Vitamin D is a fat-soluble vitamin that can be found in animals, fish, eggs, and some plant foods like mushrooms. It also helps in absorbing calcium and phosphorus from the intestines and is important for bone growth.
Vitamin D provides benefits such as improved immune function and reduced risk of type 2 diabetes, multiple sclerosis, heart disease. However, it may not be safe for pregnant women because it can lead to increased risks of miscarriage.
In terms of where vitamin D comes from – for humans it comes from the sun. In terms of making vitamin D – our body makes vitamin D when exposed to sunlight or UVB rays from sunlight.
Vitamin D deficiency
Vitamin D deficiency leads to lower bone mineral density, which increases risk of reduced bone density, osteoporosis and fractures, as vitamin D deficiency alters the mineral metabolism in the body. One of the most important tasks of vitamin D is to maintain calcium balance in the skeleton by promoting calcium absorption from the intestines, promoting bone absorption, increasing the osteoclast count, retaining calcium and phosphate levels for bone formation, proper functioning of parathyroid hormones and maintaining calcium levels in serum. Vitonin – activation of VDR in intestine, bones, kidneys and parathyroid glands (glandular cells) leads to the maintenance of calcium and phosphorus levels in the blood with help of parathyroid hormone and calcitonin to maintain bone content.
Vitamin D is a fat-soluble vitamin known to help the body absorb and store calcium and phosphorus because these minerals are crucial for bone growth. Vitamin D helps the body to use these minerals to form stronger bones and teeth. Laboratory studies have shown that vitamin D reduces the growth of cancer cells, fights infections and reduces inflammation.
Those who avoid the sun, suffer from a milk allergy or follow a strict vegan diet may have a vitamin D deficiency risk. Studies suggest that people who consume sufficient amounts of vitamin D and calcium slow bone mineral loss which can help prevent osteoporosis and reduce bone fractures. Ask your doctor if you need calcium or vitamin D supplements to prevent or treat osteoporosis.
Vitamin D is known as a “sunshine vitamin” and is produced in response to the sunlight from the skin by the body. Many older adults that are not regularly exposed to sunlight have difficulty absorbing vitamin D. If your doctor suspects that you are not getting enough vitamin D, perform a simple blood test to check the vitamin D concentration in your blood.
The recommended daily intake of vitamin D is 400 international units (IU) for children under 12 months of age, 600 IU for people between 1 and 70 years of age and 800 IU for people over 70 years of age. However, too much vitamin D in high intake of dietary supplements, high intake of foods containing vitamin D or exposure to excessive sunlight is more likely to cause toxicity in the case of vitamin D exposure but not vitamin D toxicity. The safe upper vitamin D intake for adults and children over 8 years is 100 mg / day or 4,000 IU / day.
The IOM also points out that people should not try to increase vitamin D production by increasing exposure to sun as this could increase their risk of skin cancer .
The amount of sun you need to reach a normal vitamin D level in your blood is more than safe for your skin, and most people need supplements to reach a normal vitamin D level. Vitamin D deficiency may occur if their normal intake is too low or is limited over time. The recommended exposure to the sun is limited, the kidneys do not convert 25 (OH) D into its active form or the absorption of vitamin D by the digestive tract is insufficient. Low-vitamin D diets are more common in people with milk allergies or lactose intolerance, especially if they are taken as part of an OVO diet (vegetarian or vegan) (1).
Studies into Vitamin D
A new research study by University of Chicago Medicine has shown that COVID-19 could lower the infection risk in black people if vitamin D levels are considered sufficient. The study, which was published in the JAMA Open Network on March 19, examined the association between vitamin D levels and the likelihood of being positive for coronavirus.
Data from more than 3,000 UChicago Medicine patients whose vitamin D levels were tested within 14 days of a COVID-19 test were analyzed for the study. The study is an extension of an earlier study that showed that vitamin D deficiency of less than 20 ng / ml increases the risk of a positive test for Covid-19. A team of researchers recruited participants for two separate clinical trials to test the efficacy of vitamin D supplements in preventing COVID.
A separate study found that more than 80% of COVID-19 diagnosed patients had a vitamin D deficiency. A prospective study of young adults in Sweden found a 61% lower MS risk in people with high serum vitamin D levels;  a prospective study of young Finnish women found that low serum vitamin D levels were associated with a 43% increase in the MS risk;  and another prospective study linked high vitamin D levels to reduced disease activity and progression in people with MS. Current evidence suggests that low vitamin D can play a causal role in MS and that 40% of cases can be prevented by correcting vitamin D deficiency.
In one study, people who consumed daily calcium and vitamin D lost more weight than subjects who took a placebo. Scientists say the supplement could have an appetite-suppressing effect. The clinical trial of Women’s Health Initiative described the effects of Vitamin D 3 and Calcium supplements on colon cancer rates.
The intake of vitamin D and calcium from food and supplements was investigated in a 20-year study. In another study, obese people taking vitamin D supplements daily improved their risk of heart disease. The dose response analysis showed an average decrease of 23% in the risk of progression of type 2 diabetes in a 4 ml (10 nmol / l ) increase in serum 25 hydroxyvitamin D concentration (210 ng / mL ) increase.
A review of the data on vitamin D needs by a committee of experts of the Food and Nutrition Board (FNB) of the National Academies of Sciences, Technology and Medicine (NASEM) concluded that people are exposed to vitamin D deficiency when the concentration of serum 25 (OH) D is less than 30 nmol / L 12 (see Table 1 for the definition of deficiency and inadequacy  ). In addition, people at 30-50 nmol / l 12 in 20 ml may be at risk of deficiency.
In 2014 the Office of Dietary Supplements of the National Institutes of Health launched the Vitamin D Initiative in the United States to track current research and educate consumers. When children start eating solid foods, parents should ensure that their children get enough vitamin D from foods and supplements. 1-quarter of the formula daily may need an alternative way to get 400 IU of vitamin D per day, such as vitamin D supplementation.
The Women’s Health Initiative study was challenged for reasons including poor compliance and the fact that some participants were allowed to take supplementary vitamin D and calcium supplements which may have skewed results.
In studies of the effect of vitamin D and calcium on skeletal health of postmenopausal women, the use of hormone replacement therapy was furthermore not considered [57-76], which is an important disturbing factor in this population. Furthermore, no randomised calcium and vitamin D assessments have been recorded, and some studies report that oral vitamin D in combination with calcium (1000 mg / day ), 3,800 IU / day, does not prevent the occurrence of osteoporotic fractures in older adults who suffer minor trauma due to these fractures, .