Vitamin D and Calcium Absorption - Biochemistry Lesson

Summary

This video explains the crucial role of Vitamin D in calcium absorption. It describes how Vitamin D is processed in the body, first as Vitamin D3 (cholecalciferol), then converted into its active form, calcitriol, in the liver and kidneys. Calcitriol enhances calcium absorption in the small intestine by increasing calcium transporters, calbindin-D, and calcium pumps. The video also provides the recommended dietary intake of both Vitamin D and calcium across various age groups to support proper calcium absorption and overall bone health.

Takeaways

• 😀 Vitamin D is crucial for calcium absorption in the body, and it is either absorbed from food or produced in the skin as cholecalciferol (vitamin D3).
• 😀 Cholecalciferol (vitamin D3) must be converted into the active form, calcitriol, through processes in the liver and kidneys to facilitate calcium absorption.
• 😀 In the liver, cholecalciferol is converted into calcidiol, which then travels to the kidneys to become calcitriol, the active form of vitamin D.
• 😀 The conversion of vitamin D into calcitriol requires healthy liver and kidney function, highlighting the importance of these organs for proper calcium absorption.
• 😀 Calcitriol binds to vitamin D receptors in the intestines, triggering a genetic program that increases calcium transporters and calbindin D within enterocytes.
• 😀 Increased levels of calbindin D and calcium transporters help the intestines absorb more calcium from food into the bloodstream.
• 😀 Calcitriol also enhances the activity of ATP-dependent calcium pumps, ensuring efficient calcium movement from the intestinal cells into the blood.
• 😀 Healthy kidney and liver function is essential for converting vitamin D into its active form, making it critical for individuals with renal issues or kidney failure.
• 😀 The recommended dietary intake of vitamin D varies by age: 400 IU/day for infants, 600 IU/day for children aged 1-7, and 800 IU/day for those over 70.
• 😀 The recommended dietary intake of calcium also varies by age: 200 mg/day for infants (0-6 months), 1,300 mg/day for teenagers (9-18 years), and 1,200 mg/day for adults over 70.
• 😀 Both calcium and vitamin D are essential for maintaining bone health, and their intake needs to be balanced according to age and specific health conditions.

Q & A

What is the main role of vitamin D in calcium absorption?

Vitamin D is crucial for calcium absorption because it helps to activate the process that allows calcium to be absorbed through the small intestine and utilized in the body. It enables the expression of calcium transporters and proteins needed for calcium uptake.

How is vitamin D processed in the body to aid in calcium absorption?

Vitamin D is initially absorbed as cholecalciferol (vitamin D3) either from food or produced in the skin. It then travels to the liver, where it is converted to calcidiol. From there, it goes to the kidneys and is converted into calcitriol, the active form that aids in calcium absorption.

What organs are involved in the conversion of vitamin D into its active form?

The liver and kidneys are the key organs involved in converting vitamin D into its active form, calcitriol. The liver converts cholecalciferol into calcidiol, and the kidneys further process calcidiol into calcitriol.

Why is having healthy liver and kidney function important for calcium absorption?

A healthy liver and kidneys are necessary for the proper conversion of vitamin D into its active form, calcitriol. Without these organs functioning properly, the body cannot produce enough calcitriol, which impairs calcium absorption.

How does calcitriol enhance calcium absorption in the intestines?

Calcitriol binds to the vitamin D receptor in intestinal cells, triggering a genetic program that increases the expression of calcium transporters, calbindin-D (a protein that helps transport calcium), and the ATP-dependent calcium pumps that move calcium into the bloodstream.

What role does calbindin-D play in calcium absorption?

Calbindin-D is a protein in the intestinal cell cytoplasm that binds to calcium. It helps transport calcium through the cell from the gut lumen to the blood, ensuring efficient calcium absorption.

What happens if a person has a deficiency in vitamin D?

A vitamin D deficiency can impair calcium absorption, leading to problems such as weakened bones or osteoporosis, as the body cannot efficiently absorb and utilize calcium without sufficient vitamin D.

What is the recommended daily intake of vitamin D for children aged 1-7 years?

For children aged 1-7 years, the recommended daily intake of vitamin D is 600 international units (IU).

What is the recommended daily intake of calcium for teenagers aged 9-18 years?

For teenagers aged 9-18 years, the recommended daily intake of calcium is 1300 milligrams (mg).

How does calcitriol interact with calcium pumps in the intestinal cells?

Calcitriol increases the activity of ATP-dependent calcium pumps in the intestinal cells, which helps to pump more calcium from the cells into the bloodstream, thereby enhancing calcium absorption.