Nutrition Ch. 11 (Bone Health)

Bones act as calcium store

Body will compromise bones to maintain proper blood levels (meaning if your body doesn't have enough calcium circulating through it, the body will trigger the PTH (parathyroid hormone) which will trigger the release of osteoclasts to break down bone and release the calcium stored there)

Osteoporosis and Calcium

*Dietary calcium is the key to prevention *Other nutrients play a supporting role -Vitamin D -Phosphorous

*Vit. D synthesis dependent on UV exposure (The body can either make its own vitamin D using a process that requires sunlight or obtain vitamin D directly from the diet)

*Stored in adipose tissue and liver

Trabecular (Spongy) bone

*Super strong but super light (muse for the eiffel tower) Bone has spaces filled with red bone marrow

Cortical (Compact) bone

*Very dense Ostenons (Each osteon consists of layers, or lamellae, of compact bone tissue that surround a central canal. Osteoblasts form the lamellae sequentially, from the most external inward toward the central canal.) -central canal (The blood supply for the osteocytes then passes through these channels; contains the bone's nerve and blood supply) -blood vessels -osteocytes (Osteocytes are mature osteoblasts that have become trapped within the very bone matrix they produced. Aka individual bone cells. Osteocytes continue to form bone to some degree, which is important for maintaining the strength and health of the bone matrix. They also call osteoblasts or osteoclasts when needed)

Functions of calcium (besides bones)

-Heart contractions -Smooth muscle contractions -Enzymatic co-factors -Prevents hypertension (high blood pressure) -Helps maintain body weight

Which nutrients are essential for bone health? (besides calcium)

-Vitamins D (promotes absorption and use of calcium and phosphate) -Vitamin K (necessary for synthesis of proteins found in bone) -Phosphorous -Magnesium -Fluoride

Skeletal System Functions

1. Supports the body 2. Protects the soft body parts (ribs, etc.) 3. Produces blood cells (red bone marrow) 4. Stores minerals (calcium and phosphate) and fat (yellow bone marrow) 5. Allows for movement by attaching muscles

Bone Structure

65% mineralized 35% connective tissue

Calcium

AI (adequate intake) for adults: 1000 mg/day Adolescents (1300 mg/day) and those over 50 (1200 mg/day) *Adolescents need more calcium because they're growing bones and elderly need more calcium bc osteoclasts start overpowering the osteoblasts around age 40 so they need all the calcium they can get to maintain bone strength

Fluoride

AI= *1 to 4 mg/day*, depends on age Where does our fluoride come from?: City water and toothpaste Too much- porous teeth (start like white spots and then be come darker and holey) Too little- cavities

Osteoporosis

Bones become more porous (thinner, weaker, more holey) *Due to sex hormone reductions (women's drop around age 45)

Role of osteoblasts

Build up bone *deposits hydroxiapetite (calcium and phosphate crystals); some become osteocytes

What is the most recognized nutrient associated with bone health?

Calcium

Role of osteoclasts

Crash down (break down) bone *Leave collagen fibers visible, releases calcium and phosphorous so that it can be absorbed by the blood/body

Bone modeling

Early adulthood

Vitamin D foods

Good sources: Milk (fortified), cheese, whole eggs, liver, salmon, and fortified margarine. The skin can synthesize vitamin D if exposed to enough sunlight on a regular basis *Why is milk a good source?: because it's fortified with vitamin D

Vitamin K Sources

Half comes from: gut flora Food sources: Leafy greens (spinach, lettuce, kale), cabbage, cauliflower, wheat bran, organ meats, cereals, some fruits, meats, dairy products, eggs

Vitamin D

Has lots of versions/names (all of them combine part of "calcium" in with them since vit. D helps promote the use and absorption of calcium) -Cholecalciferol (ex. provitamin D3, liver(?)) -Calcidiol: can be stored in the liver (kidneys?) -Calcitriol: Primary active form of Vit. D (ex. 1, 25-dihydroxyvitamin D3) -Ergocalciferol (D2): plants, supplements

Factors that decrease absorption

High fiber diet (because it speeds up the digestion and allows less time for minerals such as calcium to be absorbed), binders (phytates/oxalates), high phosphorous intake

Too much calcium leads to...

Hypercalcemia (usually get this through supplement intake) -PTH overproduction/cancer (If the level of calcium in the blood falls, the parathyroid glands normally produce more PTH, which pulls some calcium from the bones into the blood, normalising the level. If the calcium level in the blood rises above normal, PTH secretion falls, and the level of calcium in the blood falls back to normal. PTH may be produced in large quantities, stimulated by low levels of calcium in the blood. The PTH tries to keep the calcium level in the blood normal by increasing calcium absorption from food, but also takes calcium out of the bones. Eventually the parathyroid glands work so hard they go out of control, and cause persistently high calcium levels. This may require an operation to remove the glands) -Calcification of soft tissues (can lead to *kidney stones*)

Calcium Absorption

In adults= 25-30% of consumed calcium is absorbed Factors increasing absorption: stomach acid, vitamin D (promotes calcium absorption), lactose, GH (growth hormone)

Bone Growth

In males: Age 17 In females: Age 14

Alcohol leads to...

Increased calcium loss (because of the increased fluid loss since alcohol is a diuretic meaning it inhibits the ADH hormone which stimulates the aquaporins in the kidney to retain water so urine is less concentrated)

Vitamin D Toxicity

Leads to: -High blood Ca+ levels -Calcification of soft tissues -UL: 50ug/day Not possible from overexposure to the sun! -Rare from food sources **Main culprit: supplements

Smoking leads to...

Low bone density

Fluoride

Most found in teeth and bones (99%) Hardens teeth Fights bacteria Micronutrient- body needs it. Some tap/city water is fortified with it as well as dental objects (toothpaste and floss, etc.)

Vitamin K and Bones

Necessary for normal blood clotting (blood coagulation) and synthesis of proteins found in bone (bone metabolism) -Helps to regulate blood Ca+ levels AI= *120 ug* for males, *90 ug* for females

Functions of Vitamin D

Need vitamin D to absorb calcium and phosphorous (and other ions) *Promotes absorption and use of calcium and phosphate for healthy bones and teeth* -Needed for calcification of bones -Works with PTH (Vitamin D helps the intestines absorb calcium. However, the vitamin D must first be activated or "turned on" by parathyroid hormone (PTH). Once activated, vitamin D acts to greatly increase the amount of calcium that the intestines can absorb from food) Also involved in: -Immune system function -Brain/nervous system -Pancreas -Connective tissues

Who needs more Vitamin D?

People who get less sun -North of 40 degrees latitude -UV rays aren't strong enough to activate sometimes, in winter take vitamin D supplements

What prevents osteoporosis?

Physical activity Why?: Because weight bearing activity puts more calcium into the bones by stimulating osteoblasts

Bone remodeling

Recycling of material Change blood calcium levels Peak bone density: ~30 yrs -Loss after 40 because osteoclasts become more efficient than osteoblasts

Collagen

Strength, durability, flexibility

Vitamin K

Two forms: -In *plants phylloquinone* -In *animals menaquinone* *Only have to consume 50% Where does the other 50% of your vitamin K come from?: The good gut floria (bacteria) produce the Vitamin K (most in large intestine)

Vitamin K: deficiencies

Uncontrolled hemorrhaging (a condition in which a person bleeds too much and cannot stop the flow of blood) because Vit. K is responsible for blood coagulation (blood clotting) Antibiotics: can cause secondary deficiency -Why?: Because it targets your entire body bacteria, not just the bad All newborns receive vitamin K supplement -Why?: Because they don't have any bacteria in their gut yet

Hormones

Vitamin D= Promotes absorption and use of calcium and phosphate for healthy bones and teeth Calcitonin=Involved in helping to regulate levels of calcium and phosphate in the blood, opposing the action of parathyroid hormone Parathyroid Hormone (PTH)= Stimulates action of osteoclasts to release calcium into the blood stream

What models the bones?

Weight lifting, etc.

Vitamin D deficiencies

Who is most likely to have these?: The over-weight and elderly because they are less likely to go/spend much time outside Rickets- *in children*; the softening and weakening of bones, their legs become bowed- bent. Soft, brittle/flexible bones. Osteomalacia- *in adults*; softening of the bones, legs become bowed and bent just like rickets. Soft, brittle/flexible bones. Osteoporosis: when bones become porous and break easily

Who is most likely to get osteoporosis?

Women after menopause (mainly asians and europeans)

What is special about Vitamin D (as opposed to most of the other vitamins)?

Your body can produce it

Mineralized bone

hydroxyapatite (calcium and phosphorous crystals)