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Vitamin D is a fat-soluble vitamin that is naturally present in very few foods. It helps fight against cancer, improves physical performance, prevents osteoporosis, helps promote brain function and reduces depression. Deficiency of this vitamin may lead to brain disorders like Parkinson’s and Alzheimer’s.

Vitamin D is a very important marker to monitor, especially if you haven’t been leading the best lifestyle or you have chronic health issues. With Lab Test Analyzer you can track vitamin D levels and make sure they are always in the optimal range. Why wait until issues get out of hand and interfere with your work and daily life? Lab Test Analyzer has got you covered – it tracks your health and gives you actionable advice on how to improve it.

Vitamin D Two Part Series



Vitamin D, also known as the “sunshine vitamin”, is an essential fat-soluble vitamin. 

It can either be obtained in the diet, through food and dietary supplements, or synthesized in the skin upon exposure to sunlight (R).

Although classified as a vitamin, it should be considered a prohormone because it is involved in many metabolic processes in the body (R, R2).

Vitamin D plays a role in calcium and phosphorus balance important in bone health, and nerve and muscle activity.

It also regulates blood pressure, immune function, cell production, and insulin secretion (R, R2, R3).

It plays a potential role in prevention and therapy of cancer and chronic conditions such as autoimmune disorders, cardiovascular disease, and infections (R).

Health Benefits of Vitamin D


1) Vitamin D is Crucial to Bone Health


Vitamin D maintains calcium and phosphorus balance in the body (R, R2).

It promotes calcium and phosphorus absorption from the gut, calcium reabsorption in the kidney, and calcium mobilization in bone (R).

It suppresses parathyroid hormone and reduces bone degradation thus indirectly increasing bone mass (R, R2).

Vitamin D is needed for bone growth and formation by bone cells.

It regulates growth and function of human bone-forming cells (osteoblasts) (R, R2).

Furthermore, higher doses of this vitamin stimulate cells that degrade bone (osteoclast) due to its narrow therapeutic range (R, R2).

2) Vitamin D Prevents Rickets and Osteomalacia

Vitamin D deficiency causes rickets in infants, young children, and adolescents and osteomalacia in adults (R, R2).

Rickets is characterized by a delay in the mineralization of growth cartilage.

Bones soften over time and become deformed, leading to growth retardation, enlargement of the epiphyses of the long bones, and leg deformities (R, R2).

Maternal vitamin deficiency can affect skeletal development of fetuses

In a study of 424 pregnant women, mothers with vitamin D deficiency were more likely to have fetuses with femoral bones that had rachitic features (R).

Osteomalacia is an absence or delay in the mineralization of newly formed bone collagen (R, R2).

Adults with osteomalacia may experience global bone discomfort, and muscle aches and weakness (R).

Osteomalacia and rickets attributable to vitamin deficiency are preventable with adequate nutritional intake of this vitamin.

Varying doses and treatment regimes have been described with the aim is to achieve a blood level between 20 and 50 ng/mL (R).

3) Vitamin D Prevents Osteoporosis and Fractures

Vitamin D deficiency. symptoms and diseases caused by insufficient vitamin D. Symptoms & Signs. Human silhouette with highlighted internal organs

Low blood levels of vitamin D are associated with lower bone mineral density, mineralization defects, and an increased risk of bone loss or fracture in both men and women (R, R2, R3, R4).

This vitamin should be considered for the therapy of osteoporosis, alone or in a combination with other therapeutic bone agents (R, R2).

Studies show that in adults aged 50 years or older, vitamin D supplementation in combination with calcium has beneficial effects on bone mineral density, osteoporotic fractures and falls without evidence of harm (R, R2, R3).

In elderly women that were given 1200 mg of calcium and 800 IU of vitamin D3 daily for 3 years, the risk of hip fracture was reduced by 43%.

The risk of fracture was reduced by 32% (R).

Populations that shield themselves from the sun or who have dark skin, African American and Hispanic men, may be at elevated risk of  vitamin deficiency and fractures (R, R2).

However, annual administration of high doses of vitamin D (500 000 IU) resulted in an increased risk of falls and fractures in older community-dwelling women (R).

4) Vitamin D Can Improve Physical Performance


Clinical evidence suggests that vitamin D plays a role in muscle metabolism and function (R).

Hence the function of the muscle is either of an indirect nature or does not involve the known receptor (R).

Supplementation with this vitamin has been shown to improve muscle strength, balance, and physical performance.

It reduces falls in diverse settings including adolescents, the elderly, and chronic kidney disease patients (R, R2, R3).

Supplementation also reduced the risk of falls by more than 20% (R).

Vitamin D may increase muscle strength by improving atrophy of type II muscle fibers, which may lead to decreased falls and hip fractures (R).

Insufficiency of this vitamin is associated with increased fat infiltration in the muscles of healthy young women (R).

It may improve athletic performance in vitamin D-deficient athletes.

This vitamin deficiency appears to be correlated with increased risk of illness and injury among athletes, especially in regards to stress fractures (R, R2, R3).

5) Vitamin D May Protect Against Cancer


The majority of studies found that sufficient vitamin D protects against cancer and risk of dying (R).

Vitamin D and its byproducts inhibit the spreading of cancer and cancer cell growth. It also induces cancer cell death.

As a result, it reduces the potential for the cancerous cell to survive (R, R2, R3, R4).

Breast Cancer

Women with a high dietary intake of this vitamin and regular exposure to sunlight had significantly lower incidence, recurrence and risk of dying from breast cancer (R, R2).

Intake of 2000 IU/day of Vitamin D is associated with a reduction by 50% in the incidence of breast cancer (R).

Low vitamin levels were also associated with faster progression of metastatic breast cancer (R, R2, R3, R4, R5, R6).

In breast cancer cells, estrogen production and aromatase enzyme activity decreased, while production of androgens (testosterone, DHT) increased (R).

Breast cancer patients must maintain adequate levels of this vitamin to minimize medical complications associated with its deficiency including bone loss, falls, fractures, and infection (R, R2, R3).

Some studies did not show an association between higher vitamin D intakes and lower breast cancer risk in postmenopausal women.

Daily supplementation with 1000 mg of calcium combined with 400 IU of vitamin D3 had no effect on breast cancer incidence (R, R2).

Colon Cancer

Epidemiological studies reported that higher blood levels of vitamin D are associated with a lower risk of colorectal cancer (R, R2, R3).

Daily intake of 1000-2000 IU/day of this vitamin could reduce the incidence of colorectal cancer by 50% (R).

Prostate Cancer

Risk of dying from prostate cancer goes down in people who get more UVB, the principal source of Vitamin D (R, R2).

Deficiency of this vitamin may increase the risk of initiation and progression of prostate cancer (R, R2).

In prostate cancer cells, vitamin D deficiency increases the production of androgens (testosterone and dihydrotestosterone) (R), which increases the growth of prostate cancer.

Pancreatic Cancer

Higher intakes of vitamin D were associated with lower risks for pancreatic cancer.

Doses of 600 IU/d or more of this vitamin lowered the risk of pancreatic cancer by 41% (R).

Ovarian Cancer

It has been shown that low vitamin D levels are present in ovarian cancer patients, and are associated with lower overall survival rate (R).

Ultraviolet B (UVB) radiation is associated with lower risk of ovarian cancer (R).

6) Vitamin D is Beneficial for Brain Development and Function


Vitamin D is considered as a hormone active in the brain (neurosteroid) (R, R2).

The vitamin D receptor (VDR) and the enzyme responsible for the synthesis of the active form of this vitamin are present in the brain (R, R2, R3).

Studies indicate that this vitamin is important for brain development.

And its deficiency is associated with a wide range of psychiatric and neurological diseases (R, R2, R3, R4).

It may protect brain cells through detoxification pathways (production of antioxidant glutathione, inhibition of nitric oxide). 

Furthermore, it also helps synthesis of proteins necessary for survival of brain cells in aging and neurological diseases (neurotrophins) (R, R2, R3).

Epidemiological studies show that low concentrations of vitamin D are associated with:

  • impairments in cognitive functions such as memory and orientation (R, R2, R3).
  • diagnosis of dementia and Alzheimer’s disease (R).
  • higher rates of psychotic experiences and schizophrenia (R, R2, R3).
  • depressive symptoms (R, R2, R3).

7) Vitamin D Improves Cognitive Functions


Studies suggest that low levels of blood vitamin D are associated with low mood, impaired cognitive functions, and dementia (R, R2, R3, R4).

While, other studies suggest that blood levels of this vitamin do not influence cognitive or emotional functioning.

Supplementation of 5000 IU/daily of this vitamin for 6 weeks did not have beneficial effects on memory, depression, anxiety or anger (R, R2).

8) Vitamin D Reduces Depression


Deficiency of vitamin D was associated with an 8–14% increase in the prevalence of depression.

And a 50% increase in suicide rates (R, R2).

Supplementation may reduce depressive symptoms, and improve physical functioning in patients with depression (R, R2).

Also, some studies showed that supplementation of this vitamin neither worsened nor improved depressive symptoms.

In elderly postmenopausal women, there was no effect of hormone therapy and vitamin D either individually or in combination on depression (R).

9) Vitamin D Reduces Risk of Parkinson’s Disease

Vitamin D deficiency may contribute to the development of Parkinson’s disease.

It is present early in the disease, and vitamin levels tend to decline further as the disease progresses (R, R2, R3).

Chronically inadequate intake of this vitamin leads to a loss of dopaminergic neurons in the substantia nigra, the region of the brain affected most by Parkinson’s disease (R, R2, R3).

Higher vitamin D blood levels are associated with reduced risk of developing Parkinson’s disease.

Individuals with a blood vitamin concentration of at least 50 nmol/l had a 65% lower risk than those with values under 25 nmol/l (R).

Patients with Parkinson’s disease are more likely to have an insufficiency of this vitamin compared to aged-matched patients with Alzheimer’s disease (R, R2).

10) Vitamin D Plays a Role in Alzheimer’s Disease

Vitamin D deficiency is prevalent in Alzheimer’s disease and dementia patients.

Alzheimer’s disease patients have lower blood concentrations of this vitamin compared to age-matched healthy individuals (R, R2).

Blood levels of this vitamin less than 50 nmol/L were associated with a higher risk of Alzheimer’s disease and dementia (R).

Vitamin D stimulates immune cells to break down the buildup of amyloid-β protein in the brain, playing a role in causing the Alzheimer’s disease (R, R2).

11) Vitamin D is Beneficial in Multiple Sclerosis

Higher vitamin D blood levels protect from developing multiple sclerosis.

In women, each 10 nmol/L increase in blood vitamin levels was associated with a 20% decreased risk of multiple sclerosis (R, R2, R3).

Also, higher vitamin D levels were associated with a reduced worsening and recurrence of multiple sclerosis symptoms.

Each 10 nmol/l increase resulted in up to a 12% reduction in recurrence (R, R2).

Optimal blood concentrations of this vitamin may decrease disease-related complications, including increased bone degradation, fractures, and muscle weakness (R).

Increased sun exposure during ages 6–15 years is associated with a decreased risk of multiple sclerosis.

In addition, outdoor activities are associated with a reduced multiple sclerosis risk (R, R2).

Multiple sclerosis occurs less often if this vitamin abundant, as in sunny climates, high altitudes, and areas with dietary rich in fish oils (R).

Vitamin D has anti-inflammatory action in multiple sclerosis.

It decreases secretion of inflammatory cytokines, and results in a shift from a Th1 to a Th2 phenotype (R, R2).

12) Vitamin D Improves Sleep Quality


Vitamin D could be important for sleep disorders (R).

Higher concentrations of this vitamin were associated with better maintenance of sleep (R).

In National Health and Nutrition Examination Survey (NHANES) study, lower vitamin levels were associated with shorter sleep duration (R).

Some studies suggest improved sleep quality with vitamin D supplementation.

It has been hypothesized that its deficiency is central to a recent ‘epidemic’ of disturbed sleep patterns (RR2).

Studies have reported a high prevalence of this vitamin deficiency in obstructive sleep apnea syndrome.

This is a widespread disorder characterized by episodes of breathing cessation due to upper airway tract obstruction during sleep (R).

Its deficiency is more pronounced in severe sleep apnea and associated with abnormal glucose production (R, R2).

More studies are needed to prove this relationship between sleep quality and vitamin D supplementation.

13) Vitamin D Reduces the Risk of Cardiovascular Disease


Vitamin D deficiency is associated with increased risk of cardiovascular disease, including hypertension, heart attack, peripheral arterial disease, and stroke (R, R2, R3).

Vitamin D receptor and 1α-hydroxylase are present heart and blood vessels, suggesting a potential role in cardiovascular disease (R, R2, R3).

Study showed that this vitamin supplementation or UVB irradiation may lower blood pressure, improve blood pressure control, and regress heart enlargement (R).

Its deficiency causes atherosclerosis and blood vessel dysfunction, predisposing individuals to development of cardiovascular disease (R, R2, R3).

Low levels of vitamin D and decreased exposure to sunlight are associated with increased risk of heart disease (R, R2, R3).

However, some studies show opposite findings.

Daily supplementation with 800 IU vitamin D for 12 weeks did not impact blood pressure, renin and fat concentrations, markers of cardiovascular disease (R).

Study of healthy postmenopausal women, given 400 IU/day or 1000 IU/day vitamin D for a period of 1 year, showed no significant benefit to heart disease risk (R).

14) Vitamin D Reduces Blood Pressure

Skin exposure to UVB radiation is associated with lower blood pressure (R, R2, R3).

Blood pressure is affected by variations in skin color, geographic region and season (R, R2, R3).

Blood pressure was significantly decreased after 6 weeks of therapy in individuals receiving UVB therapy (R).

This vitamin decreases activity of the renin-angiotensin system.

In vitamin D-sufficient hypertensive rats, oral administration of vitamin D decreased blood pressure by suppression of renin-angiotensin system (R, R2).

In vitamin D deficient elderly women, there was a 9% decrease in systolic blood pressure (by 13 mmHg) with supplemental vitamin D and calcium compared with calcium alone (R).

Studies including more than 1800 patients found an increased risk of high blood pressure in those with vitamin D level <50 nmol/L compared to those >75 nmol/L (R).

However, studies conducted in women and elderly demonstrated no effect of vitamin D supplementation on blood pressure (R, R2, R3).

15) Vitamin D May Decrease the Risk of Type 1 and Type 2 Diabetes


Vitamin D plays a role in insulin production and secretion from pancreatic cells (R).

Its deficiency leads to impaired glucose and insulin secretion, and increased risk of type 1 and type 2 diabetes mellitus (R, R2, R3, R4, R5, R6, R7).

Studies show that supplementation with this vitamin restored insulin secretion (R, R2, R3, R4).

Vitamin D deficiency in early life predisposes to the later development of type 1 diabetes and its complications (R, R2).

A study found that an intake of 2,000 IU of this vitamin during the first year of life diminished the risk of developing type 1 diabetes (R).

The Diabetes Autoimmunity Study in the Young (DAISY) reported an increased presence of antibodies against pancreatic cells in newborns of mothers with low intake of this vitamin during pregnancy (R).

Studies have demonstrated that blood vitamin concentrations are lower in patients with type 2 diabetes (R, R2, R3).

In the Women’s Health Study, an intake of 511 IU/day of vitamin D or more was associated with lower risk of type 2 diabetes (R).

It may have a role in delaying the progression to diabetes in adults at high risk of type 2 diabetes.

Supplementation was associated with improved function of pancreatic cells (R).

It also had an effect on the rise of Hb A1C (shows average blood sugar levels over a period of weeks/months) that occurs over time (R).

16) Vitamin D Prevents Obesity and Metabolic Syndrome


Being overweight or obese is associated with decreased blood concentrations of vitamin D (R, R2).

There is a genetic evidence that higher body mass index (BMI) leads to lower vitamin D status (R).

Lower blood concentrations are associated with higher waist circumference, and percentage of total body fat in children, adolescents, and adults (R, R2, R3, R4, R5).

Obese individuals need higher vitamin doses than lean individuals to achieve the same vitamin D concentrations in the blood (R, R2, R3).

12 week supplementation with 25 μg of vitamin D in overweight and obese women decreased body fat mass by 7%, but did not affect body weight and waist circumference (R).

Obese African Americans are at particularly high risk for this vitamin deficiency.

Physicians should consider routine supplementation or screening of these patients for low vitamin D levels (R).

Deficiency of this vitamin may be a risk factor for the metabolic syndrome (R, R2, R3).

Higher blood levels of vitamin D were associated with a decrease in the prevalence of the components of metabolic syndrome (elevated blood pressure, elevated triglycerides, and reduced high-density lipoprotein cholesterol) in postmenopausal women (R).

17) Vitamin D has Anti-Inflammatory Role

Studies have shown potent effects of vitamin D on both innate and adaptive immunity.

It has the potential to influence a wide range of immune disorders, particularly infectious and autoimmune diseases (R, R2, R3).

Cells involved in innate and adaptive immune responses (macrophages, dendritic cells, T cells and B cells) express the vitamin D receptor and synthesize the active vitamin D byproduct (R, R2).

Effects of vitamin D on immune system include:

  • Inhibits B cell production, and antibody secretion (R, R2)
  • Decreases T cell growth, inhibits T cell activation and IL-2 production (R, R2)
  • Results in a shift from a Th1 to a Th2 phenotype (R, R2)
  • Regulates the activity of monocytes/macrophages (R, R2)
  • Inhibits dendritic cells production and growth (R, R2)
  • Decreases the secretion of inflammatory cytokines IL-1, IL-2, IL-6, IL-8, IL-17, TNF-α, IFN-γ, and IL-12 (R, R2, R3, R4)
  • Increases cytokines IL-10 and IL-4 (R, R2, R3, R4)
  • Inhibits production of IgE by B cells and enhances production of IL-10 by dendritic cells and T cells, playing an important role in allergic immune responses (R, R2)
  • Reduces the expression of MHC class II, CD40, CD80, and CD86 (R, R2)
  • Decreases TGF-beta (contributes to tissue repair by promoting tissue fibrosis) (R, R2, R3, R4)
  • Crucial for T Cell activation (R)
  • Regulates differentiation of CD4+ T cells (decreases Th1 and Th17 cell production, and increases Th2 and Treg cell production) (R, R2)
  • Increases CD8+ T  Cells, important in controlling viruses, intracellular bacteria, and cancer (R, R2)
  • Increases Natural Killer T Cells (R)
  • Releases antimicrobials in response to an infection such as cathelicidin and beta defensin 4 (R, R2)

18) Vitamin D May Be Beneficial For Inflammatory Bowel Disease and Celiac Disease



Inflammatory bowel disease (IBD) is a chronic inflammation of the gut, and includes Crohn’s disease and ulcerative colitis.

Vitamin D supplementation may have a beneficial role in IBD (R, R2).

Studies in mice indicate that this vitamin plays a crucial role in this disease (R).

Vitamin D has an anti-inflammatory effect in patients with IBD.

Oral supplementation increased blood vitamin D levels and reduced blood TNF-α levels (protein playing a main role in the gut inflammation) (R, R2).

Study showed a 32% decrease in CRP (C-reactive protein) levels and 46% decrease in ESR (erythrocyte sedimentation rate) in patients receiving vitamin D (R).

1200 IU/d vitamin D supplementation reduced recurrence of Crohn’s disease from 29% to 13% (R).

Low vitamin D level is associated with higher risk of polyps and adenomas in the colon, common complications of ulcerous colitis (R).

Almost 60% of patients with celiac disease were found to be vitamin D deficient or insufficient (R).

19) Vitamin D Plays a Role in Cystic Fibrosis

Low blood vitamin D levels are commonly found in patients with cystic fibrosis (CF).

Its deficiency occurs in 25–33% of patients with late-stage CF (R).

Absorption of this vitamin is reduced in patients with CF due to insufficient pancreatic enzymes (R).

Also, CF patients have increased oxidant and P450 activity, which could lead to faster degradation of vitamin D (R).

95% of cystic fibrosis patients required 1800 IU/day of vitamin D to achieve blood concentration above 25 ng/ml (R).

How To Increase Vitamin D Levels

Vitamin D levels can be increased by getting more natural sunlight or in supplement form.


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  • pamojja

    Agree out of my own testing that beta-carotene isn’t enough, but it needs preformed Vitamin A to keep serum levels healthy. And most probably at a much higher IUs intake than vitamin D3

    Morley arrived at his ‘ideal’ ratio because that’s in beef liver!? However, that’s totally unrelated to the intake necessary to get appropriate blood levels, according to my tests. In my experience the optimal intake A:D ratio is very individual. With high vitamin D3 intake, calcium and zinc remained low, copper too high, so almost opposite to his speculations (serum, whole blood and HTMA tested).

    Except for one point: my magnesium needs started to go up very high with vitamin D.

  • julialoha

    Great article. Wish there had been mention of Vit K2 and Vit A. I have read that calcium is deposited in soft tissue if Vit D is taken without Vit K2. Also, without adequate Vit A (10X more than Vit D) copper is dysregulated.

    1. Natcha M

      Good point. I gotta add the connection between vit D, A, and K2 soon. Thanks for the suggestion.

    2. pamojja

      quote: “Also, without adequate Vit A (10X more than Vit D) copper is dysregulated.”

      Is that in mcg or IUs? Also, in which way would copper be dysregulated?

      1. julialoha

        It’s IUs. Copper is dysregulated by a problem with making ceruplasm. This Morley Robbins guy is the one who talks about ceruplasm – not sure this is the right podcast. – the name of it is #103 Rethinking Vitamin D with Morley Robbins. He has a lot of youTube sites.

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