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Boning Up: Why Calcium is So Important

Although calcium is the most abundant mineral in the body, most people are deficient because they consume only about half of what they need—500 to 700 mg a day. Too low an intake of calcium causes calcium reserves in the bones to be withdrawn resulting in osteoporosis or osteopenia.
Should you take supplements or get your calcium from food? However you get it, the important thing is to make sure you get about 1200mg of calcium a day. And if you’re taking supplements, make sure you know how much elemental calcium (the form of calcium best absorbed by your body) is in the supplement.

The calcium in our bones acts like a bank the body can draw on when calcium stores are low. We’re most familiar with calcium’s importance in building strong teeth and bones—99 percent of the calcium in our body is found there. The remaining 1 percent is found in the blood and other tissues doing all kinds of things:

  • clotting blood

  • controlling blood pressure
  • producing enzymes and hormones that regulate digestion, energy, and fat metabolism
  • maintaining cells and connective tissues
  • helping to regulate the passage of nutrients through cell walls
  • preventing gum disease
  • maintaining proper nerve function
  • contracting muscles

Without calcium your muscles don’t move. If we don’t have the right amount of calcium, our muscles can cramp or be unable to transmit the nerve impulses that are required for muscles to contract. If blood levels of calcium are too low, calcium is pulled from our bones to keep the amount we need in our blood. If the calcium is not replenished by your diet, over time osteoporosis can set in.

Why do our muscles get tired? Calcium appears to play a big role. The following is an article by Dr. Gabe Mirkin.

Muscle Fatigue May Be Caused by Calcium Loss
New research from Columbia University in New York shows that muscle fatigue during and after exercise may be caused by loss of calcium from muscle cells and that drugs that block the release of calcium from muscle cells may prolong endurance (Proceedings of the National Academy of Sciences, February 11, 2008).

When you exercise, your cells use food to generate electricity that causes nerves to send messages and muscles to contract.  The energy from food generates electricity by driving minerals inside and outside of the cells, creating an imbalance of the minerals between the outside and inside of cells that causes electrons (electricity) to flow.  A major source of this flow of electrons is from muscle cells pushing calcium outside their cell walls.  This paper shows that muscles lose calcium continuously during exercise, and eventually do not have enough calcium to continue pumping calcium outside of cells, and therefore cannot generate as much electricity.  This causes the muscles to weaken, hurt, lose coordination and feel tired.

The authors timed mice exercising to the point of
exhaustion.  Then they gave the mice an experimental drug that
blocks the loss of calcium from muscle cells, and they were able
to exercise longer.  The researchers demonstrated the same
process of calcium loss in the muscles of trained cyclists. 
However, they have not taken the next step of testing the drug to
see if it improved endurance, because the drug has not been
approved for use in humans.

[Courtesy of Dr. Gabe Mirkin’s ezine http://www.drmirkin.com/]

Dairy products are the most commonly touted sources of calcium. But they are not necessarily the best sources: many people have lactose intolerance, many dairy products are high in saturated fat, and some studies have linked high dairy consumption to an increased risk of ovarian and prostate cancer. Other sources are broccoli, salmon, tofu and other soy products, almonds, sesame seeds, sunflower seeds, dried beans and legumes, figs, oranges, and molasses. Vitamin K, found in dark green leafy vegetables, helps to regulate calcium and plays an important role in bone formation.




Yogurt, plain, low fat

8 oz


Collards, frozen, boiled

1 cup


Skim milk

1 cup


Spinach, frozen, boiled

1 cup


Yogurt, plain, whole milk

8 oz


Cheese food, pasteurized American

1 oz


Cottage cheese, 1% milk fat

1 cup


Baked beans, canned

1 cup


Iceberg lettuce

1 head


Canned salmon

3 oz



1 cup


Trail mix (nuts, seeds, chocolate chips)

1 cup



1 oz (24 nuts)


Blackeye peas, boiled

1 cup


Green peas, boiled

1 cup


Courtesy of Harvard School of Public Health website.


Various factors affect how much of the calcium you ingest really gets into your blood. Here are facts you should know to make the most of the calcium in your diet or any calcium supplements you take:

1. Stress from tension and worry can decrease calcium absorption. The calcium in the diet is excreted rather than used.

2. Labels on calcium supplements can be misleading. The figure that is important is the amount of elemental calcium provided by the supplement. This is the actual amount of useable calcium. The rest of the calcium in the tablet is coupled with a salt that makes it unavailable to the body. For example, calcium glutamate is only 9 percent elemental calcium. A 500 milligram tablet of calcium glutamate may contain only 45 milligrams of elemental calcium, even though you may have been led to believe that you are taking 500 milligrams of calcium. Calcium carbonate, on the other hand, is 40 percent elemental calcium; 500 milligrams of calcium carbonate would provide 200 milligrams of useable calcium. Labels on some supplements make this distinction, listing both the type of calcium compound in the supplement and the amount of elemental calcium provided. Other products are not as carefully labelled. Read labels carefully and compare several brands when you shop.

3. Calcium is best absorbed when taken in smaller amounts more frequently and with meals. For example, your body absorbs more calcium if you take one 250 milligram tablet twice a day rather than one 500 milligram tablet once a day. If a higher dose calcium tablet is a better buy, break it in half.

4. Dairy products are a rich source of calcium, and lactose, the sugar contained in milk, facilitates calcium absorption. However, chocolate milk is not a good source of calcium. Because chocolate contains calcium-binding oxalates, it can interfere with calcium absorption.

5. Soft drinks that contain citric and phosphoric acid can decrease the absorption of calcium. A 12-ounce cola may rob the body of 100 milligrams of calcium.

6. Vitamin C improves the absorption of calcium, which is why calcium-fortified orange juice makes sense.

7. High-fibre diets can interfere with calcium absorption, so best not to mix a high fiber meal with a high calcium one. If you do mix them, boost your calcium as you increase your fiber.

8. The calcium-to-phosphorus ratio of a food or supplement determines how much of the calcium is absorbed. The ideal calcium-phosphorus ratio is 2 to 1, close to the proportion found in human milk, which has an almost perfect calcium-to- phosphorus ratio of 2.3 to 1. The ratio in cow’s milk is 1.3 to 1. The higher the phosphorus content of the food, the more calcium is excreted in the urine, leading to a loss of calcium. Foods high in phosphorus (such as meat, poultry, corn, potatoes, beer, buckwheat) can interfere with calcium absorption.

9. The presence of estrogen facilitates calcium absorption, so women after menopause are at increased risk of calcium deficiency and therefore need to increase their daily intake of calcium.

10. You may have read that vegans run the risk of calcium deficiency because the calcium in vegetables, like iron, is bound by the fibers and phytates (mineral-building chemicals in plants) in the vegetables and may interfere with calcium absorption. The theoretical worry may be balanced out by the lower phosphate content of vegetables, which improves calcium absorption, and by the fact that most people have the enzyme phytase, which breaks down the phytic acid in vegetables.

11. Couch-potatoism, or lack of exercise, may contribute as much, or more, to osteoporosis than lack of calcium. Weight-bearing exercise (just about any exercise except swimming or cycling) not only builds muscle, it builds bone.

12. Ignore what you read about losing bone mass while breastfeeding. After weaning, breastfeeding mothers regain the bone mass they may have lost. Some even get a perk by regaining more.

This information appears with the permission of William Sears, M.D and www.AskDrSears.com.

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