Learn About The Health Benefits Of Vitamin D | Cooper Complete
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Health Benefits of Vitamin D

Image of foods that contain vitamin D3

Getting enough of the “sunshine vitamin” has many perks. Most of us know that vitamin D is essential for building and strengthening our bones, but the health benefits of vitamin D don’t stop there.

Vitamin D is a fat-soluble vitamin stored within the liver and other fatty tissues for use when the body needs it. Found in some foods and produced by the body when the skin is exposed to sunlight, vitamin D is a key player in absorbing and retaining essential nutrients – calcium, magnesium and phosphate. Without sufficient vitamin D, the body would only absorb 10 to 15 percent of dietary calcium consumed through foods (Harvard Health, 2007). The most important compounds are vitamins D2 and D3.


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Vitamin D deficiency is still common in the United States. Results for the most recent analysis of the National Health and Nutrition Examination Surveys (NHANES) for 2001 to 2014 were published in 2022. Of 71,685 participants, 2.6 percent had severe vitamin D deficiency, while 22 percent had moderate deficiency. Deficiency is more common in women, and the highest deficiency rates were seen in young non-Hispanic black American women ages 20-29, particularly in winter when less vitamin D is absorbed through sunlight. Issues that are predictors of severe vitamin D deficiency include:

  • Age
  • Gender
  • Ethnicity
  • Season
  • Sun-protective behaviors (clothing and sunscreen)
  • Lower BMI
  • Lower socioeconomic status
  • Drinking
  • Lower milk consumption

Strong Teeth and Bones

High levels of calcium and vitamin D play an essential role in the health of our bones and oral health. Our bodies need it to absorb better calcium, which strengthens bones and can help prevent osteoporosis. Inadequate calcium intake can lead to joint pain, early-onset osteoarthritis, and tooth loss. Vitamin D deficiency is recognized as a major cause of bone disease in the elderly. Studies show that ample vitamin D can reduce the risk of cavities, tooth decay and gum disease.

Immune System Support

One of the significant health benefits of vitamin D is its ability to fight illness and infection. Studies show that those with higher amounts of vitamin D are less likely to catch colds or develop flu symptoms. Vitamin D stimulates T cells, which help promote a proper response to infectious pathogens that cause illnesses. A study published in the American Journal of Clinical Nutrition found a 42 percent decrease in the incidence of influenza in school-aged children among those taking a supplemental dose of 20 mcg (1200 IU) of vitamin D.

In a meta-analysis published in The British Medical Journal of 25 randomized clinical trials totaling 11,321 participants, vitamin D supplementation was found safe and protected against acute respiratory tract infection overall. The patients who were the most deficient and those who had daily vitamin D supplementation (rather than bolus doses monthly) experienced the most benefit. The authors conclude, “Our study reports a major new indication for vitamin D supplementation: the prevention of acute respiratory tract infection. We also show that people who are very deficient in vitamin D and those receiving daily or weekly supplementation without additional bolus doses experienced particular benefit. Our results add to the body of evidence supporting the introduction of public health measures such as food fortification to improve vitamin D status, particularly in settings where profound vitamin D deficiency is common.”

One study of 19,000 subjects related to vitamin D and immunity found that people with blood levels below 30 ng/ml were likelier to experience an upper respiratory infection, even when adjusting for variables such as season, age, gender, and weight.

People deficient in vitamin D with asthma were five times more likely to get sick than their counterparts with healthy vitamin D levels.

(Bonus: Kenneth H. Cooper, MD, MPH,  Founder and Chairman of Cooper Aerobics, shares nine tips for improving immune health.)

Vitamin D Anti-inflammatory Effect

Studies have shown vitamin D may help chronic inflammation by playing a role in regulating the body’s inflammatory response, especially against autoimmune diseases. A recent observation from a controlled trial reported that adults who took 50 mcg (2000 IU) of vitamin D3 daily for up to five years reduced their risk of all autoimmune disorders by 22 percent compared to the group that did not.

Studies also show that those who have higher amounts of vitamin D in their diet have a decreased risk of developing multiple sclerosis (MS), a disease where the immune system attacks the central nervous system.


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Going back to 2017, a large study (11,321 participants ages 0-95 years) published in The British Medical Journal, titled “Vitamin D Supplementation to Prevent Acute Respiratory Tract Infections: Systemic Review and Meta-analysis of Individual Participant Data,” showed that vitamin D supplementation was safe and protected against acute respiratory infections. Patients who experience the most benefit are those who are extremely vitamin D deficient and not those receiving single large doses.

In 2018, an analysis of vitamin D and respiratory health in the Busselton Healthy Ageing Study population (in Western Australia) showed blood levels of 25-hydroxy vitamin D less than 20 ng/mL were associated with asthma, bronchitis, wheezing and chest tightness. Higher vitamin D levels greater than 40 ng/mL were associated with a reduction of respiratory symptoms and higher levels of lung function.

The Irish Medical Journal published an article in 2020, titled “Vitamin D and Inflammation: Potential Implications for Severity of COVID-19.” The authors pointed out that vitamin D is produced in the skin primarily through sunlight exposure. It is transported to the liver and the kidney, where it is changed to an active hormone that increases calcium transport from food in the gut and ensures calcium is adequate to keep the skeleton strong and free from osteoporosis. Also, vitamin D can support the immune system through a number of immune pathways involved in fighting SARS-CoV-2. This study showed that counterintuitively, in countries at lower latitudes and typically sunny countries such as Spain and Northern Italy, people likely used sunscreen to protect against sun exposure, thus having lower concentrations of vitamin D and higher rates of vitamin D deficiencies. These countries also experienced the highest infection death rates in Europe.

Since pneumonia and respiratory problems are the most common causes of death in COVID-19 infections, findings from this meta-analysis, “Vitamin D to prevent exacerbations of COPD,” should also be considered (Pak J Med Sci volume 33, 2017). The findings support a strategy of routinely testing vitamin D status in patients with COPD who experience exacerbations and offering supplementation to those with circulating 25-hydroxy vitamin D concentrations of less than 25 ng/mL but not in those with higher levels.

Potential to Fight Against Multiple Diseases

Research suggests the health benefits of vitamin D may be associated with fighting many diseases and could play a role in:

Vitamin D and Cancer

The VITAL study was a randomized, placebo-controlled trial, enrolling almost 26,000 men (≥ 50 years of age) and women (≥ 55 years of age) who were treated with either vitamin D3 (50 mcg ( 2000 IU) per day) or placebo and marine n−3 (also called omega-3) fatty acids (1 gram per day) or placebo for the prevention of cancer and cardiovascular disease. (This is called a two-by-two factorial design.) The participants were followed for a median of 5.3 years, with a range of follow-up from 3.8 to 6.1 years. The primary endpoints were invasive cancer of any type and major cardiovascular events.

This study concluded that supplementation with vitamin D did not result in a lower incidence of invasive cancer than a placebo. “Incidence of invasive cancer” means new cancer cases diagnosed during the study’s duration. 

Recall that this study followed participants for 3.6 to 6.1 years, with half followed for less than five years. Can we really test whether any intervention reduces the risk of developing cancer in a study with this short length of follow-up? For most cancers, the answer is no.

Cancers begin as just one cancer cell. This single cancer cell doubles to become two cancer cells, then two cells double to become four cancer cells and so on. The doubling time can vary depending on many factors, such as the type of tumor and the ability of the patient’s body to resist cancer; it can range from days to years, averaging three to four months.

A single cell needs 30 doublings to reach a (generally) detectable size (1 cm, 0.4 inches or a billion cells). For example, if a cancer has a doubling time of three months, it will take 90 months (7.5 years) for it to be detectable by an imaging test or physical examination.  In one study of different types of lung cancers, the average doubling time was 303 days for adenocarcinomas and only 70 days for small-cell lung cancer. Thus, the time from cancer initiation to detection could be as long as 25 years and as short as six years. So, it is highly likely that most, if not all, of the “newly diagnosed” cancers identified in the study were already present but not yet detected.

There’s a lot of basic science work showing vitamin D can:

  • Slow the growth of cancer cells
  • Stimulate cell death
  • Reduce blood vessel growth to tumors
  • Decrease inflammation
  • Stimulate the body’s immune system to fight cancer

Thus, vitamin D may decrease tumor invasiveness and the likelihood of tumor metastases, leading to a reduced risk of death from cancer.

The results of the Vital study regarding the impact of vitamin D on death from cancer supported these basic science findings about vitamin D and cancer growth. The rate of death was not proportional during the duration of the study; this means the rate of death each year was not the same. More than one-third of the cancer deaths occurred in the first two years of the study. These participants who died early clearly had aggressive cancers once diagnosed or cancers diagnosed at an advanced stage.

When the authors analyzed the data without the early cancer deaths during the first two years of follow-up, they found that participants who took vitamin D had a 25 percent reduced risk of dying from cancer. So even though cancer was present, it was less likely to progress as rapidly, resulting in death.  These findings suggest that Vitamin D supplementation could prolong life in the presence of cancer.

In a subgroup analysis in the VITAL study, participants with a normal body mass index (BMI) < 25 who were treated with vitamin D were significantly less likely to be diagnosed with a new cancer during the study (almost a 25 percent reduction in risk) suggesting a slowing of tumor growth. This benefit was extinguished at higher BMI levels.  It is well known that excess weight is associated with an increased risk of multiple cancer types; this benefit of vitamin D at the current supplement dose appears to be extinguished at higher weights.

Finally, one very important criticism of this trial was the failure to measure vitamin D levels throughout the study in a large number of participants to confirm that vitamin D levels remained constant in the placebo group and increased in the vitamin D group.

Colorectal Cancer, also called bowel cancer, develops in the colon or the rectum, both parts of the gastrointestinal (digestive) system. The American Cancer Society says excluding skin cancers, colorectal cancer is the third most common cancer diagnosed in both men and women in the United States. The American Cancer Society estimates there will be 106,590 new cases of colon cancer and 46,220 new cases of rectal cancer in the United States in 2024.

Published by the health journal Gut, research showed a link between vitamin D and the immune response to cancer in a large human population for the first time. “People with high levels of vitamin D in their bloodstream have a lower overall risk of developing colorectal cancer,” said the study’s lead researcher Shuji Ogino, MD, PhD, from Harvard Medical School and Dana-Farber Cancer Institute. “Laboratory research suggests that vitamin D boosts immune system function by activating T [immune] cells that recognize and attack cancer cells. In this study, we wanted to determine if these two phenomena are related: Does vitamin D’s role in the immune system account for the lower rates of colorectal cancer in people with high circulating levels of the vitamin?”

There is ongoing research surrounding vitamin D and breast cancer, and prostate cancer. A study of more than 7,800 participants found that the results from seven eligible studies indicated higher vitamin D level was significantly associated with decreased all-cause mortality and prostate cancer-specific mortality. In addition, a 2019 meta-analysis found that vitamin D significantly reduced the total cancer mortality rate.


Many people with diabetes exhibit low levels of vitamin D. This nutrient deficiency is associated with decreased insulin release, which means vitamin D could slow down the progression of diabetes for those who already have it. Some studies also show that it may help lower average blood sugar levels in those with type 2 diabetes.

Potential Weight Loss Aid

An increase of vitamin D in the diet may help shed pounds. In one study, people with obesity who took vitamin D supplements, along with following a weight-loss diet plan, lost more weight and fat mass than those who only followed the diet plan.

An article (Vitamin D Deficiency: Consequence or Cause of Obesity?) published in 2019 notes that while vitamin D deficiency isn’t a cause of obesity, there is a strong link between the two, theorizing that excess fat, liver and muscle mass may halt the absorption of the nutrient.

Mood Booster and Depression Fighter

High amounts of vitamin D, especially from sunlight, are shown to help regulate mood and reduce the risk of depression. A meta-analysis of randomized controlled trials revealed that those experiencing negative emotions who took vitamin D supplements saw an improvement in symptoms. Another study involving 593 patients concluded low vitamin D levels were a risk factor for fibromyalgia, anxiety and depression.

(Bonus: Read about the nine supplements that may relieve symptoms of depression.)

Are You Getting Enough Vitamin D?

Vitamin D deficiency is the most common nutritional deficiency worldwide. Lower vitamin D levels are a result of many factors, including:

  • Sun avoidance
  • Using sun protection (though it is necessary to protect your skin during prolonged time outdoors)
  • Skin pigmentation
  • Poor dietary and supplement intake
  • Malabsorption syndromes
  • Obesity
  • Medication use

To reap the benefits of vitamin D, your body must get enough. There is only one way to determine your vitamin D level—a blood test called 25-hydroxyvitamin D. The test classifies results as follows:

BLOOD TEST 25-hydroxy vitamin D
Nanograms per milliliter
Deficient = <20 ng/mL
Insufficient = 21-29 ng/mL
Normal = 30-100 ng/mL
Toxicity >150 ng/mL
Cooper Clinic recommended range = 40-60 ng/mL
50 mcg Vitamin D3 = 2000 IU
125 mcg Vitamin D3 = 5000 IU

Vitamin D is a fat-soluble vitamin that needs fat in order to be absorbed. Taking vitamin D with a meal that contains fat can increase absorption by 50 percent. Cooper Clinic has been testing vitamin D levels in all patients since 2007 and recommends a 25 hydroxyvitamin D level of 40 ng/ml, but some doctors prefer to see lab values over 50 ng/ml.


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How Do You Get More of the Sunshine Vitamin?

Whether it’s through foods, sunlight or supplements, it is important your body gets adequate vitamin D. Here’s how:

Vitamin D From Sunshine

The best way to get vitamin D is from the sun. It’s estimated that a fair-skinned person in shorts and a tank top without sunscreen gets enough radiation to produce almost 250 mcg (10000 IU) of vitamin D from 10 minutes midday. However, the amount of vitamin D your body produces differs depending on the time of day and the time of year.  For example, the further north you live, the harder it is for your body to produce vitamin D in the winter. This effect is mirrored the further south of the equator where you live.

For your body to produce vitamin D, the sun should be positioned in the sky so your shadow is shorter than you.  If your shadow is longer than you, the sun’s UV rays are not intense enough for vitamin D production.

A good rule of thumb is to try and get sun exposure when the sun is in its highest position (typically around midday) for half as long as it takes your skin to become pink. After exposure, the nutrient is stored and released when sunlight is unavailable.

Incidentally, this is where D gets its cheery nickname, “the sunshine vitamin.” This process starts when the skin absorbs the sun’s ultraviolet B (UVB) rays. Next, your skin takes the UV light and uses a process called “photolysis” to form vitamin D. The newly created vitamin D heads to the liver to perform its bodily functions. While the sun is the most natural way to get vitamin D, many factors prohibit this process from producing optimal levels, including:

  • Some seasons
  • Where someone lives
  • Age and skin color
  • Distance from the equator

In the warmer months, sunscreen use not only prevents an uncomfortable sunburn but also prevents vitamin D absorption by blocking UVB light up to 99 percent at SPF 30. For good dermatological health, sunscreen is necessary, so conscientious users must find alternative ways to obtain vitamin D.

Vitamin D From Food

Vitamin D, though found in food, is not prevalent or abundant. Seafood is your best bet to find vitamin D naturally. Many products are being fortified with vitamin D. Fortified milk, orange juice, yogurt, and cereal are popular buys. However, it is still unlikely that you will get the desired level of vitamin D solely from food sources. Here are some food options that can help increase your intake:

  • Fatty fish such as salmon (447 IU), tuna (70 IU) and mackerel (855 IU) per 3 ounces
  • Beef liver – 50 IU in a 3.5 oz
  • Cheese – 7 IU per 1 oz cheddar
  • Egg (whole large) – 41 IU (1 mcg)
  • Mushrooms – 400 IU per serving (if exposed to UV light)
  • Fortified milk – 115-125 IU (3 mcg) per cup
  • Fortified breakfast cereal – 40 IU (1 mcg) per cup)
  • Sardines – 270 IU (7 mcg) in 3.5 oz
  • Some orange juice (137 IU), yogurt (80-120 IU) and drinks with soy (100-119 IU) are fortified

We all agree that a balanced, nutritious diet is the best way to obtain necessary nutrients, but building a 50+ mcg (2000+ IU) diet from natural and fortified foods is incredibly difficult.

Vitamin D Supplements – D3 or D2?

Getting enough vitamin D through sunlight and food can be difficult. And, as we age our bodies naturally as we age. But supplementation can help ensure you get the health benefits of vitamin D. There are two forms of vitamin D supplements available (D2 and D3). However, most studies show D3 to be more easily absorbed by the body, which is why our physician-formulated Cooper Complete vitamin D supplements use the D3 form.

Since 2007, Cooper Clinic has measured the blood level of 25-hydroxy vitamin D in more than 80,000 healthy patients. The patient population, including many people of color, mirrors the findings from studies that show people of color have lower levels of vitamin D unless they are taking vitamin D supplements. Cooper Clinic recommends all patients with values less than 40 ng/mL take at least 2000 IU (50 mcg) of vitamin D3 daily. By following this recommendation, return patients have seen 25-hydroxy vitamin D values rise from 30 ng/mL to almost 40 ng/mL over the years.

Vitamin D supplements can help treat deficiency. Cooper Complete tableted multivitamins contain 50 mcg (2000 IU) of vitamin D. Additionally, Cooper Complete offers stand-alone D3 supplements.

Your physician best understands your current health profile. Consult your physician before adding any new nutritional supplement to your diet.

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