Calcium

Calcium Used for Bone Remodeling

If 50 to 70% of calcium intake is for bones and roughly 30% of bone mass is calcium, then how much calcium do we really need? If we have roughly 1100 grams in a average human and adult skeletal structure is completely remodeled every 10 years, how much calcium is required daily? That's 300 milligrams per day for just bones.

But cant we get most of that from recycling calcium?

Bone remodeling involves both the resorption (breakdown) of old bone tissue by osteoclasts and the formation of new bone tissue by osteoblasts. The calcium released during bone resorption can be reused for new bone formation.

It's estimated that a significant majority (possibly around 70-90%) of the calcium used in bone remodeling is recycled. Meaning that a average human would only need 30 to 90 mg of calcium daily for proper bone MAINTENANCE.

However we must factor in the dietary calcium absorption rate.

Animal sources are slightly more bioavailable than plant sources. Getting enough sunlight is also crucial for optimal calcium absorption due to adequate vitamin D levels. Typical calcium absorption is around 20 to 40%. So the average human needs anywhere from 180 to 450 mg of total dietary calcium for bones and add 1% for all other uses.

Calcium Used for All Other Processes

Estimated: 370-630 mg/day for enzymatic functions, muscle contraction, neurotransmitter release, and other processes. With more than half of this coming from calcium recycling within the body.

Pregnant, Lactating, Young and Deficiency Status

Pregnant or lactating women may need to increase their total dietary intake of calcium by 50%. Growing infants, adolescents and those recovering from a deficiency will also require a higher intake.

Increased phosphorus and sodium consumption may increase needs for calcium. However phosphorus can be balanced with minerals other than calcium and in the context of magnesium and other mineral proficiencies, calcium recycling becomes more efficient lowering the need for dietary calcium and calcium supplementation. The major risk in calcium excess is when someone is electrolyte deficient. Especially when we do not have enough potassium and magnesium calcium may accumulate in soft tissues causing unnecessary destruction.

Personally I see excess vitamin A causing vitamin D deficiencies and that is the more serious cause of calcium deficiency. So it would be prudent to cut back on total vitamin A intake especially in the winter months. Lack of sunlight is the single greatest risk factor for vitamin D deficiency. Rather than supplementing vitamin D in the winter get tons of sunlight in the summer and lower A intake in the winter.

If you are not consuming dairy that is the most bioavailable source of calcium. Some might consider a balanced multi-mineral to be the best strategy for calcium adequacy and metabolism.

Taurine from meat, dairy and eggs has also been shown to improve bone density and are the only sources that can provide it. Some types of seaweed may also provide it.

Summary of Daily Calcium Loss

Urine: 100-250 mg ~ Feces: 100-200 mg ~ Sweat: 20-40 mg ~ Skin Shedding: <10 mg ~ Hair: <1 mg

Total Daily Calcium Loss ~ 220 to 501 mg

However understand that a large amount of the calcium "lost" in feces was never absorbed in the first place so much of it should not be counted. Most of the actual losses are coming from urinary excretion. The kidneys are generally very efficient at reabsorbing calcium, up to 98%. We just have so much calcium being recirculated around the body that regardless of high efficiency much can still be excreted in the process.

How much do I need?

Considering its use in bone remodeling, enzymatic process's and high recyclability, it is likely that in regular circumstances we only need  150 to 400 mg per day.

Increased needs would likely come from cofactor deficiencies, infections and a history of deficiency.