Calcium

Calcium
Chemical formula	Ca
Solubility	Reacts with water; Ca²⁺ salts vary by anion
Bioavailability	Citrate and lactate absorb well; carbonate needs acid; oxalate-rich greens absorb poorly
Dietary sources	Milk, cheese, eggshell powder, low-oxalate greens, sardines with bones
RDA (adults 19–50 y)	~1,000 mg/day (mainstream adult reference)
Upper limit	2,000-2,500 mg/day (mainstream adult UL)

Calcium is the most studied regulatory ion in biology. Mainstream advice sometimes restricts dietary calcium to prevent arterial calcification. The opposite is the case: inadequate intake worsens soft-tissue calcification while the skeleton loses mineral, and stressed cells take up excess calcium when magnesium and energy metabolism fail.

It is extremely important to realize that calcium deposits in soft tissues become worse when the diet is low in calcium.

— Ray Peat

Magnesium is the basic protective calcium blocker. Inflammation, Hypothyroidism, and protein deficiency shift ions toward sodium and calcium inside cells and away from magnesium and potassium. See Parathyroid hormone, Vitamin D, Vitamin K, Harm reduction.

History

Etymology

The name comes from Latin calx ("lime"), referring to calcium oxide and limestone, materials used in construction and mortar since antiquity.

Humphry Davy isolated metallic calcium in 1808 by electrolysis of lime.

Structure/Chemical properties

Calcium (Ca, atomic number 20) is mainly extracellular in Peat's ion summary, paired with Sodium, while magnesium and potassium dominate intracellular fluid when metabolism is efficient. Organic tissues bind metal ions selectively; respiration and metabolic acids (CO₂, lactic acid) move ions without invoking membrane "pumps".

Function/Mechanism of Action

Stressed or de-energized cells lose magnesium and potassium and absorb sodium and calcium. Mitochondrial calcium overload inactivates respiration and pushes glycolysis, starting calcification in mitochondria and spreading through inflammation and fibrosis.

The antimetabolic actions of PTH mimic those seen in aging and diabetes.

— Ray Peat

Parathyroid hormone rises when dietary calcium or magnesium is low, drawing calcium from bone and promoting inflammatory mediators including IL-6. Estrogen, Serotonin, and Prolactin interact with that cascade. Increased CO₂ and bicarbonate favor bone formation; Progesterone and Aspirin appear as opposing themes to PTH-driven calcification.

Nocturnal calcium loss

Sleep is not metabolically neutral for bone. Protein breakdown outpaces synthesis overnight even during restorative sleep, and most calcium loss from bone shows up in the following morning's urine, timed to the morning rise in stress hormones. Adequate calcium and vitamin D, sufficient to keep PTH low, help counter that nightly catabolic process alongside a bedtime carbohydrate snack to limit the nocturnal rise in free fatty acids.

Medical uses/Effects

Adequate calcium and magnesium intake had anti-inflammatory and anti-allergy effects, with links to arrhythmia relief, obesity, and emotional disturbance when minerals were chronically low. Hard-water regions with high calcium or magnesium showed lower mortality from heart disease and some cancers in epidemiology he cited.

A 10-year follow-up of 5,448 adults free of heart disease at baseline (Multi-Ethnic Study of Atherosclerosis, MESA) found high total calcium intake associated with lower risk of incident coronary artery calcification, but that protection held specifically for calcium from diet; calcium from supplements was associated with increased CAC risk instead.

Blood pressure and salt sensitivity

Ray Peat pointed to David McCarron's finding that government diet-and-hypertension data showed the opposite of the standard low-salt advice: people eating the most salt had the lowest blood pressure, and those eating the least salt had the highest. McCarron concluded calcium deficiency, not sodium excess, was the more likely explanation. A controlled feeding trial later found dairy-based diets improved blood pressure in hypertensive adults specifically through a reduction in intracellular calcium.

This gives a practical threshold for who actually needs to worry about sodium/salt intake: hypothyroidism combined with calcium deficiency is what makes someone salt-sensitive in the first place, and correcting thyroid function alone doesn't fully remove that sensitivity.

If your calcium intake is well over 1,000 mg per day and your Vitamin D is good, then there's very little likelihood that you will be one of those salt-sensitive people.

— Ray Peat

Milk concentrates usable calcium and protein while excluding much plant-sourced strontium and lead relative to vegetable-only calcium plans Peat critiqued. Animal protein supports bone mineral density in elderly women in studies Peat cited (Bell and Whiting, 2002).

Side/Adverse effects

Restricting calcium to prevent soft-tissue calcification intensified the problem: everyone has a skeleton, so cells still need dietary calcium even when arteries are calcifying. Kidney-stone patients told to avoid all milk often formed stones faster in cases he cited from Adelle Davis. Low Sodium diets increase magnesium loss via aldosterone, worsening mineral balance in stressed people.

Dosing

Peat favored milk-and-fruit or milk-and-meat patterns with generous calcium and magnesium rather than low-protein vegetarian plans marketed for bone health. Leafy greens are magnesium-rich but can carry lead and other toxins in Peat's caution.

See Egg § Eggshell calcium for the recipe and full absorption literature.

Interactions

• Vitamin D increases calcium absorption (standard physiology).
• Vitamin K and Vitamin A guide calcium deposition in Peat community framing.
• Glycine reduces inflammatory calcium entry in gut cells in animal work Peat cited.
• Aspirin inhibits PTH-driven calcification and IL-6 in Peat's calcium article.

See also

• Phosphorus
• Sleep
• Hypothyroidism

Practical sources

For those avoiding dairy, pulverized eggshell powder is a calcium source: about 2 tablespoons per day of finely ground eggshell powder incorporated into sauces, seasonings, and flour. Eggshells are roughly 40% calcium by weight, making this a practical, forageable calcium supplement for dairy-free diets. See Egg § Eggshell calcium for the recipe and the absorption/bioavailability research.

Eggshell Calcium$18.00–$49.00