Vitamin D is an essential nutrient that plays extremely important role for your health. It especially recognized for its benefits on bone health and on the immune system. Vitamin D is a nutrient that helps your body absorb calcium. Calcium and vitamin D work together to help keep your bones and teeth healthy.
Vitamin D also contributes to the proper functioning of your muscles and nerves. Recent research has shown that vitamin D may be linked to a reduced risk of diseases like multiple sclerosis and certain cancers. However, most people have a vitamin-D deficiency.
Vitamin D deficiency is a common and underdiagnosed problem. It is estimated that globally a billion people would be affected.
What is vitamin D?
Vitamin D is a fat-soluble vitamin, a family of compounds that includes vitamins D2 (ergocalciferol) , and D3 (cholecalciferol) . Meaning that it does not dissolve in water and can dissolve in fats and absorbed along with fats in the diet and can be stored in the body’s fatty tissue, For this reason, it’s recommended to take vitamin D supplements with a meal to enhance absorption. Vitamin D is called also the “sunshine vitamin” because it’s produced in your skin in response to sunlight. When your skin has direct sun exposure, the body makes vitamin D 3 in a chemical reaction that produces cholecalciferol, and the liver converts it to calcidiol.
Vitamin D metabolism goes through several successive stages:
- First hepatic hydroxylation under the effect of 25-hydroxylase to convert cholecalciferol (or vitamin D3) to calcidiol (or 25 (OH) -vitamin D). The latter is the circulating form of vitamin D, reflecting storage. This is the one that is dosed.
- It is then transported to the kidney for a second hydroxylation by the 1-alpha hydroxylase which transforms it into its active form (“the hormone”): 1-25 (OH) -vitamin D3 or calcitriol.
These two compounds are collectively known as calcifediol.
The two forms of vitamin D (D3 and D2) differ depending on their food sources. Vitamin D3 is only found in animal-sourced foods, whereas D2 mainly comes from plant sources and fortified foods. Since vitamin D2 is cheaper to produce, it’s the most common form in fortified foods.
9 signs and symptoms you may have a vitamin D defficiency
Research has shown that a large percentage of people have a vitamin D deficiency. However, some people are more at risk than others of being deficient. What are the signs of vitamin D deficiency? This should prompt you to request a vitamin D dosage from your doctor.
1- your gut causes you a few worries
People who suffer from gluten intolerance, Crohn’s disease or inflammatory bowel disease are more at risk for vitamin D deficiency due to the consequences of these diseases on fat absorption. Since fats are less absorbed, fat-soluble vitamins, like vitamin D, are in turn less absorbed. To avoid too great a deficiency, it is sometimes enough to consume dairy products enriched with vitamin D.
2- You are overweight
Being overweight or obese does not change the way your body synthesizes vitamin D. But the higher concentration of body fat affects the levels of vitamin D in the blood. The more fat you have, the more vitamin D, which is fat-soluble, becomes diluted. This is why overweight people have higher vitamin D requirements.
3- your bones are hurting you
Do you have pain in your bones and muscles and your joints are stiffer when you get up in the morning? You may be suffering from a vitamin D deficiency. If you suffer from chronic pain, contact your doctor to have this vitamin measured.
Vitamin D plays a crucial role in calcium absorption and bone metabolism. Vitamin D deficiency can, in young children, lead to bone mineralization defects and rickets. In adults, the deficit in calciferol results in demineralization of the bone and melting of the muscle which can lead to osteoporosis. If the demineralization of the skeleton becomes significant, it can result in convulsions or tetany.
Calcium is actively absorbed from the small intestine in the presence of vitamin D. Calcium and phosphorus form hydroxyapatite crystals to mineralize and strengthen bones.
4. You have dark skin
The pigmentation of your skin is like a natural sunscreen. When you apply an index 30 sunscreen, it reduces 97% of the skin’s ability to synthesize vitamin D from the sun’s rays. It’s the same thing when you have dark or black skin. A person with very dark skin needs ten times more sunshine than a person with light skin to synthesize the same amount of vitamin D.
5- You feel muscle weakness or muscle pain
6. Decreased immunity
The major role of vitamin D in the immune system has only recently been stressed.It was in 2010  that researchers noticed the role of vitamin D on the immune system:
without vitamin D, your immune system is simply not activated and is not properly regulated either.
- Vitamin D regulates and modulates the immune system.
- Vitamin D is essential for the proper functioning of the immune system.
- Vitamin D inhibits autoimmune diseases and chronic inflammation.
- Vitamin D is particularly important in winter, to prevent and fight against the flu and colds.
This is why vitamin D is considered to be an “immunomodulator”: on the one hand, it strengthens the immune system, but it also regulates the immune reaction so that it does not take over by directing the chronic inflammations and autoimmune reactions directly against the body itself
Vitamin D deficiency is prevalent in autoimmune disease. Cells of the immune system are capable of synthesizing and responding to vitamin D. Immune cells in autoimmune diseases are responsive to the ameliorative effects of vitamin D suggesting that the beneficial effects of supplementing vitamin D deficient individuals with autoimmune disease may extend beyond effects on bone and calcium homeostasis.
Most people are affected by Seasonal Affective Disorder (SAD), a type of depression that occurs at the same time each year. It is usually occurs during winter and is related to the decrease in sunlight your body gets. Shorter days and less sunlight exposure can cause a drop in serotonin, our body’s chemical contributor to well-being and happiness.
Exposure to sunlight is thought to increase the brain’s release of a hormone called serotonin that is associated with boosting mood and helping a person feel calm and focused.
However, the drop in mood doesn’t only relate to the drop in serotonin; it can also be due to lack of the vitamin D in your body. A 2018 study found that low vitamin D concentration is associated with depression in adults.
8. Poor skin health
A vitamin D deficiency can affect your skin as well. Vitamin D plays an important role in protecting skin cell health, improving skin softness. Healthy vitamin D levels can help prevent skin from prematurely aging but too much exposure on sun leads to accelerated skin aging. The UV rays from extensive sun exposure can harm the health of your skin cells. In fact, they can be dangerous to your health. It’s important to find the right balance.
A Oregan State University study showed that upon sunlight exposure to ultraviolet-B radiation (UVB), previtamin D3 is synthesized in keratinocytes of the epidermis. Previtamin D3 isomerizes to form vitaminD3 (cholecalciferol), which is subsequently transported into the circulation or metabolized by keratinocytes. Keratinocytes can locally convert previtamin D3 to the active form, 1,25-dihydroxyvitamin D3. 1,25-dihydroxyvitamin D3 and its receptor, the (VDR), have several biological functions in skin, including regulating the proliferation and differentiation of keratinocytes, hair follicle cycling, and tumor suppression. Some cell culture and rodent studies have shown that 1,25-dihydroxyvitamin D3 exhibits photoprotective effects.
9. Hair Loss
A vitamin D deficiency may also be linked to alopecia areata, an autoimmune condition that causes patchy hair loss.
If you think you might be missing out on vitamin D, connect with your doctor about.
The recommended daily intakes of vitamin D:
Vitamin D intake is recommended at 400–800 IU/day, or 10–20 micrograms. However, some studies suggest that a higher daily intake of 1000–4000 IU (25–100 micrograms) is needed to maintain optimal blood levels.
There are also treatment options where people with vitamin D deficiency receive 50,000 IU weekly or monthly instead of taking a daily dose.
- Infants 0–12 months: 400 IU (10 mcg).
- Children 1–18 years: 600 IU (15 mcg).
- Adults up to 70 years: 600 IU (15 mcg).
- Adults over 70 years: 800 IU (20 mcg).
- Pregnant or lactating women: 600 IU (15 mcg).
Vitamin D toxicity
Accordind to NIH ,excessive intake of vitamin D is associated with an increase in circulating 25(OH)D, which may lead to increased intestinal absorption and bone resorption of calcium, in turn leading to hypercalcaemia and can in certain cases lead to renal failure and cardiac arrest. Signs of vitamin D intoxication include anorexia, vomiting, headache, risk of calcification of soft tissues and presence of urinary calcium stones (NIH ).
Food sources of vitamin D
Vitamin D is found mainly in fish and dairy products, especially if they are fortified. On the other hand and demonstrated to certain beliefs, there are no vegetables or
fruits rich in vitamin D especially. In the case of a vegetarian or vegan diet, supplementation may be beneficial.
- Sources of Vitamin D3 :
Oily fish and fish oil, Liver, Egg yolk, Butter, Dietary supplements
- Sources of Vitamin D2 :
Mushrooms (grown in UV light), Fortified foods , Dietary supplements
Do you need a vitamin D supplement?
It can be hard to get enough vitamin D each day through sun exposure and food alone, so taking vitamin D supplements can help. Children and adults who do not get enough vitamin D from food or who have low vitamin D levels in the blood may need a supplement. Adults who have osteopenia or osteoporosis may also need a vitamin D supplement.
Vitamin D supplements are sold freely as pills, chewable tablets or drops. Vitamin-D supplements use two forms: D2 (ergocalciferol) and D3 (cholecalciferol). The D3 is the same chemically as produced in the body and is thus the preferred form.
Check with your doctor for your vitamin D levels. A registered dietitian or doctor can help you decide if you should take a supplement and how much to take.
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Published online by Cambridge University Press: 02 January 2018