Vitamin D: Essential for Bone Health and Beyond

Vitamin D is a crucial nutrient for maintaining overall health, particularly for bone health. It plays a vital role in ensuring the body functions properly, influencing various bodily systems beyond just bones.

Functions and Benefits
Bone Health
Vitamin D is essential for calcium absorption, which is critical for developing and maintaining strong bones. Without enough vitamin D, calcium isn't adequately absorbed, leading to bone disorders such as osteomalacia in adults and rickets in children. These conditions result in soft, weak bones and muscle pain, underscoring the importance of vitamin D in skeletal health.

Immune System
Vitamin D is also a key player in immune function. It helps modulate the immune response, enhancing the body’s ability to fend off infections. Furthermore, there is emerging evidence that sufficient levels of vitamin D can lower the risk of autoimmune diseases, such as type 1 diabetes and multiple sclerosis, as it supports immune regulation.

Mood Regulation
Research indicates that vitamin D may influence brain function, particularly in mood regulation. Several studies suggest a link between low vitamin D levels and an increased risk of depression, anxiety, and even Seasonal Affective Disorder (SAD). While more research is needed, vitamin D supplementation is often considered in treatment plans for mood-related conditions.

Disease Prevention
There is growing evidence that maintaining adequate vitamin D levels may help reduce the risk of chronic diseases such as multiple sclerosis, heart disease, and certain cancers. Its role in regulating cell growth and reducing inflammation is thought to contribute to these protective effects.

Sources of Vitamin D
Sunlight
One of the most effective ways to obtain vitamin D is through exposure to sunlight. When UVB rays hit the skin, the body naturally produces vitamin D. However, factors such as geographic location, season, skin pigmentation, and sunscreen use can significantly affect how much vitamin D is synthesized.

Food
Certain foods, particularly fatty fish like salmon and mackerel, are rich in vitamin D. Fortified foods, such as milk, cereals, and orange juice, also provide significant amounts, helping those who may not get sufficient sunlight.

Supplements
For individuals with limited sun exposure or dietary restrictions, vitamin D supplements can be an important alternative. These supplements help maintain adequate levels and are particularly important for those living in northern latitudes or during the winter months.

Deficiency and Health Risks
Vitamin D deficiency can lead to several health issues. In addition to bone disorders like rickets and osteomalacia, deficiency is associated with cognitive decline, dementia, and an increased risk of Alzheimer's disease. It is crucial to monitor vitamin D levels, especially in older adults and those with limited sun exposure.

Recommended Daily Intake
The recommended daily intake of vitamin D varies by age. For infants up to 12 months, 400 IU is suggested, while adults aged 1-70 years are recommended to get 600 IU per day. For people over 70 years, 800 IU is advised to maintain optimal health and prevent bone loss.

Interesting Fact

The body's ability to produce vitamin D is influenced by several factors, including the time of day, season, latitude, and skin pigmentation. Darker skin contains more melanin, which reduces the skin’s ability to synthesize vitamin D from sunlight, making supplementation or fortified foods more crucial in certain populations.
Vitamin D: Essential for Bone Health and Beyond

Vitamin D and Heart Health: Benefits, Risks, and Overall Impact

Vitamin D, often referred to as the “sunshine vitamin,” is vital for maintaining overall health, impacting everything from bone strength to immune function. It plays a crucial role in calcium absorption, which is necessary for bone development and maintenance. Additionally, vitamin D has been shown to regulate the immune system, reducing inflammation and aiding in the prevention of autoimmune diseases. Another important but less understood aspect of vitamin D is its potential impact on heart disease, which is a leading cause of death globally.

Recent studies have examined whether vitamin D can protect against cardiovascular diseases such as heart attacks and strokes. Observational studies suggest a correlation between low levels of vitamin D and an increased risk of these conditions. Vitamin D deficiency is also linked to hypertension (high blood pressure) and type 2 diabetes, two significant risk factors for cardiovascular disease. Hypertension places extra strain on blood vessels and the heart, while diabetes can damage blood vessels over time. Both conditions contribute significantly to the risk of heart attacks, strokes, and other cardiovascular events.

However, the role of vitamin D supplementation in heart disease prevention is not straightforward. Clinical trials have yielded mixed results on whether vitamin D supplements can significantly reduce the risk of cardiovascular disease. Some studies found no meaningful reduction in heart attacks, strokes, or other heart-related events when high doses of vitamin D were administered. There is also a risk of over-supplementation, which can cause hypercalcemia—a condition where calcium levels in the blood become too high. This can lead to calcium deposits in the arteries, increasing the risk of coronary artery disease.

Despite these complexities, maintaining adequate vitamin D levels is still essential. The best strategy involves a combination of moderate sun exposure, vitamin D-rich foods (such as fatty fish and fortified dairy products), and supplements when necessary, but always under medical supervision. While vitamin D may not be a cure-all for heart disease, it remains a key component of a well-rounded approach to health, supporting overall well-being and the proper functioning of various bodily systems.
Vitamin D and Heart Health: Benefits, Risks, and Overall Impact

Discovery and Characterization of Vitamin D: A Milestone in Nutritional Science

The early 20th century marked a pivotal period in the understanding of vitamins, particularly the discovery and characterization of vitamin D. The groundwork for this discovery was laid by Sir Edward Mellanby in 1919/20 when he conducted groundbreaking experiments to investigate the cause of rickets, a bone disease that was prevalent at the time. Mellanby’s work involved raising dogs in an environment devoid of sunlight or ultraviolet light, thereby mimicking conditions that could lead to rickets. He meticulously devised a diet that allowed him to determine that rickets was indeed caused by a deficiency of a trace component in the diet. This crucial finding was a significant step forward in understanding the role of nutrition in preventing disease.

In 1921, Mellanby published his findings, stating, "The action of fats in rickets is due to a vitamin or accessory food factor which they contain, probably identical with the fat-soluble vitamin." This statement was revolutionary, as it suggested that rickets could be prevented by a dietary component found in certain fats, particularly cod liver oil. Mellanby’s identification of cod liver oil as an excellent antirachitic agent was a milestone in nutritional science, as it provided a practical means of preventing rickets through dietary supplementation.

Mellanby’s work laid the foundation for further research into the fat-soluble vitamins. Shortly after Mellanby’s discovery, E.V. McCollum and his associates conducted experiments that distinguished between two fat-soluble vitamins, vitamin A and vitamin D. By bubbling oxygen through a preparation of the "fat-soluble vitamin," they observed that vitamin A was inactivated, whereas vitamin D retained its activity. This distinction was critical in understanding the specific roles of these vitamins in human health.

The identification of the role of sunlight in vitamin D production came soon after. In 1923, Goldblatt and Soames made a breakthrough discovery when they identified that 7-dehydrocholesterol, a precursor of vitamin D found in the skin, could be converted into an active form of vitamin D when exposed to sunlight or ultraviolet light. This finding provided a biological explanation for the protective effect of sunlight against rickets, further cementing the connection between sunlight exposure and vitamin D synthesis.

Hess and Weinstock later confirmed this connection through an innovative experiment. They excised small portions of skin from rats, irradiated the skin with ultraviolet light, and then fed it to groups of rachitic rats. The irradiated skin provided absolute protection against rickets, while the unirradiated skin did not, conclusively demonstrating that irradiated skin could produce sufficient quantities of vitamin D to prevent rickets. This experiment also suggested that vitamin D might not be an essential dietary trace constituent, as it could be synthesized in the body through exposure to light.

In parallel studies, Steenbock and Black discovered that food irradiated with ultraviolet light also acquired antirachitic properties. This finding underscored the importance of vitamin D in preventing rickets and further solidified its classification as a vitamin. The rapid advances in nutritional science during this period, particularly the identification of water-soluble and fat-soluble vitamins, played a crucial role in establishing vitamin D as a key nutrient necessary for bone health and the prevention of rickets.
Discovery and Characterization of Vitamin D: A Milestone in Nutritional Science

Evolution of Vitamin D: From Ancient Awareness to Modern Health

Human awareness of vitamin D dates back to early antiquity, with ancient civilizations recognizing the importance of sunlight and certain foods for health. The first scientific descriptions of vitamin D deficiency, particularly rickets, emerged in the 17th century. Dr. Daniel Whistler in 1645 and Professor Francis Glisson in 1650 provided detailed accounts of rickets, a disease characterized by bone deformities in children.

The significant breakthrough in understanding rickets came between 1910 and 1930, a period marked by the advancement of nutrition as an experimental science. Researchers discovered vitamins, including vitamin D, as essential nutrients required for various bodily functions. This era saw the identification of vitamin D's role in calcium absorption and bone health. The fortification of foods with vitamin D and increased understanding of its synthesis through sunlight exposure significantly reduced the prevalence of rickets.

Recent research continues to highlight the importance of vitamin D, linking its deficiency to various health issues, such as osteoporosis, immune dysfunction, and cardiovascular diseases. Modern studies advocate for adequate vitamin D intake through diet, supplements, and safe sun exposure to maintain overall health.
Evolution of Vitamin D: From Ancient Awareness to Modern Health

The Essential Role of Vitamin D in Human Health

Vitamin D stands out among fat-soluble vitamins because the body can synthesize it using sunlight from a precursor derived from cholesterol. Unlike other vitamins that must be ingested, this unique process highlights the crucial role of sunlight in human health. Known as calciferol or activated ergosterol, vitamin D is essential for various bodily functions.

Vitamin D is vital for normal tooth and bone formation. It facilitates the absorption of calcium, a critical component for building and maintaining strong bones. This synergy between vitamin D and calcium is instrumental in preventing osteoporosis, a condition characterized by fragile and brittle bones. Additionally, vitamin D is crucial for muscle function, enabling movement, and for nerve function, facilitating communication between the brain and the rest of the body.

A deficiency in vitamin D can lead to serious health issues, such as rickets in children, which causes bone deformities like bow-legs and curvature of the spine, as well as dental problems. In adults, insufficient vitamin D can result in osteomalacia, leading to soft bones and increased fracture risk.

Dietary sources of vitamin D include fish oils and especially fish liver oils, which are among the richest sources. The body can also produce vitamin D when the skin is exposed to ultraviolet (UV) light from the sun. This endogenous production underscores the importance of regular, safe sun exposure. To ensure adequate intake, vitamin D is routinely added to milk and other fortified foods.

There are two forms of vitamin D supplements: D2 (ergocalciferol) and D3 (cholecalciferol). Both increase blood levels of vitamin D, but D3 is often considered more effective in raising and maintaining these levels over time. Since vitamin D is fat-soluble, its absorption is enhanced when consumed with a meal containing fat.

In summary, vitamin D is crucial for bone health, muscle function, and overall well-being. Adequate levels can be maintained through a combination of sunlight exposure, diet, and supplementation, ensuring the body receives this indispensable nutrient.
The Essential Role of Vitamin D in Human Health

Balancing Sun Protection and Vitamin D: Ensuring Optimal Health

Our skin evolved to synthesize vitamin D when exposed to the sun's ultraviolet (UV) rays. In equatorial regions, where most of the world's population originally resided, sunlight exposure was plentiful, enabling the body to produce between 10,000 and 20,000 international units (IUs) of vitamin D daily. However, as humans migrated to higher latitudes over millennia, the availability of UV rays diminished significantly during certain times of the year, hindering the skin's ability to produce sufficient vitamin D.

In recent decades, awareness of the dangers of excessive sun exposure, such as sunburns and skin cancer, has led to increased use of sun-blocking clothing and sunscreen, even in high-latitude regions. While these measures are essential for skin protection, they inadvertently reduce the skin's natural vitamin D production. This reduction poses a significant health concern, as numerous studies have highlighted the importance of vitamin D beyond its well-known role in calcium absorption and bone health.

Traditionally, vitamin D was primarily recognized for its contribution to bone health by enhancing calcium absorption. However, research over the past decade, particularly in the last five years, has uncovered a broader range of benefits associated with adequate vitamin D levels. Studies have shown that vitamin D plays a crucial role in fighting cancers and diabetes, acts as a key component in hormone production for muscle protection, and inhibits various autoimmune disorders, including multiple sclerosis, lupus, and inflammatory bowel disease.

Furthermore, these newly recognized health benefits of vitamin D often require blood concentrations significantly higher than those needed merely for bone protection. While these levels may seem high by dietary standards, they are not truly megadoses. Instead, they reflect the natural amounts the skin can generate through ample sun exposure, particularly in low-latitude regions.

Modern lifestyles and work routines, however, limit our time spent outdoors, reducing the body's natural production of vitamin D. Consequently, we must rely on our diets to obtain this essential nutrient. Unfortunately, few foods are naturally rich in vitamin D, and only a select few, such as fortified milk, provide more than minimal amounts. As a result, many people do not achieve the higher vitamin D levels required for optimal health.

Vitamin supplements can provide the recommended daily intake (RDI) of vitamin D, which ranges from 200 to 600 IU depending on age. However, bone and mineral researchers have recently advocated for significantly higher intakes. Some scientists have suggested that the federal government increase the RDI to at least 1,000 IU and raise the certified-safe upper limit beyond the current 2,000 IU. These recommendations are based on growing evidence that higher vitamin D levels are necessary to harness the full spectrum of health benefits.

In conclusion, while modern measures to protect the skin from harmful UV rays are essential, they have the unintended consequence of reducing natural vitamin D production. Given the wide range of health benefits associated with adequate vitamin D levels, it is crucial to ensure sufficient intake through diet and supplements. Public health guidelines may need to be updated to reflect these findings, promoting higher vitamin D consumption to support overall health and well-being.
Balancing Sun Protection and Vitamin D: Ensuring Optimal Health

The Stealth Epidemic: Unveiling Diseases Associated with Vitamin D Deficiency

In the 21st century, the prevalence of vitamin D deficiency has reached alarming proportions, manifesting as a silent epidemic with widespread health implications. Traditionally, vitamin D inadequacy has been linked to conditions like rickets and osteomalacia, characterized by bone deformities and weakness. However, recent research underscores a broader spectrum of disorders associated with insufficient vitamin D levels.

Symptoms of vitamin D deficiency extend beyond musculoskeletal issues, encompassing a myriad of health concerns. Muscle weakness, chronic pain, fatigue, and even psychological symptoms like depression are commonly reported manifestations. Moreover, this deficiency significantly compromises immune function, leaving individuals more susceptible to infections and illnesses.

Central to its impact is vitamin D's pivotal role in calcium and phosphorus absorption. Inadequate levels impede mineralization of the bone matrix, escalating the risk of osteoporosis and fractures. Chronic deficiency triggers a cascade effect, leading to hypocalcemia and secondary hyperparathyroidism, exacerbating bone health and metabolic stability.

Beyond bone health, emerging studies illuminate vitamin D's role in broader disease pathways. Evidence suggests associations between deficiency and respiratory tract infections such as colds, bronchitis, and pneumonia, underscoring the importance of optimal vitamin D levels in immune defense.

Researchers are delving into vitamin D's potential in combating abnormal cell growth. Studies explore its role in conditions like psoriasis and various cancers, including lung, blood, and cervix. This burgeoning field underscores the multifaceted impact of this vitamin on cellular health.

Furthermore, vitamin D deficiency appears intertwined with heightened risks for chronic diseases. Studies have linked low levels to cardiovascular disease, multiple sclerosis, rheumatoid arthritis, and type 1 diabetes, illuminating its far-reaching implications beyond bone health.

The relevance of vitamin D deficiency is underscored by contemporary health challenges. Notably, hypotheses around vitamin D's impact on prostate cancer incidence highlight the intricate interplay between sunlight exposure, vitamin D synthesis, and disease prevalence.

As research progresses, public health initiatives must prioritize strategies to address and prevent vitamin D deficiency. Efforts to enhance dietary intake, promote sunlight exposure, and tailor supplementation regimens are critical to mitigating the stealthy impact of this pervasive deficiency. By elevating awareness and adopting proactive measures, we can combat the insidious reach of vitamin D deficiency and safeguard global health in the modern era.
The Stealth Epidemic: Unveiling Diseases Associated with Vitamin D Deficiency

Hypervitaminosis D

Vitamin D toxicity, also called hypervitaminosis D, is a rare but potentially serious condition that occurs when excessive amounts of vitamin D in human body. It is usually the result of taking high-dose vitamin D supplements. Hypervitaminosis D is characterized by a considerable increase in circulating 25(OH)D levels up to a level of approximately 160–500 ng ml−1 plasma.

It is usually due to taking more than the recommended daily value of vitamin D. Some prescription medications used to treat high blood pressure (thiazide diuretics) and heart diseases (digoxin) can cause an increase in vitamin D in the blood.

Hypervitaminosis D and its clinical manifestation, severe hypercalcemia, are related to excessive long-term intake of vitamin D, malfunctions of the vitamin D metabolic pathway, or the existence of coincident disease that produces the active vitamin D metabolite locally.

The main consequence of vitamin D toxicity is a buildup of calcium in human blood (hypercalcemia), which can cause nausea and vomiting, weakness, and frequent urination.

The most often noted clinical symptoms of Hypervitaminosis D include: confusion, apathy, recurrent vomiting, abdominal pain, polyuria, polydipsia, and dehydration. Vitamin D toxicity might progress to bone pain and kidney problems, such as the formation of calcium stones.

Long-term high-dose D supplement intake may result in adverse health effects, increase in mortality, greater risk of pancreatic cancer, cardiovascular events, and increased falls and fractures in the elderly.
Hypervitaminosis D

Foods that are high in vitamin D

Many foods contain added vitamins and minerals that might not be in a person’s diet or that have been destroyed or lost in processing. Common nutritional additives include vitamin D in milk, vitamin A in margarine, vitamin C in fruit drinks, and iodine in salt.

Vitamin D is a nutrient found in some foods that is needed for health and to maintain strong bones. It does so by helping the body absorb calcium (one of bone’s main building blocks) from food and supplements.

The main sources of natural vitamin D are fatty fish, such as salmon, mackerel or tuna, mushrooms and also egg yolks. Vitamin D can also be obtained from food fortified with vitamin D, such as cereal products, bakery products, baby food, butter, and margarine. The most commonly used vehicles for vitamin D fortification are dairy products (milk, cheese and yogurt). Bread fortified with vitamin D could serve as a good source of vitamin D due to its common consumption.

Such fortification has helped prevent nutritional deficiency diseases that were once common, such as rickets (due to deficiency of vitamin D).

Foods that are high in vitamin D

Research of Vitamin D by Harry Goldblatt

Vitamin D became classified as a vitamin through a historical accident. It was in 1919/20 that Sir Edward Mellanby, working with dogs raised exclusively indoors, devised a diet that allowed him to unequivocally establish that their bone disease, rickets was caused by a deficiency of a trace component present in the diet.

The transformation of the vitamin D precursor (7-dehydrocholesterol) by UVB has been discovered in 1923 by Harry Goldblatt and Katherine Soames, research that was later developed by Alfred Fabian Hess and Mildred Weinstock.

Harry Goldblatt (1891-1977) was an American pathologist whose research and experiments on renovascular hypertension were an important contribution to understanding and treating this disease. He was born in Iowa, the son of Phillip and Jennie Spitz Goldblatt. He grew up in Canada, received a B.A. from McGill University, and graduated from its medical school in 1916.

During the course of extensive nutritional research, in 1923 Harry Goldblatt and Katherine Soames clearly identified that when a precursor of vitamin D in the skin (7-dehydrocholesterol) was irradiated with sunlight or ultraviolet light, a substance equivalent to the fat-soluble vitamin was produced.

Goldblatt and Soames irradiated rat livers that had been excised from rachitic rats with ultraviolet light and found that when the irradiated tissue was ground and fed to other rachitic rats, there was a remission of the D deficiency, whereas the livers from unirradiated rats were not.
Research of Vitamin D by Harry Goldblatt

Mushroom Is A Natural Source Of Vitamin D

Vitamin D is in category of fat-soluble vitamin therefore human body can store extra amounts of vitamin D.

It is necessary to get enough vitamin D from the diet because it helps human bodies absorb and use calcium and phosphorous to build strong bones and teeth. In this case, vitamin D can help protect older adults against osteoporosis and reducing the risk of falls in the elderly.

Vitamin D is important to the body in many other ways as well. Vitamin D is responsible for brain development. Muscles need it to move, for example, nerves need it to carry messages between the brain and every body part, and the immune system needs vitamin D to fight off invading bacteria and viruses.

Many other studies suggest that vitamin D may reduce the risk of cardiovascular disease, neurodegenerative diseases, diabetes and infectious disease e.g. respiratory tract infection.

The two main dietary category of vitamin D are D2, found in fungi and yeast, and D3, found in animals; lesser amounts of vitamin D3 and D4 are also found in fungi.

Certain foods in the Western diet are a good source of vitamin D, with the best example of naturally occurring dietary source being oily fish. Even though, vegetable foods generally contain low vitamin D, mushrooms provide some vitamin D.

Mushrooms are a natural source of vitamin D2 with lesser amounts of vitamins D3 and D4. The vitamin D2 content of mushrooms can be increased dramatically by exposed to a source of ultraviolet (UV) radiation, such as sunlight or a UV lamp, whereby ergocalciferol is formed from ergosterol.

Worldwide mushroom consumption has improved markedly in the past four decades, and mushrooms have the potential to be the only non-animal, unfortified food source of vitamin D that can deliver a substantial quantity of vitamin D2 in a single serve.
Mushroom Is A Natural Source Of Vitamin D

Food sources of vitamin D

Vitamin D is a fat-soluble vitamin. This means that human body can store extra amounts of vitamin D. Vitamin D works with calcium and phosphorus for healthy bones, muscles and teeth.

Vitamin D is a nutrient found in some foods that is needed for health and to maintain strong bones. It does so by helping the body absorb calcium (one of bone’s main building blocks) from food and supplements. Human body needs vitamin D to help absorb calcium. Vitamin D may help to prevent or manage some chronic diseases.

The main source of vitamin D comes from sunlight. The high vitamin D deficiency is strongly associated with low sun exposure. The sources of vitamin D in food was limited.

Oily fish such as sardines, pilchards, trout, herring, kippers and eel contain reasonable amounts of vitamin D. Salmon, tuna, and mackerel are among the best sources. Beef liver, cheese, and egg yolks provide small amounts. Mushrooms provide some vitamin D. In some mushrooms that are newly available in stores, the vitamin D content is being boosted by exposing these mushrooms to ultraviolet light.

Now there are many kinds of foods which contain fortified vitamin D, particularly milk products, biscuits, and cereals. Margarine, some breakfast cereals, infant formula milk and some yoghurts have added or are ‘fortified’ with vitamin D.

People can get vitamin D from some foods including fortified foods and everyone is recommended to take a supplement, especially during autumn and winter.

Vitamin D is found in supplements (and fortified foods) in two different forms: D2 (ergocalciferol) and D3 (cholecalciferol). Both increase vitamin D in the blood.
Food sources of vitamin D

Vitamin D deficiency can cause heart disease

Vitamin D, a fat-soluble prohormone, has wide-ranging roles in the regulation of many physiological processes through their interactions with the vitamin D receptors (VDR). It plays a major role in bones and calcium metabolism.

Recent research has linked inadequate vitamin D status to non-skeletal major chronic diseases, especially cardiovascular diseases. Existing data from laboratory studies, epidemiologic and experimental research and prevention trials, suggest that vitamin D reduces the risk of cardiovascular disease.

Through increased renin and angiotensin II synthesis, vitamin D deficiency can increase the production of reactive oxygen species and G protein RhoA, resulting in inhibition of the pathways necessary for intracellular glucose transporter and thus the development of insulin resistance and metabolic syndrome. In addition, direct effects of vitamin D upon smooth muscle calcification and proliferation could contribute to their effects on cardiovascular health.

Studies have also demonstrated a link between vitamin D deficiency and progression of atherothrombosis and vascular calcification. Vitamin D has been found to regulate macrophage maturation and infiltration into the vasculature, subsequently regulating the expression of pro-inflammatory cytokines and adhesion molecules, which are critical components in the progression of atherosclerosis. These findings are also in line with observations that vitamin-D deficient patients have increased plaque instability and incidence of myocardial infarction.

Vitamin D deficiency can cause heart disease

Elmer McCollum - Discovering Vitamin A, Vitamin B and Vitamin D

Elmer Verner McCollum (March 3, 1879 – November 15, 1967) was born and raised in Kansas and attended the University of Kansas. His studies were initially directed toward medicine, but he eventually decided that chemistry better captured his interests, and he completed his work for a Masters degree in chemistry at Kansas. He was accepted into the Ph.D. program at the Sheffield Scientific School at Yale.

Contrary to the dogma that all fats had similar nutritional value, in 1913, Elmer McCollum and his associate Marguerite Davis at Wisconsin showed butter and egg yolk were not equivalent to lard and olive oil in supporting the growth and survival of rats. The growth-supporting ‘accessory factor’ became known as ‘fat-soluble A’ in 1918 and then ‘vitamin A’ in 1920.

“Fat-soluble A” was first believed to be a single vitamin capable of curing xerophthalmia and rickets. Cod-liver oil was first used as a therapeutic agent in the 1770s. McCollum showed that cod-liver oil aerated at the temperature of boiling water for 12 to 20 hr retained its antirachitic activity in rats, but was ineffective against xerophthalmia. In addition, these properties were unequally distributed in certain foods. Apparently, two separate factors were involved. The factor effective against rickets later was named vitamin D.

The discovery of vitamin A by McCollum and Davis in 1913 ushered in the era of accessory food substances culminating in the achievement of that goal. It included the discovery of vitamin D and its production in skin caused by ultraviolet light. This was followed by a description of its actions at the physiological level that resulted in a healthy skeleton and beyond.

In 1915 McCollum and Davis had found that when water oralcohol extractions of wheat germ or rice polishing were added, polished rice was greatly improved in nutritional quality. These experiments constituted the basis for their discovery that the anti-beriberi factor, necessary to relieve polyneuritis in pigeons, was necessary for rats and that there were apparently only two unidentified nutrients necessary for such animals.

They proposed the term fat-soluble A and water-soluble B, respectively, to designate the two unidentified nutrients. The isolation of B1was achieved in 1926 by Dutch scientists in Java using small “rice birds” fed on washed white rice supplemented with cod liver oil for their assays.

Elmer McCollum - Discovering Vitamin A, Vitamin B and Vitamin D

Adding vitamin D in milk

Milk normally contains vitamin D, but the amount varies with cow’s diet, and with her exposure to sunlight.

Milk has a relatively low content of vitamin D particularly in the winter. Summer milk may have approximately 30 IU in each quart but in winter, the content falls very much below this level. The vitamin D level in milk may be raised by simply adding the milk a dispersible preparation of the vitamin.

This generally is accomplished by adding a concentrate to the milk, prior to pasteurization, to increase the potency to at least 400 IU of vitamin D per quart of milk.

Pasteurization of milk and sterilization of evaporate milk do not destroy vitamin D. Most of the milk consumed in the United States contains added vitamin D.
Adding vitamin D in milk

The first scientific description of a vitamin D-deficiency by Dr. Daniel Whistler

The term ‘rickets’ first appeared in 1634 when listed as a cause of death in London’s Annual Bill of Mortality.

The first scientific description of a vitamin D-deficiency, namely rickets, was provided in the 17th century by both Dr. Daniel Whistler and Professor Francis Glisson.

It was that English physician Dr. Daniel Whistler described its symptoms in 1645. The publication by Whisker was a concise monograph of only 14 pages and was written when author was 26 years old. It represented the thesis required for his degree of doctor of medicine. His thesis was ‘De morbo perili Anglorum’ - The Children’s disease of the English.

The Latin thesis was read at Leiden on 18th October 1645. The importance of this thesis lies in the fact that it contained the first complete clinical account of rickets. Whistler's book was published a short time after the reading of his thesis in 1645. It was a small quarto volume of some eighteen pages, though when it was reprinted in 1684, it was in octavo.

In his thesis Dr. Whistler proposed a wide range of suggestions for treatment from crow’s or frog’s livers, application of leeches, purgation, poultices of snails and salt placed on the belly, and grease from mainly pork fat, goosegrease and butter to be smeared on the swollen epiphyses.
The first scientific description of a vitamin D-deficiency by Dr. Daniel Whistler

Edward Mellanby and study of rickets

Rickets in young children, known for centuries as the English disease, was fully described in 1650 by Francis Glisson, Regius Professor of Physic at Cambridge, and also four years earlier in a thesis presented to the University of Leyden by Daniel Whistler, a medical student from Oxford. Whistler published a monograph titled “Inaugural medical disputation on the disease of English children which is popularly termed the rickets.”

Whistler provided a succinct description of the signs and symptoms of rickets in his thesis and used an alternate term called “Paedosteocaces” to describe the clinical symptoms of rickets.

It was in 1919/20 that Sir Edward Mellanby, an English physician, working with dogs raised exclusively indoors (in the absence of sunlight or ultraviolet light), devised a diet that allowed him to unequivocally establish that the bone disease, rickets was caused by a deficiency of a trace component present in the diet.

Vegetable oils such as olive oil, cotton seed oil and linseed oil permitted development of rickets, where as it could be prevented or cured with cod liver oil or egg yolk. Mellanby concluded that a vitamin substance preventing rickets was present in these fats.

In 1921 he wrote, "The action of fats in rickets is due to a vitamin or accessory food factor which they contain, probably identical with the fat-soluble vitamin." Furthermore, he established that cod liver oil was an excellent antirachitic agent.

Mellanby had presumed that calcium and phosphorus were adequate in all of his rachitic diets but it was soon established that all of his diets were relatively deficient in calcium and lacked favorable calcium phosphorus ratios. Mellanby’s work clearly established the role of diet in the cause of rickets.
Edward Mellanby and study of rickets

7-Dehydrocholesterol

7-Dehydrocholesterol is a biosynthetic precursor to previtamin D 3 in human skin and to cholesterol in tissues. Although the level of 7-dehydrocholesterol is normally low in human tissues and fluids, it is significantly elevated in a number of human disorders, including Smith Lemli-Opitz syndrome (SLOS) and cerebrotendinous xanthomatosis.

The Smith-Lemli-Opitz syndrome (SLOS) is a common birth defect syndrome characterized biochemically by low plasma cholesterol levels and high concentrations of the cholesterol precursor 7dehydrocholesterol. It is a metabolic and developmental disorder caused by mutations in the gene encoding the enzyme 7-dehydrocholesterol reductase (Dhcr7).

In SLOS, the tissue cholesterol and total sterol levels are markedly reduced while the concentrations of 7-dehydrocholesterol are greatly elevated. This elevation in 7-dehydrocholesterol inhibits the activity of Hmgcr, thus further exacerbating the cholesterol deficit.

Cholesterol in mammals is synthesized from acetate with the final two steps being the conversion of lathosterol to 7-dehydrocholesterol and 7-dehydrocholesterol to cholesterol.
7-Dehydrocholesterol

Vitamin D for normal bone

Vitamin D comes from two sources in humans; it could either be synthesized in form of vitamin D3 (cholecalciferol) under the influence of solar UV-B radiation in the epidermis, or be absorbed from the diet or from supplements and food additives, which in some countries may contain vitamin D2 (ergocalciferol).

This vitamin is necessary for normal tooth and bone formation. Vitamin D contributes to bone health by regulating calcium absorption. Vitamin D is crucial for maximizing gut absorption of calcium via vitamin D dependent Ca receptors. It is estimated that adequate vitamin D status increases Ca absorption to 30–40% of intake compared with only 10–15% absorption without adequate vitamin D.

Adequate vitamin D is necessary for absorption of calcium. Vitamin D is made in the skin after exposure to sunlight. Estimates include 5-16 minutes of sun exposure 3 times a week on the face, hands, and arms will meet vitamin D needs.

The recommended adequate intake (AI) of vitamin D for children and adults up to 50 years is 200 IU, whereas the recommended AI for adults 51–70 years and 71+ years is 400 IU and 600 IU, respectively.
Vitamin D for normal bone

Disease of growing bone: Rickets

Rickets is a disease that affects bone structure, resulting in soft and weakened bones and is particularly damaging to the weight-bearing bones in the legs, spine, and pelvis. A similar disease process occurs in adults and is known as osteomalacia, or simply soft bones.

It is characterized by malformed and weak bones because of poor calcium and phosphorous deposition.

Rickets is more likely to occur in children eating a poor diet and living in northern countries, where there is less sunshine. Vitamin D allows the body to absorb calcium from food and makes sure that the calcium is passed from the blood into the bone when the bone is being formed.

Defective mineralization of both bones and cartilaginous material in the epiphyseal growth plate becomes apparent as the child grows.

In rare cases, there may be rickets of urinary origin, where there are excessive urinary losses of either calcium or phosphorus. Vitamin D-resistant rickets is, in most cases, a genetic disorder where excessive phosphate is lost in the urine which reduces the supply available for mineralization of bone.

Rickets was first identified in Europe in the 1600s when the lack of sunlight and meager, unbalanced diet available to working class city dwellers cause an epidemic of rickets until the early 1900s.

Disease of growing bone: Rickets