1. Skin exposure to sunlight is the main source
2. Deficiency of vitamin D causes distal muscle weakness
3. Vitamin D synthesis decreases in winter, as one moves away from equator
4. Body store accumulated during summer is consumed during winter
Select the correct answer using the code given below :
Analyzing Vitamin D Statements
The question requires identifying the correct statements about Vitamin D. The correct answer is Option A: 1, 3 and 4.
- Statement 1: Skin exposure to sunlight is the main source. This is correct. Cutaneous synthesis, triggered by ultraviolet B (UVB) radiation converting 7-dehydrocholesterol to previtamin D3 in the skin, is the principal source of Vitamin D for most people, contributing far more than dietary intake in populations with adequate sun exposure.
- Statement 2: Deficiency of vitamin D causes distal muscle weakness. This is incorrect. Vitamin D deficiency classically produces a proximal myopathy — weakness of the hip and shoulder girdle muscles causing a waddling gait and difficulty climbing stairs or rising from a squat — not distal muscle weakness. Distal weakness is more characteristic of peripheral neuropathies or certain myopathies unrelated to Vitamin D status.
- Statement 3: Vitamin D synthesis decreases in winter, as one moves away from the equator. This is correct. UVB intensity falls with the lower solar angle in winter and at higher latitudes (farther from the equator), reducing cutaneous Vitamin D synthesis. This is why populations at high latitudes are more prone to seasonal Vitamin D deficiency, especially in winter months.
- Statement 4: Body store accumulated during summer is consumed during winter. This is correct. Vitamin D is fat-soluble and is stored in adipose tissue and liver during periods of high sun exposure (summer). These stores are gradually mobilized and utilized through autumn and winter, when cutaneous synthesis is minimal, helping buffer serum levels until sunlight exposure increases again.
Conclusion
Statements 1, 3, and 4 correctly describe the sources, seasonal/latitudinal variation, and storage-utilization pattern of Vitamin D, while statement 2 incorrectly attributes distal (rather than proximal) muscle weakness to Vitamin D deficiency. Therefore, the correct combination is 1, 3 and 4, corresponding to Option A.
Important Questions from Vitamin D Deficiency
Consider the following statements with regard to Vitamin D deficiency :
1. Vitamin D deficiency is common in northern latitudes.
2. Vitamin D deficiency is more likely to develop in people with dark skin.
3. Exposure to UV light is advisable in patients with Vitamin D deficiency.
Which of the statements given above are correct?
Which of the following abnormalities occur from vitamin D deficiency in children?
1. Craniotabes
2. Bossing of frontal and parietal bones
3. Muscle hypotonia
4. Shrinking of epiphysis at the lower end of radius
Select the correct answer using the code given below.
- Which one of the following is not a feature of vitamin D deficiency rickets?
- Which one of the following is not characteristic of Vitamin-D resistant rickets ?
- What is the naturally occurring form of vitamin D in the human skin ?
