Vitamin Information Center

VITAMIN D: “The Sun Vitamin”

Nicholas H.E. Mezitis MD and Despina Komninou MD, PhD, CNS

Did you know that vitamin D, as a hormone, has an important role in metabolic harmony?

Recent studies have shown that vitamin D in its active form is vital for bone health, since it ensures dietary calcium absorption, and helps prevent heart disease, cancer (breast, prostate, lung and colon ), as well as many other illnesses such as diabetes mellitus, rheumatoid arthritis, psoriasis, multiple sclerosis and tuberculosis.

Vitamin D regulates the calcium and phosphorus levels in the blood by promoting their absorption from food in the intestinal tract and by limiting the excretion of calcium by the kidneys. It influences the cells involved in remodeling bone (osteoclasts and osteoblasts) and it inhibits the secretion of parathyroid hormone, which signals calcium release from bone matrix. Importantly, it has a role to stimulate the immune system, promoting phagocytosis and anti-tumor activity among other functions.

The body produces vitamin D when bare skin is exposed to the sun, hence the term �sun vitamin�. Exposure to sunlight for at least 15 minutes two to three times a week produces adequate quantities of this vitamin for the body�s needs. It is estimated that the body can produce more than 20000 IU (international units) of vitamin D with just 20 minutes of sun exposure.. Once adequate amounts of vitamin D have been formed the body, excess amounts formed are rapidly degraded to protect from overload, in the event of prolonged exposure to the sun. However, conditions such as cloudy skies, northern climates, and atmospheric pollution, limit solar ultraviolet radiation exposure and restrict our ability to replete vitamin D stores.

Vitamin D can also be obtained from dietary sources. It is lipid-soluble and is therefore stored in fat. That is why we find it in fatty fish (like salmon and tuna), eggs, cod-liver oil and fortified milk. In our daily diet, 3 servings of milk (about 250 ml) provide us with approximately 900 mg of calcium and 300 IU of vitamin D.

The recommended daily intake (RDI) of vitamin D is 200 IU for infants, youths and adults up to the age of 50 years. The requirement increases to 400 IU for adults ages 51 to 70 and to 600 IU for people older than 70 years. The RDI and the normal reference values for vitamin D in the blood, are based on levels reported to the prevent rickets and osteomalacia, the two main diseases attributed to lack of this vitamin. Rickets is a childhood disease characterized by poor growth and bone weakness, while osteomalacia is the clinical expression of vitamin D deficiency in adults and is characterized by demineralized bones, fractures, bone pain and generalized weakness. Osteoporosis represents abnormal weakening of bone structure with demineralization of the skeleton, and may also be associated with low levels of vitamin D.

Recent studies confirm that optimal vitamin D status is achieved when the 25- OH vitamin D level in the blood is more than 30 ng/ml. Levels between 10-30 ng / ml represent vitamin D insufficiency (hypovitaminosis D) which can either be moderate (21-30 ng/ml) or severe (10-20 ng/ml). Vitamin D levels below 10 ng/ml are considered vitamin D deficiency and have serious consequences. We now know that long before the full clinical presentation of painful osteomalacia, hypovitaminosis D may cause non-specific symptoms such as persistent musculoskeletal pain regardless of age, gender and ethnic origin.

It is worth noting, that a significant proportion of the population has insufficient levels of vitamin D, mainly due to lack of sun exposure, especially during the winter months, which is not compensated by the usual diet. Indeed, today many of us work in buildings with sealed and tinted glass windows and drive everywhere with very few opportunities to walk in the sunlight. During our limited sun exposure opportunities we frequently use a sun screen lotion further obstructing the beneficial effects of sunlight. In areas above 40˚ latitude (e.g. New York, Northern California), sunshine adequate for vitamin D synthesis in the skin is restricted to the months from May through September. Therefore, a large proportion of the population in the United States is at increased risk for vitamin D deficiency

The prevention of hypovitaminosis D has important public health implications. Millions of health care dollars are spent in dealing with the illnesses and complications associated with this problem and additional funds are lost due to curtailed productivity on a societal level. Since sun exposure has its limitations, the diet is our primary source for this vitamin to ensure an intake of at least 1000 IU daily.

The proper diet must be rich in fatty fish such as salmon, mackerel and sardines, mushrooms (Shitake, sun dried, provide 1600 international units per 100 grams), free-range eggs and fortified milk products. Supplementation of vitamin D and calcium is advisable, especially for children and the elderly. Finally, regular, weight-bearing exercise ensures that calcium absorbed through the activity of vitamin D is used to mineralize the skeleton. Similar to a musical composition, health is ensured through harmony in diet and exercise.

More on the maintenance of metabolic harmony will be discussed in our next article *.

* This article is part of medical communication produced by the MEZITIS EDUCATION AND RESEARCH INSTITUTE for the print media, television and radio programs(Cosmos FM “����� ��� ���” every Saturday at 12:30 pm on 91.5 FM and the internet, live streaming, at gaepis.org) focusing on topics in general health, metabolism and nutrition.

The human body is an amazing factory, with all kinds of parts working together to make chemicals necessary for good health. But one thing it can’t make on its own is vitamin D. Research shows that defect can be troubling, especially among children.

To create vitamin D, which plays an important role in bone health and development, the body needs exposure to sunlight. As some countries move into autumn, the days get shorter and colder and exposure to sunlight decreases, making the colder months of the year a crucial time to watch vitamin D intake. Supplements can play an important role but one question is, how much?

Most of a child’s bone mass is built up early. A vitamin deficiency can prevent a child from building adequate bone mass now, and they won’t be able to make it all up later.

Although a study released this week found that vitamin D deficiencies are common in children around the world, there is minimal data on how much supplementation is necessary or safe.

Vitamin D is a fat — soluble vitamin directly or indirectly involved in several key body processes: regulating calcium and phosphorus levels in the blood, promoting bone formation and mineralisation, restricting parathyroid hormone secretion and promoting anti-tumour activity.

A review of medical literature on the vitamin published last year in The New England Journal of Medicine found that vitamin D is also associated with a reduced risk of type 1 diabetes in children, and may inhibit future hip fracture.

The main source of vitamin D is sunlight, which the body uses to convert vitamin D into a useable form. It’s also found naturally in eggs and fatty fish like salmon or tuna, and milk and some breakfast cereals are fortified with the vitamin.

The Institute of Medicine recommends that children get 200 IUs of vitamin D daily, but some experts say that up to 800 IUs is better.

The new study found that high doses of the vitamin were safe for children, whether taken over the short-term or for a longer period of time, and helped increased bone mass in 10 to 17 year olds.

A study released this summer found that even children who are otherwise healthy can have low levels of vitamin D, resulting in low levels of bone mineral content.

The risk for low vitamin D levels begins in infancy —breast milk, like cow’s milk, is naturally low in vitamin D. And if a mother doesn’t have enough vitamin D, her breast milk won’t either.

A vitamin D deficiency can affect bone growth even if there are no obvious problems.

A bottle of vitamin supplements
The American Academy of Paediatrics says that rickets, bone softening that can lead to fractures and deformity, in infants due to low vitamin D intake is seen in several US states.

The agency recommends that breast-fed infants receive vitamin D supplement drops.

Children at risk
“It is recommended that all infants, including those who are exclusively breastfed, have a minimum intake of 200 IUs of vitamin D per day beginning during the first two months of life,” said a clinical report for the health agency done by Dr Lawrence Gartner and Dr Frank Greer.

“In addition, it is recommended that an intake of 200 IUs of vitamin D per day be continued throughout childhood and adolescence, because adequate sunlight exposure is not easily determined for a given individual.”

The risks to bone health don’t end in infancy.
A Canadian study released last year found that despite guidelines for its prevention, vitamin D-deficiency rickets in childhood is still seen in the country, with an annual incidence of 2.9 cases per 100,000.

Children living in countries where exposure to sunlight is low had the highest incidence, and most of the affected children had medium to dark skin tones and had been breast fed.

“Since there were no reported cases of breast-fed children having received regular vitamin D (400 IU/d) from birth who developed rickets, the current guidelines for rickets prevention can be effective but are not being consistently implemented,” the study concluded.

Adequate vitamin D levels in the blood are important because the body can’t absorb dietary calcium without vitamin D, so in its absence it steals calcium from the bones, which increases the risk of rickets, osteoporosis and fractures.

This also places teenagers at risk because they have weaker bones that are more likely to fracture.

Children at particular risk include infants who are breast-fed exclusively and don’t receive supplementation, children who use sunscreen in summer, children who don’t use sunscreen in the summer but spend less than 15 minutes a day in direct sunlight, children who receive no supplementation in the winter, and children with chronic diseases that affect fat malabsorption, such as cystic fibrosis or celiac disease, according to the Hospital for Sick Children.

TORONTO (Reuters) - The human body is an amazing factory, with all kinds of parts working together to the make the chemicals necessary for good health. But one thing it can’t make on its own is vitamin D. Research shows that defect can be troubling, especially among children.

To create vitamin D, which plays an important role in bone health and development, the body needs exposure to sunlight. As we move into autumn, the days get shorter and colder and our exposure to sunlight decreases, making the colder months of the year a crucial time to watch vitamin D intake. Supplements can play an important role but one question is, how much?

Most of a child’s bone mass is built up early. A vitamin deficiency can prevent a child from building adequate bone mass now, and they won’t be able to make it all up later. Although a study released this week found that vitamin D deficiencies are common in children around the world, there is minimal data on how much supplementation is necessary or safe.

Vitamin D is a fat-soluble vitamin directly or indirectly involved in several key body processes: regulating calcium and phosphorus levels in the blood, promoting bone formation and mineralization, restricting parathyroid hormone secretion and promoting anti-tumor activity. A review of medical literature on the vitamin published last year in The New England Journal of Medicine found that vitamin D is also associated with a reduced risk of type 1 diabetes in children, and may inhibit future hip fracture.

The main source of vitamin D is sunlight, which the body uses to convert vitamin D into a useable form. It’s also found naturally in eggs and fatty fish like salmon or tuna, and milk and some breakfast cereals are fortified with the vitamin. The Institute of Medicine recommends that children get 200 IUs of vitamin D daily, but some experts say that up to 800 IUs is better.

This week’s study found that high doses of the vitamin were safe for children, whether taken over the short-term or for a longer period of time, and helped increased bone mass in 10-17-year olds.

Vitamin D deficiency is particularly a problem for North Americans, research shows, due in part to the higher latitudes at which they live. As well, because of concerns about skin cancer, many people now wear sunscreen, which inhibits the body’s ability to use sunlight to make the vitamin. The Hospital for Sick Children in Toronto says that sunscreen with an SPF above 8 blocks all vitamin D production through the skin. And darker-skinned individuals living in Canada and the United States may be at particular risk because they have more melanin in their skin, which means they need more sunlight than a lighter-skinned person to make the same amount of vitamin D.

A study released this summer found that even children who are otherwise healthy can have low levels of vitamin D, and resulting low levels of bone mineral content. More than 12 percent of the 400 kids studied by researchers at the Children’s Hospital in Boston had levels of vitamin D in their blood low enough to qualify them as deficient, and 40 percent of the children had less than the recommended level
The risk for low vitamin D levels begins in infancy - breast milk, like cow’s milk, is naturally low in vitamin D. And if a mother doesn’t have enough vitamin D, her breast milk won’t either.

A vitamin D deficiency can affect bone growth even if there are no obvious problems. The American Academy of Pediatrics says that rickets (), bone softening that can lead to fractures and deformity, in infants due to low vitamin D intake is seen in several U.S. states. The agency recommends that breast-fed infants receive vitamin D supplement drops.

“It is recommended that all infants, including those who are exclusively breastfed, have a minimum intake of 200 IUs of vitamin D per day beginning during the first 2 months of life,” said a clinical report for the health agency done by Drs. Lawrence Gartner and Frank Greer. “In addition, it is recommended that an intake of 200 IUs of vitamin D per day be continued throughout childhood and adolescence, because adequate sunlight exposure is not easily determined for a given individual.”

The risks to bone health don’t end in infancy. A Canadian study released last year found that despite guidelines for its prevention, vitamin D-deficiency rickets in childhood is still seen in the country, with an annual incidence of 2.9 cases per 100,000. Children living in the northern part of the country, where exposure to sunlight is the lowest, had the highest incidence, and most of the affected children had medium to dark skin tones and had been breast fed.

“Since there were no reported cases of breast-fed children having received regular vitamin D (400 IU/d) from birth who developed rickets, the current guidelines for rickets prevention can be effective but are not being consistently implemented,” the study concluded.

Adequate vitamin D levels in the blood are important because the body can’t absorb dietary calcium without vitamin D, so in its absence it steals calcium from the bones, which increases the risk of rickets, osteoporosis and fractures. This also places teenagers at risk because they have weaker bones that are more likely to fracture.

Children at particular risk include infants who are breast-fed exclusively and don’t receive supplementation, children who use sunscreen in the summer, children who don’t use sunscreen in the summer but spend less than 15 minutes a day in direct sunlight, children who receive no supplementation in the winter, and children with chronic diseases that affect fat malabsorption, such as cystic fibrosis or celiac disease, according to the Hospital for Sick Children.

Because natural sources are so rare, it’s difficult to get adequate vitamin D in the diet. One tablespoon of cod liver oil has 1,360 IUs, a serving of cooked salmon has 360, a cup of fortified milk has 98 and a whole egg has 20. Fifteen minutes of direct sunlight is enough for many people to reach their needs for vitamin D, but darker-skinned people need longer exposure and because winter sunlight in North America is indirect, supplementation may be recommended.

Do you supplement with extra vitamin D? Let us know: HealthMatters@reuters.com