Calcium is an essential mineral that is required in the body in large amounts (macro mineral) and serves several primary functions within the body. The body regulates blood calcium levels primarily through parathyroid hormone and vitamin D, which plays a major role in calcium absorption from the intestines. The average RDA (recommended dietary allowance) for calcium is set at around 1000 mg per day, but the actual amount required varies by age, hormonal status, and current calcium and bone density status. There are current arguments over the exact requirements for calcium and some critics of the high calcium recommendations point to the dairy industry as being responsible.


  • Provides the main mineral for bone structure and formation (where most of the calcium in the body is found).
  • Required for shaping biological proteins.
  • Needed for proper muscle functioning.
  • Essential in nerve transmissions.
  • Hormone release and balance.
  • Proper blood clotting.
  • Keeping normal heart rhythm.

Primary deficiency symptoms and diseases

  • Osteoporosis (long term)
  • Osteopenia (long term)
  • Abnormal nerve firing
  • Muscle cramps
  • Confusion
  • Memory loss
  • Hallucinations
  • Depression
  • Tetany (a state caused by low calcium or hypocalcemia)

Food Sources

These are typically the richest sources of calcium, but many of these rich sources also have poor absorption due to nutrient inhibitors. Proper preparation of foods like legumes, nuts, and seeds would be advised to limit calcium absorption inhibition. Keep in mind that almost all whole foods contain at least some calcium and many typically poor sources have better absorption rates due to lower nutrient inhibitors. Bones and citrus have some of the easiest to absorb calcium because of the lack of nutrient inhibitors.

  • Dairy products (arguable, depending on personal tolerance to dairy and how dairy can have a lower absorption rate than other sources)
  • Edible bones - think small, soft bones like those in small fish
  • Green leafy vegetables (calcium absorption can be limited by oxalic acid)
  • Broccoli and other cruciferous vegetables
  • Beans and legumes (calcium absorption can be limited by phytic acid or phytates)
  • Nuts and seeds (phytic acid and phytate can limit absorption)
  • Citrus fruits like oranges

Supplementing with Calcium

If you decide to supplement with calcium, be aware that the research is quite contradictory on whether or not it may actually help in conditions like osteoporosis (where weight bearing exercise is a better predictor). Also, the body is typically bad at absorbing large amounts at once, so doses should be spread out over the day and you should preferably avoid foods high in nutrient inhibitors. Calcium requires an adequate amount of Vitamin D, Vitamin K2, and Magnesium in order to be properly utilized in the body, and many supplements are beginning to include these. Calcium also competes with minerals like Zinc for absorption when high amounts are consumed at the same time, so the typical Calcium/Magnesium/Zinc combo may lead to worse absorption.

Supplemental forms of calcium differ in their absorption rates and quality. The most common is essentially just limestone (chalk), but other forms are starting to come about which are easily used by the body.

  • Calcium carbonate (limestone, chalk) - typically poor quality and low absorption
  • Calcium citrate - one of the better forms to take in terms of absorption, but has a low calcium content by weight
  • Calcium lactate - decently absorbed, and is formed when lactic acid interacts with calcium and can be found in fermented veggies and milk products
  • Algae Calcium - usually labeled as "plant calcium," this has the best absorption of all forms tested so far
  • Calcium Aspartate - typically the form found in many foods and easily absorbed

Who Needs it Most?

  • Women of all ages due to their higher likelihood of osteoporosis.
  • People with dietary sensitivities to or restrictions against calcium rich foods.
  • Those with gut mobility issues.
  • People with long term use of diuretics.

Other Tips

  • Preferably, calcium should be obtained from foods and not supplements. (I get most of my calcium through things like bone-in sardines, sweet potatoes, and cruciferous vegetables)
  • Calcium aspartate, citrate, and algae or plant based calcium supplements are the best absorbed forms and would be the best supplements.
  • Make sure that adequate Vitamin D, K2 and Magnesium are present when supplementing calcium to ensure proper utilization.
  • When your body doesn't use calcium properly, it may end up in places you don't want it (i.e. the kidneys and arteries)