VITAMIN D – How Important is it Really?

How Important is Vitamin D? In many parts of the world, the winter can be cold with short, dark days. This season often raises concerns about vitamin D, which is sometimes called the sunshine vitamin.

But why should we be concerned in Bali where we have enough sunshine pretty much all year round? Vitamin D levels have become a concern even in sunny parts of the globe due to our “cover-up” lifestyles. Our windows in cars and homes have UV light screens, we protect our skin from sunlight to avoid the risk of skin cancer, we spend long hours in front of computers in our offices and homes away from natural light. Some cultures & religions also require (especially women) to cover-up.


What is Vitamin D?

Vitamin D is technically not a vitamin because humans have the capacity to produce it themselves through exposure to sunlight. Vitamin D is biologically inert and must undergo two chemical processes in the body for activation. The first occurs in the liver and converts vitamin D to a prehormone called   calcidiol. The second occurs primarily in the kidney and forms the physiologically active hormone calcitriol. Consequently, when we don’t get enough vitamin D, we will not have enough calcitriol inside our tissues (e.g. prostate, breast, colon etc.), and not having enough of a hormone can be very bad news.

Vitamin D is important in prevention and treatment of a range of conditions including asthma, heart failure, and autoimmune diseases, such as multiple sclerosis and inflammatory bowel diseases.

Vitamin D is important for bone health. For example, vitamin D deficiency causes rickets in children and osteomalacia or osteoporosis in adults. Further, vitamin D does have many non-bone functions in the body. Indeed, evidence is accumulating that vitamin D is important in prevention and treatment of a range of conditions including asthma, heart failure, and autoimmune diseases, such as multiple sclerosis and  inflammatory bowel disease (Crohn’s disease, ulcerative colitis).


How Do We Get Vitamin D?

Vitamin D is rare in standard human diets, as there are very few natural dietary sources. One major natural source is oily fish (salmon, sardines, etc.), but to get enough vitamin D from oily fish alone, you would need to eat two or more large servings every single day! In some countries, it is mandatory to fortify milk with vitamin D. However, fortified dairy generally contains very low levels of vitamin D. Some other products can contain added vitamin D but this varies depending on the region and even the food supplier. Mushrooms are one of the few natural plant-based sources of vitamin D, but only when they have been exposed to sunshine (or ultraviolet B). Even then, the amount they contain will be low.

Sunshine is the major source of vitamin D for most humans on the planet. When the ultraviolet (UV) light from the sun penetrates human skin, it triggers a chemical reaction that generates vitamin D. If a person with fair skin goes out in the sun for about 20 minutes wearing a bathing suit, 20,000IU (International Units) of vitamin D can be produced. For  comparison, a large fatty piece of fish might contain about 1,000IU. Importantly, persons with darker skin will also generate vitamin D from sun exposure, but not as efficiently due to the fact that darker skin contains more UV blocking melanin. This is a main reason why vitamin D deficiency can be more severe among people of color. People also lose some of their ability to produce vitamin D from sunshine as they age, putting the elderly at a greater risk for deficiency as well.


Insufficient Sun Exposure

The major factor for vitamin D deficiency is insufficient sun exposure. Geographical location, specifically latitude (distance from the equator) has a major influence on vitamin D levels. The further we are from the equator, the lower the strength of the sun and the lower our potential to produce vitamin D. Season is also important. In the summer, the sun is higher in the sky, which means less UV radiation is filtered by the atmosphere, and the daytimes are longer.


Does Sunscreen Use Lead to Vitamin D Deficiency?

High-SPF sunscreens are designed to filter out most of the sun’s UVB radiation, since UVB damage is the major cause of sunburn and can lead to skin cancers. UVB wavelengths happen to be the specific wavelengths that trigger vitamin D production in the skin. Nonetheless, clinical studies have  never found that everyday sunscreen use leads to vitamin D insufficiency. In fact, the prevailing studies show that people who use sunscreen daily can maintain their vitamin D levels. One of the explanations for this may be that no matter how much sunscreen you use or how high the SPF, some of the sun’s UV rays reach your skin.


Should You Supplement Vitamin D?

Vitamin D deficiency affects around 1 billion people, making it one of the biggest nutritional issues worldwide. A vitamin D blood level of around 30ng/ml (75nmol/L) is optimal (the blood test is called 25-hydroxyvitamin D or 25(OH)D – which is available at Prodia lab albeit rather costly). To obtain this blood level, evidence supports moderate and regular sun exposure for most humans. If the sun is strong enough exposure every other day for 10-20 minutes of will be sufficient. Darker skin will generally need longer. However, this may not be possible if you live far from the equator and it’s winter. This also may not be practical if your schedule and lifestyle makes it difficult for you to get outside. In these scenarios, a vitamin D supplement is worth considering. Menopausal women, and the elderly should also consider a supplement.

In conclusion, vitamin D is not a cure all magic bullet, but it is important. Aim for moderate sun exposure when possible and consider vitamin D supplementation when it is not.


Kim Patra is a qualified Midwife & Nurse Practioner who has been living and working in Bali for over 30 years. She now runs her own Private Practice & Mothers & Babies center at her Community Health Care office in Sanur.


Kim is happy to discuss any health concerns that you have and may be contacted via email at, or office phone 085105-775666 or  

Copyright © 2019 Kim Patra

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