Vitamin D deficiency: problem runs bone-deep

More than half of Delhi’s population is suffering from vitamin D deficiency, according to a recent survey by ASSOCHAM, the Associated Chambers of Commerce and Industry of India.  

An October 2017 to March 2018 survey by ASSOCHAM also showed that most of the people were not aware that they were suffering from the deficiency and that those between 21-35 years had maximum insufficiency of vitamin-D. 

Estimates by doctors and researchers show that as many as 80 per cent of urban population and 70 per cent of rural population of India is deficient in the sunshine vitamin in the country.

The report says that 88 per cent of Delhi’s population is suffering from vitamin D deficiency and eight out of 10 people are affected. As much as 85 per cent of the deficiency is due to non-exposure to sunlight and staying indoors for long hours during the day.

Recently, the Food Safety and Security Authority of India launched project Dhoop urging schools to shift their morning assembly to noon time, mainly between 11 am and 1 pm to ensure maximum absorption of vitamin D in students through natural sunlight.     

About 90 per cent of vitamin D, also known as calciferol, needed by a person is produced in the body. Skin exposure to ultraviolet (B) rays, converts provitamin D in the skin gets into previtamin D. It is isomerised by body heat to the precursor of vitamin D3, which is then transported to the liver through blood. Here, vitamin D3 gets converted into 25-hydroxy vitamin D and is sent to the kidneys where its active form calcitriol is formed.

Calcitriol is important for maintaining calcium balance in the body. It also functions as a hormone and regulates the concentration of calcium and phosphate in the blood. 

The recommended exposure time to obtain this UV dose depends on the skin type, time and location as well as ambient conditions and clothing. Studies carried out in developed countries show that a full body exposure to UVB radiation that results in pinkness of skin (one erythemal dose) is equal to an oral intake of 250–625μg (10,000–25,000 IU) of 25-hydroxy vitamin D. Exposing one-quarter of skin, for instance just hands, arms and face, to one erythemal dose of UVB rays can form dietary equivalent vitamin D dose of about 1,000 IU. However, no such calculation has been done for India, where the complexion of people varies from light to dark.

Why the deficiency

India seems to be a curious case. People in other tropical countries like those in Latin America, Australia and New Zealand have adequate levels of vitamin D. Deficiency in regions like West Asia and Africa that receive ample sunshine is easily explained. In West Asia people wear long robes and head coverings for religious reasons and avoid the scorching sun. This interferes with the production of vitamin D. In Africa, greater amounts of melanin pigments in the skin hinder synthesis of the vitamin. But people in India are neither overclad nor excessively dark. Experts pin down the deficiency in India to a combination of factors: changing lifestyle, dietary habits and rising pollution levels.

"The urban Indian has moved indoors," says Ambrish Mithal, chairperson of the endocrinology division at Medanta-The Medicity.

A study published in the Journal of the Association of Physicians of India in 2008 shows the vitamin level is six and three times higher in men and women respectively in rural areas than those in urban areas. The study was carried out in a village near Delhi. Ravinder Goswami, one of the authors of the study and associate professor of endocrinology at AIIMS, explains that urban areas are congested, which limits exposure to sunlight. Besides, rising levels of pollution restrict penetration of UVB rays into the atmosphere, he adds.

Jacob Puliyel, head of the paediatrics department at St Stephen’s Hospital in Delhi, had demonstrated this a decade ago. He studied vitamin D levels in 34 children who lived in Delhi’s highly polluted area, Mori Gate. He compared the data with the vitamin D levels in children from a less polluted area in Gurgaon. The results showed that children from Mori Gate had less (12.4 ng/ml) vitamin D levels than those from Gurgaon (27.1 ng/ml). Measurement of haze levels as an indicator of the amount of sunlight reaching the ground showed Mori Gate was hazier.

Goswami provides another reason for the deficiency across the country: Indian diets are deplorably low in vitamin D. Oily fish like salmon and sardine and cod liver oil are two of the best sources of the vitamin in diet. These protect people in high latitude countries from the deficiency despite the fact that they receive less sunshine. People at higher altitudes have sun seeking behaviour coupled with the fact that their light-coloured skin quickly converts the sunlight into the nutrient. Added to this is their regular consumption of cod liver oil, which provides a whopping dose of vitamin D. Nordic people have the tradition of feeding cod liver oil to children and pregnant women as a nutritional supplement.

Though egg yolk and milk have some amount of vitamin D, the poor in India cannot afford them. The National Sample Survey Organisation’s report on key indicators of household consumer expenditure in 2009-2010 shows that in rural areas a person consumes about 4 litres of milk in a month. In urban areas, one consumes 5.3 litres of milk. Besides, vegetarians in the country do not have eggs and cod liver oil.

In such a scenario, doctors are increasingly testing their patients’ vitamin D levels and prescribing daily supplements to raise them. For health food manufacturers, this wonder treatment has become a selling point. They are fortifying their products with vitamin D even though the understanding of the science of the vitamin is awfully inadequate in India.

Why the fuss about vitamin D?

Most multivitamins at the supermarket contain some vitamin D. Many people living far north of the equator supplement their diet with it, especially during dark winter months. This is because the body’s primary source of vitamin D is produced in our skin after UVB irradiation by the sun. Vitamin D is also found in oily fish, eggs, fungus and yeast.

Some countries even fortify milk and other food products with vitamin D to prevent deficiencies from inadequate sun exposure or dietary intake. The role of vitamin D in maintaining strong bones has been understood for quite some time. More than a century ago Frederick Gowland-Hopkins suggested using it to cure rickets.

The link between vitamin D and treatment for TB came from antiquated practices. These include giving patients cod liver oil, rich in vitamin A and D, and sunbathing TB patients in sanatoriums or under light therapy. But the way vitamin D may work against TB wasn’t unravelled until the early 1980s when it was discovered that the active form of vitamin D could be produced in immune cells. Nearly two decades later it was discovered that vitamin D also caused these immune cells to make a small protein with antimicrobial properties that could kill the TB bacteria.

In the past 10 years vitamin D has become something of a catch-all in disease prevention and treatment. Both communicable and non-communicable diseases are associated with vitamin D deficiency. These include respiratory infection, HIV progression, type 1 and 2 diabetes mellitus, rheumatoid arthritis, cardiovascular disease, osteoporosis, multiple sclerosis, depression, irritable bowel disease, asthma and multiple cancers, including colorectal, lung and breast cancers.

Sound science or hype?

According to the Down To Earth story in March 2013, there is no standard in India for determining how much 25-hydroxy vitamin D (25D), the form of vitamin D that circulates in blood, is adequate. While some diagnostic labs follow the standard set by the US National Osteoporosis Foundation, most researchers have set their own standards.

For instance, during the study on infants and their mothers, the paediatricians of AIIMS defined deficiency of vitamin D as 25D levels below 15 ng/ml and insufficiency as 15-20 ng/ml. This was different from the standards used by the endocrinologists of Medanta-The Medicity for their study on doctors and endocrinologists from Sanjay Gandhi Postgraduate Institute of Medical Sciences in Lucknow for the study on rural people. They termed those with less than 20 ng/ml of 25D levels as vitamin D deficient and those with 20-30 ng/ml of 25D levels as insufficient.

The lack of standards can result in overestimation of the prevalence of vitamin D deficiency as seen in the US.

In 2010, the Institute of Medicine (IOM), an advisory body to the US government, assessed over 1,000 studies on vitamin D and calcium. It found that there was an overestimation of the levels of vitamin D deficiency in the population due of different cut off points for 25D levels. Initial studies had set 11 ng/ml as the optimum level of 25D from birth through 18 years of age. In adults this was set at 12 ng/ml. Later on, some studies set the level for adults at 50 ng/ml, and this artificially increased the estimates of the prevalence of vitamin D deficiency, IOM said in its report. Following the assessment, IOM suggested new guidelines which say 20 ng/ml of 25D is adequate. The older guidelines had set the standard for adults at 30 ng/ml.

Using the new guidelines, researchers from Stritch School of Medicine of Loyola University Chicago calculated that 80 million Americans would not need vitamin D supplements. The researchers examined data from 15,099 adults who participated in the Third National Health and Nutrition Examination Study. More than 70 per cent of the adults had vitamin D levels that would be considered insufficient under the previous guidelines. Under the new guidelines, only 30.3 per cent of them had insufficient vitamin D levels. The results were published in the October 24, 2012, issue of journal, PLoS ONE.

The study underscores how imperative it is for the health experts to decide the optimum level of the vitamin for Indians. People’s vitamin D levels are influenced by whether they have light or dark skin, where they live, how much time they spend outdoors and whether they eat fish, milk or eggs.

In developed countries, there are recommendations on the amount of time people should spend in the sun to produce sufficient amounts of the vitamin. But in India, there is not much information available. The biggest gap is the fact that there is no long-term study on how much UVB radiations, the source of vitamin D, people receive. Sachchidanand Singh, senior scientist at Radio and Atmospheric Sciences Department of National Physical Laboratory in Delhi, says while there is some satellite-derived long-term data on UVB rays, it does not show any trend over India. “Short-term (two years) data for UVB is available for Delhi and it is difficult to comment on the trend of UVB over the city from this,” Singh adds.

In 1981, the National Institute of Nutrition had said exposure to sunlight for just five minutes is enough to produce sufficient amount of vitamin in the body. If this is correct, it becomes difficult to explain the reports of deficiency among people who stay out in the sun for long hours. The 2008 study by Goswami showed most people did not produce adequate levels of vitamin D even after five hours of exposure to sun.

In 2004, Jacob Puliyel from Delhi’s St Stephen’s Hospital sought answer to a similar question. To understand the impact of seasons on the production of vitamin D, Puliyel studied its levels in children from two adjoining slums of Delhi, first in the winter month of February and then in August. To his surprise, he found that in Rajiv Colony, 84 per cent children were deficient in vitamin D even in August. However, in the adjoining Sundernagari colony, the levels were normal in the majority of the children. To figure out the possible reason, his team met the community health workers in Sundernagari and found a diet awareness programme was underway in the area. Most of the diet fed to children was vegetarian, which is a poor source of vitamin D. “The better vitamin D levels seen in children from this area are, therefore, difficult to explain on the basis of good diet advice either,” the researchers said in journal, Indian Pediatrics. They called for more studies to understand better vitamin D levels seen in Sundernagari.

While Indian research fraternity may or may not look into the issue, there are some clear indications worth exploring. In areas like Rajiv Colony and rural areas, contaminated environment could be a reason for poor vitamin D levels. A recent study based on the data of the US National Health and Nutrition Examination Survey shows exposure to pesticides could suppress the production of vitamin D. The researchers studied blood samples of 1,275 adults in 2003-2004, and found those with high concentrations of organochlorine pesticides such as DDT had lower 25D levels. The study was published in PLoS ONE in January 2012.

For the skin colour-conscious Indian, here is another probable reason for the deficiency. The sunscreen creams and skin-lightening products that block the UVB radiation are often implicated in vitamin D deficiency. However, in 2010 Adam Handel and Sreeram Ramagopalan, scientists from University of Oxford, wrote in The Lancet that use of sunscreens did not reduce the incidences of skin cancer. This means sunscreens may not be blocking UVB radiation, they said. This means use of sunscreen might not impair vitamin D production in the body.

IOM has also suggested carrying out further studies to verify if sunscreen is indeed reducing vitamin D synthesis.

The epidemic of vitamin D deficiency could also be because of the rising levels of obesity in the country. Since vitamin D is a fat-soluble vitamin, it gets stored in fat cells. So more the fat, lesser is the amount of 25D circulating in the bloodstream. Finally, there seems to be a genetic basis to the amount of vitamin D a person can produce. A review of epidemiological studies, published in The Lancet in July 2010, shows at least three, and probably four, genes contribute to the variability of serum concentrations of 25D. This, too, is yet to be proved conclusively.

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