Which of the following conditions is an example of a food intolerance?

A. Glycosylated hemoglobin (HbA1c) is a form of hemoglobin bound to glucose, used as a marker of long-term blood sugar control in diabetes. It is not an energy molecule produced by cells.

B. Saturated fatty acids are a type of dietary fat or stored fat in the body. While they can be broken down to produce energy, they are not the direct energy currency within the cell.

C. Hydrogen phosphate is an ion involved in cellular chemistry and pH buffering, but it is not the main energy molecule for cellular processes.

D. Adenosine triphosphate (ATP) is the primary energy currency of the cell. Cells convert glucose through glycolysis, the Krebs cycle, and oxidative phosphorylation, or fatty acids through beta-oxidation and the Krebs cycle, into ATP. ATP stores energy in its high-energy phosphate bonds and releases it to power cellular processes such as muscle contraction, nerve transmission, active transport, and biosynthesis of macromolecules.

A. Vitamin E is present in breast milk at levels generally sufficient for healthy, full-term infants. It functions as an antioxidant, protecting cell membranes from oxidative damage. Deficiency is very rare in breastfed infants unless there is a fat malabsorption disorder or premature birth with very low birth weight, as these conditions limit fat-soluble vitamin absorption. Therefore, routine supplementation is not required for most term infants.

B. Vitamin C is water-soluble and abundant in breast milk when the lactating mother has an adequate diet. It supports collagen formation, immune function, and antioxidant activity. Deficiency in breastfed infants is uncommon unless the mother’s intake is severely inadequate, which is rare in most populations.

C. Calcium is a critical mineral for bone and teeth development, and breast milk generally contains sufficient calcium to meet the needs of full-term infants. The infant’s calcium requirements are met even if maternal intake is moderate because the mammary gland actively regulates calcium content in milk. Deficiency in calcium is therefore not a common concern in healthy, exclusively breastfed infants.

D. Vitamin D is naturally present in breast milk in very low amounts, insufficient to meet the infant’s needs, particularly if sunlight exposure is limited. Vitamin D is essential for calcium absorption and bone mineralization. Without supplementation, breastfed infants are at risk for rickets, delayed bone growth, and skeletal deformities. Health organizations, such as the American Academy of Pediatrics, recommend daily vitamin D supplementation (typically 400 IU/day) for all exclusively breastfed infants.