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What a time we live in. People in the cities, particularly those with desk jobs, are becoming deficient in Vitamin D and are having to take supplements for something that the sun gives us freely.
Although it feels intuitive, it was not always known that sunlight was a major factor in the health and wellbeing of human beings. The long and interesting history behind that discovery began with Theobald Adrian Palm (1848-1928). The medical missionary had recently returned to England to practice medicine after spending ten years in Japan, and was stunned to see how stunted the children were in Birkenhead, near Liverpool, UK.
The contrast was striking. Suddenly he was encountering deformed children, something he had never seen all these years overseas. The children writhed in pain and suffered from weak and deformed bone development. He recalled that despite the squalor, malnutrition and poverty in colonial regions, and the spread of cholera and tuberculosis, he had hardly encountered children suffering from rickets.
The mystery behind rickets
This was happening as England was in the throes of the Industrial Revolution. The affliction among children was especially pronounced in Scotland. Dubbed the ‘English Disease’, it was seen in as high as 90 per cent of the children’s population in Glasgow and Edinburgh and England’s coal-bearing regions. These cities were hazy and smoggy, and the air was filled with soot.
The minerals calcium and phosphorus are key to strengthening bones and teeth. But even if one consumes food rich in these minerals, they are poorly absorbed by the body without vitamin D. This causes bones to become underdeveloped, resulting in rickets.
Mystified, Palm wrote and sought information from medical missionaries in the southeast region of Asia and North Africa. Further, he collected data on the spread of rickets in the UK and other parts of Europe. When he assembled all the data he had collected from across the world, the result was illuminating.
Children from China, Mongolia, India, Morocco, Ceylon and Japan rarely or never encountered rickets. Southern Italy, southern Spain, Turkey and Greece in Europe were essentially free from it. But in England, rickets abounded in large industrialized towns such as Glasgow, Edinburgh, the Clyde-Forth region, Tyne area, Lancaster, Yorkshire, Birmingham, Manchester, Cardiff and Swansea. London’s labour quarters suffered immensely while the prosperous localities were relatively free of the disorder. Inexplicably rickets was always more prevalent in the cities than in the countryside.
In 1890, Palm put all his deductions into his work ‘The Geographic Distribution and Aetiology of Rickets’ published in the medical journal ‘Practitioner’. “Rickets is essentially a form of malnutrition … sunlight is essential to the healthy nutrition of growing animals and is the most important element in the aetiology of rickets,” he wrote.
Unfortunately, Palm’s crucial findings were largely ignored by the medical world until resurrected a few decades later.
Indoors, outdoors, town and country
The first known treatise on rickets was written by Francis Glisson (1597–1677), a physician in 1650. He studied patients suffering from rickets and described its effects. Today, we know that rickets, caused by Vitamin D deficiency, results in bone pain and weak and deformed bone development in children.
The minerals calcium and phosphorus are key to strengthening bones and teeth. But even if one consumes food rich in these minerals, they are poorly absorbed by the body without vitamin D. This causes bones to become underdeveloped, resulting in rickets.
Before the advent of the industrial revolution, rickets was chiefly a disease of the poor, associated with malnutrition. Hardly anyone cared. With the industrial revolution, it came to be associated with child laborers working indoors and or in mines during the few sunshine hours Britain had.
As many families flocked to the booming industrial cities, and lived in cramped, gloomy flats on narrow alleyways between tall buildings, children were never really outdoors in the sun even during playtime. The burning of coal and gas for lighting hung in the air like a thick blanket of smog, further preventing the entry of sunlight. Now the disease broke the class barrier and began spreading to the wealthy, and the condition became worthy of serious investigation.
Influenced by the ‘germ theory’ of diseases during the 18th century, European physicians began searching for pathogens behind every disease and ailment. This led to a number of discoveries about various deficiencies causing disease as well, apart from those carried by pathogens. The path-breaking work of Christiaan Eijkman, the physician and professor of physiology, was one of the first. He found that beriberi was a disorder caused not by a pathogen but by a lack of specific micronutrients, namely vitamins.
The role of nutrition in preventing health disorders
Eijkman noted that the natives in the Dutch East Indies (Indonesia) who ate brown rice scarcely contracted beriberi but that the incidence was high among Europeans and the natives who ate polished white rice. By feeding two groups of chickens with polished and unpolished rice, Eijkman demonstrated that an unknown substance in the unpolished rice was responsible for preventing beriberi.
Later in 1912, the Polish biochemist Casimir Funk isolated the substance and found it part of the “amine” family of chemicals. As this chemical was vital for human well-being, he named it vitamin. Of course, later researchers found that not all vitamins are part of the amine family.
American biochemist Elmer McCollum, meanwhile, found that rats fed with just protein, minerals, fat and carbohydrates had impaired growth. However, when the diet was supplemented with cod liver oil, butter or eggs, the animals were fit as a fiddle. Examining cod liver oil, he isolated the essential substance vitamin A.
Mistaken identities and a mix up of vitamins
Taking a cue from Christiaan Eijkman and McCollum, English physician Sir Edward Mellanby postulated that rickets could also be a dietary deficiency disease. He studied puppies he fed with the primary meals of Scots, namely oatmeal. Incidentally, these dogs were kept indoors, away from sunlight. And sure enough they developed rickets.
Mellanby experimented and found that cod liver oil or egg yolk could prevent or cure rickets. He concluded that the substance that cured rickets was fat-soluble, and that since cod liver oil was rich in vitamin A, he mistakenly attributed rickets to the lack of vitamin A.
McCollum decided to test this theory. When oxygen is bubbled through cod liver oil, vitamin A is destroyed. Nonetheless, the sick puppies recovered when fed with this vitamin A deficient cod liver oil. In that case, the dogs afflicted with rickets must not show any recovery symptoms. But the dogs did indeed recover. McCollum’s further research did however show that cod liver oil devoid of vitamin A did not cure the vitamin A deficiency disease such as xerophthalmia. But, some “anti-rachitic factor” in the cod liver oil did the miracle in the dogs with rickets.
When Palm’s buried researched saw sunlight
McCollum named this unknown vitamin as vitamin D, following the nomenclature of the already known vitamin A and vitamin B. Before and after World War I, Europe had witnessed an epidemic of sorts of rickets. Palm’s 1890s suggestions of a link between sunshine and rickets began to assume importance as many medical professionals began noting that the incidence of rickets increased during dark winters and eased during the summer.
Meanwhile, a chance event at a hospital in Vienna also brought more clarity. Between 1914 -1918 when Europe was engulfed in World War I, many cities, including Vienna, faced food shortages and hunger. Several children suffered from rickets and were brought to hospitals. British biochemist Henriette Chick noticed that one of a pair of twins with severe rickets housed in a well-ventilated room with sunshine entering through a window recovered. But the other twin in a relatively dark room did not. This prompted Chick to postulate that somehow, our body produces a substance reacting with sunlight the way plants produce food through photosynthesis.
The science of Vitamin D and ultraviolet rays
Pediatrician Kurt Huldshinsky in Berlin found that ultra-violet radiation from a mercury vapor lamp had a healing effect in rickets, as did sunlight. Soon, it was found that sunlight’s ultraviolet rays were crucial. But sunlight passing through glass windows was inadequate to prevent rickets as most of the UV rays are absorbed by glass.
Vitamin D was finally isolated in 1932. This fat-soluble vitamin was present in cod-liver oil and egg yolk. Most people in the world where sunshine is abundant obtain it through a photochemical mechanism. When exposed to sunlight, the 7-dehydrocholesterol, a type of cholesterol naturally present in our body, absorbs UV radiation and converts it to pre-vitamin D3, which in turn isomerizes into vitamin D3.
Vitamin D is key to the health of body and mind
Today, we know that 13 vitamins are essential for the normal functioning of the human body. All of these vital nutrients are available in various foods, except vitamin D. Our body can produce vitamin D with exposure to sunlight.
While the deficiency of Vitamin D was mainly associated with rickets and bone and tissue deformities until now, increasingly it is becoming clear that vitamin D is involved in a host of important biochemical reactions in the body.
Vitamin D is now known to be the key to maintaining metabolic functions, having a healthy immune system, and better bone health and mental health. Clinical studies have also demonstrated vitamin D’s crucial role in preventing depression, mood swings, anxiety, and insomnia.
This is why Vitamin D is considered closer to a hormone than a vitamin. Vitamin D is chiefly produced as cholecalciferol, which the liver converts to calcidiol. The kidneys then convert the substance to calcitriol, which is the active form of the hormone in the body.
Soon, it was found that sunlight’s ultraviolet rays were crucial. But sunlight passing through glass windows was inadequate to prevent rickets as most of the UV rays are absorbed by glass.
Vitamin D stimulates several biochemical activities. It is required to absorb calcium from the gut into the bloodstream and impacts the immune system. Nearly every cell in our body has a vitamin D receptor protein. The hormone binds and influences many different body processes.
Earliest hormone to evolve
Vitamin D was one of the earliest hormones to evolve. A certain kind of phytoplankton from 750 million years ago and some zooplankton have been discovered as the earliest forms of life to make vitamin D from sunlight. From thereon, evolution ensured that all land animals too began to synthesize vitamin D on their skin from sunlight.
In fact, one of the theories of the extinction of dinosaurs that attribute the event to the after-effects of an asteroid strike and the resultant lack of sunlight. The world was said to be enveloped in a thick cloud of dust and smoke and not much UV rays from sunlight could reach the ground. The dinosaurs thus became extinct as they could not make enough vitamin D,the theory goes.
Humans and how much sunlight we need
Human beings do not really need much sunlight exposure to make the vitamin D our bodies require. Exposing our hands, legs and face about two to three times a week for about 15 minutes each is more than sufficient. Nowadays, vitamin D deficiency is on the rise, as we live in constructed and enclosed spaces. These contemporary challenges are not dissimilar to the lifestyle and living conditions that caused the epidemic of rickets in the 19th century.
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