FN 1070/2070A Bone Health Part II Quiz

FN 1070/2070A Introductory Human Nutrition

Course name: Introductory Human Nutrition
Course code: FN 1070/2070A
Chapter: 13, Bone Health Part II
Date: Thursday, November 28, 2024
Instructor: Holly N. Schaafsma, RD, MScFN, PhD (c)
Email: [email protected]

Agenda

Topics covered: Vitamin D, Magnesium, Fluoride, Vitamin K (bone health), Highlight 13, and Final Exam Information

Vitamin D

Synthesis: Body synthesizes Vitamin D with the help of sunlight (precursor from cholesterol). Sunlight transforms 7-dehydrocholesterol into inactive Vitamin D3, which is absorbed directly into the blood.
Activation: The liver and kidney convert the precursor to the active form of Vitamin D3 (a hormone), which is needed for the body to transport it to other organs. Lack of this process may result in a deficiency.
Function: Assists in the absorption of calcium and phosphorus for bone growth and maintenance. Increases blood concentrations of these minerals in three ways: 1) enhanced absorption from the Gl tract (sufficient diet), 2) reabsorption in the kidneys (with parathyroid hormone - insufficient diet), 3) mobilization from bones. This influences bone growth, health of bones and teeth. Other roles include: impact on immune system, brain and nervous system, pancreas, skin, muscles, cartilage, and reproductive organs; disease prevention is uncertain.
Recommendations (RDA, UL):
- Adults (19-70 years): 600 IU/day (15 µg/day)
- Adults (>70 years): 800 IU/day (20 µg/day)
- UL (Upper Limit): 4000 IU/day (100 µg/day)
Sources: Sunlight, fortified milk and margarine, egg yolks, fatty fish (salmon, sardines).
Deficiency: Rare overt signs. Common is inadequate status leading to decreased calcium absorption through the Gl system (e.g., Calbindin, protein that binds to calcium in intestinal cells). Insufficient absorption with adequate dietary calcium intake impacts bone development and results in calcium deficiency.
- Rickets (in children): Bones fail to calcify normally, causing growth impairments, skeletal abnormalities (bowed legs), and improperly formed bone attachments to cartilage (beaded ribs).
- Osteomalacia (in adults): Bones become unusually soft, flexible, brittle, deformed. Causes pain in the bones, and curving of the spine and legs.
- Osteoporosis (in adults): Inadequate Vitamin D results in loss of calcium from bones, causing porous bones and increasing the risk of fractures
Deficiency - Sun Exposure: Body needs ~5-10 minutes of 2-3x a week sunlight exposure for Vitamin D production. Sunscreen (SPF 8 or higher) reduces synthesis, but even SPF 30 still allows synthesis in ~10-20 minutes. Melanin in skin limits synthesis; time of day and season affect synthesis (midday, summer better), and geographic location (cities, smog). Latitude is a factor; people in areas with limited sunlight exposure may have deficiency.
Populations at Risk: Older adults have reduced ability to synthesize and activate Vitamin D due to aging skin, liver, and kidneys. Dietary vitamin D intake is often low. Less exposure to sunlight, covered in clothing makes them more prone to deficiency. Recommended supplement of 400 IU/day is also important. People in northern climates (dark skinned and/or covered by clothing) are at higher risk.
Toxicity: Excess vitamin D from supplements may raise calcium levels, resulting in kidney stones & hardening of blood vessels (impacting major arteries in brain, heart, and lungs).

Magnesium

Location: Half in bones, remaining in muscles and soft tissues, a small portion in extracellular fluid (1%).
Function: Essential role in bone mineralization, heart function, energy metabolism. Works with calcium in muscle contraction and blood clotting. Inhibits calcium contraction and promotes relaxation. Involved in maintaining blood pressure and lung function. Needed for various processes (protein, fat, nucleic acid and cell's membrane transport systems).
Recommendations (RDA, UL): Men (19-30 years): 400mg/day; Women (19-30 years): 310mg/day
- UL (Upper Limit): 350mg of non-food based magnesium/day (supplements).
Sources: Hard water, nuts, legumes, whole grains, dark green vegetables, seafood, chocolate, cocoa.
Deficiency: Average intake falls below recommended levels. Can cause inflammation, constricting arteries/capillaries, impacting blood pressure & central nervous system. Potential for tetany (similar to calcium tetany), possible hallucinations. High calcium and magnesium water is correlated with a reduced prevalence of heart disease.
Toxicity: Can be fatal, Upper limit (UL) applies to nonfood sources.

Fluoride

Presence: Found in most soils, water supplies, plants, and animals. Trace mineral.
Function: Replaces hydroxyl in hydroxyapatite crystals (formed from calcium and phosphorus) to form fluorapatite. Strongens bones and teeth, making them more resistant to decay.
Sources: Fluoride-containing water (fluorinated drinking water), fish and most teas.
Recommendations (AI, UL): Men: 4mg/day; Women: 3mg/day; UL: 10mg/day
Deficiency: Can impact dietary intake. Only ~39% of Canadians have fluorinated drinking water. Access varies regionally (e.g., Ontario & Alberta >75%, Quebec <49%) in Canada.
Toxicity: Fluorosis: discolouration & pitting of tooth enamel caused by excess fluoride during development.. May result in small white specks or permanently stained teeth (cannot be reversed). Mouthwash or toothpaste should not be swallowed.

Vitamin K

Function in bone health:
- Needed in bone protein metabolism (Osteocalcin). Vitamin K is needed to bind this protein to necessary minerals needed for bone formation/growth.
- Adequate intake of Vitamin K helps decrease bone turnover, protecting against fractures.

Highlight 13

Highlight 13 in the course: Topics include stages of osteoporosis, risk factors for osteoporosis (non-modifiable and modifiable), and protective modifiable factors. Discusses growing strong bones, achieving peak bone mass, maximizing bone retention, minimizing bone loss. Highlights include Calcium supplements, if required due to dietary insufficiency of calcium/Vitamin D.