Water Soluble Vitamins

Energy Metabolism Recap

• When energy expended equals energy consumed, weight remains stable.

• Three main components influencing energy requirements:

  • Basal Metabolic Rate (BMR)

  • Thermogenic Effect of Food

  • Physical Activity Levels

Factors Influencing Basal Metabolic Rate (BMR)

• Factors that Increase BMR:

  • Height

  • Growth

  • Body composition

  • Fever (body under stress)

  • Environmental temperature

  • Smoking

  • Caffeine

  • Certain hormones (premenstrual, thyroid)

• Factors that Decrease BMR:

  • Aging (approximately 5% decrease per decade after age 30)

  • Starvation and Fasting

  • Lower levels of thyroid hormones

Satiety vs. Satiation

• Satiety: Feeling of fullness and satisfaction after eating.

  • Proteins and fiber contribute to prolonged satiety.

• Satiation: Communication with the brain to stop eating.

  • Stretch receptors in the stomach and hormones like cholecystokinin signal the brain.

Calorimetry

• Definition: Method to determine the amount of energy released from foods or by exercise.

• Types:

  • Direct Calorimetry: Measures heat released from food or a person in a chamber. An increase in the temperature of surrounding water corresponds to the amount of heat being released.

  • Indirect Calorimetry: Measures the ratio of oxygen consumed to carbon dioxide expelled to estimate energy utilization.

Water Soluble Vitamins: Week 9 Focus

• Key objectives:

  • Describe the functions of water-soluble vitamins in the body.

  • Relate recommended intakes to food sources, bioavailability, and toxicity levels.

  • Identify requirements and upper levels of intake.

  • Describe deficiency symptoms and diseases related to water-soluble vitamins.

• The content of vitamins and minerals can be quite heavy, so creating tables with functions, RDIs, and food sources is recommended for revision.

• In the exam, specific RDIs don't need to be known by heart, but a general understanding of vitamin importance and food sources is important.

Vitamins Overview

• Vitamins are micronutrients that do not yield energy but are important for various functions.

• Vitamins are organic (contain carbon), while minerals and water are inorganic (do not contain carbon).

• Vitamins are chemically unrelated carbon-containing compounds found in living tissues.

• Required in minute quantities for normal cellular function.

• Essential for life events like reproduction, growth, and health.

• 13 vitamins are recognized as essential for humans.

• Most vitamins must be derived from food.

Vitamin Requirements

• Vitamin requirements vary according to life stage, from infancy to elderly.

• Inadequate food intake can lead to vitamin deficiencies.

• RDIs (Recommended Dietary Intakes) are generally higher than needed by most individuals and are regularly revised.

• Australian RDIs are used.

• RDI is the Estimated Average Requirement plus two standard deviations, meeting 97-98% of individuals' requirements.

• RDIs have a buffer margin and likely exceed actual needs.

• Requirements can vary depending on infection, illness, physiological stress, environmental factors, and lifestyle.

• Some drugs can interfere with vitamin metabolism.

Vitamin Supplementation

• Misconception: More vitamins equal better health.

• After a certain point, the body's absorption of vitamins plateaus, and excess is excreted via urine.

• Some vitamins have upper intake levels; exceeding these levels can cause harm.

• Watch the "Vitaminia" documentary to understand the implications of the supplement industry.

• Studies show no benefit from vitamin supplements, and vitamin intake from food sources is generally better.

• One study showed increased risk of death from cancer in people consuming lots of calcium supplements, but not from food. Supplements may have detrimental effects when over consumed.

• Dietitians generally recommend supplements only when a true deficiency is confirmed through blood tests or when medical conditions impede vitamin metabolism (e.g., celiac disease, vegan diets leading to B12 deficiency).

Vitamin Storage and Absorption

• Water-soluble vitamins (B group and C) are stored in peripheral tissues, and deficiency takes time to manifest.

  • Vitamin C deficiency takes 80-90 days to show.

  • Vitamin A deficiency takes 2-3 months.

  • Vitamin B12 deficiency takes 2-3 years.

• Water-soluble vitamins are absorbed directly into the blood, circulate freely, and are excreted in the urine.

• Fat-soluble vitamins (A, D, E, and K) are packaged into chylomicrons, absorbed into the lymph, and then into the blood.

• Fat-soluble vitamins require protein carriers and are stored in cells associated with fat (e.g., liver).

• Fat-soluble vitamins are less readily excreted and more likely to reach toxic levels when over consumed.

Roles of Vitamins

• Vitamin E, C, and carotenoids: Antioxidant functions.

• B vitamins: Coenzymes in metabolism reactions, TCA cycle.

• Vitamin D and K: Bone health.

• Vitamin A: Vision.

• Vitamin K: Blood clotting.

Bioavailability

• Bioavailability: The amount of the vitamin consumed, absorbed, and the extent to which it is utilized.

  • `` rate and extent that a nutrient is absorbed and being used.

• Vitamins can be destroyed by exposure to light, oxidation, cooking, and storage, particularly water-soluble vitamins.

Methods to Minimize Nutrient Losses

• Refrigerate fruits and vegetables.

• Store fruits and vegetables in airtight wrappers.

• Clean fruits and vegetables before cutting.

• Microwave, steam, or simmer in small amounts of water.

• Save cooking water for stews or casseroles.

• Avoid long cooking times.

How Vitamins Work

• Vitamins are involved in many catalytic actions of enzymes in body cells.

• B vitamins are part of the enzyme system that controls energy release from food.

• Enzymes cannot work without specific vitamins in coenzyme form, something learned during energy metabolism discussions. See the textbook for a diagram of this process.

• Coenzymes facilitate enzyme activity (they are not actually changed in the process).

Water Soluble Vitamins: Specifics

• Key water-soluble vitamins: B1, B2, B3, B5, B6, B12, Biotin, Folate, and Vitamin C.

• For each vitamin, we will be looking at forms, functions, deficiency symptoms, toxicity outcomes, food sources, and nutrient reference values.

• Today's focus: B1, B2, B3, and B5. The other vitamins will be covered the following week.