Vitamin D

  • Vitamin D is fat-soluble
  • It is a steroid
  • It is one of the 24 “essential” micronutrients.

How we get it

  • Sun is most common natural source of the nutrient
    • UVB radiation
  • also found in fish and eggs
  • added to milk

Why is it important

  • improved cognition
  • immune system health
  • bone health

Possible risks

  • fat-soluble vitamin (A, D, E and K) can accumulate in the body to toxic levels (dose dependent

Major benefits

  • rickets due to deficiency of D
  • reduction of testosterone
  • bone loss due to reduction in parathyroid hormone (PTH)
  • increased risk of colo-rectal cancer
  • A decrease in bone fracture risk

An improvement in muscular and neural functionality in the elderly is thought to underlie the reductions of fall risk and reduced bone fracture rate seen in elderly cohorts
– also decrease in falls (in elderly) that can contribute to those fractures
Cohorts of people with higher serum Vitamin D appear to die less frequently than cohorts with less serum Vitamin D; this may be heavily influenced by reducing falls in the elderly (reduction of falls and subsequent hospitalizations reducing death rates)

Minor benefits

  • decreases cardiovascular disease risk
  • less frequency asthmatic attacks
  • slight lowering of blood pressure
  • if vitamin D very low, increase in respiratory tract infections in general. Supplementing shows reduction in the rate of upper respiratory tract infections overall
  • deficiency may inhibit fat loss in weight-loss dieting.
  • reduction in the risk for influenza (inconsistent findings)


An improvement in insulin secretion is noted in diabetics (type II mostly) and in persons at risk for diabetes, which is thought to be secondary to protective effects at the level of the pancreas.

Improvements in insulin sensitivity can occur secondary to increasing pancreatic insulin secretion


[] Supplementation maintained Interleukin-5 concentrations during exercise, where they would normally be lowered.

[wikipedia] Interleukin-5 has long been associated with the cause of several allergic diseases including allergic rhinitis and asthma, wherein a large increase in the number of circulating, airway tissue, and induced sputum eosinophils have been observed.[11] Given the high concordance of eosinophils and, in particular, allergic asthma pathology, it has been widely speculated that eosinophils have an important role in the pathology of this disease.[12]

Calcium absorption

[]Superloading Vitamin D (rather than staying sufficient) does not appear to further increase absorption rates of calcium, although normalizing a deficiency can aid in absorption which is hindered.


The risk of developing MS is significantly reduced by both sunlight, latitude, and supplemental Vitamin D

Joint pain

May reduce symptoms of athralgia


There is less risk of breast cancer associated with Vitamin D supplementation

The association between serum Vitamin D at 37ng/mL and colorectal cancer is is approximately a halving of risk according to one meta-analysis, which is a notable risk reduction

Why we are deficient

  • not enough sun, especially north or south of the 37th parallels


  • the RDA of 400 to 800 IU is too low for adults
  • upper recommended limit is 4000 IU
    • research suggests that the limit is actually 10,000 IU
  • a moderate level would be 1000 to 2000 IU
    • lowest “therapeutic” dosage
  • higher doses in range of 20 to 80 IU per Kg of body weight
  • Vitamin D3 (cholecalciferol) is recommended D2 (ergocalciferol)
    • D3 is used more efficiantly
  • Should be with meals or with a source of fat.


[] The risk of falls in the elderly (and subsequently, rate of bone fractures) appears to be significantly reduced with Vitamin D supplementation at 700 IU or greater, with most research in the 700-1000 IU range. Lower doses do not appear effective, and a greater protective effect appears to exist alongside calcium supplementation (and possibly Vitamin K supplementation)

Why is milk fortified with vitamin D?

The short answer is rickets. Vitamin D is required for the absorption of calcium and without that …

childhood bone disorder that can lead to weak and soft bones, stunted growth and sometimes skeletal deformities ―was rampant. Roughly 80 percent of children in Boston suffered from it. The cause of rickets is a deficiency in vitamin D or calcium. Vitamin D is synthesized in our bodies when our skin takes in the sun, and our bodies need Vitamin D to be able to absorb calcium.

The discovery that vitamin D prevented rickets was an important one.

According to Ivor Cummins:

  • D2 is plant form
  • D3 is the animal form
  • Gov DA is 600 IU
  • Endocrine Society (US) 4~5,000 IU for anyone low
  • Body makes 20,000 IU in 20 minutes

You can be low in D if you have

  • Insulin resistance
  • chronic inflammation
  • metabolic syndrome


-Vitamin D is not “just a vitamin”; it’s a steroidal hormone, which means it can find its way into the cell nucleus.
-The vitamin D receptor (VDR) is one of the nuclear receptor/steroid home receptor superfamily.
-VDRs function as ligand-activated, transcriptional regulatory proteins
-so the VDR selectively binds the 1,25-dihydroxivitamin D3 hormone and controls the expression of selected genes in target cells. In other words, this has a signalling (endocrine) function that actually effects the behaviour of the cell
-VDRs exist in various cell types, including the immune cells
-VDR receptors in leucocytes (white blood cells)
-MedCram COVID update 83 – high-fructose corn syrup can inhibit conversion

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