Calcium is best known for being important for bone formation, but actually plays a much larger role than just that in the body. Calcium is involved in vascular contraction, vasodilation (increase synthesis of nitric oxide), muscle functions, nerve transmission, intracellular signaling, and hormonal secretion (R). Most of these effects are due to lowering parathyroid hormone.
Lactose intolerance due to lactase deficiency is a common cause of low calcium intake (R).
Calcium lowers the thyroid antagonist, parathyroid hormone
Thyroid increase calcium excretion and parathyroid hormone (PTH) increases calcium retention. During a calcium deficiency, PTH is increased and thyroid decreased. Chronic calcium deficiency can lead to hypothyroidism, as PTH has an anti-metabolic effect. Chronic elevated PTH also leads to fat gain and insulin resistance. This can explain why dairy (which is a rich source of bioavailable calcium) increase fatty acid oxidation and adiponectin (R), which leads to greater fat loss, less fat gains and greater insulin sensitivity, which aids in preventing diabetes and obesity.
Chronic elevated PTH leads to hypercalcemia in the blood. This effect suppresses growth hormone release and can lead to retarded growth. (R) Milk consumption is positively associated with height and muscle growth, as milk is a great source of both calcium and vitamin D.
PTH has many other effects, such as causes mast cells to release promoters of inflammation, such as histamine and serotonin, and it decreases mitochondrial efficiency (reducing energy production) and causes bicarbonate to be lost in the urine (making the body more acidic). Acidic cells are catabolic and cannot grow. Thus alkaline minerals such as Ca, Mg, etc can promote anabolism (muscle protein synthesis).
So in a sense, calcium (together with vitamin D) can prevent all these effects, just by lowering PTH.
Boosts Fat loss
Not only does Ca increase fat oxidation, but also glucose oxidation. Ca activates the enzyme pyruvate dehydrogenase (PDH), which takes the pyruvate produced by glycolysis, converts it to Acetyl-Co-A and also activates isocitrate dehydrogenase and α-ketoglutarate dehydrogenase, which are two enzymes in the TCA cycle. This will help that glucose is more effectively burned and not turned to lactate.
Intracellular calcium (which is bad, and is a sign of hypothyroidism) inhibits lipolysis and fatty acid oxidation. The thyroid helps to keep calcium out of the cells, Mg in the cells and to keep metabolic rate fast. This could all be explained by calcium-lowering PTH.
When PTH is kept low, cells increase their formation of the uncoupling proteins (UCPs), that cause mitochondria to use energy at a higher rate, which increases heat production (thermogenesis), and decreases the enzyme that makes fat, namely fatty acid synthase. Again, this is what thyroid can do, only is PTH is low.
Although studies on calcium and fat-loss are conflicting, calcium enhances fat-loss when 1) you are in a caloric deficit, 2) when ≥1.2g of calcium a day is consumed and 3) when calcium is ingested in the form of dairy.
As a matter of a fact, in a study, one group consumed more dairy (and calories, due to the extra dairy) and gained no extra weight, despite the extra calories even while not being in a caloric deficit (R, R, R, R, R, R, R, R).
Calcium is a necessity when it comes to fat loss!Tweet
The RDA for calcium is 1000mg daily. That’s because the absorption rate of food is roughly 30%, which will provide you with 300mg calcium a day, which all you need apparently. However, the absorption rate of foods differ.
Animal sources of calcium:
- Milk, full cream (11% Ca per 100g) Requires 1L for RDA.
- Milk, skim (12% Ca per 100g) Requires 1L for RDA
- Bone meal (90% Ca per 3g) Requires 3.4g for RDA
- Fish (salmon & sardines), with bone (38% Ca per 100g) Requires 265g for RDA
Plant sources of calcium:
- Collard greens (61% absorption, 23% Ca per 100g) Requires 212g for RDA.
- Bok choy (54% absorption, 11% Ca per 100g) Require 545g for RDA.
- Turnip greens, boiled (52% absorption, 19% Ca per 100g) Require 304 for RDA.
- Kale (49% absorption, 15% Ca per 100g) Require 408g for RDA.
- Mustard greens (40% absorption, 12% Ca per 100g) Require 652g for RDA. (R)
- Ca citrate malate (35% absorp.) (Amazon)(iHerb)
- Ca carbonate (27% absorp.) (Amazon)(iHerb)
- Tricalcium phosphate (25% absorp.) (R, R, R, R).
Dietary protein and sugars enhance calcium absorption. (R, R) Dietary protein is required to provide serum IGF-1 which in turns interacts with the renal system (kidney) to transform vitamin D into its active form. The active vitamin D then binds to vitamin D receptors and move the calcium across luminal, basolateral, or intercellular compartments as needed to maintain serum levels. (R) Low vitamin D levels will also decrease the enzyme that converts it to its active form.
Calcium absorption is also better with a meal.
Inulin-type fructans significantly increase calcium absorption and enhance bone mineralization during pubertal growth. (R)