Chapter 7 | Vitamins

Nutrition & You, Sixth Edition

Chapter 7 Overview by Joan Salge Blake

Learning Outcomes:

• Understand vitamins: their classification, functions in the body, and importance in food preservation.

• Gain knowledge about proper storage methods for fat-soluble vitamins to ensure their effectiveness.

• Identify the functions, sources, and deficiency/toxicity symptoms of various vitamins, including A, E, K, D, B-complex, and C.

• Recognize the role of vitamin-like substances and understand the significance of dietary supplements and fortified foods in maintaining health.

Vitamins Defined:

• Vitamins are essential, tasteless, organic compounds needed in small amounts for various bodily functions. Each vitamin plays a crucial role in maintaining health, and deficiencies can lead to specific deficiency symptoms, while excess intake can cause toxicity symptoms that can be harmful.

Vitamins by Food Group:

• Vegetables: Rich sources of Folate, Vitamin A, Vitamin C, and Vitamin E which are essential for bodily functions such as DNA synthesis and antioxidant protection.

• Fruits: Also provide significant amounts of Folate, Vitamin A, and Vitamin C; they are vital for immune function and skin health.

• Grains: Whole grains are important sources of Niacin, Riboflavin, Thiamin, Vitamin B6, and Vitamin B12 (if the grains are fortified), which are crucial for energy metabolism.

• Protein Foods: Include essential vitamins such as Vitamin A, Vitamin B12, and Vitamin D. These vitamins support various health functions including immune health and calcium absorption.

• Dairy Products: Provide Vitamins A, B12, and D, which are important for bone health and energy production.

Classification:

• Fat-soluble Vitamins: Includes Vitamins A, D, E, and K. These vitamins can be stored in the body's fatty tissues and liver for later use, which makes it possible to accumulate them in the body.

• Water-soluble Vitamins: Includes the B vitamins and Vitamin C. They are not stored in the body, and excess amounts are typically excreted through urine, requiring regular consumption in the diet.

Antioxidant Properties:

• Vitamins A, C, E, and beta-carotene are known for their antioxidant properties. These vitamins help combat oxidative stress by neutralizing free radicals that can lead to chronic diseases including heart disease and cancer.

Bioavailability:

• The bioavailability of vitamins can be significantly influenced by factors such as food preparation methods, cooking, storage, and food pairings. For instance, exposure to air, heat, or water can lead to vitamin degradation, thus lowering their nutritional value.

Vitamin Toxicity Risks:

• While vitamin toxicity is rare, it primarily occurs from excessive supplementation rather than food sources. Understanding the appropriate doses is essential, as fat-soluble vitamins can accumulate in the body and cause adverse effects.

Specific Vitamins Overview:

• Vitamin A: Crucial for vision, immune function, and skin health. Recommended daily intake: Men: 900 μg RAE, Women: 700 μg RAE. Sources include carrots, sweet potatoes, and leafy greens.

• Vitamin E: Functions as a powerful antioxidant that protects cell membranes from damage. Daily intake: Men and Women: 15 mg. Sources include nuts, seeds, and vegetable oils.

• Vitamin K: Important for blood clotting and bone health. Daily intake: Men: 120 μg, Women: 90 μg. Found in green leafy vegetables and fermented foods.

• Vitamin D: Key for regulating calcium and phosphorus in the body, maintaining healthy bones and teeth. Daily intake: 15 μg (600 IU), synthesized through sunlight exposure. Found in fatty fish and fortified dairy.

• Water-soluble Vitamins: The B-complex vitamins play vital roles in energy metabolism, while Vitamin C is essential for collagen synthesis and antioxidant protection. Daily intake for B-complex: Men: 90 mg, Women: 75 mg. Sources include whole grains, fruits, and vegetables.

Conclusion:

• While food sources are preferred for obtaining vitamins, supplements may be necessary in certain circumstances, such as dietary restrictions or specific health conditions. It's crucial to use supplements with caution to avoid toxic effects, and fortified foods can play a beneficial role in addressing nutrient gaps when necessary.