Vitamin D: deficiency and excess, causes, symptoms, treatment

From a nutritional standpoint, two forms of vitamin D are important.

• Vitamin D2 (as ergocalciferol). This form is synthesized from plants and yeast precursor products. This form is commonly used in high dose supplements.
• Vitamin D3 (as cholecalciferol). It is the most active form of vitamin D. It forms in the skin when the skin is exposed to direct sunlight. The most common food source is fortified foods, mainly cereals and dairy products. Vitamin D is also found in fish liver oil, oily fish, egg yolks and liver.

Human breast milk contains only small amounts of vitamin D.

Vitamin D is stored primarily in the liver. Ergocalciferol and cholecalciferol are not active in the body. Both forms must be processed (metabolized) in the liver and kidneys into an active form called active vitamin D, or calcitriol. This active form promotes the absorption of calcium and phosphorus from the intestines. The minerals calcium and phosphorus are found in bones and provide strength and density (a process called mineralization). Thus, calcitriol is essential for bone formation, growth, and repair.

Vitamin D requirements increase with age.

Vitamin D is fat soluble. It is fat soluble and must be supplied with some fat for absorption to occur.

Vitamin D deficiency

• The most common cause is lack of exposure to sunlight, usually when there is not enough vitamin D in the diet, but some diseases can also cause a deficiency.
• With a lack of vitamin D, muscles and bones weaken and pain can occur.
• Babies develop rickets. The skull is soft, the bones grow abnormally, and children begin to sit and crawl late.
• Blood tests and sometimes x-rays are done to confirm the diagnosis.
• From birth, breastfed newborns should receive vitamin D supplements because breast milk is low in vitamin D.
• Vitamin D supplements, given by mouth or by injection, lead to complete recovery.

Vitamin D deficiency is common throughout the world. It most often occurs when the skin is not sufficiently exposed to sunlight. Natural (unfortified) foods alone rarely provide enough vitamin D to avoid a deficiency. Vitamin D-fortified foods and vitamin D supplements can help prevent vitamin D deficiency when sunlight is insufficient.

When vitamin D is deficient, less calcium and phosphate is absorbed in the body. Since calcium and phosphate are not enough to maintain bone health, vitamin deficiencies D can cause damage to the bones, which is called rickets in children and osteomalacia in adults. In osteomalacia, the body does not have enough calcium and other minerals in the bone tissue, which leads to weak bones.

In pregnant women, vitamin D deficiency causes a deficiency in the fetus, and the newborn is at high risk of developing rickets. Sometimes the deficiency is so severe that it can cause osteomalacia in a woman. Vitamin D deficiency exacerbates osteoporosis.

Vitamin D deficiency results in low blood calcium levels. By trying to raise low blood calcium levels, the body can make more parathyroid hormone. However, when parathyroid hormone levels rise (a disorder called hyperparathyroidism), the hormone pulls calcium out of the bones to raise blood calcium levels. Parathyroid hormone also causes more phosphate to be excreted in the urine. Both calcium and phosphate are essential for maintaining healthy bones. As a result, the bones are weakened.

Do you know that…

1. Lack of exposure to sunlight can cause vitamin D deficiency.
2. Many older adults require vitamin D supplements.

Causes

- Insufficient exposure to the sun.

The most common cause of vitamin D deficiency is inadequate sun exposure.

Thus, the deficit occurs mainly in people who spend little time outdoors: these are the elderly, and people living in care facilities, for example, in a nursing home. Deficiency can also occur in winter in northern and southern latitudes or in people who completely cover their bodies, such as Muslim women.

Since breast milk contains only small amounts of vitamin D, breastfed babies who do not get enough sunlight are at risk of developing a deficiency of this vitamin and rickets.

Some experts recommend leaving your arms and legs or face, arms and hands exposed to sunlight for 5-15 minutes minimum 3 once a week, but some people, such as the elderly or those with darker skin, may need longer exposure to the sun Sveta. However, many dermatologists do not recommend increased sun exposure due to the increased risk of skin cancer.

Vitamin D deficiency usually develops in people who are not exposed to sunlight and do not get enough vitamin D in their diet.

- Other reasons.

When the skin is sufficiently exposed to sunlight, the body usually produces enough vitamin D. However, in some circumstances, the risk of developing vitamin D deficiency is increased even when exposed to sunlight.

• In some groups of people, the skin produces less vitamin D in response to sunlight. These include darker-skinned people (especially dark-skinned people), the elderly, and people who use sunscreen.
• The body may be unable to absorb enough vitamin D from food. In diseases associated with malabsorption, the body is unable to absorb fats normally. They also cannot absorb vitamin D because it is a fat-soluble vitamin that is normally absorbed with fats in the small intestine. As a person ages, less vitamin D may be absorbed from the intestines.
• The body may be unable to convert vitamin D to its active form. Some diseases of the kidneys and liver, as well as some rare hereditary diseases (such as hypophosphatemic rickets) interfere with this transformation process; some drugs, such as some anticonvulsants and rifampin, do the same.

- A Look at Aging: Vitamin D Deficiency

Older adults are more likely to develop vitamin D deficiency for several reasons: Their need is higher than that of younger people. They usually spend less time outdoors and thus are not sufficiently exposed to sunlight. They may not be sufficiently exposed to sunlight because they are homebound, live in long-term care facilities, or have to stay in hospital for extended periods. Sunlight does not produce enough vitamin D in their skin. Their diet may be so low in vitamin D that even low-dose vitamin D supplementation (such as 400 units per day) does not prevent deficiency. They may be suffering from medical conditions or taking medications that interfere with the processing of vitamin D. Older adults should take 800 IU of vitamin D every day to maintain bone health. There is no evidence that vitamin D is useful in the prevention of cancer or other diseases, or in the prevention of falls in the elderly. Research into other vitamin D benefits is ongoing. Older adults taking high doses of vitamin D supplements should have periodic blood tests to check their calcium, vitamin D, and parathyroid hormone levels.

Symptoms and Signs

A deficiency can cause muscle pain, weakness, and bone pain in people of all ages.

Muscle cramps (tetany) may be the first sign of rickets in newborns. They are caused by low blood calcium levels in people with severe vitamin D deficiency. If pregnant women are deficient in vitamin D, their newborns may have cramping. Spasms can affect the face, hands, and feet. If the spasms are severe, they can cause seizures.

In infants with rickets, the entire skull may be soft.

Older infants may sit and crawl late, and the spaces between the bones of the skull (fontanelles) may close slowly.

Children 1-4 years of age may have bone growth abnormalities, causing abnormal curvature of the spine (scoliosis), O-shaped curvature of the legs or X-shaped legs. Such children may start to walk late.

Older children and adolescents experience pain when walking. Severe deficiency can cause O-shaped curvature of the legs or X-shaped legs. The pelvic bones can flatten, narrowing the birth canal in adolescent girls.

In adults, bones become weak, especially the spine, pelvic bones, and legs. The affected areas can be painful to touch and fractures can occur.

In older people, bone fractures, especially hip fractures, may result from only a light blow or a minor fall.

Diagnostics

Diagnostics include:

• Blood tests;
• Sometimes X-ray examination.

Doctors suspect vitamin D deficiency in the following people:

• People who report an inadequate diet or inadequate sun exposure;
• Newborns with tetany;
• Children with signs of rickets;
• Elderly people, especially those with low bone density (eg, osteoporosis) or bone fractures.

Blood tests to determine vitamin D levels may be done to confirm a deficiency. Calcium and phosphate levels are measured. Levels of other substances can be measured to rule out other causes of decreased bone density.

X-rays may also be taken. Characteristic changes in bones can be seen on radiographs before symptoms become noticeable.

The diagnosis of rickets or osteomalacia caused by vitamin D deficiency is based on symptoms, the characteristic appearance of bones on radiographs, and low levels of vitamin D in the blood.

Prophylaxis

Many people need to take vitamin D supplements. Getting enough exposure to sunlight can be difficult, especially because the skin also needs to be protected from the harmful effects of the sun. Natural foods rarely contain enough vitamin D to compensate for the lack of sunlight.

Vitamin D supplementation is especially important for people who are at risk (for example, the elderly, people tied to their homes, or people living in long-term care settings). To prevent deficiency, seniors should take 800 IU of vitamin D daily as a supplement. Higher doses are rarely required.

In many countries, commercially available drinking milk (but not cheese and yoghurt) is fortified with vitamin D. In many other countries, milk is not fortified with vitamin D. Breakfast cereals can also be fortified.

It is especially important for breastfed newborns to start supplementing immediately after birth, as breast milk is low in vitamin D. Supplements are given until the baby is 6 months old, when he begins to eat more varied foods. For infants who receive formula, commercial infant formula contains adequate amounts of vitamin D.

Treatment

Treatment includes:

• Vitamin D supplements;
• Sometimes calcium and phosphate supplements.

Treatment for vitamin D deficiency involves taking high doses of vitamin D, usually by mouth daily, for about 1 month. After 1 month, the dose is usually gradually reduced to the usual recommended dose.

If muscle cramps occur or calcium deficiency is suspected, calcium supplements are also given. If there is a lack of phosphate, supplements containing phosphate are given. Usually, this treatment leads to a complete recovery.

People with chronic liver or kidney disease may need special forms of vitamin D supplements.

Excess vitamin D

Vitamin D toxicity:

• Vitamin D toxicity causes high blood calcium levels.
• People with vitamin D toxicity can lose appetite, feel nauseous, vomit, and become weak and nervous.
• Doctors diagnose a deficiency by measuring the levels of calcium and vitamin D in the blood.
• Treatment includes stopping vitamin D supplements and giving fluids and sometimes drugs.

Taking high daily doses of the vitamin, for example, 60 to 100 times or more of the recommended intake (RDA) can cause toxicity and high blood calcium levels for several months (hypercalcemia). Calcium levels rise because the following happens when vitamin D levels are high:

• Bones decompose more than they regenerate. (Usually, bones are continuously decomposed and rebuilt in a process called remodeling to adapt to changes in stress on them.) As a result, calcium is released from the bone into the bloodstream.
• More calcium is absorbed from food into the intestines.

People with vitamin D toxicity may have symptoms due to high blood calcium levels.

Symptoms and Signs

Early symptoms of vitamin D toxicity include loss of appetite, nausea and vomiting, subsequently weakness, nervousness and high blood pressure.

Because calcium levels are high, calcium can be deposited throughout the body, mainly in the kidneys, blood vessels of the lungs, and heart. The kidneys can be permanently damaged and work intermittently, resulting in renal failure.

Diagnostics

An excess of vitamin D is usually diagnosed when blood tests reveal high levels of calcium in a person taking high doses of vitamin D. Doctors also measure vitamin D levels in the blood.

Treatment

Treatment includes:

• Stop taking vitamin D supplements
• Intravenous fluid administration;
• Medications.

Treatment for vitamin D toxicity includes stopping vitamin D supplements to offset the effects of high blood calcium levels. Fluids are given intravenously as needed.

Medicines such as corticosteroids or bisphosphonates are prescribed to suppress the release of calcium from the bones.