Chapter 12

NTR 306: Fundamentals of Nutrition

Overview of Major Minerals

  • Minerals: Inorganic, essential nutrients required in small amounts in the diet for normal growth and health.

    • Similarities with Macronutrients:

    • Essential for life and health.

    • Have Estimated Average Requirements (EARs), Recommended Dietary Allowances (RDAs), and Adequate Intakes (AIs).

    • Differences from Macronutrients:

    • Structure: Individual elements, not linked together (unlike amino acids or glucose).

    • Function: Do not yield energy (no kilocalories).

    • Elements: Inorganic.

    • Amounts: Required in smaller quantities (measured in milligrams).

    • Have Tolerable Upper Intake Levels (ULs).

    • Differences from Vitamins:

    • Elements: Inorganic.

    • Amounts: Needed in larger quantities (measured in milligrams).

    • Stability: Cannot be destroyed by heat, air, or acid.

Varied Roles of Minerals in the Body

  • Functions: Nuanced roles including fluid balance, growth, health maintenance.

  • **Classification:

    • Major Minerals:** Present in the body and required in larger amounts.

    • Trace Minerals: Present in the body and necessary in smaller amounts.

    • Note on human physiology: Typical 60 kg (132 lb) body composition of minerals as discussed (Whitney & Rolfes, Understanding Nutrition, 16th ed.).

Stability and Bioavailability of Minerals

  • Inorganic Nature: Minerals retain their chemical identity and are not altered through the cooking process.

  • Destruction: Cannot be destroyed by heat, air, acid, or mixing, but can be lost through leaching into cooking water.

  • Factors Impacting Bioavailability:

    • Food Binders: Chemically interact with minerals to inhibit absorption.

    • Mineral Interactions: For instance, high sodium levels may affect calcium excretion.

  • Absorption and Transport:

    • Some minerals, like potassium, can be readily absorbed and excreted.

    • Others, like calcium, require carrier proteins for absorption and transport.

Sodium

  • Biological Roles:

    • Primary cation of extracellular fluid.

    • Regulates fluid volume in the body.

    • Maintains the body's acid-base balance.

    • Essential for nerve impulse transmission and muscle contraction.

  • Absorption:

    • Travels freely in the bloodstream.

    • Kidneys filter sodium for reabsorption, assisted by the Na+/K+ ATPase pump.

  • Homeostatic Mechanism:

    • Increased sodium levels trigger thirst, prompting fluid intake and excess sodium excretion by the kidneys.

Sodium Deficiency

  • Causes: Not typically due to insufficient dietary intake, but rather from excessive losses.

  • Condition: Hyponatremia (low blood sodium).

  • Causes of Imbalance: Vomiting, diarrhea, heavy sweating, over-hydration.

  • Symptoms:

    • Headache.

    • Confusion.

    • Near-unconsciousness.

    • Seizures.

    • Coma.

Sodium Recommendations

  • Adequate Intake (AI):

    • Men: 1500 mg/d.

    • Women: 3100 mg/d.

  • Tolerable Upper Intake Level (UL):

    • Men: 3500 mg/d.

    • Women: 2300 mg/d (within the daily intake range).

  • Nutritional Concern:

    • Overconsumption is prevalent with 90% of the U.S. population exceeding the UL.

    • Underlying factors: flavor enhancement in cooking and preservation properties of sodium.

    • Typical dietary source: sodium chloride (salt). Notably, 1 tsp of salt equals 2300 mg of sodium, corresponding to the UL of sodium.

Sodium Toxicity

  • Acute Toxicity Effects: Edema and heart failure.

  • Chronic Effects: Hypertension (high blood pressure).

Sodium Sources in Diet

  • Processed Foods: Highest sodium content found.

  • Unprocessed Sources: Present in smaller amounts; examples include milks, meats, vegetables, fruits, and grains.

    • Notable examples include:

    • Processed Foods: High sodium levels found in items such as instant meals and snacks.

    • Whole Foods: Sodium is naturally present but in significantly lower amounts.

Strategies to Reduce Sodium Intake

  • Recommendations to emphasize fresh fruits and vegetables.

  • Strategies such as baking or cooking at home to control sodium levels.

  • Alternatives such as “lite salt” to reduce sodium intake while retaining flavor in meals.

Chloride

  • Biological Roles:

    • Principal anion of extracellular fluid, associates closely with sodium.

    • Moves passively across cell membranes.

    • Functions as co-regulator of fluid volume and plays a role in maintaining the body's acid-base balance, including hydrochloric acid (HCl) in the stomach.

  • Recommendations:

    • AI for men: 2300 mg/d; UL: 3600 mg/d for men.

    • Women: Qualifying dietary intake reflects the adequacy of intake by adults aged 19-30.

Potassium

  • Biological Roles:

    • Principal cation of intracellular fluid.

    • Critical for maintaining fluid and electrolyte balance and cell integrity.

    • Ensures proper nerve impulse transmission and muscle contraction.

  • Absorption and Excretion:

    • Potassium is absorbed passively in the small intestine (~90% absorption) and is primarily excreted in urine.

Potassium Recommendations

  • Adequate Intake (AI):

    • Men: 3400 mg/d; Habitual intake varies around 2600 mg/d.

    • Women: 2300 mg/d; actual intake may also be less.

  • Public Health Concern: Underconsumption noted in recent data.

  • Recognized Effects of Deficiency:**

    • Acute effects include irregular heartbeat and muscle weakness.

    • Chronic deficiency relates to conditions such as hypertension and elevated kidney stones.

Potassium Food Sources

  • Variety of foods available to contribute to potassium intake include:

    • Fruits (bananas, oranges, strawberries, watermelon).

    • Vegetables (broccoli, potatoes).

    • Dairy (milk and yogurt).

Calcium

  • Overview: The most abundant mineral in the body, with 99% found in bones and teeth.

  • Biological Roles: Adequate calcium intake helps in:

    • The development of a healthy skeleton during early life.

    • Minimization of bone loss during later life.

    • Functions in blood pressure maintenance and blood clotting support.

    • Necessary for various calcium-dependent proteins in the body.

Calcium Homeostasis

  • Mechanisms:

    • Three organ systems involved: intestines, bones, and kidneys regulate calcium balance.

    • Hormonal Regulation:

    • High blood calcium: Calcitonin inhibits vitamin D action, decreases calcium resorption and absorption.

    • Low blood calcium: Parathyroid hormone increases renal resorption and intestinal absorption of calcium, facilitates bone dematerialization.

Calcium Recommendations

  • RDA:

    • Men: 1000 mg/d.

    • Women: 890 mg/d (may vary by individual age and sex).

  • Tolerable Upper Intake Level (UL):

    • Men: 2500 mg/d.

    • Rare deficiencies noted in populations, especially leading to osteoporosis in adults and stunting in children.

    • Risks associated with high intake: constipation or kidney stone formation linked to supplements, not typically from whole food sources.

Calcium Food Sources

  • Notable sources include dairy products (milk, yogurt, and cheese), fortified foods, certain vegetables (broccoli), and nuts.

Phosphorus

  • Overview: The second most abundant mineral in the body after calcium, constituting 85% as hydroxyapatite crystals in bones and teeth.

  • Biological Roles:

    • Integral part of the cellular buffer system, DNA and RNA composition, ATP molecule for energy metabolism, and lipid transport in blood.

Phosphorus Recommendations

  • RDA:

    • Men: 700 mg/d; Women: 1200 mg/d.

    • Minimal deficiency noted due to the widespread nature of phosphorus in protein-rich foods and typical dietary habits.

Magnesium

  • Overview:

    • Over 50% located in bones; important for regulating blood concentrations.

    • Also present in soft tissues and extracellular fluid.

  • Biological Roles:

    • Crucial in energy metabolism and enzyme activity, facilitating muscle contraction and blood clotting, while supporting immune system functioning.

Magnesium Recommendations

  • RDA:

    • Men: 400 mg/d; Women: 310 mg/d.

    • Common deficiencies linked to inflammation and chronic diseases including cardiovascular conditions and diabetes.

Summary & Wrap-Up

  • Preparation for upcoming lecture topics, including trace minerals and water.

  • Reminder for assignment due dates and concepts discussed in class.