Naomi,
The last paragraph says not to take more than 500 mg at a time
because your body can't absorb it. I know this is a lot of info, but
I thought there was some very important statements made that effect
us.
Lizanne
Table 1: Recommended Adequate Intake by the IOM for CalciumMale and
Female Age Calcium (mg/day) Pregnancy & Lactation
0 to 6 months 210 N/A
7 to 12 months 270 N/A
1 to 3 years 500 N/A
4 to 8 years 800 N/A
9 to 13 years 1300 N/A
14 to 18 years 1300 1300
19 to 50 years 1000 1000
51+ years 1200 N/A
*mg=milligrams
What foods provide calcium?
In the United States (U.S.), milk, yogurt and cheese are the major
contributors of calcium in the typical diet. The inadequate intake of
dairy foods may explain why some Americans are deficient in calcium
since dairy foods are the major source of calcium in the diet. The
U.S. Department of Agriculture's Food Guide Pyramid recommends that
individuals two years and older eat 2-3 servings of dairy products
per day. A serving is equal to:
1 cup (8 fl oz) of milk
8 oz of yogurt
1.5 oz of natural cheese (such as Cheddar)
2.0 oz of processed cheese (such as American)
A variety of non-fat and reduced fat dairy products that contain the
same amount of calcium as regular dairy products are available in the
U.S. today for individuals concerned about saturated fat content from
regular dairy products.
Although dairy products are the main source of calcium in the U.S.
diet, other foods also contribute to overall calcium intake.
Individuals with lactose intolerance (those who experience symptoms
such as bloating and diarrhea because they cannot completely digest
the milk sugar lactose) and those who are vegan (people who consume
no animal products) tend to avoid or completely eliminate dairy
products from their diets. Thus, it is important for these
individuals to meet their calcium needs with alternative calcium
sources if they choose to avoid or eliminate dairy products from
their diet. Foods such as Chinese cabbage, kale and broccoli are
other alternative calcium sources. Although most grains are not high
in calcium (unless fortified), they do contribute calcium to the diet
because they are consumed frequently. Additionally, there are several
calcium-fortified food sources presently available, including fruit
juices, fruit drinks, tofu and cereals.
Table 2: Selected Food Sources of Calcium
Food Calcium (mg) % DV*
Yogurt, plain, low fat, 8 oz. 415 42%
Yogurt, fruit, low fat, 8 oz. 245-384 25%-38%
Sardines, canned in oil, with bones, 3 oz. 324 32%
Cheddar cheese, 1 ½ oz shredded 306 31%
Milk, non-fat, 8 fl oz. 302 30%
Milk, (2% milk fat), no solids, 8 fl oz. 297 30%
Milk, whole (3.25% milk fat), 8 fl oz 291 29%
Milk, buttermilk, 8 fl oz. 285 29%
Milk, lactose reduced, 8 fl oz.** 285-302 29-30%
Mozzarella, part skim 1 ½ oz. 275 28%
Tofu, made w/calcium sulfate, ½ cup*** 204 20%
Orange juice, calcium fortified, 6 fl oz. 200-260 20-26%
Salmon, pink, canned, with bone, 3 oz. 181 18%
Pudding, chocolate, made w/ 2% milk, ½ cup 153 15%
Cottage cheese, 1% milk fat, 1 cup unpacked 138 14%
Spinach, cooked, ½ cup 120 12%
Instant breakfast, various brands, prepared with water, 8 fl oz.
105-250 10-25%
Frozen yogurt, vanilla, soft serve, ½ cup 103 10%
Ready to eat cereal, calcium fortified, 1 c 100-1000 10%-100%
Turnip greens, boiled, ½ cup 99 10%
Kale, cooked, 1 cup 94 9%
Kale, raw, 1 cup 90 9%
Ice cream, vanilla, ½ cup 85 8.5%
Soy beverage, calcium fortified, 8 fl oz. 80-500 8-50%
Chinese cabbage, raw, 1 cup 74 7%
Tortilla, corn, ready to bake/fry, 1 medium 42 4%
Tortilla, flour, ready to eat, one 6" dia 37 4%
Sour cream, reduced fat, cultured, 2 Tbsp 32 3%
Bread, white, 1 oz 31 3%
Broccoli, raw, ½ cup 21 2%
Bread, whole wheat, 1 slice 20 2%
Cheese, cream, regular, 1 Tbsp 12 1%
*DV=Daily Value
**Content varies slightly according to fat content; average =300 mg
calcium
*** Calcium values are only for tofu processed with a calcium salt.
Tofu processed with a non-calcium salt will not contain significant
amounts of calcium.
Daily Values (DV) were developed to help consumers determine if a
typical serving of a food contains a lot or a little of a specific
nutrient. The DV for calcium is based on 1000 mg.
The following are strategies and tips to help you meet your calcium
needs each day:
Use low fat or fat free milk instead of water in recipes such as
pancakes, mashed potatoes, pudding and instant, hot breakfast cereals.
Blend a fruit smoothie made with low fat or fat free yogurt for a
great breakfast.
Sprinkle grated low fat or fat free cheese on salad, soup or pasta.
Choose low fat or fat free milk instead of carbonated soft drinks.
Serve raw fruits and vegetables with a low fat or fat free yogurt
based dip.
Create a vegetable stir-fry and toss in diced calcium-set tofu.
Enjoy a parfait with fruit and low fat or fat free yogurt.
Complement your diet with calcium-fortified foods such as certain
cereals, orange juice and soy beverages
What affects calcium absorption and excretion?
Calcium absorption refers to the amount of calcium that is absorbed
from the digestive tract into our body's circulation. Calcium
absorption can be affected by the calcium status of the body, vitamin
D status, age, pregnancy and plant substances in the diet. The amount
of calcium consumed at one time such as in a meal can also affect
absorption. For example, the efficiency of calcium absorption
decreases as the amount of calcium consumed at a meal increases.
Age:
Net calcium absorption can be as high as 60% in infants and young
children, when the body needs calcium to build strong bones.
Absorption slowly decreases to 15-20% in adulthood and even more as
one ages. Because calcium absorption declines with age,
recommendations for dietary intake of calcium are higher for adults
ages 51 and over.
Vitamin D:
Vitamin D helps improve calcium absorption. Your body can obtain
vitamin D from food and it can also make vitamin D when your skin is
exposed to sunlight. Thus, adequate vitamin D intake from food and
sun exposure is essential to bone health. The Office of Dietary
Supplement's vitamin D fact sheet provides more information:
http://ods.od.nih.gov/factsheets/vitamind.asp.
Pregnancy:
Current calcium recommendations for nonpregnant women are also
sufficient for pregnant women because intestinal calcium absorption
increases during pregnancy. For this reason, the calcium
recommendations established for pregnant women are not different than
the recommendations for women who are not pregnant.
Plant substances:
Phytic acid and oxalic acid, which are found naturally in some
plants, may bind to calcium and prevent it from being absorbed
optimally. These substances affect the absorption of calcium from the
plant itself not the calcium found in other calcium-containing foods
eaten at the same time. Examples of foods high in oxalic acid are
spinach, collard greens, sweet potatoes, rhubarb, and beans. Foods
high in phytic acid include whole grain bread, beans, seeds, nuts,
grains, and soy isolates. Although soybeans are high in phytic acid,
the calcium present in soybeans is still partially absorbed. Fiber,
particularly from wheat bran, could also prevent calcium absorption
because of its content of phytate. However, the effect of fiber on
calcium absorption is more of a concern for individuals with low
calcium intakes. The average American tends to consume much less
fiber per day than the level that would be needed to affect calcium
absorption.
Calcium excretion refers to the amount of calcium eliminated from the
body in urine, feces and sweat. Calcium excretion can be affected by
many factors including dietary sodium, protein, caffeine and
potassium.
Sodium and protein:
Typically, dietary sodium and protein increase calcium excretion as
the amount of their intake is increased. However, if a high protein,
high sodium food also contains calcium, this may help counteract the
loss of calcium.
Potassium:
Increasing dietary potassium intake (such as from 7-8 servings of
fruits and vegetables per day) in the presence of a high sodium diet
(
Level of 2300 mg for sodium per day) may help decrease calcium
excretion particularly in postmenopausal women.
Caffeine:
Caffeine has a small effect on calcium absorption. It can temporarily
increase calcium excretion and may modestly decrease calcium
absorption, an effect easily offset by increasing calcium consumption
in the diet. One cup of regular brewed coffee causes a loss of only 2-
3 mg of calcium easily offset by adding a tablespoon of milk.
Moderate caffeine consumption, (1 cup of coffee or 2 cups of tea per
day), in young women who have adequate calcium intakes has little to
no negative effects on their bones.
Other factors:
Phosphorus: The effect of dietary phosphorus on calcium is minimal.
Some researchers speculate that the detrimental effects of consuming
foods high in phosphate such as carbonated soft drinks is due to the
replacement of milk with soda rather than the phosphate level itself.
Alcohol: Alcohol can affect calcium status by reducing the intestinal
absorption of calcium. It can also inhibit enzymes in the liver that
help convert vitamin D to its active form which in turn reduces
calcium absorption. However, the amount of alcohol required to affect
calcium absorption is unknown. Evidence is currently conflicting
whether moderate alcohol consumption is helpful or harmful to bone.
Calcium and bone health
Your bones are living tissues and continue to change throughout life.
During childhood and adolescence, bones increase in size and mass.
Bones continue to add more mass until around age 30, when peak bone
mass is reached. Peak bone mass is the point when the maximum amount
of bone is achieved. Because bone loss, like bone growth, is a
gradual process, the stronger your bones are at age 30, the more your
bone loss will be delayed as you age. Therefore, it is particularly
important to consume adequate calcium and vitamin D throughout
infancy, childhood, and adolescence. It is also important to engage
in weight-bearing exercise to maximize bone strength and bone density
(amount of bone tissue in a certain volume of bone) to help prevent
osteoporosis later in life. Weight bearing exercise is the type of
exercise that causes your bones and muscles to work against gravity
while they bear your weight. Resistance exercises such as weight
training are also important because they help to improve muscle mass
and bone strength.
Examples of weight bearing exercise
walking
running
dancing
aerobics
skating
Examples of NON-weight bearing exercise
swimming
bicycling
water aerobics
Osteoporosis is a disorder characterized by porous, fragile bones. It
is a serious public health problem for more than 10 million
Americans, 80% of whom are women. Another 34 million Americans have
osteopenia, or low bone mass, which precedes osteoporosis.
Osteoporosis is a concern because of its association with fractures
of the hip, vertebrae, wrist, pelvis, ribs, and other bones. Each
year, Americans suffer from 1.5 million fractures because of
osteoporosis.
Osteoporosis and osteopenia can result from dietary factors such as:
chronically low calcium intake
low vitamin D intake
poor calcium absorption
excess calcium excretion
When calcium intake is low or calcium is poorly absorbed, bone
breakdown occurs because the body must use the calcium stored in
bones to maintain normal biological functions such as nerve and
muscle function. Bone loss also occurs as a part of the aging
process. A prime example is the loss of bone mass observed in post-
menopausal women because of decreased amounts of the hormone
estrogen. Researchers have identified many factors that increase the
risk for developing osteoporosis. These factors include being female,
thin, inactive, of advanced age, cigarette smoking, excessive intake
of alcohol, and having a family history of osteoporosis.
In 1993 the FDA authorized a health claim for food labels on calcium
and osteoporosis in response to scientific evidence that an
inadequate calcium intake is one factor that can lead to low peak
bone mass and is considered a risk factor for osteoporosis. The claim
states that "adequate calcium intake throughout life is linked to
reduced risk of osteoporosis through the mechanism of optimizing peak
bone mass during adolescence and early adulthood and decreasing bone
loss later in life".
Various bone mineral density (BMD) tests, including those that
measure your hip, spine, wrist, finger, shin bone, and heel, can help
determine bone mass. These tests provide a T-score which is a measure
of bone mineral density that compares an individual's BMD to an
optimal BMD of a 30 year old healthy adult. See Figure 2 below. A T-
Score of -1.0 and above indicates normal bone density. A T-score of -
1.0 to -2.5 indicates that a person is considered to have low bone
mass (osteopenia). A score below -2.5 indicates osteoporosis.
Calcium and Medication Interactions
Calcium supplements have the potential to interact with several
prescription and over the counter medications. Further information
about these interactions is described below. Some examples of
medications that may interact with calcium include:
digoxin
fluroquinolones
levothyroxine
antibiotics in tetracycline family
tiludronate disodium
anticonvulsants such as phenytoin
thiazide, type of diuretic
glucocorticoids
mineral oil or stimulant laxatives
aluminum or magnesium containing antacids
Calcium supplements may decrease levels of the drug digoxin, a
medication given to heart patients. The interaction between calcium
and vitamin D supplements and digoxin may also increase the risk of
hypercalcemia. Calcium supplements also interact with
fluoroquinolones (a class of antibiotics including ciprofloxacin),
levothyroxine (thyroid hormone) used to treat thyroid deficiency,
antibiotics in the tetracycline family, tiludronate disodium (a drug
used to treat Paget's disease), and phenytoin (an anti-convulsant
drug). In all of these cases, calcium supplements decrease the
absorption of these drugs when the two are taken at the same time.
Thiazide, and diuretics similar to thiazide, can interact with
calcium carbonate and vitamin D supplements to increase the chances
of developing hypercalcemia and hypercalciuria (elevated levels of
calcium in urine). Aluminum and magnesium antacids can both increase
urinary calcium excretion. Mineral oil and stimulant laxatives can
both decrease dietary calcium absorption. Furthermore,
glucocorticoids (for example: prednisone) can cause calcium depletion
and eventually osteoporosis, when used for more than a few weeks.
Supplemental Sources of Calcium
The two main forms of calcium found in supplements are carbonate and
citrate. Calcium carbonate is the most common because it is
inexpensive and convenient. The absorption of calcium citrate is
similar to calcium carbonate. For instance, a calcium carbonate
supplement contains 40% calcium while a calcium citrate supplement
only contains 21% calcium. However, you have to take more pills of
calcium citrate to get the same amount of calcium as you would get
from a calcium carbonate pill since citrate is a larger molecule than
carbonate. One advantage of calcium citrate over calcium carbonate is
better absorption in those individuals who have decreased stomach
acid. Calcium citrate malate is a form of calcium used in the
fortification of certain juices and is also well absorbed [116].
Other forms of calcium in supplements or fortified foods include
calcium gluconate, lactate, and phosphate.
The amount of calcium your body obtains from various supplements
depends on the amount of elemental calcium in the tablet. The amount
of elemental calcium is the amount of calcium that actually is in the
supplement. Calcium absorption also depends on the total amount of
calcium consumed at one time and whether the calcium is taken with
food or on an empty stomach. Absorption from supplements is best in
doses 500 mg or less because the percent of calcium absorbed
decreases as the amount of calcium in the supplement increases.
Therefore, someone taking 1000 mg of calcium in a supplement should
take 500 mg twice a day instead of 1000 mg calcium at one time.