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. (1) Most of these effects are due to lowering PTH as will be discussed below.
Lactose intolerance due to lactase deficiency is a common cause of low calcium intake. (1)
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 (3), 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. (4) Milk consumption is positively associated with height and muscle growth, as milk is a great source of both calcium and vitamin D.
The hypercalcemia caused by elevated PTH also leads to soft tissue calcification, myocardial fibrosis and hypertension (as the arteries cannot relax) (5). Consuming a low calcium diet with the hopes of preventing this will only make the problem worse by further increasing PTH and aldosterone.
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. (8, 9, 10, 11, 12, 13, 14, 15)
Calcium improves health by lowering oxidative stress & inflammation
Dietary calcium reduced reactive oxygen species, as well as biomarkers of oxidative stress and inflammation, probably due to lower PTH and higher thyroid.
Ca citrate treatment significantly reduce the generation of intracellular reactive oxygen species (ROS) and increase the activities of the antioxidant enzymes in the body, namely superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase. Ca citrate also lowers the expression of pro-inflammatory factors, such as iNOS, COX-2, and NF-κB and inhibits the production of pro-inflammatory cytokines, namely IL-1β, IL-6, and TNF-α. (16)
Calcium is also part of the compound, calcium fructoborate which also potent anti-inflammatory. (17)
Calcium has a solid positive effect on androgens
Calcium-binding protein, calmodulin, that subsequently activates (by phosphorylation) protein kinase C, analogous to cAMP and diacylglycerol, activates other specific protein kinases. Meaning, this activation of PKC leads to the synthesis of androgens and also their receptors. As seen here, a calcium deficiency decreases androgen receptors. (18)
This could be due to lower PTH which increases thyroid, which increases androgen production. Overactive PTH leads to significantly lower testosterone and increases prolactin (20, 21, 22) The higher prolactin could be due to elevated PTH, which suppresses the thyroid. Elevated thyroid stimulating hormones (TSH), which is elevated to stimulate the thyroid to release more thyroid hormones, also increases prolactin.
Calcium increases total and free testosterone and lowers prolactin.
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. (23)
- Ca citrate malate (35% absorp.)
- Ca carbonate (27% absorp.)
- Tricalcium phosphate (25% absorp.) (24, 25, 26, 27).
Dietary protein and sugars enhance calcium absorption. (28, 29) 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. (1) Low vitamin D levels will also decrease the enzyme that converts it to its active form.
Low calcium is associated with elevated PTH, which in turn increase aldosterone. (30) Aldosterone causes less sodium to be lost in the urine and sweat, but it increases the excretion of potassium, magnesium, and calcium. (31) This leads to hypertension, inflammation, bone and muscle loss. Increased intake of salt decreases PTH and increase ionized calcium. Thus salt is also pro-thyroid. Low salt intake also increases serotonin, which is associated with depression, low energy, no motivation, etc… high levels of aldosterone (due to low salt) also increases PTH. (32) Moral of the story, eat salt to taste. If you crave salt, ingest some. And I’m not talking about junk food with artificial salt flavors, but real sea salt/mountain salt or meat or something.
Calcium absorption is also better with a meal.
Inulin-type fructans significantly increase calcium absorption and enhance bone mineralization during pubertal growth. (33)