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Your Guide To Vitamin D

 Over the past two decades, tests to measure vitamin D levels have become some of the most frequently ordered from laboratories. This is due to the increased awareness of the...

 Over the past two decades, tests to measure vitamin D levels have become some of the most frequently ordered from laboratories. This is due to the increased awareness of the beneficial effects of vitamin D on many aspects of health and the high prevalence of deficiency.

Vitamin D is a fat-soluble vitamin. The main source of vitamin D for most humans is through the action of UVB light from the sun on bare skin which triggers the synthesis of cholecalciferol (vitamin D). Vitamin D is found in small quantities in some high fat animal foods but it is often not well absorbed from food. Tom Oliver Nutrition’s Vitamin D contains Vitamin D3 and K2.


 What is Vitamin K2?

Vitamin K refers to a family of fat-soluble compounds known as quinones. Vitamin K2 (menaquinone) aids the utilisation of vitamin D and calcium in the body. It is found in some fermented foods such as natto, and is produced by some intestinal organisms.


 Vitamin D Deficiency

Although vitamin D can be made in the body through the action of sunlight on the skin most people living in temperate zones are deficient for the following reasons:

The strength of the UV rays from the sun in the winter months is not sufficient for the manufacture of vitamin D in the body.

  • Cloud cover and pollution limit UVB availability even in the summer.
  • Fears about the sun causing skin cancer and skin ageing means that many people wear sun screen or cover up when outside.
  • Many people cover their skin for religious or cultural reasons.
  • Dietary malabsorption of vitamin D may also contribute to low vitamin D status.


Benefits of Vitamin D3 and K2

People deficient in both vitamin D and K are at an increased risk of death from all causes compared to those with adequate vitamin D and K status (1). Here are some conditions that may be prevented or mitigated by ensuring you have sufficient vitamin D3 and K2:



Many people around the world have had Covid-19 in the last 3 years. A small percentage have been seriously ill or died from the disease. And it hasn’t gone away yet.

Research shows an association between vitamin D deficiency and severity of Covid-19 (2). Vitamin D may be helpful in a variety of ways: it stimulates antimicrobial proteins; reduces inflammation; and enhances autophagy which helps to combat pathogens including viruses (3).

As we move into winter in the northern hemisphere it is worth ensuring your vitamin D status is optimal to reduce your risk of getting severe Covid-19 and other respiratory tract infections (4).

Vitamin K may also be helpful in the treatment of Covid-19 due to its anti-coagulant effects (5).



Osteoporosis is characterized by increased porosity of the bones leading to a greater risk of fracture. Supplementing with vitamin K2 and D3 has been shown to have positive effects on bone formation and bone mineral density (6,7).

Post menopausal women are particularly at risk of osteoporosis due to the hormonal changes that take place at this time of life. Research on postmenopausal women with osteopenia and osteoporosis found that supplementing with vitamin K2 and D3 for 2 years increased vertebral bone mass. No adverse reactions were observed (8,9).

Osteoporosis is also one of the chief complications of anorexia nervosa. Supplementing anorexic patients with vitamin D3 or vitamin K2 prevents further decreases in bone mineral density (10).


Inflammatory Diseases

Vitamin D acts as an immuno-modulator with potent anti-inflammatory effects. Chronic inflammation is an underlying factor in many diseases including type 2 diabetes, Alzheimer’s disease, cardiovascular diseases, arthritis, inflammatory bowel disease and multiple sclerosis. 

For example, in those with osteoarthritis of the knee sufficient levels of vitamins D and K are associated with better lower-extremity function, including improved gait speed and ability to get up and down from a chair (11).

 Low levels of vitamin D are more prevalent in patients with Inflammatory Bowel Diseases (IBD). Vitamin D has been shown to regulate gastrointestinal microbiota function and promote anti-inflammatory immune responses. Improved vitamin D status may help to prevent the onset of IBD as well as reducing disease severity (12).


Too Much of a Good Thing

Just because something is good for you doesn’t mean that more is better. Quite the opposite in fact. As with many other supplements overdosing on vitamin D carries the risk of serious side effects. Vitamin D toxicity may cause vomiting, dehydration, abdominal pain, apathy, muscle weakness, confusion and loss of appetite (13). In the long term excess vitamin D intake may lead to hypercalcaemia, hypercalcuria, and mineral deposits in soft tissues (14,15,16).

 The dose of vitamin D that is deemed safe is up for debate but it is likely that 800IU of vitamin D or 10 µg per day of calcifediol is safe for most people (16).

Who Could Benefit from Supplemental D3?

The Department of Health recommends that the following people supplement with vitamin D:

  • Babies and children from 6 months to 5 years old
  • Pregnant and breast feeding women
  • Anyone over the age of 65
  • Those who cover their skin for religious or cultural reasons
  • Those who are inside for much of the day
  • People with darker skins
  • Those with, or at risk of, osteoporosis


If you are taking anticoagulants such as Coumadin or Warfarin check with your health care practitioner before supplementing with vitamin K.

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