Nutrient bioavailability is the proportion of a nutrient that is absorbed and utilized. Which factors affect it?

• A. Time of day eaten
• B. Brand of product
• C. Nutrient form; food matrix; preparation; interactions with other nutrients; gut health; and age
• D. Color of food

Answer: (C)

Bioavailability is about how much of a nutrient the body can absorb and actually use, and many factors influence that process. The chemical form of a nutrient matters because different forms are absorbed at different rates; for example, iron from animal sources (heme iron) is typically absorbed more readily than iron from plants (non-heme iron), and fat-soluble vitamins need dietary fat to be efficiently absorbed. The food matrix—the way nutrients are packaged inside the food—also affects release and uptake; compounds in plants like phytates and the overall structure of the food can hinder or help absorption, and processing can alter this matrix.

How a food is prepared matters too. Cooking, soaking, fermenting, or sprouting can reduce anti-nutrients and make nutrients more available, or conversely, degrade heat-sensitive nutrients. Interactions with other nutrients can enhance or inhibit absorption; for instance, vitamin C boosts non-heme iron absorption, while calcium can compete with iron, and fat improves absorption of fat-soluble vitamins.

Gut health plays a role, since the integrity of the intestinal lining, the microbiome, and overall digestive function influence how efficiently nutrients are taken up. Age brings physiological changes that affect bioavailability, such as changes in gastric acidity, enzyme activity, and intestinal absorption capacity across the lifespan.

Things like the time of day you eat, the brand of a product, or the color of the food don’t fundamentally alter the body's ability to absorb and utilize nutrients in the same way, so they’re not primary determinants of bioavailability.