FOOD RICH IN VITAMIN D.SOURCES OF VITAMIN D.VITAMIN D REQUIREMENT ,DEFICIENCY AND SYMPTOMS

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Vitamin D is an essential nutrient that the body needs to absorb calcium and phosphorus, which are vital for building and maintaining strong bones and teeth. It also plays a role in supporting muscle function, nerve function, and immune health. Vitamin D can be obtained through sunlight exposure, certain foods, and supplements.
Key Functions of Vitamin D:
Bone Health:
Sources of Vitamin D:
Sunlight: The body naturally produces vitamin D when skin is exposed to sunlight.
Food: Some foods naturally contain vitamin D, such as fatty fish (salmon, mackerel, tuna), egg yolks, and mushrooms.
Fortified Foods: Many foods, like milk, yogurt, and cereals, are fortified with vitamin D.
Supplements: Vitamin D supplements are available in various forms,
Vitamin D deficiency can lead to bone pain, muscle weakness, fatigue, and an increased risk of infections.
Consequences:
Severe vitamin D deficiency can cause rickets in children and osteomalacia in adults. Why do I need vitamin D?Vitamin D metabolism is a multi-step process that begins with the conversion of vitamin D to 25-hydroxyvitamin D (25OHD) in the liver and then to the active hormone 1,25-dihydroxyvitamin D (1,25(OH)2D) in the kidneys. This process is tightly regulated, with the active form, 1,25(OH)2D, playing a crucial role in calcium and phosphate homeostasis, bone health, and other biological processes.
Here's a more detailed breakdown:
1. Initial Activation:
Sunlight or Diet:
Vitamin D (either D3 from sunlight exposure or D2 from diet) is initially inactive.
25-Hydroxylation:
Vitamin D travels to the liver where it's converted to 25OHD by the enzyme CYP2R1. This is the major circulating form of vitamin D and is used to assess vitamin D status.
2. Kidney Activation and Regulation:
1α-Hydroxylation:
When the body needs more calcium (e.g., due to low calcium levels or parathyroid hormone stimulation), 25OHD is transported to the kidneys.
CYP27B1:
In the kidneys, the enzyme CYP27B1 (also known as 25-hydroxyvitamin D3 1α-hydroxylase) converts 25OHD to the active form, 1,25(OH)2D (also known as calcitriol).
Regulation of 1α-Hydroxylase:
CYP27B1 activity is primarily regulated by parathyroid hormone (PTH), which is secreted in response to low calcium levels.
3. Degradation and Inactivation:
24-Hydroxylation:
The active form, 1,25(OH)2D, can also be metabolized to 24,25-dihydroxyvitamin D.
CYP24A1:
The enzyme CYP24A1 (also known as 25-hydroxyvitamin D3 24-hydroxylase) is responsible for this inactivation step.
Regulation of CYP24A1:
CYP24A1 is induced by 1,25(OH)2D itself, providing a mechanism for regulating its own degradation and preventing excessive vitamin D activity.
4. Beyond the Kidney:
While the liver and kidneys are the primary sites for vitamin D metabolism, other tissues like the brain and bone cells also contain the enzymes needed for vitamin D activation and inactivation. This suggests that vitamin D can have local, autocrine, or paracrine effects in various tissues.
5. Vitamin D Binding Protein (DBP):
Both 25OHD and 1,25(OH)2D circulate in the blood bound to DBP (vitamin D binding protein).
DBP plays a role in vitamin D transport and may also influence the availability of vitamin D for cellular uptake.
In essence, vitamin D metabolism involves a series of enzymatic conversions, primarily in the liver and kidneys, to produce the active hormonal form (1,25(OH)2D) that regulates calcium and phosphate homeostasis and other important biological functions.
Vitamins are substances that your body needs to grow and develop normally. Vitamin D is important to your body because:
It helps your body absorb calcium. Calcium is one of the main building blocks of bone. A lack of vitamin D can lead to bone diseases such as osteoporosis or rickets.
It also has a role in your nerve, muscle, and immune systems:
Your muscles need it to move
Your nerves need it to carry messages between your brain and your body
Your immune system needs vitamin D to fight off bacteria and viruses

Foods that naturally have vitamin D include egg yolks, saltwater fish, and liver.Vitamin D is available in supplements. It is also included in many multivitamins. The two forms of vitamin D in supplements are D2 and D3. Both types increase vitamin D in your blood, but D3 might raise it higher and for longer than D2. Vitamin D is fat soluble. You can absorb it better when you take your supplements with a meal or snack that includes some fat.How much vitamin D do I need?
The amount of vitamin D you need each day depends on your age. The recommended amounts, in international units (IU), are:Birth to 12 months: 400 IU
Children 1-13 years: 600 IU
Teens 14-18 years: 600 IU

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