Minerals - Calcium (Ca)

Question 1

Calcium (Ca)

Answer 1

Calcium (Ca) is the most abundant mineral in the body accounting for 2% of body weight and 39% of the body’s mineral content
* 99% of calcium in the body is found in mineralized connective tissues (bones and teeth)
* The rest (1 %) is found in extra-cellular fluid, muscles and other tissues
* Calcium levels in blood are tightly regulated by parathyroid hormone (PTH), vitamin D and calcitonin (at the expense of the skeleton when dietary intake is in adequate)

Question 2

Food sources

Answer 2

• Calcium is found mostly in plant and dairy foods
• Vegetable sources have the highest bio-availability, e.g. calcium from cruciferous vegetables is absorbed 2x as efficiently as calcium from dairy

Key food sources / Per 100 g:
Dark green and cruciferous veg e.g. Kale / 135 mg
Nuts and seeds; e.g. sesame, almonds / 975 mg
Beans; e.g. edemama, haricot / 102 mg
Herbs and spices; e.g. sage, coriander leaf / 1652 mg
Sardines including the tiny bones / 382 mg
Dairy foods: e.g. cow’s milk full fat / 119 mg

Question 3

Functions:

Answer 3

• Bone health
• Cell signalling
• Muscle contraction
• Blood clotting
• Neuro-transmitters

Question 4

Bone Health: functions and therapeutic uses

Answer 4

Functions:
* Building and preserving bone mass; Calcium is an abundant mineral that binds to the collagen framework in bone, increasing its density. It is hence needed mostly during growth
Therapeutic uses:
* Osteoporosis
* Osteomalacia
* Fracture repair

Question 5

Cell Signalling: functions and therapeutic uses

Answer 5

Functions:
* Influences the transport of ions across the membranes of organelles
* Nerve impulses (Synapses)
* Regulates cardiac muscle function and mediate vasoconstriction (from increased concentration of Ca²+ ions in vascular smooth-muscle cells)

Therapeutic Uses:
* Blood pressure
* Muscle cramps
* Muscle spasms
* Confusion
* Memory loss

Question 6

Muscle contraction

Answer 6

Functions:
* Required (along with ATP) for the binding of actin and myosin fibres – Ca is stored in muscle cells in the sarcoplasmic reticulum

Therapeutic Uses:
* Leg cramps in pregnancy
* Pre-eclampsia

Question 7

Blood clotting

Answer 7

Functions:
* Calcium ions are needed to activate vitamin-dependent clotting factors

Therapeutic Uses:
* Bleeding disorders
* Haemorrhaging

Question 8

Neuro-transmitters

Answer 8

Functions:
* Required for the conversion of tryptophan to serotonin (It is a cofactor)

Therapeutic Uses:
* Mood-related PMS symptoms

Question 9

Absorption

Answer 9

Calcium is absorbed by all parts of the small intestine, but especially in the duodenum, where conditions are more acidic due to the acidic chyme that enters from the stomach, which increases absorption.

Calcium is absorbed both actively and passively

Question 10

Active absorption

Answer 10

Active absorption is controlled by vitamin D (Calcitriol), which binds to the enterocyte vitamin D receptor (VDR) and increases the transcription of calcium transporters called calbindins, which increase calcium movement from the GIT to the blood.

Cal = calcium, bindin = bind / attach to, enterocyte = intestine cell

Question 11

Passive absorption

Answer 11

Passive absorption occurs without vitamin D, when calcium is consumed.
50 - 70% of ingested calcium is not absorbed and lost in the faeces.

Question 12

Deficiency

Answer 12

Calcium deficiency is extremely rare as blood levels are typically maintained even with inadequate intake at the expense of bones
Unlike other diseases, loss of bone mineral density is asymptomatic

Question 13

Factors that inhibit absorption

Answer 13

• Low vitamin D status
• Low stomach acid (HCl dissolves calcium salts)
• High intake of phytates/oxalates
• Gastrointestinal dysfunction
• Other minerals (e.g. Mg, Fe, Zn)

Question 14

The Factors that increase excretion

Answer 14

• Menopause (Low oestrogen)
• High animal-protein diets (Due to high levels of urea and sulphuric acid – Ca is alkaline, the body pulls on Ca to offset acidity)
• High salt diet (table salt)
• High caffeine intake (binds to Ca and is a diuretic)
• Medications (see drug interactions)

Question 15

Calcium and dairy

Answer 15

Despite dairy being a rich source of calcium, there are clear associations between high cow’s milk dairy consumption and osteoporosis risk

• The protein components of cow’s milk is likely that problem, as dairy is high in sulphur-based amino acids (e.g. methionine), which can increase sulphuric acid formation– leeching calcium (an alkaline mineral) from bone
• Countries with a high dairy consumption have often also a high intake of other animal proteins (i.e. meat) which contributes to calcium loss from bone

Question 16

Naturopathic diet

Answer 16

Naturopathically, our primary focus should be on addressing individual calcium intake, absorption and utilisation
* Prioritise plant-based food sources (with a low animal protein intake), and optimize both vitamin D and K levels

Question 17

Supplementation

Answer 17

• Studies mostly show that calcium supplementation is ineffective at preserving bone density when dietary intake is sufficient, and it can present risks e.g. kidney stones; soft tissue calcification, especially when vitamin D and K levels are inadequate
• Although calcium carbonate is often recommended, calcium citrate is far easier to absorb. A maximum absorption of calcium is usually 500 mg per sitting.

Question 18

Nutrient interactions: Magnesium

Answer 18

• Magnesium competes for absorption with calcium. High supplemental Ca doses (2g / day for 11-30 days) decreases Mg absorption and plasma levels

Question 19

Nutrient interactions: Iron

Answer 19

• Some studies show that Ca supplementation decreases the absorption of non-haem iron in a dose-dependent manner

Question 20

Nutrient interactions: Zinc

Answer 20

• High calcium intake (either from high dairy or supplements) decreases Zn absorption. High Zn intake also interferes with Ca absorption if dietary intake is low

Question 21

Nutrient interactions: Phosphorus

Answer 21

• High Ca intake has been reported to interfere with P absorption