Vitamin D3 Benefits: Not Just For Strong Bones Anymore

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If you have been asking, “What does D3 do for your body?” then you’re on the right page. Keep reading to learn why you need to maintain sufficient vitamin D levels in this article.

RELATED: Calcium to Magnesium: How the Ratio Affects Your Health

In this article:

  1. What’s in a Name?
  2. Vitamin D Developments
  3. Current Research
  4. Promising Indications
  5. Vitamin D3, You, and Me
  6. Calcium Absorption, Vitamin D3, and Bones
  7. What Does D3 Do for Your Body? Other Benefits
  8. How to Meet the Recommended Dietary Allowance
  9. Dr. Treadwell Answers Your Questions

What Does D3 Do for Your Body? How Vitamin D Can Help Prevent Disease and Strengthen Bones

Depending on who you talk to, you may hear different opinions on taking vitamins.

However, recent research indicates that at least some of us, especially as we get older, may need more nutrition than our diet is providing.

Certain vitamins may also help protect us from health concerns associated with aging. Take vitamin D3, for example, and its potential benefits related to type 2 diabetes.

What’s in a Name?

Vitamin D3 is actually a steroid-like hormone that was misclassified. By definition, a vitamin is a micronutrient our cells cannot produce in sufficient quantities for optimal health.

In fact, the body is able to manufacture enough of this substance under the right conditions: exposing the skin to sunlight.

Vitamin D3 is actually a steroid-like hormone that was misclassified.

Early researchers didn’t make this connection. Instead, they observed that rickets (malformed bones related to vitamin D deficiency) didn’t occur in people on fish-rich diets.

Since the nutrient was supplied by fish oil, not the body, it was considered a vitamin. What the scientists didn’t realize was that the fish oil “vitamin” was in the sun-activated form (D3).

Vitamin D Developments

Vitamin D Softgel | Vitamin D3 Benefits: Not Just For Strong Bones Anymore | iu vitamin

In recent years, we’ve learned a lot more about vitamin D3. It binds to specific receptors on cells to elicit its response.

Contrary to earlier theories, these receptors are found in many other cells in addition to those associated with calcium transport for bone formation. Scientists have discovered them in the liver, brain, pancreas, and fat cells, to name a few.

Type 2 diabetes may be affected by vitamin D deficiency.

The list of health concerns that may be associated with vitamin D deficiency has expanded dramatically too. Along with abnormal bone formation, they may now include obesity, depression, immune system imbalances, type 2 diabetes, even cancer.

However, to establish definite connections, there’s a lot more research to be done.

Current Research

In a very recent clinical trial at Tufts University, a research team set out to determine the effects of supplementing with vitamin D3 on a specific population.

These are people at high risk of developing type 2 diabetes, or already in the early stages of the condition. Potential participants were carefully screened for experimental consistency.

The results of the Tufts University vitamin D3 clinical trial were encouraging.

Before starting the 16-week protocol, the 92 subjects underwent a series of tests to establish various baseline levels for comparison at the end of the study. They included blood sugar before and after injection of intravenous glucose and plasma blood hemoglobin protein, HbA1c (elevated in diabetic patients).

Participants were randomly assigned to one of three groups:

  • Group one took 2,000 IU of vitamin D3 only each day.
  • Group two also took 2,000 IU of vitamin D3 daily but combined with 800 mg of calcium.
  • Group three took a placebo capsule that contained neither vitamin D3 nor calcium.

Promising Indications

The results were encouraging. The vitamin D3 group, compared to the placebo group, showed a significant increase in the secretion of insulin in response to intravenous injection of glucose.

This improvement in pancreatic function means the body is better able to metabolize glucose, preventing potential damage.

The vitamin D3 group showed an improvement in pancreatic function.

Consistent with this finding, the rate of increase of HbA1c trended lower with those taking vitamin D3.

Although this data was not statistically significant, the investigators felt it was meaningful, particularly in such a short-term study. (Side note: Adding calcium didn’t produce any effect, positive or negative.)

Vitamin D3, You, and Me

Woman doing a test for diabetes | Vitamin D3 Benefits: Not Just For Strong Bones Anymore | calcium and vitamin

Because participants in the Tufts University trial were borderline type 2 diabetics (pre or early stage), the results can really only be theoretically extrapolated to this segment of the population.

The authors comment that it will take longer-term trials to support vitamin D3’s effectiveness in reducing the probability of diabetes for individuals already at high risk. They never suggest their results apply to everyone.

They didn’t imply that we all should take 2,000 IU of vitamin D per day to improve glucose metabolism and slow the onset of type 2 diabetes.

Could vitamin D3 help regulate pancreatic insulin secretion and glucose metabolism?

However, many vitamin experts do feel the optimal intake of D3 is significantly greater than the RDA of 600 mg. Many also believe the older we are, the higher the dosage should be.

Aging skin seems to be less able to absorb the sunlight needed for the body to activate enough of this micronutrient.

The upper safe limit for vitamin D was recently raised to 2,000 IU per day. Although this is still controversial (many experts feel it should be much higher), the vitamin appears to be far less toxic than previously thought, even at very high doses.

In any case, more and larger trials are definitely called for. Research needs to corroborate these preliminary indications that vitamin D3 could be key to regulating insulin secretion by the pancreas, as well as glucose metabolism.

RELATED: Eat This With That – Pairings are Greater than the Sum of Their Parts

Calcium Absorption, Vitamin D3, and Bones

In the previous paragraphs, you learned how vitamin D3 helps regulate glucose levels. In this section, we expound on an essential question: what does vitamin D3 do for your body, particularly the bones?

To answer that, let’s look into the connection between calcium and vitamin D intake.

Calcium is one of the most abundant elements in the body. It is essential for maintaining and improving skeletal health; although you can also detect calcium levels in your blood and soft tissues.

This nutrient is also necessary for the secretion of hormones and blood clotting.

Despite being vital for life, the body cannot produce it. Instead, you get calcium from calcium supplements or, better yet, a healthy diet.

Like many types of food, calcium goes through the small intestine, where it is absorbed.

Absorption of calcium, however, may not be optimal at all times. For instance, oxalates, which are naturally occurring substances in some foods, can bind to it.

The role of vitamin D3 is to help the intestines absorb calcium, so the body can finally use it.

What Does D3 Do for Your Body? Other Benefits

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Other studies highlight how vitamin D deficiency can affect the body, as well as its other potential health benefits.

1. Multiple Sclerosis

A 2018 comprehensive review showed a connection between vitamin deficiency and multiple sclerosis. Also known as MS, it is one of the autoimmune diseases that affect the central nervous system (CNS).

The immune system attacks the myelin sheath, which protects the nerve fibers. These fibers serve as communication pathways between the brain and the rest of the body.

In the review, the researchers cited a positive correlation. This means the studies associated a higher risk of MS with lower levels of vitamin D.

In some studies they looked into, they found a causal relationship. It implies lower vitamin D levels may actually lead to the autoimmune disease.

2. Crohn’s Disease

Meanwhile, a 2014 study in Inflammatory Bowel Diseases also linked lower vitamin D blood levels with Crohn’s disease.

Crohn’s Disease Definition: An inflammatory bowel disease affecting the digestive tract, especially the intestines

What does vitamin D3 do for your body in relation to your immunity (or autoimmunity)? It turns out the vitamin helps regulate your immune system and, thus, inflammatory response.

Vitamin D receptors regulate the expression of nearly a thousand genes. Some of these impact the production of T cells, which are white blood cells that search and destroy threats to immunity.

3. Alzheimer’s Disease

Some studies, such as this one in Nutritional Neuroscience, claim a relationship between vitamin D deficiency and dementia, particularly Alzheimer’s disease.

One of the possible reasons is the vitamin’s ability to reduce inflammation and protect the neurons or nerve cells. It may also promote nerve growth.

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Note, however, there is still limited information in this area. Some research studies also have mixed results.

4. Cardiovascular Disease

Many studies suggest that a deficiency in vitamin D can increase the odds of cardiovascular disease and stroke. The mechanism was unclear until a 2017 study.

Using nanosensors, scientists were able to identify how the vitamin could help maintain heart health. They learned the nutrient triggers nitric oxide, a compound that dilates blood vessels.

Nanosensors Definition: Extremely small devices used in healthcare to retrieve biological information such as changes in the body

They also found out that vitamin D helps reduce oxidative stress, a condition where there are more free radicals than antioxidants.

How to Meet the Recommended Dietary Allowance

Fish oil capsules with omega 3 and vitamin D in a glass bottle | Vitamin D3 Benefits: Not Just For Strong Bones Anymore | vitamin d supplementation

For vitamin D production, maximize the sun. You need only 20 minutes in the morning.

But unless you’re living near the equator, enough sunlight isn’t available all the time. If you have skin cancer or predisposed to it, exposure may not be the best idea.

To meet your daily dose, you may consider dietary sources of vitamin D. These include:

  • Fatty fish such as salmon and herring
  • Cod liver oil
  • Orange juice fortified with vitamin D
  • Cheese
  • Egg
  • Mushrooms

Vitamin D supplementation is also another option. It may be especially necessary to treat rickets in children.

The American Academy of Pediatrics (AAP) recommends a high dose of vitamin D of 1,000 units for infants daily. Babies between 1 and 12 months old may require up to 5,000 units every day.

For your baby’s safety, do not initiate treatment or change of dose without your pediatrician’s guidance and approval. Adults, meanwhile, should be cautious with dietary supplements containing vitamin D.

When your vitamin D levels are high, you may increase your risk of developing kidney stones. Before taking it, make sure you can test your blood levels.

Also, in the market, you’ll come across two types of vitamin D supplements:

  • Cholecalciferol (D3), which is from animal sources
  • Ergocalciferol (D2), which is from plants

Between the two, vitamin D cholecalciferol is more effective than D2. You can find this type in supplements like Juvenon Essential Multi Vitamin.

As more studies point toward the benefits of vitamin D, we learned there’s more than what meets the eye. They give you more reasons to go outdoors and soak up the sun.

What does vitamin D3 do your body? What changes did you notice? Share your experiences in the comments section below!

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Dr. Treadwell Answers Your Questions

Question: I have read about the potential benefits from taking vitamin D. I was wondering whether there is a danger in taking too much vitamin D, as some suggest taking as much as 5,000-10,000 IU per day. – D

Answer: Vitamin D is actually a hormone synthesized by the body, although often not in sufficient amounts for optimal health (hence, the “vitamin” label). How much vitamin D the body makes depends on skin tone, age (less for those of us over 50), whether your diet is high in fat, and your daily sunlight exposure.

The potential benefits of Vitamin D supplements have received a lot of attention in recent years. But scientists are still debating how much the body needs to prevent or attenuate health conditions that may be associated with deficiency.

Many feel we need a lot more than the current RDA of 400-600 IU. 2,000 IU is generally accepted as the safe upper limit.

Because of all the variables, I recommend consulting your health professional on the best dosage. I suggest staying below 2,000 IU until more research is done.

You’ll also want to select a good quality D3 supplement. Vitamin D3 is ready to be modified by the liver, kidney and various body tissues for a range of biological activities.

Dr. Benjamin V. Treadwell is a former Harvard Medical School professor.


With the growing popularity of processed foods that are high in sugar, type 2 diabetes is becoming more common. A group of
Boston-area investigators set out to determine whether supplementing with vitamin D3 would positively affect this health concern.

The team – from Tufts Medical Center, USDA Human Nutrition Research Center on Aging at Tufts University, the Departments of Nutrition and Epidemiology at the Harvard School of Public Health, and the Channing Laboratory research division of Brigham and Women’s Hospital and Harvard Medical School – recently published their findings in The American Journal of Clinical Nutrition.

Early observational studies on a possible association between low levels of plasma vitamin D and a higher risk of type 2 diabetes prompted the group’s interest. Theirs would be the first clinical trial to study the effects of supplemental vitamin D3 in humans.

The research involved 92 participants, prescreened for higher risk of developing type 2 diabetes. All the subjects were examined before the start of the trial to establish baseline levels for glucose tolerance, HbA1c (marker for blood glucose level/glycemia), insulin secretion and insulin sensitivity. These tests confirmed that 93% were at high risk and 7% were in the early stages of the condition.

The population was divided into three groups. The participants received either 2,000 IU of vitamin D3 alone, 2,000 IU of D3 plus 800 mg of calcium, or a placebo daily.

After 16 weeks, the investigators repeated the pre-trial tests.

The results? A statistically significant improvement in insulin release (pancreatic function as measured by the glucose tolerance test) for the D3 groups, as compared to the placebo group. There was, however, no change in insulin sensitivity for either D3 group. (Adding calcium had no effect within the parameters of this trial.)

Although the rate of HbAc1 formation (glycemia) trended lower in the D3 groups, as compared to placebo, this result was not statistically significant.

The research team noted their trial suggests that supplementing with vitamin D may help improve glycemia and slow the progression to clinical type 2 diabetes in adults at high risk. However, they also cautioned that, because their study lasted only 16 weeks and wasn’t powered for hard clinical outcomes, larger, longer trials are needed to confirm their findings.

Read the abstract here.

This Research Update column highlights articles related to recent scientific inquiry into the process of human aging. It is not intended to promote any specific ingredient, regimen, or use and should not be construed as evidence of the safety, effectiveness, or intended uses of the Juvenon product. The Juvenon label should be consulted for intended uses and appropriate directions for use of the product.

Editor’s Note: This post was originally published on June 21, 2011, and has been updated for quality and relevancy.