Calcium is present in a wide range of foods such as dairy products, dark-green leafy vegetables, sea vegetables, canned salmon, sardines, tofu, dried fruits, nuts (almonds, brazil nuts) and seeds – especially sesame seeds.
The mineral Calcium (Ca) is one of the most studied and familiar supplement ingredients today.
Most flour is fortified with calcium carbonate so bread and cereals can be a good source. If you live in an area with hard water, that may be a good source. Meat is a very poor source of calcium.
Calcium content of foods (mg per 100gm / 3.5oz portion):
|Source||mg per 100gm (3.5oz)|
|Human Breast Milk||33 (low!)|
|Beans (can: pinto, black)||135|
|Beet greens (cooked)*||99|
|Cow's Milk (whole)||276|
|Swiss Chard (raw)*||88|
|Collards (raw leaves)||250|
|Kale (raw leaves)||249|
|Kale (cooked leaves)||187|
|Lettuce (light green)||35|
|Lettuce (dark green)||68|
|Molasses (dark-213 cal.)||684|
|Mustard Green (raw)||183|
|Mustard Green (cooked)||138|
|Okra (raw or cooked)||92|
|Peanuts (roasted & salted)||74|
|Sweet Potatoes (baked)||40|
|Turnip Greens (raw)||246|
|Turnip Greens (boiled)||184|
* NOTE: According to the USDA nutrient database, a cup of cooked spinach has 245mg of calcium and a cup of milk has 290mg. However, the oxalic acid content of spinach means that only about 5% of its calcium is absorbed – the same is true of other high oxalate greens such as chard and beet greens.
Calcium comes in various forms:
Calcium balance can be affected by a range of other factors, and a number of substances can inhibit the absorption of calcium. Phytic acid, found in bran, whole cereals and raw vegetables is one of these. Uronic acid, a component of dietary fiber, and oxalic acid, found in certain fruits and vegetables can also bind calcium. However, diets habitually high in these acids are not thought to have a major effect on calcium absorption. Saturated fats can also lessen calcium absorption.
Calcium is lost in the feces, urine and sweat. Calcium loss is roughly equal to dietary calcium in adults, and reduced if dietary calcium is low. Adaptation to both high and low calcium intakes occurs automatically, i.e. reduced intake leads to increased efficiency of absorption. In infants and children calcium is retained for new bone growth. Calcium is also lost during lactation in breast milk.
Calcium is essential for a healthy Central Nervous System, muscle and cardiac function. Its deficiency is associated with hypertension and palpitations. Supplemented calcium replaces the calcium that is lost by chelating substances.
The current USRDA for Calcium is 1000mg.
As you age, the need for absorbable calcium, in conjunction with other essential minerals and vitamins, can be increased.
One study found that a supplement containing calcium, manganese, zinc and copper prevented bone loss in postmenopausal women, whereas calcium alone was ineffective. Calcium supplements for osteoporosis should contain other minerals as well, or the form of calcium used should have been proven to be of benefit.
Intake of supplemental calcium (1000mg per day or more) and vitamin D was associated with reduced tooth loss (due to bone loss) over a five year period in a study of 145 healthy subjects aged 65 years and older who completed a 3-year trial of the effect of calcium and vitamin D supplementation on bone loss from the hip, as well as a 2-year follow-up study after discontinuation of the study supplements. [Am J Med 2001;111(6): pp.452-6]
There are products using compounds of calcium which have been proven to reverse osteoporosis. One such is AdvaCAL.
High levels of urinary calcium, due to an excess of non-absorbable calcium being consumed, can cause crystallization and subsequent stone formation. Those with a tendency to form calcium stones are advised to abstain from taking non-prescribed calcium pill supplements.
Children of mothers who took calcium during pregnancy were still reaping the benefits seven years later in one Argentinian study. Blood pressure was lower in these youngsters – especially among overweight children – than those in the non-supplement-taking group. [Belizan JM, et al. Brit Med J 1997;315(7103): pp.281-5] Taking calcium may also decrease a woman's chance of developing pre-eclampsia, pregnancy-related hypertension. [Moutquin HM, et al. Can Med Assoc J 1997;157(7): pp.907-19]
A growing baby acquires most of its calcium during the last trimester of pregnancy; an additional amount is needed during breastfeeding. This translates into a greater need for calcium during and after pregnancy. A pregnant woman who fails to consume adequate calcium -1,200mg per day is recommended – increases her risk of developing osteoporosis later in life, especially if she becomes pregnant again. [Vandecandelaere M, et al. Rev Med Interne 1997;18(7): pp.571-4]
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