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Vitamin D – everything you need to know about it!


Vitamin D is a fat-soluble nutrient. Soluble means ” able to be dissolved” therefore vitamin D needs fat to be dissolved ( healthy fat such as avocados, cheese, eggs, nuts, olive oil), unlike other vitamins, for example, the vitamin B complex which is water-soluble meaning it needs water to be dissolved.

There are two main forms of vitamin D, vitamin D2- ergocalciferol ( found in mushrooms) and vitamin D3- cholecalciferol ( found in animal foods like egg and salmon). Recent studies have suggested that the latter one is superior to the first one, ergocalciferol ( D2).





Sunlight exposure

It is the simplest way to get vitamin D. But even after exposure to UV B light, its synthesis is influenced by latitude, season, use of sunblock and skin pigmentation. Those with fair skin need about 45 minutes of exposure, while those with darker skin require up to 3 hours a week to maintain sufficient levels.



In areas with limited sunlight, like Chicago for example where there is not a lot of sunlight for more than half of the year, supplementation is a common way to get sufficient vitamin D.

Current guidelines suggest that consuming 400–800 IU of vitamin D should meet the needs of the majority of all healthy people.



In a study in India called ‘ Vitamin D and Alzheimer’s Disease’ researchers found that lower levels of vitamin D are associated with an increased risk of Alzheimer’s Disease. In addition, the clinicians found that vitamin D has neuroprotective properties.

Research shows that a response to infection is hampered when vitamin D status is suboptimal. Seasonal infections are lowest in the summer and highest in the winter because in winter there is no exposure to sunlight (sunlight is a trigger for the synthesis of vitamin D). Unknowingly, before the arrival of effective antibiotics, doctors used vitamin D to treat infections such as tuberculosis. The patients were sent to sanatoriums where treatment included exposure to sunlight which was thought to directly ” kill” tuberculosis.

” A growing number of studies point to vitamin D deficiency as a risk factor for heart attacks, congestive heart failure, peripheral arterial disease (PAD), strokes, and the conditions associated with cardiovascular disease, such as high blood pressure and diabetes.” says Dr. Erin D. Michos, Assistant Professor of Medicine at The Johns Hopkins Hospital.

Vitamin D promotes mineralization of the collagen matrix in bone, therefore, it’s necessary for strong bones. Without Vitamin D, our bodies cannot effectively absorb calcium, which is essential to good bone health.

Studies show that high levels of vitamin d might improve muscle strength and that low levels may lead to fatty muscles.

” More than 60 years ago clinical studies were carried out administering oral vitamin D as a treatment for mycobacterial infections with high success rates.” – source.

A new study conducted in Milan, Italy by doctor Dr. Luisella Vigna suggests that the administration of vitamin D daily to people that are obese/overweight and already have low levels ( fat cells absorb vitamin D and keep it from circulating throughout the bloodstream) might help them lose weight.

They recruited 400 obese/overweight adults, put on the same low-calorie diet and divided them into three groups:

  1. The first group did not take supplements;
  2. The second took 25,000 IU of vitamin D per month;
  3. The third took 100,000 IU of vitamin D per month.

After six months, the second and third group, the ones that were supplemented with vitamin D experienced weight decrease and reduction in waist circumference compared to the first group who did not take any supplements. The second group lost an average of 8.4 pounds ( 3.8 kg) and 4cm from their waist, while those in the third group who took 100,000 IU of vitamin D/month lost an average of 11.9 pounds ( 5.4 kg) and 5.5cm from their waist.

According to the WHO ( World Health Organization), depression is the leading cause of disability worldwide, affecting more than 300 million people.

There are several studies that prove a connection between mood and vitamin D deficiency.  The Natural Center for Biotechnology Information states in a study conducted in Toronto, Canada that the intake of vitamin D was associated with improved wellbeing. In another study of healthy students, it was concluded that 10 or 20 mcg (400 or 800 IU)/day for only 5 days during winter improved mood.

According to the WHO ( World Health Organization), depression is the leading cause of disability worldwide, affecting more than 300 million people. Exactly how vitamin D works in the brain isn’t fully understood but taking a vitamin D supplement when needed can improve or prevent depression.

A study in the Netherlands involving 1,102 people aged 18-65 years with a current depressive disorder and 790 with former but not current depressive disorder, found lower vitamin D levels among those with a current depressive disorder and lower symptom severity for those with higher vitamin D levels. ( Source)

In a study conducted by Johnson and Johnson Skin Research Center – USA, researchers observed a correlation between vitamin D levels and skin moisture content, individuals with lower levels of vitamin D had lower average skin moisture.




People with light skin need about 45 minutes of exposure, while those with darker skin require up to 3 hours a week to maintain sufficient levels.

Fat cells absorb vitamin D and keep it from circulating throughout the bloodstream.

People with darker skin have more melanin ( what gives skin its color) which means they have a natural sun protection. Melanin is able to absorb UV-B radiation from the sun and reduce the skin’s capacity to produce vitamin D3 by 95%.

As people get older they absorb less vitamin D from their diet and produce less vitamin D in their skin. Also, their reduced activity forces them to spend more time indoors.



One study in Boston found that vitamin D deficiency may be a risk factor for depression, especially in older adults.

Another one with the title ‘ Vitamin D and depressive symptoms in women during winter’ suggested that supplemental vitamin D3 reduces depressive symptoms.

One of the most important roles of vitamin D in our body is maintaining a strong immune system so can fight off the viruses and bacteria. Getting sick often is a sign that your immune system is not functioning properly which can mean that your vitamin D levels are low.

Another study in India revealed a correlation between low levels of vitamin D and back pain.

The biggest cause of hair loss is stress, but vitamin D might have a role as well. However, in both cases when it’s severe it might be a sign of a disease.

There is not a lot of research on this topic but several studies show there is a correlation between hair loss and low levels of vitamin D. One study in Egypt- Cairo concluded that low levels of vitamin D2 are associated with hair loss in females.

A study conducted at University of Florida College of Medicine found that low levels of vitamin D are associated with excessive daytime fatigue. In another one performed at Louisiana State University Health Sciences Center – Sleep Medicine Program researchers evaluated a 28-year-old woman for 4 months of excessive daytime sleepiness. After concluding that her levels of vitamin D are low, they prescribed her a dose of 50,000 IU once weekly. Her symptoms improved within two weeks.

A study in Norway investigated vitamin D levels in patients with non-specific musculoskeletal pain, headache, and fatigue. It revealed a high prevalence of hypovitaminosis D in the examined patients which means muscle pain is associated with low vitamin D levels.


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