Vitamins Forum - How Do You Know?

"here is the calcium needs for people in general, as per human nutrition 220" an acredited science class at the university of phoenix

notice that mg is not mentioned in this.

Calcium (ca)
all cells need calcium, but more than 99% of the calcium in the body is used to
strengthen bones and teeth. This calcium represents 40% of all the minerals present
in the body and equals about 2.5 pounds (1200 grams). As calcium circulates in the
bloodstream, it supplies the calcium needs of body cells. Growth and bone development
require an adequate calcium intake.
Unlike sodium, potassium, and chloride, the amount of calcium in the body
hinges greatly on its absorption from the diet. Calcium requires an acidic environment
to be absorbed efficiently. Absorption occurs primarily in the upper part of the
small intestine. This area tends to remain acidic because it receives the acidic stomach
contents. Much calcium absorption in the upper small intestine depends on the active
vitamin d hormone.
Adults absorb about 25% of the calcium in the foods eaten, but during times when
the body needs extra calcium—such as in infancy and pregnancy—absorption might
reach as high as 60%. Young people tend to absorb calcium better than do older people,
especially those older than 70. Postmenopausal women generally absorb the least
calcium, unless they receive supplements of the hormone estrogen. Estrogen therapy
is associated with an increased synthesis of the active vitamin d hormone, which aids
calcium absorption.
Many other factors end up enhancing calcium absorption: parathyroid hormone,
dietary glucose, and lactose; and normal intestinal motility (flow). Factors limiting
calcium absorption include large amounts of phytic acid in dietary fiber from grains;
great excess of phosphorus in the diet; polyphenols (tannins) in tea; a vitamin d deficiency;
menopause; diarrhea; and old age.
Because we have excellent hormonal systems to control blood calcium, a normal
value can be maintained despite an inadequate calcium intake. The bones, however,
pay the price. Bone loss caused by insufficient calcium intake proceeds slowly. Only
after many years are clinical symptoms apparent. By not meeting calcium needs, some
people—especially women—are most likely setting the stage for future bone fractures.
However, because we don’t know how efficiently each individual absorbs calcium, we
often cannot predict who is at the highest risk.
■ functions of calcium
forming and maintaining bones are calcium’s major roles in the body. This is discussed
in detail in the nutrition issue on osteoporosis. However, calcium is important
in many other processes as well. Calcium is essential for blood clotting and for muscle
contraction. If blood calcium falls below a critical point, muscles cannot relax after
contraction; the body stiffens and shows signs of tetany. In nerve transmission,
calcium works to release neurotransmitters and permits the flow of ions in and out of
nerve cells. Without sufficient calcium, nerve function fails, opening another path to
tetany. Finally, calcium helps regulate cellular metabolism by influencing the activities
of various enzymes and hormonal responses. It is the hormonal regulation of blood
calcium that keeps all of these processes going, even if you fail to consume enough
calcium on a daily basis.
Other possible health benefits of dietary calcium
adequate dietary calcium can reduce the risk of colon cancer, especially in people
who consume a high-fat diet. A decreased risk of some forms of kidney stones and
reduced lead absorption are other possible benefits. Calcium intakes of 800 to 1200
milligrams per day also can decrease blood pressure, compared with intakes of
400 milligrams per day or less (see the nutrition insight). In addition, as covered inchapter 5, when people with elevated ldl-cholesterol consume a low-fat, lowcholesterol
diet, intakes of calcium at 1200 milligrams per day further reduces ldlcholesterol.
An adequate calcium intake might also reduce the risk of premenstrual
syndrome in women. Practical dietary recommendations stemming from all of this research
indicate that meeting the adequate intake for calcium or exceeding it somewhat
may be beneficial for a variety of conditions, not just bone health.
■ calcium in foods and needs
dairy products, such as milk and cheese, provide about 75% of the calcium in north
american diets. The exception is cottage cheese, because most calcium is lost during
production. Bread, rolls, crackers, and other foods made with milk products areare
secondary contributors. Other calcium sources are leafy greens (such as spinach),
broccoli, sardines, and canned salmon. However, much of the calcium in some leafy
green vegetables, notably spinach, is not absorbed because of the presence of oxalic
acid. This effect is not as strong, however, in kale, collard, turnip, and mustard greens.
Overall, nonfat milk is the most nutrient-dense (milligrams per kcal) source of calcium
because of its high bioavailability and low energy value, with some of the
vegetables just noted following close behind (fig. 9.5). The new calcium-fortified versions
of orange juice and other beverages, as well as calcium-fortified cottage cheese,
breakfast cereals, breakfast bars, snacks, and certain chewable chocolate candies, also
follow as close competitors. Another source of calcium is soybean curd (tofu) if it is
made with calcium carbonate (check the label). Note that it is the bones in canned
fish, such as salmon and sardines, that supply the calcium.
One reason why the food guide pyramid contains a milk, yogurt, and cheese
group is to supply calcium to the diet. People who do not like milk can use productsmade with milk, such as chocolate milk, yogurt, cheese, and ice cream. All forms of
milk, yogurt, and cheese allow about the same degree of calcium absorption. Moderation
in use of either cheese or ice cream as a calcium source is advised, because they
are usually high in saturated fat. However, some low-fat cheeses and frozen desserts
are good calcium sources and have a low saturated fat content.
Information about calcium is mandatory on food labels. The daily value for calcium
used for food and supplement labels is 1000 milligrams.
The adequate intake for calcium for adults ranges from 1000 to 1200 milligrams
per day. In the united states, average calcium intakes range from only approximately
600 to 800 for women and 800 to 1000 for men. Thus, dietary intakes of calcium by
many women, especially young women, are well below the adequate intake, whereas
intakes by most men are roughly equivalent to the adequate intake. The greater food
consumption by men, to support their higher energy outputs, accounts for part of the
difference. An easy way for women to increase calcium intake is to increase their physical
activity and, in turn, their food consumption. It is especially important for vegetarians
to focus on eating good plant sources of calcium as well as on the total
amount of calcium ingested.
To estimate your calcium intake, use the rule of 300s. Give yourself 300 milligrams
to account for calcium in the small amounts provided by a moderate energy intake
from foods scattered throughout the diet. Add to that another 300 milligrams for
every cup of milk or yogurt or 1.5 ounces of cheese. If you eat a lot of tofu, almonds,
or sardines, or drink calcium-fortified beverages, use table 9.5 or your diet analysis
software to get a more accurate account of your calcium intake.
■ calcium supplements
calcium supplements can be used by people who don’t like milk or who can’t incorporate
enough milk products, foods made with milk, or calcium-fortified foods into
their diet. Calcium carbonate, the form commonly found in calcium-based antacid
tablets, is the most common supplement used. People with ample output of stomach
acid should take this supplement at bedtime or between meals in doses of about 500
milligrams. This practice enhances absorption and limits its negative impact on absorption
of other minerals. People with low acid production, such as older adults,
should take the calcium carbonate supplement with meals, so that what little acid is
produced during digestion can aid absorption. People with low acid production also
can use a supplement containing calcium citrate, which is acidic itself, between meals.
Overall, taking 1000 milligrams of calcium daily in divided doses of about 500 milligrams
in the form of calcium carbonate or calcium citrate is probably safe, but people
using a supplement should notify their physician of the practice. Still, many
people have difficulty adhering to a supplement regimen. In contrast, regular food
habits can likely be integrated easily into a routine. In addition, it is difficult to consume
an excess amount of calcium using foods. All of this points to focusing first on
improving diet when addressing calcium needs.
Some calcium supplements pose a risk for lead toxicity. Chapter 16 points out that
lead produces an array of deleterious effects on the body. Currently, fda has no standards
for lead in food supplements. However, fda does plan to regulate the lead content
of supplements, including calcium, in the future. Until then, it is important to
avoid bonemeal, the worst offender when it comes to lead. Tablet or liquid calcium
supplements with the usp seal of approval are less likely than others to contain high
concentrations of lead or other contaminants.
An intake of more than 2000 milligrams of calcium per day in some people can
cause high blood and urinary calcium concentrations, irritability, headache, kidney
failure, soft tissue calcification, kidney stones, decreased absorption of other minerals,
and possibly prostate cancer. Note that the upper level for calcium intake is 2500
milligrams per day, based on the observation that greater intakes increase the risk for
some forms of kidney stones.