Question

Which vitamin is synthesised in the body by intestinal bacteria?

• A. Vitamin B1
• B. Vitamin B4
• C. Vitamin D
• D. Vitamin K

Hint:

Think about which fat soluble vitamin the gut flora make and which one the liver needs for clotting factors.

Answer 1

The Correct Option is D

Step 1: Understanding the Question.
The question asks which vitamin the body gets from bacteria living inside the intestine, not from food or sunlight.

Step 2: Key Concept.
Vitamin K is a fat soluble vitamin. A large part of the vitamin K a person uses comes from bacteria that live in the large intestine. These bacteria make a form of vitamin K called menaquinone, which the gut wall absorbs along with fat.

Step 3: Detailed Explanation.
Vitamin K is needed by the liver to build clotting factors II, VII, IX and X. Without enough vitamin K, blood takes longer to clot and small cuts bleed for longer.
Now check the other options.
Vitamin B1, also called thiamine, comes mainly from cereals and pulses in the diet. Gut bacteria do not supply a meaningful amount of it, and its lack causes beriberi.
Vitamin B4 is not a vitamin that current nutrition science recognises as part of the B group. The name was used long ago for compounds like adenine, but it was dropped once its role was found to be different from a true vitamin, so it cannot be the answer here.
Vitamin D is mostly made in the skin. Sunlight changes a compound called 7 dehydrocholesterol into vitamin D3, and this happens in skin cells, not in the gut.
So only vitamin K matches a vitamin made by intestinal bacteria.

Step 4: Final Answer.
The vitamin synthesised in the body by intestinal bacteria is vitamin K.