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Chapter 8 – Vitamins
8.1 Introduction to Vitamins
Malia paha he iki ‘unu, pa‘a ka pōhaku nui ‘a‘ole e ka‘a
Perhaps it is the small stone that can keep the big rock from rolling down
Figure 8.1. Karat bananas look very similar to mangos with an orange flesh, which is high in vitamin A. (Image by University of Hawaii at Mānoa licensed CC BY-NC-SA.)
Chapter 8 Learning Objectives
By the end of this chapter, you will be able to:
Define vitamins and explain how they differ from macronutrients in terms of function, structure, and energy contribution.
Classify vitamins as fat-soluble or water-soluble and describe how this classification affects absorption, transport, storage, and excretion in the body.
Identify the major functions of each vitamin and explain how vitamins support metabolism, growth, immunity, vision, bone health, and blood clotting.
Recognize common food sources of each vitamin and distinguish between vitamins obtained from animal foods, plant foods, and fortified foods.
Explain the role of vitamins as coenzymes and antioxidants, including their involvement in energy metabolism and protection against oxidative stress.
Describe the health consequences of vitamin deficiencies, including populations at higher risk due to life stage, dietary patterns, or health conditions.
Discuss vitamin toxicity and upper intake levels, with emphasis on why excessive intake—especially from supplements—can be harmful.
Interpret Dietary Reference Intakes (DRIs) for vitamins, including the RDA, AI, UL, and how these values are used to assess nutrient adequacy.
Compare food sources versus supplements as ways to meet vitamin needs and evaluate when supplementation may or may not be appropriate.
Vitamins and the Case of the Karat Banana
Vitamins are essential nutrients that our bodies require in small amounts to maintain good health. They come from the foods we eat—so when a diet lacks certain types of food, vitamin deficiencies can occur.
A striking example comes fromPohnpei, a Pacific island in the Federated States of Micronesia. For generations, people there have eaten traditional foods such as fresh papaya, mango, pineapple, coconut, bananas, and seafood. But in recent years, many residents have shifted toward imported, processed foods that are low in vitamins and minerals.
This change has led to serious health problems. In one study of children aged two to five, over half (53%) were deficient in vitamin A. [1]
To address this issue, the Island Food Community of Pohnpei began promoting the bright-orange karat banana—a traditional variety packed with beta-carotene, which the body can convert into vitamin A. Encouraging families to return to this local, nutrient-dense food has helped reduce vitamin A deficiency and preserve cultural food traditions.
Vitamins are organic compounds—carbon-containing molecules that play essential roles in metabolism, growth, and overall health. They’re grouped into two main categories based on how they dissolve and function in the body.
Figure 8.2. The Fat- and Water-Soluble Vitamins (Image by Allison Calabrese licensed CC BY 4.0)
Fat-soluble vitamins dissolve in fats (they are hydrophobic). They are stored in body fat and help protect cell membranes from free-radical damage. The major fat-soluble vitamins are A, D, E, and K.
Water-soluble vitamins dissolve in water (they are hydrophilic). They act primarily in the watery parts of cells—such as the cytosol and the blood—and, unlike fat-soluble vitamins, are not stored extensively in the body. This group includes vitamin C and the B-vitamins.
Although our bodies can produce small amounts of certain vitamins, most must be obtained from the foods we eat—reminding us that a varied, nutrient-rich diet is essential for optimal health.
Yamamura CM, Sullivan KM. Risk factors for vitamin A deficiency among preschool-aged children in Pohnpei, Federated States of Micronesia. J Trop Pediatr. 2004; 50(1):16-19. https://www.ncbi.nlm.nih.gov/pubmed/14984164 ↵
