Calcium

[liveonearth]

CALCIUM
most common mineral in body
hydroxyapatite in bone
blood and extracellular concentrations tightly regulated

ABSORPTION
absorption averages 30%
small amounts absorbed better than large amounts
high demand causes increased absorption, ie. deficiency states and pregnancy
adequate vitamin D
with a meal absorb better (exception: phytates and oxalates block absorption, spinach)
does not depend much on type of calcium compound
calcium carbonate not absorbed well on empty stomach
sodium causes you to loose more calcium in urine
high protein diet increases calcium loss in urine
caffiene has minor loosing effect
phosphorus: effects unclear

CALCIUM DEFICIENCY
low blood levels dt pathology: low PTH, kidney dysfx, vit D def (not diet)
chronic low dietary Ca++ affects bone density
not achieve peak bone mass in youth
not maintain bone mass in middle age
accelerated bone loss with age

1997 AI (adequate intake) SET TO OPTIMIZE LONG TERM BONE HEALTH
children 9-18, 1300mg/day
young adult 1000 mg
older adult 1200 mg
setting RDA complicated dt complex interactions th genetics, hormones, and physical activity

BEST SOURCES
milk products
tofu, calcium processed
Asian greens: Kale, Chinese cabbage, Bok Choi
fortified foods and beverages
food sources not equally absorbable
beans are high calcium but also high in phytates (wheat bran)
grains with yeast digests phytates, also germination, sprouting eliminates phytates
spinach is poor source of calcium because of high phytate content
Asian greens, tofu and dairy products are his favorite sources for absorbability
chicken cacciatore with bone-in chick cooked in tomato: my recipe, he likes the idea

CALCIUM SUPPLEMENTATION
best absorbed with food and in amounts smaller than 500mg at a time
multis provide small proportion of daily needs
variable amounts of elemental calcium in supplements
label says how much calcium, not how much of other substance it's with
calcium carbonate delivers more calcium per pill because 40% of supplement is calcium
so less pills needed to get requirement
calcium gluconate, you have to take the most mg to absorb enough Ca++ (9% is Ca++)
easy to get enough with carbonate or tricalcium phosphate (40% 38% respectively)
citrate and lactate less but better than gluconate (21, 3something% respectively)

24 hour cycle of calcium/bone metabolism
bone loss happens at night
LARGE NIGHT TIME DOSE MAY BEST PREVENT OVERNIGHT BONE LOSS
he's saying 1200 at bedtime in spite of his previous statement that says not over 500mg/dose

CONNECTION TO OSTEOPOROSIS
US calcium requirement higher here because we do other things that hurt our bones
too much sodium and protein in diet, not enough exercise
supplementation while growing increases bone mass
supplementation in perimenopause reduces bone loss
supplementation does NOT affect bone loss in perimenopause when estrogen effect is lost***
after 5 years then supplementation reduces bone loss and prevent fx in elders, esp w/ vit D

DISEASE PREVENTION
COLORECTAL CANCER
best favorable connection
calcium may bind carcinogens in gut
high intake esp w/ vit D reduced risk of precancerous lesions
recent RCT found no benefit in healthy women (research flawed) p 23 in notes
KIDNEY STONES
calcium prevents dietary oxalate absorption when consumed with meals
reduces stone formation
HTN
calcium may help prevent pregnancy-induced HTN
minor effects on essential HTN, not enough to be therapeutic

MILK
pro: concentrated source of absorbably calcium, available and inexpensive
con: optimal requirement is controversial
lactose intolerance common
milk contains unhealthy fats and extra calories
possible cancer risks, probably small, ovarian CA risk less than originally thought

SAFETY
hypercalcimia from calcium ingestion unlikely
UL = 2500mg/day
can you block absorption of other minerals with Ca++? yes but only if take lots
Iron, magnesium, zinc deficiency could be exacerbated by big Ca++ supplementation

LEAD
supplements have rarely been contaminated
esp if contains dolomite, or oyster shell
look for lead free guarantee if supplement contains these

PROSTATE
mechanism compelling: body might not activate as much vit D if supplement supplies Ca++
meta-analysis found only small risk
LPI recommends men keep total intake below 1200 mg/day