Bone Health: Nutrition and Vit D Flashcards
Increase in bone mass happens with age and is rapid in puberty and continues in adult life. At what point does bone mass lower?
Peak bone mass is 35years old
and for women after menopause bone mass rapidly declines
Increased intake of what during rapid bone growth increases peak bone mass?
Calcium and vit D
Bone health varies markedly between countries independently of what?
Calcium Intake
Calcium intakes are actually higher in certain countries but still have an increased incidence of what?
Hip Fractures
In Gambian and China there is less cases of osteoporosis and few fractures, why???
Dietary factors
Less diary
More fish and more veggies
Dietary calcium intakes appear unrelated to bone health why?
The adaptation hypothesis
- -dietary calcium intake above a min low level is unimportant as a regulator of bone health
- -since plasma free calcium is regulated so finely, adaptive mechanisms exist to maintain calcium bones over a wide range of intakes.
Plasma Ca2+ concentration is highly regulated by what?
Vit D
PTH
–maintain plasma Ca2+ at a supersaturating level with respect to bone mineral and to prevent hypocalcemic neuromuscular tetany
What are the adaptive responses to low calcium intakes?
Low Dietary Ca —- reduction in plasma Ca — Increased PTH secretion
Increased Active Vit D — increased intestinal Ca absorption
Decreased urinary Ca —increased conservation of dietary Ca
The body, however, can not adapt to very low intakes of dietary calcium. This can cause what?
Rickets (African) (w/o Vit D deficiency)
- -increased amounts of unmineralized bone
- -fibroblast growth factors
Adequate calcium is needed for peak bone mass (PBM) development. Long-term low Ca2+ intakes results in what?
Impair peak bone mass development
–pubertal girls only partially adapt to very low dietary Ca2+ intakes
Extra calcium reduces what?
Bone Mass Loss
Supplementation with milk improves the nutritional quality of the diet of what kind of individuals?
Post menopausal women to a greater extent than Ca2+ alone
Fruits and veggies are important for bone health. Why?
Provide alkali to neutralize dietary acid
Cereals and high protein foods produce what?
Acid
–bone mineral balance is therefore sensitive to this
Bone mineral balance is extremely sensitive to what?
Acid base balance with demineralization occurring as pH drops below a critical point
Dietary acid can be buffered by what foods?
Fruits and veggies
We have markedly reduced dietary ____ and ____ and increased dietary ____ and _____ since preagricultural times
K and HCO3
Na and Cl
As people age the ability to excrete acid declines and they become slightly more _____?
Acidic
What supplementation improves Ca2+ and PO4 balance
KHCO3
–as does carbonated mineral water
Fruit and vegetable intakes are associated with better what?
Bone Health
DASH (dietary approaches to stop hypertension), high in fruits and vegetables and low-fat diary products, report what?
Improved calcium balance
What supplements supplies alkali and this may be part of their effectiveness for bone health?
Ca Citrate/malate
Vitamin D regulated what?
Ca2+ and PO4 homeostasis
Keeping Ca-P homeostasis in the body involves, what from the intestine, bone and kidney?
Intestine: Ca absorption
Bone: Ca release
Kidney: Ca retention
What is a measure of vitamin D status?
25-OH vitamin D
What is the active hormone in the body in the vitamin D pathway?
1,25(OH)2D3
Vit D has a wide range of tissue functions, what is the pathway?
1 alpha hydroxylase —- 1.25(OH)2D3 — various functions
Where do we get vit D from?
Sunlight is the major source
- -few foods (oily fish, cod and liver oils, butter/cream/cheese, and fortified breakfast cereals)
- -small quantities in fortified foods
- -larger quantities in fish
The global burden of vitamin D deficiency disease is high. Deficiency disease is defined as what?
v-low 25OHD: less than 25nmol/l
What populations are at risk for vit D deficiency?
Infants, prego women and elderly
Ethnic minorities in temperature countries
Limited sun exposure
What is the cut-off point for rickets?
less than 25.0nmol/l
What is the cut off point for deficiency in most labs?
less than 40nmol/l
What are the causes for vitamin D?
- Reduced skin synthesis
- Decreased bioavailability
- Increased catabolism
- Decreased synthesis of 25-hydroxyvitamin D
- Increased urinary loss of 25-hydroxyvitamin D
What is the main cause for the recurrence of Rickets in the past 14 years?
Sunlight avoidance
What are the consequences of vit D deficiency?
- Classical Vit D deficiency disease
- Children: rickets and osteomalcia
- Adults: osteomalacia
- -occurring in the US and UK
Rickets is a particular problem amongst what population?
Asian Community in the northern hemisphere
–due to decreased sun exposure, diet and inadequate calcium requirements
Vit D is a multifactoral chronic disease, that can cause what?
- –Falls/neuromuscular function
- –type I diabetes
- –CVD
- –Cancer
- –HTN
Vit D deficiency is believed to be a major _____ _____ problems which requires action
Public health
