Micronutrients: Minerals and Bone Health

Minerals

• Minerals are one of the six major nutrient classes.
• They are found on the periodic chart.
• Essential minerals cannot be made by the body and must be obtained from food.
• The majority of minerals come from the soil, either directly or through animals that eat plants.
• Minerals are inorganic, meaning they do not contain two or more carbons (homogeneous atoms).
• Major minerals are needed in amounts greater than 100 milligrams a day.
• Trace minerals are needed in amounts less than 100 milligrams a day.
• There are 16 minerals with specific functions in the body, but we will only touch on a few.
• Calcium is the most abundant mineral in the body, primarily stored in bones and teeth.
• Phosphorus is the next most abundant, also stored in bone structure.
• Other minerals to be discussed include sodium, iron, and iodine.

Minerals in Food

• A variety of foods provides a variety of micronutrients.
• Plant-based diets, proteins, dairy, fruits, and vegetables all contribute minerals.
• We're not going to discuss every mineral (e.g., magnesium, boron), but focus on others.
• Minerals are important for:
  • Transport within the body
  • Energy production
  • Structural components

Mineral Bioavailability

• Minerals come from plants and animals.
• Minerals from animal sources are generally more bioavailable than from plants.
• Plant foods contain substances like phytic acid, fiber, and oxalates that bind to minerals, reducing their bioavailability.
• Hydrochloric acid (gastric acid) increases absorption and bioavailability of most minerals.

Functions of Minerals

• Roles vary widely: muscle contraction, nerve impulse conduction, fluid balance.
• Cofactors: Minerals partner with a protein to perform a function (similar to how coenzymes, which are vitamins, partner with proteins).
• Deficiencies: Still an issue in the U.S., potentially due to food processing or poor dietary choices.
• Toxicities: More likely from supplementation than food sources; examples include iron and zinc.

Key Mineral Information

• Know the name, function(s), food source (if mentioned), deficiencies (if any), and toxicities of the minerals discussed.
• Minerals to be covered: sodium, potassium, calcium, iron, zinc, iodine, and possibly fluoride.

Sodium and Potassium

• Sodium and potassium oppose each other in function.
• Sodium is extracellular (outside the cell), while potassium is intracellular (inside the cell).
• Both play similar roles in muscle contraction and nerve impulse conduction.

Differences:

• Location: Extracellular (sodium) vs. intracellular (potassium).
• Source: Sodium primarily from processed foods; potassium from minimally processed or unprocessed foods. Food processing typically increases sodium and reduces potassium content.
• Blood Pressure: Sodium elevates blood pressure in about 25% of the population (sodium-sensitive individuals), while potassium helps maintain healthy blood pressure in most individuals.

Chloride

• Plays similar roles to sodium and potassium in muscle contraction and nerve impulse conduction.
• Component of hydrochloric acid in stomach acid, aiding in food breakdown and enzyme actions.

Other Minerals

• Calcium: Will be discussed in the context of bone health.
• Iron: Discussion reserved for later.
• Zinc: Important for the immune system and taste buds.
  • Deficiency can lead to lack of appetite and decreased taste acuity.
  • Excessive zinc (above 40-42 mg/day) can depress the immune system and taste acuity.
• Iodine and Fluoride: Major details to be discussed later (or summarized briefly if not covered in detail).

Micronutrient Functions

• Micronutrients (both vitamins and minerals) play various roles in metabolic processes.
• Bone health involves multiple micronutrients, but focus will be on vitamin D and calcium.

Micronutrients and Energy Production

• Carbohydrates utilize B6; athletes may need more B6 to access glycogen stores.
• Various micronutrients, mostly vitamins but also some minerals, enable the body to produce energy.

Coenzymes and Cofactors

• Cofactor: A mineral that partners with an enzyme (protein) to create a process.
• B vitamins act as coenzymes.
• Flavin adenine dinucleotide and nicotinamide adenine dinucleotide play a role in energy metabolism.

Bone Health

• Involves calcium and vitamin D (primary focus), but is more complex.

Vitamin D:

• Obtained from food or synthesized in the skin from cholesterol upon exposure to sunlight.
• Dietary sources of vitamin D are not very available.
• Vitamin D synthesis from sunlight has decreased due to more time being spent indoors, making dietary intake or supplementation more important.
• Made from cholesterol when the sun hits our skin.
• Requires two activations: first in the liver (intermediate activation), then in the kidneys (final activation).
• Dietary sources include fish oil and fortified products like milk.

Calcium:

• Major component of bone structure; essential for bone development and maintenance.
• Plays a role in the clotting cascade, nerve impulses, and muscle contractions.
• 99% of calcium is stored in bones and teeth, leaving 1% available in body fluids for critical functions.
• The body manages the 1% of calcium in the blood through hormones:
  • Calcitonin: Released when calcium levels are high; slows calcium release from bones and increases calcium excretion.
  • Parathyroid Hormone: Released when calcium levels are low; causes the release of calcium from bones into the bloodstream.

Vitamin D Deficiency

• Rickets: Occurs in children due to softening of bones; causes bowing of the legs.
• Osteomalacia: Occurs in adults; bones soften due to lack of mineralization, leading to fractures.

Vitamin D Toxicity

• No toxicity from sunlight exposure.
• Excess vitamin D and calcium can lead to calcium deposition in soft tissues, muscles, arteries, and veins.

Osteoporosis

• Different from osteomalacia.
• Osteoporosis involves a decrease in bone mass, while osteomalacia is a lack of bone mineralization.
• DEXA scan is used to measure bone density.

Maintaining Good Bone Density

• Weight-bearing activities (weight lifting, running) put stress on bones, promoting strength.
• Nutrition: Adequate phosphorus, potassium, calcium, and vitamin D intake.
• Smoking increases acidification, causing calcium to be removed from bones to neutralize the acid.
• Medications can help maintain current bone density, but may not recover lost bone mass.