by research are discussed here, plus how it can help overall health.
10 Health Benefits of Vitamin D
While most people know that vitamin D is needed for healthy bones, along with calcium, it’s not widely known how essential this nutrient is for nearly every other aspect of health.
1. Promotes Healthy Sleep
When people have lower levels of vitamin D, they sleep worse. In fact, low levels can be blamed for disturbed sleep patterns and shorter sleep duration. (source)
Research finds that higher blood concentrations of vitamin D are associated with better regular sleep. Sleep quality can also be improved by supplementing with vitamin D. (source)
Beyond regular sleep disturbances, low vitamin D levels are also associated with sleep apnea. This condition results in numerous nightly episodes of breathing cessation and can lead to serious health problems.
Optimizing vitamin D levels, with other treatments, can address this condition. (source)
2. Supports Neurological Health and Cognition
Vitamin D is an essential nutrient for the brain, cognition, and neurological health. Receptors for vitamin D are found in the brain and research shows that this nutrient and hormone is vital for proper brain development and function. (source)
Deficiency of vitamin D creates problems that could lead to psychiatric or neurological disorders. These can include:
- Alzheimer’s (source)
- Dementia (source)
- Poor cognitive function (source)
- Parkinson’s disease (source)
Vitamin D protects the brain and nervous system in many ways. It promotes healthy detoxification and antioxidant levels, which help to prevent brain cell degradation.
It also creates proteins that help brain cells fight premature aging and promote normal function. (source)
3. Defends Against Certain Types of Cancer
Overall, vitamin D is protective against many types of cancer and lowers the overall risk of death when levels are optimal. (source)
It helps the body to prevent the spread of cancer cells and can even rally the protective mechanisms in the body that destroy and remove cancer cells. (source)
Research shows vitamin D to be especially protective against breast cancer. Women with higher intake levels and regular sun exposure were shown to have a reduced risk of developing or dying from breast cancer. (source)
Supplementation with at least 2,000 IU daily reduces the chance of developing breast cancer by 50 percent. (source) Conversely, when vitamin D levels are too low, breast cancer can progress faster, metastasize, and be harder to treat. (source)
Vitamin D also reduces the risk of colon cancer, with at least 1,000 to 2,000 IU daily reducing the chances by 50 percent. (source)
Men who get more vitamin D from the sun have a reduced risk of dying from prostate cancer, too. But when men have too little vitamin D, their risk of developing prostate cancer significantly goes up. (source)
Pancreatic and ovarian cancer risks, too, are reduced by vitamin D. Intake of 600 IU or more daily reduced pancreatic cancer risk by more than 40 percent, and research finds that overall low levels of vitamin D are associated with a lower survival rate from ovarian cancer. (source, source)
4. Decreases Depression
The benefits of vitamin D for brain health extend well beyond cognition and neurological disorders. Having too little vitamin D or being deficient in it is related to a 14 percent higher chance of depression.
Boosting levels through supplementation and sun exposure can reduce depression. It can also help to improve the ability to function in people who are depressed. (source)
5. Supports Optimal Bone Health
Vitamin D is important for helping keep calcium levels properly balanced in the body, which is essential for bone health. (source)
Vitamin D works to optimize calcium levels by helping the intestines more effectively absorb calcium from the diet and to resorb it from the kidneys. (source)
Bone mass is also influenced by parathyroid hormone, which can lead to bone loss. Vitamin D suppresses the elevated activity of parathyroid hormone, helping to protect bone density. (source)
Without enough vitamin D, bones also struggle to grow and form. Vitamin D helps promote the function of osteoblasts, the cells that rebuild bone. (source)
Vitamin D is so important that deficiency in the mother can even affect fetal bone skeletal development. (source)
It’s also an important nutrient for preventing and treating osteoporosis and osteopenia. Low levels of vitamin D in the blood lead to higher risks of fracture, poor bone density, and mineralization problems. (source)
Those at highest risk for osteoporosis and fracture can reduce the chance by 43 percent when taking a combination of eggs and vitamin D3 together. (source)
6. Lowers Risk of Heart Disease
When you don’t have enough vitamin D, many aspects of health can suffer. It is especially noted that there is an increased risk of heart disease when vitamin D is deficient.
This also includes a higher risk for high blood pressure, heart attack, and stroke. (source)
Supplementing with vitamin D and boosting levels via sun exposure have been shown to reduce blood pressure, protect blood vessel function, and reduce several risk factors for atherosclerosis. (source)
With blood pressure specifically, people whose blood levels are lower than 30 ng/mL face a higher risk of hypertension than those whose levels are above 30 ng/mL.
7. Reduces Risk of Diabetes
Vitamin D is essential for healthy glucose levels and insulin management. It helps optimize insulin production and secretion from the pancreas.
Without enough vitamin D, the risk goes up for type 1 and type 2 diabetes, as well as metabolic syndrome. (source)
When insulin problems exist, supplementing with vitamin D helps to restore insulin sensitivity and production. (source)
Vitamin D is so crucial for pancreatic and insulin function that drastically low levels in childhood can increase the chance for later developing type 1, or autoimmune, diabetes. (source)
Research also associated lower blood levels of vitamin D with a diagnosis of type 2 diabetes. Supplementing daily with at least 500 IU helps reduce the risk. (source)
8. Fights Inflammation and Boosts Immunity
Vitamin D is an important component of the immune system. While inflammation can be a healthy response to healing, when it turns into chronic inflammation, it can wreak havoc on the body and lead to disease.
Vitamin D can influence immunity from boosting the ability to fight infectious disease to calming the immune system’s attack of self in autoimmune disorders. (source)
It can also cool the body’s chronic inflammatory levels and provide relief for disorders like rheumatoid arthritis, Hashimoto’s thyroiditis, fibromyalgia, and more.
9. Supports Intestinal Health
Vitamin D can promote intestinal health, especially when it comes to inflammatory bowel disease, which primarily affects the large intestine, and celiac disease, which affects the small intestine. (source, source)
Both are critical components of the digestive system.
Supplementing with vitamin D helps to reduce blood markers associated with gut inflammation and can also decrease C-reactive protein, another inflammatory marker, by as much as 46 percent. (source)
10. Supports Fertility and Pregnancy
Vitamin D is critical for both male and female fertility. Animal studies show that vitamin D is needed for healthy sperm count and motility, as well as healthy testicles. (source)
Men with vitamin D levels that are lower than 20 ng/mL are considered deficient and research shows that they have less healthy sperm than men with higher vitamin D levels. (source)
Women need healthy vitamin D levels for overall fertility, too. It’s also important when facing fertility challenges, like PCOS (also known as polycystic ovary syndrome).
Optimizing vitamin D levels is beneficial for addressing glucose imbalance and regulating the menstrual cycle in PCOS. (source)
Vitamin D is also important for a healthy pregnancy for both mother and baby. When levels are too low, the fetus could have bone growth and skeletal problems and the mother could experience greater amounts of bone density loss. (source)
Having adequate vitamin D levels can also help to protect against the risk of preterm birth. (source)
When vitamin D levels are not healthy during pregnancy there is a greater risk for preeclampsia and bacterial vaginosis. (source)
Supplementing with at least 4,000 IU daily during pregnancy is considered to be both safe and effective. During breastfeeding, 6,400 IU daily is needed to ensure that the infant gets enough via breast milk.
How to Get Enough Vitamin D
It is important to get enough vitamin D for many reasons, but how to accomplish that isn’t always so straightforward.
You can boost vitamin D levels in three ways: sun exposure, food sources, and supplements.
Sun: The sun is the best and most efficient way to have healthy vitamin D levels. However, being in the sun is not an option for everyone.
Additionally, people who live far enough above or below the equator cannot get enough direct sun exposure approximately six months out of the year, making supplementation necessary.
If you have lighter skin, spending 10 to 15 minutes in the sun per day is often enough to optimize levels. The key is that you have to have most of your trunk, arms, and legs exposed and cannot be wearing sunscreen during this time.
Those with darker skin complexions will need 20 to 30 minutes to achieve the same results.
Unless you live near the equator, this can only be accomplished from about April through September each year in the northern hemisphere and October through March in the southern hemisphere.
Food: There are few foods that are rich sources of vitamin D. The best sources are fatty fish like salmon and mackerel, along with cod liver oil, beef liver, egg yolks, cheese, and mushrooms.
Other foods are fortified with vitamin D, but the type used is not as absorbable (vitamin D2). More on that below.
Supplements: Supplements are widely available in both vitamin D2 and D3 forms. Vitamin D3 is the closest to the type the body makes from the sun and is highly absorbable.
Vitamin D2 does not successfully raise blood levels. Doses range from a few hundred to 10,000 IU or more per dose.
Doses: It’s important to consult your doctor for recommendations on vitamin D doses. The minimum requirements are as follows:
- Children under age one—400 IU
- Adolescents and children under 19—600 IU
- Adults ages 19-70, including pregnant women—600 IU
- Adults over age 70—800 IU
Most health professionals recommend 2,000 IU daily as the minimum supplemental dose, but testing needs to be done to verify that levels are adequate.
Certain health factors can reduce the body’s ability to absorb vitamin D, requiring higher levels of supplementation just to prevent deficiency.
Vitamin D Deficiency and Toxicity
Vitamin D deficiency is one of the most common nutritional problems across the world. As many as 80 percent of people on all continents have a vitamin D deficiency or insufficiency. (source)
The best way to evaluate levels is to test via the blood using the 25(OH)D method. Deficiency is a result lower than 20 ng/mL, whereas insufficiency is lower than 30 ng/mL.
Optimal levels are defined differently by practitioners, but most agree that between 40 and 65 ng/mL is ideal.
Symptoms of vitamin D deficiency can include:
- Muscle aches and weakness
- Joint pain
- Back pain
- Digestive problems
- Mood swings
- Poor immunity
- Frequent infections
- The presence of chronic or autoimmune conditions
While vitamin D deficiency is dangerous for health and has negative consequences, too much is also not ideal.
Vitamin D toxicity can occur because it is a fat-soluble nutrient, so taking too much in supplemental form can get stored in the tissues and result in serious problems, including:
- Calcification of tissues
- Kidney damage
- Heart damage and problems
Symptoms of too much vitamin D include:
- Metallic taste in the mouth
- Poor appetite
- Nausea and vomiting
- Kidney stones
Always check with your doctor about supplement doses and get your blood levels assessed at least once per year and more often if you take vitamin D supplements.
This article was fact checked for accuracy by Aimee McNew, MNT, a certified nutritionist. As always, this is not personal medical advice and we recommend that you talk with your doctor.
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Aimee McNew, MNT, CNTP, is a certified nutritionist who specializes in women’s health, thyroid problems, infertility, and digestive wellness. She ate her way back to health using a Paleo diet, lost 80 pounds, and had a healthy baby after numerous miscarriages. She focuses on simple nutrition practices that promote long-lasting results.