Vitamin D

Summary

In this educational video, Dr. Mike explores the importance of Vitamin D, a fat-soluble nutrient essential for growth and development. He explains how UV exposure from sunlight is the primary source of Vitamin D, which is then converted into its active form, calcitriol, in the liver and kidneys. This active form is crucial for calcium and phosphate regulation, impacting bone health. Dr. Mike also discusses the consequences of Vitamin D deficiency, such as rickets in children and osteomalacia in adults, and the risks of over-supplementation, including kidney stones and nervous system depression.

Takeaways

• 🌞 Vitamin D is a fat-soluble vitamin, one of the four (D, E, K, A), and is essential for normal growth and development.
• 💧 Our primary source of Vitamin D is UV exposure or sunlight, which triggers the conversion of 7-dehydrocholesterol in the skin to cholecalciferol (Vitamin D3).
• 🥩 We can also obtain Vitamin D from certain foods, such as fish and liver (animal products) and UV-activated mushrooms (plant products), but in smaller amounts.
• 🔄 The liver plays a crucial role in the synthesis of Vitamin D by converting cholecalciferol into 25-hydroxycalciferol (calcidiol) through the action of 25-hydroxylase enzyme.
• 🔎 The kidneys further metabolize calcidiol into the active form of Vitamin D, calcitriol (1,25-dihydroxycalciferol), facilitated by the 1-alpha hydroxylase enzyme.
• 🔑 Vitamin D's active form, calcitriol, is vital for increasing calcium and phosphate levels in the blood, which are crucial for bone health.
• 🚫 Vitamin D deficiency is widespread, affecting about 50% of the world's population, often due to inadequate sunlight exposure and can lead to rickets in children and osteomalacia in adults.
• 💡 The parathyroid gland releases parathyroid hormone (PTH) in response to low calcium levels, which in turn stimulates the kidneys to activate more Vitamin D and increase calcium absorption.
• ⚠️ Both Vitamin D deficiency and excess can have serious health implications, with the latter potentially leading to hypercalcemia, kidney stones, and nervous system depression.
• 💊 Supplementation is a common way to address Vitamin D deficiency, but it's important to monitor intake to avoid the risks associated with over-supplementation.

Q & A

What are the four fat-soluble vitamins?

The four fat-soluble vitamins are D, E, K, and A.

How does vitamin D differ from water-soluble vitamins?

Vitamin D, being fat-soluble, can be stored in the body's fatty layers, whereas water-soluble vitamins are often excreted more quickly.

What is the primary source of vitamin D for humans?

The primary source of vitamin D is through UV exposure or sunlight.

What happens in the skin when it's exposed to UV light?

UV light triggers the conversion of 7-dehydrocholesterol into cholecalciferol (vitamin D3).

How does the liver process cholecalciferol?

In the liver, cholecalciferol is converted to 25-hydroxycholecalciferol (calcifediol) by the enzyme 25-hydroxylase.

What is the role of kidneys in the activation of vitamin D?

The kidneys convert calcifediol into calcitriol (1,25-dihydroxycholecalciferol) using the enzyme 1-alpha hydroxylase.

Why is the enzyme 1-alpha hydroxylase significant?

1-alpha hydroxylase is significant because it's activated by low calcium and phosphate levels, and it's responsible for converting calcifediol into the active form of vitamin D, calcitriol.

What does active vitamin D (calcitriol) do in the body?

Active vitamin D increases calcium and phosphate levels in the blood by enhancing absorption in the gastrointestinal tract, reabsorption in the kidneys, and bone resorption.

How does vitamin D deficiency affect bone health?

Deficiency in vitamin D can lead to rickets in children, characterized by bendy bones, and osteomalacia in adults, resulting in brittle bones.

What are the recommended daily intakes of vitamin D for different age groups?

For someone under one year, it's about 400 international units, for those between 1 to 70 years it's 600 international units, and for those above 70 years, it's 800 international units.

What are the symptoms of vitamin D overdose?

Overdosing on vitamin D can lead to kidney stones, bone pain, abdominal pain due to muscle contractions, and nervous system depression.