Depriving the body of vitamin D can favor the appearance of skeletal malformations in the case of children, while in adults it causes osteomalacia, manifested by intense muscle and bone pain.
In the presence of prolonged vitamin D deficiency, the body generates a series of compensatory mechanisms to maintain constant calcium and phosphorus concentrations by hyperstimulating the parathyroid glands. Along with hypocalcemia, hyperparathyroidism secondary to vitamin D deficiency can be manifested by muscle weakness, muscle cramps, chronic fatigue and depression.
Sources of vitamin D
The most important forms of vitamin D are represented by vitamin D2 - ergocalciferol derived from plants and vitamin D3 - cholecalciferol which comes either from animal products and food supplements, or from skin synthesis favored by exposure to sunlight.
Vitamin D can only be found in certain foods, but its optimal intake can be ensured by consuming milk and fortified cereals or fatty fish such as salmon, sardines or mackerel. Red meat, cod liver and egg yolk are other food sources rich in vitamin D.
Another way to ensure the necessary vitamin D is represented by exposing the skin to natural light , thus facilitating the chemical processes of converting vitamin precursors into the active form of the calciferol compound under the direct action of UV radiation. The amount of vitamin D, also known as the vitamin of the sun, synthesized in the skin, depends on the time of exposure to UV radiation, the season, the latitude of the geographical area and, last but not least, the pigmentation of the skin given by melanin.
In order to ensure the optimum vitamin D requirement of the body, it is necessary to expose the face, arms, lower limbs and back chest to the sun for 10-15 minutes 2-3 times a week. Skin production of vitamin D decreases physiologically with age, so that, in the 7th decade of life, it is 50% lower than that recorded at the age of 20.
These conditions explain why, in certain situations, the synthesis of vitamin D recorded during the cold season drops dramatically or becomes non-existent in certain population categories, depending on their lifestyle, but also on the geographical area where they live. For the majority of the population, regular exposure to the sun's rays in the time interval between March and September ensures the optimal vitamin D requirement for the proper functioning of the body.
Children older than 1 year, women who are breastfeeding and people at risk who have a severe deficiency of vitamin D, require a daily amount of the compound of 600 IU. Up to the age of 1 year, the daily requirement of vitamin D is 400 IU, and for the elderly over 70 years old, the recommended daily dose is 800 IU.
It is important to know that excess vitamin D can be harmful, so it is recommended not to exceed 4000 IU per day for adults, pregnant women, nursing women, the elderly and children aged between 11 and 17 years. Children aged between 1 and 10 years should not exceed a daily intake of 2000 IU/day, and infants 1000 IU/day.
When is vitamin D administration recommended?
Supplementing vitamin D intake is recommended:
- For children in the growing period
- Immobile people who cannot benefit from exposure to the sun during various outdoor activities
- People who present a high risk of complications due to avitaminosis D.
The synthesis of vitamin D under the direct action of ultraviolet rays can also be diminished in people who live in unfavorable weather conditions (near the polar circles) and adopt thick clothing that covers the whole body throughout the year and in African American individuals .
Rickets is a condition found in children, whose clinical manifestations are caused by severe and prolonged vitamin D deficiency . Avitaminosis D causes a decrease in the fixation rate of calcium and phosphorus in the bone matrix during the period of growth and development, with the appearance of pronounced bone deformations. Food supplements based on vitamin D correct to some extent the bone deformities associated with rickets, but there are also situations in which they require surgical intervention for reconstruction in children with chronic vitamin D deficiency.
In addition to bone deformities, the long-term complications of rickets are represented by weight-loss retardation, deficient dentition and tonic-clonic seizures.
Osteomalacia or soft bone disease is an adult condition caused by avitaminosis D, which is manifested by osteo-muscular pain, recurrent fractures in the long bones and muscle weakness. The deficiency of vitamin D in this category of patients can be due both to the inadequate oral intake of the nutrient, as well as to its low absorption rate at the intestinal level or to kidney diseases that affect the metabolism of the mineral.
Patients diagnosed with cystic fibrosis, Crohn's disease or those who have undergone gastric bypass represent other population categories that require vitamin D supplementation, by taking oral supplements.
Pregnant and lactating women, infants up to 1 year old, children under 4 years old and the elderly represent the main population categories that show an indication for the administration of vitamin D supplements due to the increase in the body's needs or the decrease in the rate of absorption of vitamin D. nutrients specific to these periods.
Benefits of vitamin D on the muscle and bone system
Due to its involvement in maintaining the phospho-calcium balance, vitamin D plays an important role in the bone remodeling process . The main function of vitamin D is fulfilled after its interaction with specific receptors, which induce the expression of certain bone proteins - osteopontin, osteocalcin and alkaline phosphatase responsible for suppressing type I collagen synthesis.
Vitamin D increases bone resorption in synergy with the action of parathormone after stimulating immature osteoclastic receptors, which thus transform into mature osteoclasts (cells responsible for bone remodeling). Mature osteoclasts remove calcium and phosphorus from the bone, maintaining an optimal level of them at the blood circulatory level.
Optimal concentrations of calcium and phosphorus in the blood promote osteoid mineralization, while severe vitamin D deficiency is responsible for the appearance of rickets in children and osteomalacia in adults, by destabilizing bone metabolism. At the same time, vitamin D also benefits the muscular system, nails, teeth and hair.
Benefits of vitamin D on the nervous system
Vitamin D receptors located in the brain favor the action of this compound on the central nervous system (CNS), by slowing down cellular aging processes and contribute to maintaining cognitive abilities in the elderly, by removing amyloid plaque. Amyloid plaques are deposits of beta amyloid, a protein that accumulates in the brain tissue of patients diagnosed with Alzheimer's. In addition, the studies carried out so far attest to the benefits of vitamin D supplements in the case of patients predisposed to the occurrence of multiple sclerosis .
In children, the administration of vitamin D can prevent the appearance of changes in the skeletal and muscular system of children, manifested by deformations in the lower limbs - genu varum or genu valgum , deformations of the chest - flared chest at the base, sunken sternum and changes in the cranial box with the absence of ossification of the anterior fontanelle after the age of 18 months. In adults, the optimal intake of vitamin D decreases the risk of bone fragility due to decreased bone density and bone fractures in the elderly.
