Which factor is NOT a risk factor for Vitamin B12 deficiency in the provided scenario?

Vitamin B12 deficiency occurs when there is inadequate absorption or intake of the vitamin, which is essential for red blood cell production and proper neurological function. Certain factors can increase the risk of developing this deficiency, while others may not have a direct impact.

A strict vegan diet is a significant risk factor because Vitamin B12 is primarily found in animal products. Individuals following this type of diet often do not receive sufficient amounts of B12 without supplementation. Similarly, intermittent diarrhea can lead to malabsorption of nutrients, including Vitamin B12, thereby increasing the risk of deficiency.

The use of metformin, a medication commonly prescribed for type 2 diabetes, can also affect Vitamin B12 levels. Long-term use of metformin has been associated with reduced absorption of B12, thus posing a risk for deficiency in some patients.

In contrast, a family history of thalassemia does not directly correlate with Vitamin B12 deficiency. Thalassemia is a blood disorder primarily affecting hemoglobin structure and function, and while it can lead to anemia, it is not linked to the body's ability to absorb or utilize Vitamin B12. Thus, this factor is not a known risk factor for Vitamin B12 deficiency in the scenario provided.