ASIN 500 Introduction to Nutrition Lecture 7 Vitamins & Major Minerals

Introduction to Nutrition Lecture 7: Vitamins & Major Minerals

Lecture Objectives

  • Describe the key functions for vitamins and major minerals.
  • List significant food sources for vitamins and major minerals.
  • Discuss the factors that affect mineral bioavailability.
  • Outline the regulation of blood calcium.
  • Discuss how major minerals affect health.

Common Myths & Truths

  • Myths:
    • If a little is good, then a lot is better.
    • Vitamins are energy boosters.
    • Vitamins work exclusively of one another.
  • Truths:
    • Vitamins are categorized as either water- or fat-soluble.
    • The amount of vitamins in food depends on many factors, including soil content, growing conditions, maturity at harvest, food processing, and cooking.

Understanding Vitamins

Fat-Soluble Vitamins

  • Vitamins A, D, E, K.
  • Absorbed like fat, into the lymphatic system.
  • Stored in larger quantities and can be toxic in excess.
  • May have precursors.
  • Less vulnerable to cooking losses.

Water-Soluble Vitamins

  • B vitamins and Vitamin C.
  • Stored in small amounts.
  • Readily excreted; thus, deficiencies are more likely to occur.

Vitamin A

Functions

  • Key roles in vision, cell development, and immunity.
  • Vision.
  • Cell Differentiation.
  • Immunity.
  • Reproduction.
  • Growth.

Food Sources

  • Preformed vitamin A (retinol): liver, milk, egg yolks, cheese.
  • Provitamin A (beta-carotene): carrots, sweet potato, spinach, red pepper, broccoli, mango, dried apricots, dried prunes, green beans, peaches.

Deficiency

  • Eyes, skin, and epithelial tissues affected.
  • Night blindness.
  • Xerophthalmia.
  • Hyperkeratosis.
  • Infection.
  • Death.

Toxicity

  • Can be fatal.
  • Death.
  • Liver damage.
  • Bone fracture.
  • Skin disorders.
  • Birth defects.

Adequate Intake

  • 700 – 1300 ug retinol (RAE).

Carotenoids

Classification

  • Classified as a phytochemical – not an essential nutrient.

Functions

  • Important source of vitamin A.
  • Antioxidant – reducing inflammation.
  • Has roles in boosting immune function, enhancing vision, and preventing cancer.

Food Sources

  • Yellow-orange vegetables.
  • Orange fruits.
  • Dark-green leafy vegetables.

Vitamin D

Nature of Vitamin D

  • Technically a nutrient but acts more like a hormone.

Synthesis

  • UV radiation converts a cholesterol precursor beneath the skin.
  • Cholecalciferol activated in the liver and finally in the kidney to form calcitriol (\approx 90\% of active Vit D is synthesized from the skin).

Functions

  • Regulates blood calcium levels.

Food Sources

  • Cod liver oil, liver, salmon, sardines, fortified milk, eggs.

Deficiency

  • Rickets in children.
  • Osteomalacia and osteoporosis in adults.

Toxicity

  • Hypercalcemia – caused by excessive vitamin D intake.

The B Vitamins

General Information

  • B Vitamins act primarily as coenzymes.
  • Function as catalysts in energy-producing metabolic reactions.
  • Involved in other aspects of cellular metabolism.
  • Found in all food groups.

Thiamin (B1)

Functions

  • Coenzyme in energy metabolism (pyruvate acetyl CoA).
  • Assists with neurotransmitter synthesis.

Food Sources

  • Sweet potato.
  • Pork, ham, salmon, tuna.
  • Whole and enriched grains.
  • Sunflower seeds, wheat germ, sesame seeds, Brazil nuts.
  • Beans & legumes – soybeans, navy beans, lentils.

Deficiency

  • Beriberi.

Riboflavin (B2)

Functions

  • Coenzyme in energy metabolism (FAD and FMN).
  • Supports antioxidants.

Food Sources

  • Liver.
  • Milk and dairy products.
  • Whole and enriched grains.
  • Squid, oysters, herring, turkey, chicken, beef, pork, ham.
  • Spinach, broccoli, egg, mushrooms, almonds, peach.

Deficiency

  • Ariboflavinosis.

Folate (B9)

Functions

  • Coenzyme in DNA synthesis and cell division.
  • Normal red blood cell synthesis.
  • Prevention of heart disease with B6 and B12.

Food Sources

  • Liver, spinach, lentils, asparagus, beans, wheat germ.

Deficiency

  • Megaloblastic anemia.
  • Can contribute to neural tube defects.

Toxicity

  • Can mask vitamin B12 deficiency.

Cobalamin (B12)

Functions

  • Required for normal folate function.
  • Maintains myelin sheath around nerves.
  • Reduces heart disease with B6 and folate.

Food Sources

  • Only animal foods: seafood, meats, liver, milk, eggs.

Deficiency

  • Pernicious anemia.
  • Megaloblastic anemia and nerve damage.

Vitamin C

Functions

  • Antioxidant.
  • Needed for collagen synthesis.
  • Enhances nonheme iron absorption.

Food Sources

  • Fruits: citrus, strawberries, kiwifruit.
  • Vegetables: bell peppers, broccoli, spinach, tomatoes.

Deficiency

  • Scurvy.

Toxicity

  • May cause GI distress in high doses.

Vitamin and Mineral Bioavailability

Factors Affecting Bioavailability

  • Time of transit through GI tract.
  • Acidity of intestinal environment.
  • Oxalate / Phytate / Phosphoric Acid.
  • Polyphenols / Tannins / fiber.
  • Person’s need.
  • Other nutrients competing for absorption.
  • Source of nutrient.
  • Method of cooking.

Sodium

Functions

  • Fluid balance.
  • Nerve impulse transmission.
  • Fluid balance and glucose absorption.

Food Sources

  • Processed and convenience foods.
  • Salt, soy sauce, pickled foods, salty or smoked meats, cheese, instant soups.

Potassium

Functions

  • Muscle contraction.
  • Nerve impulse transmission.
  • Fluid balance.

Food Sources

  • Unprocessed foods: fruits, vegetables, grains.
  • Sodium to potassium ratio critical for regulating blood pressure – 1:2 is ideal.

Calcium

Functions

  • Bone structure.
  • Blood clotting.
  • Nerve impulse transmission, muscle contraction, cellular metabolism.

Food Sources

  • Milk and dairy products.
  • Tofu, canned fish with bones, sesame seeds, green vegetables.

Regulation of Blood Calcium

Hormones

  • Calcitriol (active form of Vitamin D):
    • Increases Ca absorption in the small intestine.
  • Parathyroid hormone (PTH):
    • Increases osteoclast activity in bone.
    • Increases kidney reabsorption of Ca.
    • Stimulates calcitriol production in the kidney.
  • Calcitonin:
    • Decreases osteoclast activity.

Target Tissues

  • Small intestine.
  • Kidneys.
  • Bone.

Magnesium

Functions

  • DNA and protein synthesis.
  • Blood clotting, muscle contraction, ATP production.

Food Sources

  • Seafood, sesame seeds, almonds, cashews, peanuts.
  • Spinach, tofu, yogurt, whole grains.

Iron

Food Sources

  • Heme: Seafood, liver, red meat.
  • Non-heme: Spinach, sunflower seeds, tofu, lima beans, legumes.
  • Absorption of non-heme iron is inhibited by:
    • Phytic acid (unprocessed bran, oatmeal, whole grains).
    • Phosphoric acid (legumes, wholegrains, and soy products).
    • Polyphenols (tea, coffee, fruits, and vegetables).
    • Oxalic acid (spinach, silverbeet, rhubarb and soybean products).
    • Tannic acid (tea and to a lesser extent coffee).
  • Non-heme iron absorption is enhanced by:
    • Foods rich in vitamin C and meat.

Iron: Functions

Major functions of iron

  • Enzyme cofactor or constituent
  • Brain function
  • Oxygen transport
  • Immune function

Iodine

Functions

  • Thyroid hormone production.
  • Thyroid metabolism, immune function.

Food Sources

  • Iodized salt, fish, seafood, dairy products, potato, egg, oats.

Deficiency

  • Goiter – enlarged thyroid gland.
  • Cretinism – mental retardation.
  • Occurs in the fetus when a pregnant woman is deficient.

Major Minerals and Health

Sodium and Hypertension

  • High blood pressure.
  • \approx 15\% of the adult population have medicated hypertension (most >65 years of age).
  • Major risk factor for heart disease, kidney disease, and stroke.

Calcium and Osteoporosis

  • “porous bone”.
  • \approx 3\% of adults in NZ have known osteoporosis, with the prevalence being much higher in older females.
  • The leading cause of bone fractures in older adults.