Why Is Vitamin D Supplementation So Important

Why Is Vitamin D Supplementation So Important

There has been an explosion of vitamin D research in the last 10 years and more than ever we are learning how important it is for many aspects of health. Ideally, we should get 80% of our vitamin D from sunlight and 20% from diet.

Researchers have discovered that our ancestral population who were exposed to sun all year-round averaged levels of 115 nmol.

The Benefits of vitamin D include:

  • Increases bone mineralisation.
  • Increases absorption of calcium and phosphate.
  • Increases insulin secretion.
  • Supports the integrity of red blood cells.
  • Protects immunity.

The most effective form of vitamin D is cholecalciferol (D3), whereas Vitamin D2 is a plant-derived form and has been shown to have less biological efficacy than D3 and less effective in raising serum levels.

Despite the current climate, there is still a widespread vitamin D deficiency!

Vitamin D deficiency is associated with chronic pain with more than 60% of headache sufferers being deficient (27). In fact, vitamin D adequacy (serum level of 50 ng/mL to 100 ng/mL) is associated with 80% lower odds of migraines (28). In a randomised controlled trial (RCT) 80 episodic migraineurs took 2,000 IU/d of vitamin D3 for 12 weeks with significantly fewer headache days per month, reduced duration and severity of attacks (29). Possible mechanisms for vitamin D’s benefits include reducing inflammation and supporting magnesium absorption.

Supplementation is even more important as sun exposure does not always provide adequate levels. Population surveys from Australia and New Zealand have shown that 40-57% of newborns are deficient in vitamin D, which leads to higher risk factors for developmental delays, poor skeletal mineralisation and lower immune functioning. Recent research indicates that vitamin D deficient mothers who are breastfeeding may require as much as 4000-6000 IU/d per day to ensure that enough vitamin D is transferred into breast milk to support development.

Who is most at risk of becoming deficient?
  • Individuals on certain medications, antifungals glucocorticoids, anticonvulsants and cortisone.
  • Individuals with conditions that reduce fat absorption, such as Coeliac diseases, inflammatory bowel disease and cystic fibrosis
  • Obesity individuals, likely due to the greater volume of distribution of vitamin D in larger tissue masses
  • Individuals with poor microbiota balance
  • Those who work or live indoors, including residential care
  • Individuals with dark skin pigmentation – sunscreen and darker skin pigmentation can reduce UVB mediation of D3, even SPF factor sunscreen can reduce production by up to 99%.

For overweight or obese individuals, daily supplementation may need to be 2-3 times greater than an average weight person.

In deficient conditions, to maintain healthy serum levels:

  • Normal BMI – 6000IU/ day
  • Overweight BMI – 7000IU/day
  • Obese BMI – 8000IU /day
Vitamin D and Magnesium

Poor vitamin D levels are also associated with magnesium deficiency. A large percentage of the population (estimated as high as 60%) are not reaching the recommended daily dose, this is due to several factors such as:

  • A declining soil content affecting magnesium levels in fresh foods.
  • Processed foods
  • Medications
  • Stress

Magnesium is essential to support the conversion of vitamin D to its active form and binding to transport it to tissues.

Vitamin D and Bone and muscular health

Vitamin D deficiency has an impact on bone health, increasing the risk of rickets, osteoporosis and osteomalacia (softening of the bones due to defective mineralisation in adults). Deficiency also impacts muscle weakness.

In combination with calcium, research shows that it improves bone mineral density and reduces bone turnover. Recent studies have shown that oral vitamin D supplementation between 700-800 IU reduces the risk of hip fracture in institutionalised elderly persons and in conjunction with calcium improves muscle strength, again reducing the risk of falling.

Vitamin D and Chronic disease

Vitamin D deficiency is associated with the progression and severity of several chronic diseases, including cancer, Diabetes mellitus and cardiovascular disease. Vitamin D receptors are found in various organs and the active form of vitamin D acts as a hormone that mediates calcium homeostasis, bone formation, cellular proliferation and differentiation, immune function, bile acid transport, renin production, endothelium and vascular walls and the endocrine system.

In the case of cancer, vitamin D inhibits proliferation, invasiveness, angiogenesis and metastatic potential, effects which may reduce the aggressiveness of cancerous lesions.

Vitamin D has the ability to modulate the immune system, this is of great benefit when treating inflammatory and autoimmune conditions. Several studies have shown that supplementation with vitamin D prevents the initiation and progression of inflammatory arthritis (so far in shown in animal studies). Increased serum vitamin D levels are associated with a lower incidence of Multiple Sclerosis (MS). During relapses, MS patients have been found to have lower levels of vitamin D than when in remission

Vitamin D for Fertility and pregnancy

Observational studies show that vitamin D deficiency is a risk marker for reduced fertility and various adverse pregnancy outcomes and is associated with a low vitamin D content of breast milk. Maternal vitamin D deficiency is associated with higher risk of preterm birth, preeclampsia, small for gestational age (SGA) and gestational diabetes. The active form of vitamin D has many roles in female reproduction where calcitriol controls the genes involved in making oestrogen.

The uterine lining produces calcitriol in response to the embryo as it enters the uterine cavity, shortly before implantation. Calcitriol controls several genes involved in embryo implantation. Once a woman becomes pregnant, the uterus and placenta continue to make calcitriol, which helps organize immune cells in the uterus, so that infections can be fought without harming the pregnancy.

Cautions and Contraindications


  • Hypercalcaemia (abnormally high calcium levels in the blood


  • Impaired renal function
  • Cholestyramine (Questran), colestipol (Colestid), orlistat (Xenical), or mineral oil may decrease the intestinal absorption of vitamin D. Separate intake by at least 2 hours.
  • Aluminium: As the protein which transports calcium across the intestinal wall can also bind and transport aluminium, and is stimulated by vitamin D, this may increase aluminium absorption. Avoid concurrent use of vitamin D supplements and aluminium-containing antacids.
  • Calcipotriol: A vitamin D analogue used topically for psoriasis; this can be absorbed in significant amounts. Theoretically, therefore, vitamin D supplements should be avoided unless a deficiency has been established via serum testing.
  • Digoxin: Hypercalcaemia induced by high doses of vitamin D can increase the risk of fatal cardiac arrhythmias with digoxin. Avoid vitamin D doses above 2,000 IU (50 mcg) daily and monitor serum calcium levels.
  • Calcium channel blockers – verapamil, diltiazem: Hypercalcaemia due to high doses of vitamin D can reduce the effectiveness of verapamil (and theoretically diltiazem) in atrial fibrillation. If total vitamin D intake is more than 2,000 IU (50 mcg) daily, monitor serum calcium levels.
  • Thiazide diuretics decrease urinary calcium excretion, which could lead to hypercalcaemia if vitamin D supplements are taken concurrently. If total vitamin D intake is more than 2,000 IU (50 mcg) daily, monitor serum calcium levels.
  • Histoplasmosis, sarcoidosis, tuberculosis, and some forms of lymphoma: Vitamin D may increase calcium levels, as in these conditions the metabolism to calcitriol may be increased. If total vitamin D intake is more than 2000 IU (50 mcg) daily, monitor serum calcium and calcitriol levels.

Want to know if you are Vitamin D deficient?

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