CALCIUM
Most of us think calcium is important only because it builds strong bones and
teeth, which contain 99 percent of the body's calcium. However, the remaining 1
percent circulates in the blood and serves other vital functions. For instance,
calcium is necessary for conduction of nerve impulses, for heart function, for
muscle contraction, and for blood clotting.
The level of calcium circulating in the
blood is closely regulated to ensure a constant and adequate supply to our
cells. One way our body maintains that level is by pulling calcium from our
bones if we do not consume enough. Over time, this leads to osteoporosis
(literally, "porous bones") and can result in broken bones.
Low calcium intake has also been linked to
other medical problems such as hypertension, and toxemia in pregnancy, which is
characterized by high blood pressure. Although there is not yet enough
information to support specific recommendations for either of these medical
problems, consumption of calcium at the current Recommended Dietary Allowance
(RDA) levels is extremely important.
How much calcium do you need
each day?
The amount of calcium require each day
depends on your age and stage in life. Children and adults require 800
milligrams per day, while teenagers need 1200 milligrams. Women who are
pregnant or nursing require an additional 400 milligrams a day.
Recent government surveys indicate that
many Americans, especially adults, consume significantly less calcium than is
recommended. For example, experts estimate that the average calcium intake for
women is only 450 to 550 milligrams per day!
The amount of calcium absorbed by the
body decreases as we grow older. In women, this starts at menopause since
estrogen promotes calcium absorption. Many medical and nutrition experts
suggest that post-menopausal women increase their intake of calcium to 1000 to
l500 milligrams per day to counteract this effect. Until more research is
conducted on possible harmful effects at this level, consult your physician
before regularly consuming such large amounts. Remember, most adults do not
get the amount of calcium now recommended. For example, in this country on any
given day, two-thirds of all females between the ages of 18 and 34 consume
less than the adult RDA for calcium.
How can you get enough calcium?
All milk (whole, 1 percent lowfat, 2
percent lowfat, skim, nonfat dry, buttermilk, chocolate, or malted) and other
dairy products such as cheese, yogurt, ice cream and ice milk are excellent
sources of calcium. However, butter, cream, cream cheese, and whipped cream
contain mostly fat and are not considered good sources of calcium.
If you dislike drinking milk, you can
increase your consumption by eating foods containing milk, such as puddings,
custards, and milk-based soups and sauces. Other ways to include milk in foods
is to add unreconstituted nonfat dry milk to meatloaf, casseroles, mashed
potatoes, meatballs and croquettes. Or blend ice cold milk with sweetened
fresh or frozen fruit.
Main dishes such as cheese pizza,
macaroni and cheese, cheese souffle, quiche, chili con carne with beans, and
even spaghetti and meatballs topped with cheese provide significant amounts of
calcium. Bread products prepared with milk, such as pancakes or waffles, also
add to your calcium intake.
If you need to increase the calcium in
your diet, seek ways to add cheese, milk or yogurt to the foods you prepare.
Instead of a hamburger, have a cheeseburger. Top your baked potato with yogurt
or cottage cheese instead of butter or sour cream. Not only does this add
calcium, it reduces calories.
Non-dairy foods with significant amounts
of calcium include oysters and shrimp as well as sardines and canned salmon,
if both are eaten with the bones. Plant sources of calcium include dried
beans, broccoli, rhubarb, and greens (beet, collards, spinach, kale, mustard,
turnip). Tofu (soybean curd) is a good calcium source if processed with
calcium sulfate.
The absorption of calcium from plant
foods is quite poor, however. This is one reason why it is extremely difficult
to get enough calcium without consuming dairy products. Also, lactose (milk
sugar) in dairy products appears to enhance the absorption of calcium.
Another regulator of calcium absorption
is vitamin D. The major dietary sources of vitamin D are fortified milk, fatty
fish, cheese, butter, fortified margarine, eggs and liver. However, exposure
to sunlight is probably much more important since our bodies can manufacture
vitamin D if we are exposed to ultraviolet light. This production of vitamin D
by your bodies requires only normal exposure to sun, not extensive tanning.
Use the foods listed in FOOD SOURCES OF
CALCIUM and the ideas presented above to plan your menus for a few days to
assure an adequate calcium intake each day. Below are four examples of food
combinations which would provide at least 800 milligrams of calcium.
- 1 cup lowfat milk; 2 ounces cheddar
cheese; 1/2 cup broccoli
- 8 ounces yogurt with fruit; 1 cup
cream of chicken soup prepared with milk; 1 cup ice milk; 1/2 cup cooked
spinach.
- 3 ounces sardines with bones; 2
pancakes; 1 cup lowfat milk
- 1 cup chili con carne with beans
topped with 1 ounce shredded cheddar cheese; 1/2 cup baked custard; baked
potato with 1/3 cup plain yogurt; l cup hot chocolate
What about calcium supplements?
It is best to meet your calcium
requirements from food which contains other nutrients your body needs.
However, if this isn't possible, calcium supplements can help you meet the
RDA. Since too much calcium, like too little calcium, may cause medical
problems such as kidney stones, consult with your physician before taking any
calcium supplements. this is especially important for those containing vitamin
D, which is toxic in high concentrations.
The source of calcium in supplements
varies, depending on the brand. Calcium carbonate, calcium lactate, calcium
gluconate and oyster shells (basically calcium carbonate) are the most common
sources. Most people prefer calcium carbonate -- since more calcium is
present, fewer pills are needed.
Bone meal and dolomite should not be
taken. Extensive analyses of both have revealed dangerously high levels of
lead. Moreover, dolomite may not dissolve in the gastrointestinal tract,
making it an unreliable source of calcium.
A few antacids contain calcium. TUMS,
for example, provides 200 milligrams per tablet in the form of calcium
carbonate, which is used to neutralize acid. However, it can, over time, cause
the stomach to produce more acid. Therefore, TUMS and similar products should
be taken with meals. Other antacids containing aluminum decrease the
absorption of calcium and are a poor calcium choice. Some antacids also
contain sodium, so beware if you are on a salt- or sodium-restricted diet.
If you decide to take calcium
supplements, the label should tell you how many tablets you need to reach your
RDA level, and the conditions under which you should take them. To know how
much calcium you are getting in each tablet, note whether the label lists the
calcium content in terms of pure calcium or as calcium carbonate, calcium
lactate or calcium gluconate. It's tricky. For instance, if the label says
that one tablet provides 600 milligrams of calcium, you are getting that much
calcium in each pill. But, if it says 600 milligrams of calcium carbonate, you
are only getting 240 milligrams per tablet (calcium carbonate is only 40
percent calcium).
Advice on the best way to take calcium
supplements is contradictory. Some experts suggest that taking them between
meals promotes greater absorption by the body. However, some manufacturers
recommend taking the tablets with meals to avoid the possibility of an upset
stomach. Furthermore, you are more likely to remember to take them with a
meal.
Summary
It is clear that we need adequate
calcium for strong bones and teeth throughout our life span. Recent evidence
suggests that we also need it to prevent other medical problems. In general,
Americans particularly adults do not consume enough calcium each day. Dairy
products supply the most calcium and it is well absorbed. Certain plant foods
can contribute to our calcium intake.
Mention of brand names does not imply
endorsement nor criticism of that product.
Sue Snider, Ph.D.
Food and Nutrition Specialist
University of Delaware Cooperative Extension
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