Illustration: Shyam G Menon

Few things encapsulate the relevance of the outdoors as vitamin D does. It has been aptly called the sunshine vitamin. When human life recedes indoors – as it has in recent times dominated by work and workplace, sedentary lifestyle and growing atmospheric pollution – we turn our back on sunshine. In India, that should provoke thought because we were already a population associated with vitamin D deficiency. This blog spoke to two doctors who lead an active lifestyle for an overview of the role vitamin D plays in our life:

“ In the basket of vitamins, vitamin D is an important one. Yet ironically, it isn’t strictly a vitamin. Vitamins cannot be produced by the human body. What we call vitamin D is more a hormone. Thereby, it is the only vitamin, which can be produced in the body,’’ Colonel Muthukrishnan Jayaraman, an endocrinologist with the Indian Army and a regular runner, said. The main role of vitamin D is in bone mineralization and calcium metabolism. Research has shown that vitamin D has receptors in many cells. It has an anti-cancer role; cancer can get out of control in cells that are deficient in vitamin D. Although not yet established beyond doubt, vitamin D is believed to influence immunity. Deficiency in vitamin D can lead to inflammation and autoimmune diseases. Further, there are connections between vitamin D levels and diabetes.

In general, nutritionists advise a Recommended Dietary Allowance (RDA) of 600 to 800 units of vitamin D (600 being for those up to the age of 70 years; 800 for those above 70). Over time, the body needs more vitamin D. There is also an optimum level of 30 nanograms per milliliter, assigned for vitamin D in the blood. Below 20 nanograms is deemed deficient. Above 30 is good for bone health. However, above 100 is toxic. “ Between 30 to 100 nanograms – that is what we need. There has been a recommendation that the RDA be more,’’ Col Jayaraman said. The body gets vitamin D through synthesis and supplementation. In the latter, sources of vitamin D include select fishes and egg. “ Some of the food items we turn to for vitamin D are expensive. But we have an inexpensive avenue to process vitamin D in sunlight. The sun’s ultraviolet B (UVB) rays affect cholesterol in the skin cells and provide the energy for vitamin D synthesis. It is generally noted that the sunshine available between 11AM and 3PM works best for this purpose. The recommended period of exposure to sunlight is 15-20 minutes. You can expose as much of your skin as you wish. Don’t go overboard. Excessive exposure, prolonged exposure – these can be counter-productive. We are all familiar with the sensation of sunburn. At about the point of being sunburnt, you may conclude that you have done enough to synthesize a month’s worth of vitamin D. That is a practical thumb rule,’’ he said.

The population of South Asia – including India – is generally deficient in vitamin D. This has been attributed to the darker skin of the region, which is not very efficient at vitamin D conversion. The predicament has been compounded by acquired habits like excessive use of sunscreen (especially brands sporting high PF value) and emergent environmental problems like atmospheric pollution. “ A study from Mumbai last year showed that almost 80 per cent of the survey sample was deficient in vitamin D. There was another from North India, which showed deficiency of 15-30 per cent. Deficiency was higher in urban areas and less in rural areas. It betrays the impact of lifestyle and varying degrees of exposure to sunlight therein. However what should worry us in India is that even solders and farmers, who are generally associated with greater time spent in the outdoors, have vitamin D deficiency,’’ Col Jayaraman said. Further, contemporary lifestyles are not helpful for vitamin D production. “ Modern day life has grown progressively sedentary and courted the indoors. We don’t indulge in sports; we spent less time outdoors. What we should note is that the risk associated with fair skin – that of excessive exposure to sunlight causing skin cancer – is not high in the Indian context, ‘’ he said.

“ Vitamins refer to a group of nutrients which are not synthesized by the body and are required in small amounts through dietary sources. In Latin, vita means life. Vitamine was the original word as Thiamine was the first vitamin to be discovered. At that time it was thought that all such nutrients would be amines (they are organic compounds which contain and are often actually based on one or more atoms of nitrogen). The amine angle wasn’t found to be true.  So the `e’ in vitamine was dropped to de-emphasize the amine reference,’’ Dr Pravin Gaikwad, a pediatrician based in Navi Mumbai, who is also a runner and triathlete, said.

Vitamins are micronutrients necessary for cell function, growth and development. There are 13 essential vitamins required for the body to work properly. Vitamin D, through a historical accident, became classified as a ` vitamin.’ It is produced in the human body. It is absent from most natural foods except certain fish and egg yolk. Even when it’s obtained from food, it must be transformed by the body before it can do any good.  It’s actually a fat soluble pro hormone steroid that has endocrine (hormonal) and extra hormonal functions. Hormonal function is involved in calcium homeostasis and extra hormonal function is related to genetic mechanisms required in cell multiplication, differentiation and death (apoptosis). The dietary sources of vitamin D are oily fish such as salmon, mackerel (100 gm gives 1006 units); cod liver oil and egg yolk (100 gm egg yolk offers 218 units of vitamin D; each measure of egg yolk is approximately 18 gm, so 5-6 eggs would be required). Red meat and animal liver supply negligible amounts of vitamin D.

Illustration: Shyam G Menon

The main raw material for vitamin D is sunlight. Therefore, it is also known as the sunshine vitamin. The recommended requirements are: adults up to 70 years – 600 IU per day, beyond 70 – 800 IU per day. Vitamin D has been found to regulate the expression of almost 900 genes involving calcium phosphate metabolism, immune system and brain development. It is well-known that vitamin D deficiency causes rickets in children and osteomalacia (softening of bones) in adults. It also aggravates osteoporosis. Further, vitamin D deficiency causes chronic muscle pain and muscle weakness. Several observational studies have demonstrated the association between robust levels of vitamin D and reduced mortality and the risk of developing certain types of chronic diseases.

“ Vitamin D has been found to be important for physiological functions such as muscle strength and neuromuscular coordination. Deficiency may lead to increased risk of falling, especially in the elderly. This vitamin’s role in preventing development of colo-rectal cancers, breast and prostate cancers has also been observed. Vitamin D’s role in brain development and function has been a subject of study lately. It has been found to be so crucial that it is also regarded as a `neurosteroid.’ Further, it has been documented that vitamin D can influence fundamental processes for brain development in the embryonic brain. The influence of vitamin D is also suggested in complex planning and formation of new memories. Vitamin D deficiency could be responsible for the patho-physiology of schizophrenia,’’ Dr Gaikwad said.

As said earlier, the main raw material of vitamin D for human beings is sunlight. It is derived through the photo conversion of 7 dehydrocholesterol to cholecalciferol (vitamin D3) in the skin by UVB radiation – 299-310 nm – following exposure to sunlight. The amount of vitamin D produced depends on several variables like environmental factors, personal variations and personal habits. The environmental factors include latitude; season, time of day, weather conditions, amount of air pollution, natural ozone layer and surface reflection. Personal variations include skin type; age and obesity. Habits include sociocultural habits like clothing and religious preferences, lifestyle, workplace and sun avoidance-practices like using sun block. Exposing the whole body to UVB radiation inducing a light pink color for 15-20 minutes will prompt production of up to 10000 IU of vitamin D. As per the Endocrine Society’s clinical practice guidelines, vitamin D deficiency in blood is less than 20 ng/ ml; insufficiency is 21 to 29 ng/ ml and sufficiency: 30 – 100 ng/ ml. “ Over 50 per cent of the world’s population and around 75 per cent of the Indian population is supposed to have insufficiency or deficiency of vitamin D,’’ he said.

The solar radiation between 11AM to 3PM is maximally helpful for vitamin D production. Over 7AM to 11AM and 3PM to 7PM, the radiation is around 40 per cent of what you get at the earlier mentioned time. “ It’s obvious that most of us (including children nowadays) are not outdoors at the time of peak exposure,’’ Dr Gaikwad said. According to him, a study published in 2018 from Pune indicates that men in western India, living in an urban setting at 18.5 degrees north and having dark skin, required over one hour of casual sunlight exposure to the face, forearm and hands (15 per cent of surface area) between 11AM and 3PM or scaled equivalent time to maintain vitamin D level above 20 ng / ml and 2 hours for 30 ng / ml.

Challenges to proper vitamin D synthesis include: increased air pollution, which makes solar radiation available less on the planet’s surface and the thinning of the natural ozone layer, which actually helps with getting radiation but is found to increase incidence of skin cancer. To note further is that it is direct sunlight and not reflected sunlight from surfaces (of buildings) which has maximum UVB for vitamin D production. “ We Indians have skin type 5 (Fitzpatrick type 5) due to which we are able to produce less vitamin D compared to lighter skins. However, the same factor plays a favorable role in preventing skin cancers,’’ Dr Gaikwad said (according to Wikipedia, the Fitzpatrick scale was developed in 1975 by Thomas B. Fitzpatrick as a way to estimate the response of different types of skin to ultraviolet [UV] light. Type 5 is described therein as: very rarely burns; tans very easily).

The older one’s age, less is the skin thickness. That leads to decreased capability for vitamin D production. With incidence of overweight and obesity increasing alarmingly, cases of vitamin D deficiency have also increased because vitamin D available in the blood reduces as it gets deposited more in fat cells. Sociocultural habits like clothing also makes production of vitamin D that much more difficult. Our present day lifestyle and workplaces offer no outdoor exposure during the peak hours. Sunblock with SPF 15 and more reduces UVB penetration by more than 95 per cent. High fiber phosphate in the diet makes calcium in food less available for absorption. Low calcium in diet exhausts vitamin D stores fast. Finally, in South Asians, there is a gene which may also contribute to low body stores of vitamin D by activating its turnover thereby exhausting its stores, Dr Gaikwad said. Generally, we get around 10 per cent of vitamin D from food and the rest from the sunlight. In August 2018, FSSAI allowed fortification of food with vitamin D. Certain milk brands are now fortified with vitamin D. It is also pushing for the fortification of oils.

There’s no evidence to suggest that very high doses of vitamin D can prevent or treat COVID-19 and that individuals with limited access to sunlight should consider a supplement, a British Medical Journal (BMJ) report on nutrition, prevention and health has stated, Dr Gaikwad pointed out.

Illustration: Shyam G Menon

Immunity depends on many variables of which sunlight is just one factor. If we maintain a healthy lifestyle – meaning thereby proper nutrition, exercise (at home in the present pandemic situation) and adequate sleep – and ensure ways to withstand the stress of modern life, immunity would not be compromised. In general, given that modern lifestyle demands we be less exposed to sunlight, vitamin D production would obviously be less. The best option seems to be to monitor the blood levels of vitamin D and take supplements, if necessary. Vitamin D is a fat soluble vitamin (not water soluble like vitamin C and B complex vitamins). It remains stored in the body for a long time and does not get excreted if taken beyond required levels. In Nordic countries, where the winter lasts for a long time, blood vitamin D levels are known to fall by only 20 to 40 per cent. “ If lockdown extends for a long time, a blood test to check vitamin D levels – especially in the elderly population above 70 years of age – may be considered,’’ Dr Gaikwad said.

The risk of taking very high doses of vitamin D is vitamin D toxicity. As it is a fat soluble vitamin, vitamin D accumulates in the body gradually and shows symptoms of hypervitaminosis D after a few months, which are largely reversible but may cause kidney damage and calcium deposition in arteries. So it is always recommended to be taken under medical guidance with monitoring of blood levels, if necessary.

(Compiled and edited by Shyam G Menon, freelance journalist based in Mumbai.)