Vitamin D

It’s not just about bones!

Vitamin D is one of 4 fat soluble vitamins, and one of the most important.

We want to explain a few things about vitamin D and its importance and why we suggest taking supplements.

In the strictest sense, vitamin D is not a vitamin.  Vitamins are minerals essential for life, that we do not make so we must consume them.  Vitamin D is actually a hormone that we do make starting in the liver.  Many years ago when we lived outside, naked, we made enough D, but today our living situation is much different and most of us do not get enough sunlight.  So, as a result we do not make much and therefore it must be consumed; hence, it is called vitamin D.

How do we make it ?

Vitamin D comes from cholesterol, that comes from our diet or is made in our liver.  The cholesterol travels in the blood to the skin.

The sebaceous glands in the skin turn the cholesterol into 7-dehydrocholesterol, which is oily.  It is secreted onto the skin and helps keep the skin soft.

When exposed to sunlight, the UV rays change the 7-dehydrocholesterol into Previtamin D.  After about 2-3 days this further changes into Vitamin D3.  Those who wash often, wash the Vitamin D3 off the skin .

Once the Vitamin D3 forms, it sinks into the deeper layers of the outer skin layer, the epidermis.  Here a protein in the blood, DBP, picks it up to bring it to the liver.

Dietary sources of Vitamin D3 (not a lot) move from the intestine to DBP in the blood, then to the liver.

In the liver Vitamin D3 is changed into the storage form Vitamin 25-D3 (calciferol). The main storage site for Vitamin 25-D3 is blood, where it can last up to 3 weeks.

If our blood calcium level drops, a hormone called parathyroid hormone (PTH) is made that activates the kidney.  Vitamin 25-D3 travels to the kidney on DBP and is changed into Vitamin 1,25 D3(calcitriol).  This is the active form of Vit D3, which in turns absorbs calcium from the intestine, kidney and bone; this is bad.  This effect on bone is reduced if one is physically active and has an adequate intake of calcium, vitamin C, strontium and has good levels of either estrogen/testosterone.

By the way, the conversion of Vitamin 25-D3 to active Vitamin 1,25 D3 also occurs in:

Lymph nodes (part of the immune system that fights infection)

Alveolar macrophages (the cells in the lungs that eat bacteria/viruses etc.)

Alveoli (cells that line the air sacs in the lungs where oxygen is picked up)

So, there is a lot of activity in the lungs where a lot of microbes gain access to the body, like COVID-19!

Many have heard that Vit D is important to protect against COVID-19, now you have a better idea why.

For Vitamin D3 to cause an action, it must bind to something called a receptor.  This acts as a lock that a key (Vit D3) fits into to open or close.  The vitamin D3 receptor is called VDR (vitamin D receptor) and is distributed throughout the body.

The expression of vitamin D receptors (VDRs) declines in muscle with aging. As a result, the muscles weaken and get smaller (called sarcopenia). This leads to increased falls and injury.

People who take any level of vitamin D supplements, reduce falling by 22% (better sense of balance and stronger muscles).

Some functions to vitamin D :

  • Intestinal absorption of calcium, phosphorous (essential for energy production).
  • Mineralization of bones
  • Immune system modulator
  • Insulin secretion
  • Blood pressure regulation
  • VDRs are expressed in several white blood cells (to fight infection), including monocytes.
  • T and B cells (cells that also fight infection and make antibodies)
  • Affects the synthesis of neurotropic factors (nerves), nitric oxide synthase (blood vessels), and
  • glutathione (strong antioxidant).
  • Not only bones need Vit D!

Vitamin D deficiency is associated with :

  • Cancer (especially breast and colon)
  • Diabetes
  • Rheumatoid arthritis
  • SLE (lupus)
  • Autoimmune diseases
  • Endothelial dysfunction (vascular disease)
  • Band Keratopathy (scarring across the eye)
  • Sarcopenia- weakness
  • Overactive bladder: poorer coordination of bladder wall muscles.
  • Pulmonary function
  • Age related macular degeneration
  • Cognitive impairment
  • Dementia/cognitive decline

Interesting facts:

Generally, those who supplement with vitamin:

2,000 IU/d have a blood level of 32

4,000 IU/d have a blood level of 52

Vitamin D excess:


Thirst, polyuria, constipation, nausea and vomiting, confusion,

Abdominal pain, heart arrhythmias, muscle weakness, HA


Increase in calcium and phosphate stones; metastatic calcification

In 2011, there was a mislabeling error with a vitamin D supplement and many people were taking 1,000 times the recommended dose.  One person was taking 1,864,000 units a day (you read that right, almost 2 million units) for three months.  These people became toxic with weakness, headaches and GI upset, but, amazingly, no one died. That was a thousand times the recommended dose!  Toxicity is rare with a daily dose of 10,000 units a day or greater.

Toxic side effects are due to high levels of 25-vitamin D (the storage form not the active form).

It appears that vitamin D supplementation is safe.  Science is still trying to determine what the best dosing is.

A lot of literature indicates the following blood values:

  • Deficient less than 50
  • Optimal 50 to 65
  • Cancer treatment 65 to 90
  • Excess greater than 100

Males and females with baseline D levels less than a blood level of 25 are more than twice as likely to develop sarcopenia, which is less muscle mass and, hence, strength (more falls).

Working outdoors at any point in life resulted in a 40% reduction in breast cancer risk.

Drinking at least nine glasses of milk per week between ages 20 and 29 years was significantly associated with reductions in breast cancer risk.  The regular consumption of cod liver oil for at least 10 years did the same.

Those with low levels of vitamin D had an increased risk of a heart attack.

An analysis in 2009 of 99,745 patients in the United Kingdom noted that those with the highest level of vit D had a 43 % lower rate of cardiometabolic disease and was also associated with

less heart disease, Type 2 diabetes and metabolic syndrome.

People with a history of depression saw a dramatic improvement in that depression with Vit D supplementation.

Vitamin D blood levels of 35 is associated with a 20% reduction in the risk of breast cancer.

An average blood level of 52 vitamin D had a 50% lower risk of breast cancer.

Vitamin D blood levels of 82 and higher was associated with a 50% lower risk of developing colorectal cancer.

Those with a blood vitamin D level less than 31 had a risk of colon cancer, 2.5 times greater than those above 31.

It is projected that raising the minimum year-round serum 25 Vitamin D3 levels from 40 to 60 ng/mL would prevent approximately:

  • 58,000 new cases of breast cancer
  • 49,000 new cases a colorectal cancer each year
  • And 3/4 of deaths from these diseases in United States and Canada

Such intakes are also expected to reduce case-fatality rates of patients who have breast cancer, colorectal cancer, and prostate cancer by half.

Following are some excerpts from numerous articles from peer reviewed articles:

J of Musculoskeletal Med. June 2007 :

Women with serum D levels < 31 had odds ratio risk of 2.53 for colon cancer.

When D levels were at or above 58 the ratio was 1.0.

Increased muscle pain and hyperparathyroidism was seen in women with Vit D deficiency.

20% of osteoporosis are men.

Aging Male. 2010 Dec;13(4):215-232; Lauritano et al.

  • Vitamin D in Older Population: New roles for this ‘Classic Actor’?
  • Roles for. Vitamin D:
  • Bone metabolism
  • muscle strength
  • Reducing falls
  • Reducing cardiovascular disease
  • Reducing neurological disease
  • Reducing insulin resistance and diabetes
  • Reducing malignancies
  • Reducing autoimmune diseases
  • Reducing infections

Maturitas. 2010 Mar;65(3):225-236-Parker J, et al

Levels of Vitamin D and Cardiometabolic disorders: Systematic Review and Meta-analysis.

We found that the highest levels of serum 25(OH)Vit-D were associated with a 43% reduction in cardiometabolic disorders.

High levels of vitamin D among middle-aged and elderly populations are associated with a substantial decrease in cardiovascular disease, type 2 diabetes, and metabolic syndrome. July 6, 2012:

Women with a moderate to severe depression had substantial improvement in their symptoms of depression after they received treatment for vitamin D deficiency.

Both the presence and severity of depression are associated with decreased serum levels of vitamin D and increased levels of parathyroid hormone in older patients.

OB GYN News 2008 Mar 1: Jancin B

Evidence backs vitamin D as a longevity booster.

Supplementation of around 1,000 units of vitamin D daily reduce all causes of mortality by 7%.

Ann Epidemiol.2009 Jul;19(7):468-483- Garland C, et al.

  • Vitamin D for Cancer Prevention: Global Perspective
  • Higher levels of the main circulating form of vitamin D, 25(OH)VitD, are associated with substantially lower incidence of:
  • Colon cancer
  • Breast cancer
  • Ovarian cancer
  • Renal cancer
  • Pancreatic cancer
  • Aggressive prostate cancer
  • Other cancers

You see, Vit D3 is not just about bone.  It is so much more.

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