A vitamin D However, it is becoming increasingly common to see people with a deficiency of the nutrient, which can be found in some foods, but in low amounts.

The best ways to consume the vitamin are through oily fish and fortified foods. In addition, egg yolks, cheese, and beef liver also contain smaller amounts, and mushrooms that have been exposed to ultraviolet light have traces of the nutrient.

Thus, food sources account for only 10 to 20 percent of the amount needed by humans, while the rest is obtained through sun exposure and/or the use of supplements.

Read more: 82% of covid-19 patients lack vitamin D, study says

After all, what is vitamin D and what is it used for?

Vitamin D's main function is to act in the musculoskeletal system It acts directly on the body's calcium and phosphorus concentrations.

The lack of calcium therefore reduces calcium levels in the body, impairing bone health and growth in children, and bone remodeling in adults, evolving into osteopenia and osteoporosis. In children, rickets is the most serious condition.

In addition to these changes The lack of it further compromises muscle strength and contraction, leading to muscle weakness and, ultimately, global muscle impairment with sarcopenia.

Currently, vitamin D has been involved in many other processes within the body, such as:

• Metabolism of collagen ;
• Magnesium regulation;
• Release of insulin by the pancreas and of prolactin by the pituitary gland;
• Association with autoimmune diseases (type 1 diabetes mellitus, multiple sclerosis, inflammatory bowel disease, systemic lupus erythematosus, and rheumatoid arthritis);
• Association with some tumors (breast carcinoma, melanoma, some types of leukemia, prostate and intestinal carcinoma);
• Association with hypertension and obesity.

All these factors have been the subject of much scientific research. However, to date, there are no standardized recommendations for the use of vitamin D in people with normal rates on laboratory tests. Reference values change according to age and individual conditions, so it is necessary to consult a doctor and not to start self-medicating.

Read also: Does vitamin D help you lose weight after all?

Benefits of Vitamin D

Strengthens bones

First, the vitamin is necessary for the body to absorb calcium, an essential mineral in bone formation.

As the years pass, we are more prone to fractures and osteoporosis. Vitamin D, however, helps to ensure that calcium is deposited in the right place.

What's more, according to a review of 53 studies published in the American journal The Cochrane Library, elderly people who took a vitamin D supplement with calcium had a lower risk of hip fractures.

It is associated with increased muscle strength

After evaluating 116 healthy adults between the ages of 20 and 74, the researchers noted that vitamin D produced when the skin is exposed to the sun had a link to lean mass in women.

Therefore, those with more muscle mass would probably have higher levels of the nutrient in their blood.

Improves the immune system of people with vitamin D deficiency

In an international study that looked at nearly 11,000 people in more than 25 trials, researchers found that those with lower vitamin D levels who took a daily or weekly supplement had lower risks of an acute respiratory infection (such as pneumonia or influenza) and an upper respiratory tract infection (such as a cold and sinusitis).

In another study, published in Frontiers in Immunology, it was also found that vitamin D may be therapeutic for those with an autoimmune disease, such as lupus and multiple sclerosis.

Improves the chances of a healthy pregnancy

Researchers at the Eunice Kennedy Shriver National Institute of Child Health and Human Development in the United States have discovered two possible connections between vitamin D and motherhood.

After analyzing several studies involving women who were undergoing in vitro fertilization, they concluded that those with higher vitamin D levels also had higher pregnancy rates. In addition, they also noted that mothers-to-be who had sufficient levels of the vitamin before becoming pregnant were 10% more likely to become pregnant and had a reduced risk of miscarriage of12% in pregnancy.

Read also: After all, how important is vitamin D during pregnancy?

Vitamin D sources

As said before, vitamin D can be found in some foods, but also through ultraviolet light and by supplements. Learn more about each type:

Food sources

According to an article published by Harvard School of Public Health some foods are naturally rich in vitamin D3 .

According to the publication, the property can be found in larger quantities in fish and vegetable oils, while in smaller portions it is present in egg yolk, cheese, and liver.

A vitamin D2 In turn, some mushrooms are rich in the property.

The article also points out that there are some foods that are fortified with vitamin D, such as cereals, for example. See below for the list:

• Cod liver oil;
• Salmon;
• Swordfish;
• Tuna;
• Orange juice fortified with vitamin D;
• Dairy and vegetable milks enriched with vitamin D;
• Sardines;
• Liver steak;
• Egg yolk;
• Fortified cereals.

Ultraviolet light

Contact of ultraviolet light with human skin also provides vitamin D3. The amount absorbed, however, can vary greatly.

See below for conditions that decrease exposure to UVB light and therefore impair the absorption of the vitamin:

• Use of sunscreen, as it can reduce the absorption of vitamin D by more than 90%;
• Clothes that cover the whole body;
• Spend little time outdoors;
• Darker skin tones, because the greater amount of melanin acts as a type of natural sunscreen;
• Older ages: it occurs with people who have low 7-deshydrocholesterol levels and skin changes, and who spend more time indoors.

It is worth remembering, however, that ultraviolet rays can cause skin cancer, so it is important to avoid excessive exposure to the sun.

Dietary supplements

According to National Institutes Of Health the dietary supplements may contain both vitamin D2 and D3.

"Vitamin D2 is manufactured using UV irradiation of ergosterol in yeast, while D3 is typically produced with irradiation of 7-dehydrocholesterol, from lanolin obtained from sheep's wool," the article explains.

It is worth noting, moreover, that it is also possible to find the version free of animal sources.

Types of vitamin D supplements

In drops

Each drop contains from 200 IU of vitamin D. It is indicated against deficiency and in the prevention of osteoporosis.

In capsules

In addition, the elderly tend to consume more of the nutrient, since they have greater difficulty in producing the vitamin.

The overdose

It is administered in drops or capsules, starting at 10,000 IU per day, and has been prescribed for more serious diseases. It requires, above all, careful monitoring by the doctor.

Recommended daily intake of vitamin D

Supplementation is probably necessary for most adults, but a doctor can confirm this for sure - and determine your dosage.

According to some studies, the sufficiency level of vitamin D is above 30mcg/mL, because this is where the best calcium absorption occurs.

However, these numbers are quite difficult to achieve and maintain, especially in regions with less sunlight. For this reason, taking supplements is usually necessary for most adults, under medical advice.

How do you measure your vitamin D level anyway?

It is possible to measure through a blood test the dosages of the vitamin after it has passed through the liver.

This quantity measures the vitamin produced by the body and the vitamin ingested from food or supplements.

The normal levels are:

• Healthy population under 60: Above 20 ng/mL.
• Population over 60 and risk groups: 30 to 60 ng/mL.

The groups at risk for hypovitaminosis D, that is, lacking the vitamin in the body, are:

• Women who are pregnant or breastfeeding;
• Patients who cannot have sun exposure;
• Individuals with osteomalacia, rickets, osteoporosis, or hyperparathyroidism;
• Patients who suffer from recurrent fractures or falls;
• People with autoimmune diseases, chronic kidney disease, or malabsorption syndromes (such as after bariatric surgery and inflammatory bowel disease);
• Patients using medications that may interfere with the formation and degradation of vitamin D, such as antiretroviral therapy, glucocorticoids, and anticonvulsants).

Read also: Is too much vitamin D bad for you?

Signs of vitamin D deficiency or excess

Deficiency

According to the Harvard School of Public Health, the vitamin D deficiency can happen by dietary lack, malabsorption, or metabolic need for larger amounts.

The problem, therefore, usually occurs in cases where the person is not getting enough vitamin D and not enough sun exposure for a long period.

In addition, patients with intolerance or who do not consume milk, eggs, and fish are at greater risk of deficiency.

Finally, the article also indicated other cases where there is a high risk of vitamin D deficiency:

• People with inflammatory bowel disease (ulcerative colitis, Crohn's disease) or other conditions that disrupt normal fat digestion, because vitamin D is a fat-soluble vitamin that depends on the ability of the intestine to absorb fat from the diet.
• Obese people: The vitamin accumulates in excess adipose tissue, but is not readily available for use by the body when needed. Therefore, higher doses of vitamin D supplementation may be required to achieve a desirable blood level. On the other hand, vitamin D blood levels increase when obese people lose weight.
• People who have undergone gastric bypass surgery, because the procedure usually removes the upper part of the small intestine, where vitamin D is absorbed.

Prolonged deficiency, which happens especially in the cases mentioned above, can lead to serious problems such as:

• Rickets: a condition in infants and children of soft bones and skeletal deformities caused by the failure of bone tissue to harden.
• Osteomalacia: a condition in adults of weak and softened bones, which can be reversed with supplementation. This, however, is different from osteoporosis, in which the bones are porous and brittle and the condition is irreversible.

Read also: Is lack of vitamin D normal in winter?

Toxicity

Unlike deficiency, toxicity occurs when there is more of the vitamin in the body than there should be.

This most often occurs when a person takes supplements in the wrong way, since low amounts of the vitamin found in food are unlikely to reach a toxic level, and a large amount of sun exposure does not lead to toxicity because excess heat on the skin prevents the formation of D3.

In these cases, it is best not to take daily supplements containing more than 4,000 IU (International Units), unless it is a doctor's advice.

A vitamin d toxicity can have as a consequence:

• Anorexia;
• Weight loss;
• Cardiac arrhythmia;
• Hardening of blood vessels and tissues due to increased blood levels of calcium, potentially leading to heart and kidney damage.

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References

The Cochrane Library

HARVARD SCHOOL OF PUBLIC HEALTH. The Nutrition Source: vitamin D. Available at: //www.hsph.harvard.edu/nutritionsource/vitamin-d/

NATIONAL INSTITUTES OF HEALTH. Fact Sheet for Health Professionals: vitamin D Available at: //ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/#h7

ILSI BRAZIL INTERNATIONAL LIFE SCIENCES INSTITUTE DO BRASIL. Fully Recognized Nutrient Functions: vitamin D . 2018. available at: .