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.