Vitamin D is essential for the maintenance of homeostasis of the organism to act in various ways in controlling calcium levels in the blood and bones. Recent surveys show that the recommended daily amount can be much greater than the value that so far is widely used.
Vitamin D belongs to the group of fat-soluble vitamins and cholesterol is derived. There are two forms in nature, cholecalciferol or vitamin D2, which has animal origin and ergocalciferol or vitamin D3, which comes from plant sources. In the human body, both of which are metabolized in liver and kidney to calcitriol, which is its active form.
- 1 What is vitamin D?
- 2 What are the symptoms of vitamin D deficiency?
- 3 What are the sources of vitamin D?
- 4 What is the recommended dose of vitamin D?
- 5 Causes of lack of Vitamin D
- 6 Tips
What is vitamin D?
Vitamin D exerts its function by binding to specific receptors in the nuclei of target cells. This interaction generates a change in the proteins produced by these cells the result will be the action that cell on any aspect related to calcium.
In the intestine, Vitamin D stimulates the synthesis of proteins that act in direct and indirect calcium ion absorption of food into the bloodstream. It also stimulates the absorption of phosphate and magnesium.
In the kidneys, it promotes resorption of calcium and phosphate filtered, which would be excreted in the urine back into the blood stream.
In the bones, the vitamin D promotes the synthesis of proteins involved in bone formation, increase the number and activity of osteoblasts (cells that produce bone tissue), is fundamental to the growth and maintenance of bone density.
Vitamin D levels also affect PTH secretion by the thyroid. Low concentrations of vitamin D stimulate the secretion of parathyroid hormone that stimulates bone tissue to release calcium into the blood.
In addition to the effects on calcium homeostasis, vitamin D can also have effects on other functions such as cell apoptosis (programmed cell death), cell differentiation, cardiovascular, immune and skeletal muscle systems and also in insulin metabolism. Thus, vitamin D may be important in treatment of various conditions such as glucose intolerance, type 1 and 2 diabetes, hypertension and multiple sclerosis.
What are the symptoms of vitamin D deficiency?
Lack of vitamin D can cause a number of symptoms and health problems, given their importance to the homeostasis of the organism.
Symptoms include muscle weakness and bone pain and can be quite subtle. However, the long-term consequences can be quite serious, even in the absence of symptoms. Lack of vitamin D can lead to lack of calcium, which in turn impairs the formation of bones causing rickets in children and osteomalacia in adults. Rickets is characterized by low bone mineralization, where the children have affected their growth and development. The osteomalacia leads to weak bones, pressure sensitive and more likely to fracture.
Low levels of vitamin D have been also associated with a higher incidence of some cancers (such as colorectal and breast), severe asthma in children, depression and cognitive impairment in old age, infections, autoimmune diseases, increased risk of death cardiovascular diseases, hypertension, periodontal disease, chronic pain and osteoporosis in postmenopausal women.
What are the sources of vitamin D?
We must always keep our levels of vitamin D to keep us healthy. Here's how we have access to it and how to reset in the event of disability.
There are three ways to get vitamin D. One is from the food. There is a wide variety of food sources of vitamin D, the richest are fish liver oils, especially the cod; meat oily fish such as salmon, tuna, sardines and tilapia; dairy products such as butter and fat cheeses; mushrooms, oysters and eggs (specifically the yolk).
The second way to get Vitamin D is through sun exposure. The ultraviolet rays cause the biochemical reactions that lead to production of vitamin from cholesterol derivatives.
Finally, the third way of obtaining vitamin D is vitamin supplements through and medicines containing the substance. When it is not possible to obtain adequate amounts from the two previous forms, the use of vitamin D supplementation is necessary.
What is the recommended dose of vitamin D?
The values that a person should consume vitamin D daily is still controversial subject. In the United States the first defined values were 200 IU (international units IU means, and in this case equal to 5 micrograms of vitamin). This is the current value in Brazil to date, which appears on the labels of food and medicine. However, the National Academy of Sciences of the United States, based on research, revised this amount to between 400 and 800 IU. Studies further indicate that recent doses of 7,000 IU would be needed to ensure the full functioning of the dependent functions of vitamin D in the body.
the safe dose is believed to be up to 10,000 IU per day, but there is no definitive consensus among the scientific community. The level of exposure to sunlight also has great influence on whether or not higher amounts of vitamin D from food.
The determination of sun exposure time is also very complicated, because the amount of vitamin produced depends on many factors, such as time, latitude in which the individual lives, season, skin color, diet, genetic factors and clothing.
Causes of lack of Vitamin D
Studies in several countries show a great deficiency of vitamin D in populations. In Brazil, for example, despite being a tropical country with high incidence of sunlight, the statistics indicate that about 60% of adolescents, up to 58% of adults and up to 83% of the elderly have insufficient vitamin D.
Some points are listed as possible causes of the lack of vitamin D, such as:
- insufficient exposure to the sun: populations of countries with low incidence of the sun's ultraviolet rays, people who leave little house, for example, the elderly, people who work in conditions that minimize exposure to the sun or using clothes covering much of the body for religious reasons for example, they are candidates to develop vitamin D deficiency does not achieve a reasonable rate of production of vitamin through the skin.
- Insufficient consumption in power: people who follow very restrictive diets or do not have access to foods rich in vitamin, which mostly are of animal origin, may lack vitamin D.
- Dark skin: The presence of a higher concentration of melanin in darker skin reduces the effectiveness in production of vitamin D.
- Impairment in renal conversion: as the kidneys are responsible for converting vitamin D into its active form, a failure in the system can lead to lower levels of calcitriol available. This situation is more common in older people.
- absorption problems: some diseases that affect the intestinal absorption of nutrients can cause poor absorption of vitamin D obtained from food. Among them we can mention celiac disease, Crohn's disease and cystic fibrosis.
- Obesity: by being lipophilic, vitamin D can be removed from the blood and stored by fat cells. Low vitamin D circulating levels are often found in people with obesity (BMI>30).
Although it is not possible to quantify vitamin D produced by the skin when exposed to sunlight, it is recommended that people get 15 to 20 minutes in the sun with sunscreen only in the face, because it blocks vitamin D synthesis since it prevents the passage of ultraviolet rays. After that time it is absolutely recommended that the sunscreen is passed around the body.
The most appropriate time for the production of vitamin D is just as harmful to the skin, when the solar radiation is most intense from 10 to 15h. UV rays are very aggressive and can lead to the development of skin cancer, so it takes common sense. Just a few minutes in the sun are enough for the skin to synthesize good amounts of vitamin D. Do not expose yourself for long periods without protection.
If your dermatologist prescribes absolute protection from the sun at all times and all regions of the body, so may need to be considered the use of vitamin D supplements to ensure adequate supply.
To always ensure that their vitamin D rates are up to date, do exams regularly and talk to your doctor about your choices on how to reset vitamin if necessary.