A patient presenting with a whitened nail bed is likely experiencing a deficiency of which nutrient?

A whitened nail bed can indicate various underlying health issues, including nutrient deficiencies. In this context, a deficiency of selenium is particularly relevant. Selenium plays crucial roles in antioxidant defense and has an impact on the health of various tissues in the body, including the nails.

When there's insufficient selenium, it can lead to alterations in nail pigmentation because selenium is essential for the maintenance of keratin, which is integral to nail structure and appearance. Changes in nail color, such as a whitish appearance, can therefore occur in response to low selenium levels.

The other nutrient deficiencies listed—calcium, vitamin B12, and folic acid—can also cause changes in nails or other systemic effects, but they typically do not specifically lead to a whitened nail bed. For instance, calcium is more associated with bone health and may cause brittleness rather than discoloration. Vitamin B12 deficiency can lead to megaloblastic anemia and changes in nail growth, but the nails may appear more pale or yellowish rather than specifically white. Folic acid deficiency can similarly affect overall health but does not commonly present as a characteristic whitened nail bed.

Thus, selenium deficiency stands out as the most likely cause for a patient exhibiting whitened nails.