Vitamin D3: Better Cognition, Bone Strength, and Heart Health

An estimated one billion people worldwide are deficient in vitamin D, also known as the sunshine vitamin. Created by skin’s exposure to sunlight, Vitamin D regulates calcium and phosphorus and prevents numbness and tingling in muscles and weak and brittle bones.

Because the deficiency of vitamin D is so prevalent, doctors often recommend taking a supplement.

In this article, you’ll learn why taking a good vitamin D supplement is essential for maintaining healthy muscles, bones, and immunity.

Why Vitamin D Deficiency is so Prevalent?

Although our body can create vitamin D from sunlight exposure, the deficiency of this essential micronutrient is prevalent. Let’s see why this is the case.

How does our body form Vitamin D?

When UVB rays fall onto the skin, they break the cholesterol and convert it into an inactive form of vitamin D. Liver and kidney then synthesize the inactive Vitamin D3 into its active form, i.e. calcitriol.

But several factors hamper the production of vitamin D, factors that include:

  • Distance from Equator: More distance from equator means less UVB rays falling on skin.
  • Skin Pigmentation: Melanin in your skin reduces the production of vitamin D.
  • High Level of Pollution: Pollution particles can deflect the UVB rays and stop them from reaching your skin.
  • Time of the year: During winters, the amount of UVB rays reaching to the surface of the earth decreases.

Symptoms of Vitamin D Deficiency

Symptoms of Vitamin D Deficiency

Symptoms of vitamin D deficiency manifest over a long period of time. It is usually calcium deficiency that displays real symptoms.

Symptoms of vitamin D deficiency include:

• Tiredness
• Aches in muscles and bones
• Numbness and Tingling
• Stress Fractures (in legs, pelvis, and hips)
• Osteoporosis (weak bones)
• Osteomalacia (soft bones)

Q. Why vitamin D deficiency can cause fasciculation (muscle twitching) and pain?

Ans. Since vitamin D enables the absorption of calcium, a lack of vitamin D leads to calcium deficiency. As an important electrolyte, calcium carries signals between nerve cells. A lack of calcium leads to fasciculations and muscle pain.

However, as soon as you start taking vitamin D and calcium supplements to correct such a deficiency, the fasciculation and pain generally disappear very quickly.

Reference Daily Intake of Vitamin D

RDI for vitamin D is measured in International Units (IU), the standard measurement for vitamins and drugs. However, we’ve mentioned the intake value in mcg as well.

Table: Vitamin D Recommended Amount according to NIH

Life StageVitamin D (IU/day)Vitamin D (mcg/d)
Children and Teens60015
Adults, up to age 7060015
Adults, ages 71+80020
Pregnant and Breastfeeding Women60015

Note: Don’t take more than 4,000 IU of vitamin D supplement per day.

Why to take Vitamin D3 1,000IU per day?

Despite the recommended limit set at 800 IU, many doctors recommend that you take 1000 IU of vitamin D, especially if you don’t get it from sunlight. Taking 1,000 IU(25mcg) of Vitamin D per day will help 50% people reach a level of 33ng/ml (82.4 nmol/l).

Benefits of Vitamin D

Vitamin D plays a vital role in modulating not only calcium and potassium channels but also the immune system.

Immunity Against Diseases

Clinical studies prove vitamin D’s ability to provide immunity against infectious diseases.

Taking vitamin D reduces the likelihood of developing the flu (influenza A).[1]

Children who were given a single high-dose oral vitamin D3 supplement with antibiotics experienced reduced episodes of pneumonia.[2]

Does Vitamin D provide immunity against Covid 19?

Vitamin D can improve the outcome of covid 19, according to many medical experts. Vitamin D supplementation can lower the incidences of respiratory tract infections caused by viruses. This is especially true for people deficient in Vitamin D.

Does Vitamin D provide immunity against Covid 19

According to a study, there is significant correlation between higher risk of Covid-19 and vitamin D deficiency.

A recent study found that 82.2 percent of covid-19 patients in a hospital in Spain were deficient in Vitamin D. Also, inflammatory markers were high in people who have covid 19 and a vitamin D deficiency, markers that have been linked to poor covid-19 outcomes.

According to José L. Hernández, Ph.D., of the University of Cantabria in Santander, Spain, “Vitamin D treatment should be recommended in COVID-19 patients with low levels of vitamin D circulating in the blood since this approach might have beneficial effects in both the musculoskeletal and the immune system.”

Improves Bone and Muscle Strength

Improves Bone and Muscle Strength

Vitamin D facilitates the absorption of calcium from food into blood. From there, vitamin K2 helps the bones in absorbing the calcium from blood into the bones, making them stronger.

Without vitamin D, your body can’t absorb calcium, leading to osteoporosis (weak bones) and Osteomalacia (soft bones). Overtime, a person deficient in vitamin d and calcium may suffer from stress fractures, especially in legs, pelvis, and hips.

In one study focused on the elderly, supplementation with vitamin D3 (cholecalciferol) enhanced blood levels of 25(OH)D and improved lower limb muscle strength, in the absence of physical exercise. Further, the supplement was well tolerated.[3]

Reduces Depression

Vitamin D has an ability to regulate mood and fight off depression. A study suggests a causal inverse relationship between levels of 25(OH)D (storage form of vitamin D in body) and symptoms of depression.[4]

Reduces Depression

Vitamin D deficiency is linked to low mood and impairment of cognitive performance. Further, it can also increase anxiety.

Vitamin D and Seasonal Affective Disorder

In the winters, the atmosphere absorbs most of the UVB radiations, so even prolonged exposure to sunlight fails to provide sufficient levels of Vitamin D. Hence seasonal vitamin D deficiency is quite common during winters.[5]

Seasonal affective disorder happens in winter and presents depression like symptoms. Vitamin D supplementation can ameliorate the symptoms of seasonal affective disorder.[6],[7]

May Prevent Heart Disease and Boost Weight loss

In cross-sectional studies, low levels of vitamin D were linked to increased risk of cardiovascular disease such as:

  • Hypertension
  • Heart failure
  • Ischemic Heart Disease
May Prevent Heart Disease and Boost Weight loss

Weight Loss

Sometimes, losing weight just seems impossible. Even on an extreme diet, it’s difficult to cut down belly fat and get to the desired body fat percentage level.

To lose weight or prevent heart disease, you should add vitamin D to your daily diet.

Taking calcium and vitamin D together can have an appetite-suppressing effect, aiding you in weight loss and improving cardiovascular disease risk markers, especially in overweight subjects.[8]

Reduces Risk of Multiple Sclerosis and other Autoimmune Diseases

Multiple sclerosis(MS) affects 2 million people worldwide[9]. Inflammation of the body may lead to inflammatory T-cell mediated autoimmune disease, causing demyelination and death of axons. Overtime, the muscles in the body become weak as the nerves die.

Reduces Risk of Multiple Sclerosis and other Autoimmune Diseases

Vitamin D regulates:

  • Immune System
  • Endocrine System
  • Autoimmune Diseases
  • Transplantation Tolerance

It’s been noted that as you move away from

As an immunomodulator, vitamin D reduces the risk of autoimmune diseases such as multiple sclerosis(MS).[10]

Vitamin D Overdose and Toxicity

How are vitamin D levels calculated?

25(OH)D (storage form of vitamin D in the body) levels are checked to ascertain the current vitamin D levels in the body.

Here’s what different levels of vitamin D mean:

  • Deficiency Levels: less than 12ng/ml (30nmol/l)
  • Insufficient Levels: less than 20ng/ml (50nmol/l)
  • Adequate levels: 30ng/ml (75nmol/l)
  • Vitamin D Council Recommendation: 40ng/ml – 80ng/ml (100nmol/l-200nmol)
  • Harmful blood levels: anything above 100ng/ml (250nmol/l)
  • Intoxication blood levels: 150ng/ml (375nmol/l)

Although vitamin D keeps your body healthy and well functioning, vitamin D toxicity is still possible. As a fat soluble vitamin, Vitamin D can be stored in the liver and excess amount isn’t excreted out via urine. Taking high dose Vitamin D supplements for a long period of time may cause toxicity.

High dose vitamin supplements are:

  • More than 4,000IU/day
  • More than 50,000IU/week after deficiency is corrected

How long do symptoms of vitamin D toxicity last?

Symptoms of vitamin D toxicity may last for up to a year. Since the nutrient is stored in body fat, it is released slowly over several months.

Symptoms of vitamin D toxicity include:

  • Nausea
  • Constipation
  • Weakness
  • Kidney Damage

If you experience any side effects, reach out to your healthcare provider immediately.

Note: Exposure to sunlight doesn’t cause vitamin D toxicity.

Vitamin D Natural Sources

Vitamin D rich foods include:

  • Salmon
  • Cod Liver Oil
  • Sardines and Herring
  • Egg Yolks
  • Canned Tuna
  • Mushrooms
  • Fortified Foods such as milk

However, we don’t always consume a balanced diet, making it necessary to rely on supplements.


Since adequate intake of vitamin D is difficult from natural sources, it is recommended by experts to take 1,000IU/day supplement for the same. Not only will this improve your bone and muscle strength but it will also reduce the risk of serious chronic illnesses such as heart disease and multiple sclerosis.


[1] Urashima M, Segawa T, Okazaki M, Kurihara M, Wada Y, Ida H. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr. 2010 May;91(5):1255-60. https://doi.org10.3945/ajcn.2009.29094
Epub 2010 Mar 10. PMID: 20219962.

[2] Manaseki-Holland, Semira et al. “Effects of vitamin D supplementation to children diagnosed with pneumonia in Kabul: a randomised controlled trial.” Tropical medicine & international health : TM & IH vol. 15,10 (2010): 1148-55.

[3] Moreira-Pfrimer, Linda D F et al. “Treatment of vitamin D deficiency increases lower limb muscle strength in institutionalized older people independently of regular physical activity: a randomized double-blind controlled trial.” Annals of nutrition & metabolism vol. 54,4 (2009): 291-300.

[4] Effects of vitamin D supplementation on symptoms of depression in overweight and obese subjects: randomized double blind trial.

[5] Michael F Holick, Vitamin D: importance in the prevention of cancers, type 1 diabetes, heart disease, and osteoporosis, The American Journal of Clinical Nutrition, Volume 79, Issue 3, March 2004, Pages 362–371,

[6] Gloth, F M 3rd et al. “Vitamin D vs broad spectrum phototherapy in the treatment of seasonal affective disorder.” The journal of nutrition, health & aging vol. 3,1 (1999): 5-7.

[7] Lansdowne, A T, and S C Provost. “Vitamin D3 enhances mood in healthy subjects during winter.” Psychopharmacology vol. 135,4 (1998): 319-23.

[8] Armin Zittermann, Sabine Frisch, Heiner K Berthold, Christian Götting, Joachim Kuhn, Knut Kleesiek, Peter Stehle, Heinrich Koertke, Reiner Koerfer, Vitamin D supplementation enhances the beneficial effects of weight loss on cardiovascular disease risk markers, The American Journal of Clinical Nutrition, Volume 89, Issue 5, May 2009, Pages 1321–1327,

[9] Revised estimate of the prevalence of multiple sclerosis in the united states.

[10] Munger KL, Levin LI, Hollis BW, Howard NS, Ascherio A. Serum 25-Hydroxyvitamin D Levels and Risk of Multiple Sclerosis. JAMA. 2006;296(23):2832–2838.