| Calcium | |||||
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- Why calcium is good for you
- Important Calcium facts
- Groups at risk of calcium deficiency
- Symptoms of calcium deficiency
- Calcium and health
- Calcium in foods
- Calcium recommended daily intake (RDI)
- Calcium works best with
- Overdosage, toxicity and cautions for calcium
Calcium is the most abundant mineral in the body. About 98% of the calcium in the body is in the bones, while another 1% is in teeth and the other 1% circulates in the blood. Calcium is required all through life to keep bones and teeth strong and healthy.
The calcium in blood has very useful and important functions to perform, so much so that the body will pull calcium from the bones to make sure there is enough in the blood.
Calcium in the blood helps regulate heartbeat, controls blood pressure, clots blood, contracts muscles and sends messages along nerves. Calcium is also required to make certain hormones and enzymes, especially the ones that control digestion, how energy is made and fats are used. It also helps build connective tissues.
Bones, while hard, are actually living tissue. Old bone is constantly being broken down and replaced with new bone at a specific rate until the age of about 35. After that age, the rate that new bone can replace old bone decreases and saved up bone is drawn upon. Some slow bone loss is a normal part of aging, but if not enough calcium is taken in, the process can happen too fast, especially in women who have reached menopause. If too much bone is lost and there is not enough calcium to help replace the old bone with new, bones become thin, brittle and break very easily. This is called osteoporosis. Osteoporosis affects many Australians - women especially - and is costly for the health system.
If the bones are strong to begin with and plenty of calcium in foods (or supplements) are taken in all through a person's life, the bones will stay strong throughout life. Even if osteoporosis has already set in, calcium may help slow it down.
- Calcium works with vitamin D to keep the blood levels of calcium normal. Vitamin D is required to help bones hold onto their calcium.
- Magnesium helps to body absorb calcium and vitamin D properly. The basic rule is: ½ as much magnesium as calcium
- Since the body needs to use calcium 24 hours a day, it is best to space out calcium over the day and have calcium-rich foods with every meal
- It is recommended to take calcium supplements between meals but with a small protein snack, such as a few spoonfuls of yoghurt, a piece of cheese or maybe a leftover chicken, to ensure the stomach produces enough acid to break down the supplement to be able to absorb the calcium in it
Groups at risk of calcium deficiency
Over half of all young people today (especially women) do not get the RDA of calcium in their diet. Calcium deficiency occurs when there is <200mg intake of calcium per day.
The following groups are most at risk of deficiency:
- People taking corticosteroid drugs - drugs such as cortisone, hydrocortisone, prednisone and dexamethasone, used by people with asthma, lupus, rheumatoid arthritis, inflammatory bowel disease and other medical problems, while they are lifesavers for people with these conditions, can also cause bone loss by breaking down bone faster than it can be replaced. Doctors previously thought that glucocorticoid drugs only caused problems with bone loss if taken in high doses, but recent research shows that taking consistent amounts of these drugs for long periods of time also cause bone loss. Talk to a medical professional about having a bone density test and about taking calcium and vitamin D supplements
- People taking thyroid drugs - large doses of thyroid drugs (eg Synthroid) over a long period can lead to bone loss.
- People taking cholesterol-lowering drugs - these drugs (eg Cholybar, Questran) can block absorption of calcium and fat-soluble vitamins such as vitamin D and vitamin A.
- People taking aluminium antacids - non-prescription antacids that contain aluminium (eg Maalox, Rolaids, Gelusil) can cause the body to store up aluminium in the bones instead of calcium. This could create weakened bones, especially in people with kidney problems. If these antacids are not used regularly, then it is not a major concern, but people taking these antacids regularly for heartburn should talk to a medical professional about other ways to control it
- Smokers and alcoholics - heavy drinkers and smokers have a higher risk for osteoporosis and those that do both are at an even greater risk. Smokers seem to have a lower bone density than non-smokers (it is a not yet known why), so that is a risk factor in itself. A recent study showed that smoking doubles the risk of hip fractures, even if osteoporosis is not present. Alcohol interferes with absorption of calcium and heavy drinkers often do not eat well and do not get enough calcium in their food
- People taking certain prescription drugs - certain drugs, while valuable therapies for specific health problems, can sometimes interfere with and block calcium absorption. Some prescription drugs do not mix well with calcium supplements and can cause major problems if taken together or even hours apart. It is very important to consult a medical professional if you are taking ANY prescription drugs and want to take calcium supplements
People in these groups at risk of deficiency should talk to a medical professional about calcium supplements BEFORE taking them.
Symptoms of calcium deficiency
Bones that are thin, brittle and break easily, teeth problems such as dentures not fitting properly – due to bone thinning, and eventually osteoporosis.
- Heart disease - two important studies showed a link between artherosclerosis and osteoporosis. In the first study, researchers found that women who had the most bone loss from osteoporosis were also most likely to have calcium-containing plaque blocking their carotid arteries. Because the carotid arteries carry blood to the brain, these women were at a higher risk of having a stroke. The second study showed that men and women with low vitamin D levels also had higher rates of calcium-containing plaque in the arteries leading to their hearts, making them more vulnerable to heart attacks. More follow-up research is being done, but these studies show how important calcium is for every aspect of long-term health
- High blood pressure - calcium may help prevent or treat high blood pressure in some people. People not getting enough calcium in their diet are more likely to get high blood pressure than people who get the RDA or more. In general, the higher level of calcium in the blood, the lower the blood pressure. Studies show that taking calcium supplements each day, can lower blood pressure for some people. People with high blood pressure should talk to a medical professional about calcium supplements BEFORE taking them, especially if taking any other prescription drugs
People who wish to take a calcium supplement should talk to a medical professional BEFORE taking it.
CURRENT RESEARCH
- Colon cancer - promising research shows that the lower that calcium intake is, the more likelihood to develop colon cancer, possibly because calcium blocks the growth of cancer cells. People at risk of colon cancer (one or both parents or other family members have had it), should discuss calcium supplements with a medical professional
People who wish to take a calcium supplement should talk to a medical professional BEFORE taking it.
| FOOD | AMOUNT | calcium (mg) |
|---|---|---|
Yoghurt, plain low-fat |
1 cup | 415 |
Ricotta cheese, part skim |
½ cup | 337 |
Milk |
1 cup | 300 |
Swiss cheese, processed |
28g | 272 |
Cheddar cheese |
28g | 204 |
Salmon (with bones) |
85g | 203 |
Colby cheese |
28g | 194 |
Pudding, instant chocolate |
½ cup | 149 |
Mozzarella cheese |
28g | 147 |
Tofu, uncooked |
½ cup | 130 |
Navy beans |
1 cup | 128 |
Spinach, cooked |
28g | 122 |
Turnip greens, cooked |
½ cup | 99 |
Sardines (with bones) |
85g | 92 |
English muffin |
1 regular | 90 |
Ice-cream, vanilla |
½ cup | 85 |
Almonds, dry roasted |
28g | 80 |
Chickpeas |
1 cup | 78 |
Brie cheese |
28g | 52 |
Swiss charrd, cooked |
½ cup | 51 |
Kidney beans |
1 cup | 50 |
Okra |
½ cup | 50 |
Black beans |
1 cup | 47 |
Kale, cooked |
½ cup | 47 |
Broccoli, cooked |
½ cup | 36 |
Sunflower seeds |
28g | 34 |
Sweet potato, baked |
1 medium | 32 |
Cabbage, cooked |
1 large | 25 |
Egg |
½ cup | 25 |
Potato, baked |
1 medium | 20 |
Collard greens, cooked |
½ cup | 15 |
Peanuts |
28g | 15 |
Calcium recommended daily intake (RDI)
| RDA | lifestage | age | AMOUNT |
|---|---|---|---|
| INFANTS | 0-6mths 7-12mths |
210mg 270mg |
|
| CHILDREN | 1-3yrs 4-8yrs |
500mg 800mg |
|
| CHILDREN | 9-18yrs |
1300mg | |
| ADULTS | 19-50yrs |
1000mg | |
| SENIORS | 51+yrs | 1200mg | |
| PREGNANT | <18yrs 19-50yrs |
1300mg 1000mg |
|
| LACTATING | <18yrs 19-50yrs |
1300mg 1000mg |
|
| TOLERABLE UPPER LIMIT | lifestage | age | AMOUNT |
| INFANTS | 0-12mths | n/a | |
| CHILDREN | 1-8yrs | 2500mg | |
| CHILDREN | 9-18yrs | 2500mg | |
| ADULTS | 19-50yrs | 2500mg | |
| SENIORS | 51+yrs |
2500mg | |
| PREGNANT | 2500mg | ||
| LACTATING | 2500mg | ||
| Toxic Levels | Generally non-toxic, but excessive levels of calcium may increase the need for magnesium | ||
The tolerable upper limits should only be taken for short periods and only under medical supervision.
Overdosage, toxicity and cautions for calcium
Calcium is generally non-toxic. Large amounts may increase the requirement for magnesium.
Symptoms of toxicity include:
- Asthma
- Depression
- Memory impairment
- Muscle weakness
If the calcium to potassium ratio is >2:1, this can result in reduced bone strength and interference with vitamin K synthesis and/or absorption. Amounts > 2grams may cause hyperparathyroidism.
CAUTION
People taking the following medications should NOT take calcium supplements (and may have to have the calcium in their foods monitored):
- Calcibind
- Digitalis
- Phenytoin (or Dilantin)
People with kidney disease should also NOT take calcium supplements.
People taking any type of medication should talk to a medical professional about calcium supplements BEFORE taking them.
references
- USDA National Nutrient Database - provides nutrient values for foods (accessed 5 January 2005)
- Osiecki, H. The Nutrient Bible. Bio-Concepts Publishing QLD, 2002
- Whitney EN, Cataldo DB, Rolfes SR. Understanding Normal and Clinical Nutrition, 6th Edition. Wadsworth/Thomson Learning, 2002
