Which two organs in the body hydroxylate vitamin D3, thereby turning it into its most active form?

The type 2 diabetes medication metformin can reduce the absorption of vitamin B12 and lead to a deficiency of the nutrient. Those who take metformin should have their vitamin B12 status evaluated periodically. A deficiency of vitamin B12 can cause nerve damage. 

All but one of the following hormones contribute to the maintenance of a normal serum calcium level of 8.5 to 10.5 mg/dL. Which one of the following hormones does NOT participate in the regulation of serum calcium?

One cause of low iron in blood circulation is bacterial infection. When bacteria invade the body, iron is transferred out of the blood and into ferritin for storage.

Folate requires intrinsic factor (IF) for absorption. IF is made by cells within the stomach lining and attaches to folate in the small intestine. This folate-IF complex facilitates folate absorption through the ileum of the small intestine. 

Microcytic hypochromic anemia is caused by a deficiency of which nutrient? In other words, which nutrient inadequacy is the primary cause of microcytic anemia?

Vitamin B12 deficiency is a common nutrient deficiency in the United States. The primary cause of vitamin B12 deficiency is not eating sufficient vitamin B12 to meet the Recommendation Dietary Allowance (RDA). In other words, the majority of Americans do not eat foods rich in vitamin B12.

Vitamin A deficiency can lead to more frequent infections. 

Which form of vitamin A is abundant in carrots, spinach, cantaloupe, apricots, and broccoli?

Which chemical form of vitamin A is needed for normal vision?