U.S. Department of Agriculture, 1977
"In the future, we will not be able to rely anymore on our
premise that the consumption of a varied balanced diet will provide all the
essential trace elements, because such a diet will be very difficult to obtain
for millions of people".
U.S. Senate Document No. 264, 1936
"Our physical well-being is more directly dependent upon minerals we take
into our systems than upon calories or vitamins, or upon precise proportions of
starch, protein or carbohydrates we consume.
Do you know that most of us today are suffering from certain dangerous diet
deficiencies which cannot be remedied until depleted soils from which our food
comes are brought into proper mineral balance?
The alarming fact is that foods (fruits, vegetables and grains) now being
raised on millions of acres of land that no longer contain enough of certain
minerals are starving us - no matter how much of them we eat. No man of today
can eat enough fruits and vegetables to supply his system with the minerals he
requires for perfect health because his stomach is not big enough to hold them.
The truth is that our foods vary enormously in value, and some of them aren't
worth eating as food... Our physical well-being is more directly dependent upon
the minerals we take into our systems than upon calories or vitamins or upon the
precise proportions of starch, protein or carbohydrates we consume.
This talk about minerals is novel and quite startling. In fact, a realization
of the importance of minerals in food is so new that the text books on
nutritional dietetics contain very little about it. Nevertheless, it is
something that concerns all of us, and the further we delve into it the more
startling it becomes.
You'd think, wouldn't you, that a carrot is a carrot - that one is about as
good as another as far as nourishment is concerned? But it is not; one carrot may
look and taste like another and yet be lacking in the particular mineral element
which our system requires and which carrots are supposed to contain.
Laboratory test prove that the fruits, the vegetables, the grains, the eggs,
and even the milk and the meats of today are not what they were a few
generations ago (which doubtless explains why our forefathers thrived on a
selection of foods that would starve us!)
No man today can eat enough fruits and vegetables to supply his stomach with
the mineral salts he requires for perfect health, because his stomach is not big
enough to hold them!
No longer does a balanced and fully nourishing diet consist merely of so many
calories or certain vitamins or fixed proportion of starches, proteins and
carbohydrates. We know that our diets must contain in addition something like a
score of minerals salts.
It is bad news to learn from our leading authorities that 99% of the American
people are deficient in these minerals, and that a marked deficiency in any one
of the more important minerals actually results in disease. Any upset of the
balance, any considerable lack or one or another element, however microscopic
the body requirement may be, and we sicken, suffer, shorten our lives.
We know that vitamins are complex chemical substances which are indispensable
to nutrition, and that each of them is of importance for normal function of some
special structure in the body. Disorder and disease result from any vitamin
deficiency. It is not commonly realized, however, that vitamins control the
body's appropriation of minerals, and in the absence of mineral's they have no
function to perform. Lacking vitamins, the system can make some use of minerals,
but lacking minerals, vitamins are useless.
Certainly our physical well-being is more directly dependant upon the
minerals we take into our systems than upon calories or vitamins or upon the
precise proportions of starch, protein and of carbohydrates we consume.
This discovery is one of the latest and most important contributions of
science to the problem of human health."
National Institutes of Health, 1994
OverviewThe National Institutes of Health
Consensus Development Conference on Optimal Calcium Intake brought together
experts from many different fields including osteoporosis and bone and dental
health, nursing, dietetics, epidemiology, endocrinology, gastroenterology,
nephrology, rheumatology, oncology, hypertension, nutrition and public
education, and biostatistics, as well as the public to address the following
questions:
(1) What is the optimal amount of calcium intake?
(2) What are the important cofactors for achieving optimal calcium intake?
(3) What are the risks associated with increased levels of calcium intake?
(4) What are the best ways to attain optimal calcium intake?
(5) What public health strategies are available and needed to implement optimal
calcium intake recommendations?
(6) What are the recommendations for future research on calcium intake?
The consensus panel concluded that:
A large percentage of Americans fail to meet currently recommended guidelines
for optimal calcium intake.
On the basis of the most current information available, optimal calcium intake
is estimated to be:
400 mg/day (birth 6 months);
600 mg/day (6 - 12 months) in infants;
800 mg/day in young children (1 - 5 years);
800 - 1,200 mg/day for older children (6 - 10 years);
1,200 - 1,500 mg/day for adolescents and young adults (11 - 24 years);
1,000 mg/day for women between 25 and 50 years;
1,200 - 1,500 mg/day for pregnant or lactating women;
1,000 mg/day for postmenopausal women on estrogen replacement therapy;
1,500 mg/day for postmenopausal women not on estrogen therapy.
Recommended daily intake for men is 1,000 mg/day (25
- 65 years). For all women
and men over 65, daily intake is recommended to be 1,500 mg/day, although
further research is needed in this age group. These guidelines are based on
calcium from the diet plus any calcium taken in supplemental form.
Adequate vitamin D is essential for optimal calcium absorption. Dietary
constituents, hormones, drugs, age, and genetic factors influence the amount of
calcium required for optimal skeletal health.
Calcium intake, up to a total intake of 2,000 mg/day, appears to be safe in most
individuals. The preferred source of calcium is through calcium-rich foods such
as dairy products. Calcium-fortified foods and calcium supplements are other
means by which optimal calcium intake can be reached in those who cannot meet
this need by ingesting conventional foods.
A unified public health strategy is needed to ensure optimal calcium intake in
the American population.
IntroductionIt has been a decade since the 1984 Consensus Development Conference on
Osteoporosis first suggested that increased intake of calcium might help prevent
osteoporosis. Osteoporosis affects more than 25 million people in the United
States and is the major underlying cause of bone fractures in postmenopausal
women and the elderly.
Previous surveys have revealed that the U.S. population experiences more than
1.5 million fractures annually at a cost in excess of $10 billion per year to
the health care system. Two important factors that influence the occurrence of
osteoporosis are optimal peak bone mass attained in the first two to three
decades of life and the rate at which bone is lost in later years. Adequate
calcium intake is critical to achieving optimal peak bone mass and modifies the
rate of bone loss associated with aging.
A number of publications have addressed the possible role of calcium intake in
the prevention of disorders other than osteoporosis, including other bone
diseases, oral bone loss, colon cancer, hypertension, and preeclampsia, a
hypertensive disorder of pregnancy. The results of recent research investigating
these issues indicate that the optimal amount of calcium intake may be greater
than the amount consumed by most Americans. At the same time, the general public
and scientists have been exposed to a body of information emphasizing the value
of ensuring adequate calcium intake throughout life.
Calcium is an essential nutrient. Optimal calcium intake may vary according to a
person's age, sex, and ethnicity. Other factors play a role in calcium intake,
including vitamin D, which is needed for adequate calcium absorption. Many
factors can negatively influence calcium availability, such as certain
medications or food components. Optimal calcium intake may be achieved through
diet, calcium-fortified foods, calcium supplements, or various combinations of
these.
In view of the great public interest in nutrition and disease prevention, the
scientific community has an obligation to integrate new data and to provide
health care practitioners and the public with guidance, even though all of the
necessary long-term studies may not have been completed. In some cases, the new
data, however exciting, point to the need for further research rather than to
specific recommendations. Future investigations in this rapidly expanding area
of research will lead undoubtedly to more definitive information, which will
provide the basis for new recommendations.
To address issues related to optimal calcium intake, the National Institute of
Arthritis and Musculoskeletal and Skin Diseases together with the Office of
Medical Applications of Research of the National Institutes of Health, convened
a Consensus Development Conference on Optimal Calcium Intake on June 6 - 8, 1994.
The conference was cosponsored by the Office of Research on Women's Health,
Office of the Director; the National Institute on Aging; the National Cancer
Institute; the National Institute of Child Health and Human Development; the
National Institute of Diabetes and Digestive and Kidney Diseases; the National
Heart, Lung, and Blood Institute; and the National Institute of Dental Research,
all of the National Institutes of Health. Conference participants included
experts from many different fields, including osteoporosis and bone and dental
health, nursing, dietetics, epidemiology, endocrinology, gastroenterology,
nephrology, rheumatology, oncology, hypertension, nutrition and public
education, and biostatistics, as well as representatives from the public.
After 1 ˝ days of presentations by experts in the relevant fields and audience
discussion, an independent, non-Federal consensus panel weighed the scientific
evidence and formulated a consensus statement in response to the following six
questions: What is the optimal amount of calcium intake? What are the important
cofactors for achieving optimal calcium intake? What are the risks associated
with increased levels of calcium intake? What are the best ways to attain
optimal calcium intake? What public health strategies are available and needed
to implement optimal calcium intake recommendations? What are the
recommendations for future research on calcium intake?
The consensus panel prepared a draft report summarizing the evidence pertinent
to the key issues regarding optimal calcium intake.
What is the Optimal Amount of Calcium Intake?
Calcium is a major component of mineralized tissues and is required for normal
growth and development of the skeleton and teeth. Optimal calcium intake refers
to the levels of consumption that are necessary for an individual (a) to
maximize peak adult bone mass, (b) to maintain adult bone mass, and (c) to
minimize bone loss in the later years.
Calcium requirements vary throughout an individual's lifetime, with greater
needs during the periods of rapid growth in childhood and adolescence, during
pregnancy and lactation, and in later adult life (see Table 1). Because 99
percent of total body calcium is found in bone, the need for calcium is largely
determined by skeletal requirements.
Most studies examining the efficacy of calcium intake on bone mass have used
measures of external calcium balance and bone densitometry as primary outcomes.
The results of balance studies suggest a threshold effect for calcium intake:
Body retention of calcium increases with increasing calcium intake up to a
threshold, beyond which further calcium intake causes no additional increment in
calcium retention.
Table 1 - Optimal Calcium Requirements
|
Group |
Optimal Calcium Daily Intake (mg) |
|
Infant |
|
Birth - 6 months |
400 |
|
6 months - 1 year |
600 |
|
Children |
|
1 - 5 years |
800 |
|
6 - 10 years |
800 - 1,200 |
|
Adolescents/Young Adults |
|
11 - 24 years |
1,200 - 1,500 |
|
Men |
|
25 - 65 years |
1,000 |
|
Over 65 years |
1,500 |
|
Women |
|
25 - 50 years |
1,000 |
|
Over 50 years (postmenopausal) |
1,500 |
|
On estrogens |
1,000 |
|
Not on estrogens |
1,500 |
|
Over 65 years |
1,500 |
|
Pregnant and nursing |
1,200 - 1,500 |
A great deal of recent data related to calcium intake and its effects on calcium
balance, bone mass, and the prevention of osteoporosis was reviewed, with
attention given to the calcium requirements over the life cycle. The current
Recommended Dietary Allowances (RDA) (10th edition, 1989) for calcium intake were
considered as reference levels and used as guidelines to determine optimal
calcium intake in light of new data on calcium-related disorders.
Infants (Birth-12 Months) and Young Children
(1-10 Years) Calcium intake of exclusively breast-fed infants during the first 6
months of life is in the range of 250-330 mg/day, with a fractional calcium
absorption between 55 and 60 percent. A lower fractional absorption of 40
percent is found with cow milk-based formulas. These formulas contain nearly
twice the calcium content of human milk; this results in comparable calcium
retentions of 150-200 mg/day from both formula and breast milk. Net calcium
absorption from soy-based formulas is comparable to, or higher than, that of
breast milk or cow milk formulas because of its considerably higher calcium
content. For infants between the ages of 6 and 12 months, calcium intake ranges
from 400 to 700 mg/day. On the basis of balance data, the current RDAs for
calcium, 400 mg/day for infants from birth to 6 months and 600 mg/day for those
from 6 to 12 months, seem sufficient to provide optimal calcium intake. However,
special circumstances such as low birth weight may require higher calcium
intake. Limited data from one recent study suggest that in children 6-10 years
old, intake above 800 mg/day may lead to increased rates of bone accumulation.
Coupled with calcium balance data, this suggests that an intake of greater than
800 mg/day may be optimal for this age group. It should also be noted that poor
calcium nutrition in childhood may be related to development of enamel
hypoplasia and accelerated dental caries.
Children and Young Adults (11-24 Years)
Calcium accumulation in bone during preadolescence is between 140 and 165 mg/day
and may be as high as 400-500 mg/day in the pubertal period. Fractional
intestinal absorption is very efficient and estimated to be approximately 40
percent. Peak adult bone mass, depending on the skeletal site examined, is
largely achieved by 20 years of age, although important additional bone mass may
accumulate through the third decade of life. Furthermore, cross-sectional
studies reveal a small but positive association between life-long calcium intake
and adult bone mass. Therefore, optimal calcium intake in childhood and young
adulthood is critical to achieving peak adult bone mass. Recent evidence
suggests that adding 500-1,000 mg/day to current calcium intake may, at least
temporarily, increase bone accretion rates in preadolescent boys and girls. With
this supplementation, total calcium intake in these studies exceeded the current
RDA of 1,200 mg/day; however, it is unclear whether the effect on bone accretion
rates persists beyond the reported 18-month to 3-year periods of treatment and
whether these increased rates of bone formation translate into higher peak adult
bone mass. Recent balance studies in adolescents indicate a calcium intake
threshold in the range of 1,200-1,500 mg/day. Collectively, these data suggest
that calcium intake in the range of 1,200-1,500 mg/day might result in higher
peak adult bone mass. Additional research is necessary, particularly
longitudinal, long-term dose-ranging studies of the effects of varying calcium
intake on bone mass, to more precisely define optimal calcium intake for this
age group. Importantly, population surveys of girls and young women 12-19 years
of age show their average calcium intake to be less than 900 mg/day, which is
well below the calcium intake threshold. The consequences of low calcium intake
during this crucial period of rapid skeletal accrual raise concerns that
achievement of optimal peak adult peak bone mass may be seriously compromised.
Special education and public measures aimed at improving dietary calcium intake
in this age group are essential.
Calcium Intake in Adults (25-65 Years of Age)
Once peak adult bone mass is reached, bone turnover is stable in men and women
such that bone formation and bone resorption are balanced. In women, resorption
rates increase and bone mass declines beginning with the fall in estrogen
production that is associated with the onset of menopause. The decline in
circulating 17-beta-estradiol is the predominant factor in the accelerated bone
loss that begins after the onset of menopause and continues for 6-8 years.
Unlike hormone replacement therapy, supplemental calcium during this initial
phase will not slow the decline in bone mass due to estrogen deficiency.
Although the effects of calcium can be shown more clearly in postmenopausal
women after the period when the effects of estrogen deficiency are no longer
dominant (approximately 10 years after menopause), it is likely that the early
postmenopausal years are also an important time to ensure optimal calcium
intake. Between 25 and 50 years of age, women who are otherwise healthy should
maintain a calcium intake of 1,000 mg/day (Osteoporosis. NIH Consensus Statement
1984 Apr 2-4;5(3):1-6). For postmenopausal women who are receiving estrogen
replacement therapy, a calcium intake of 1,000 mg/day is recommended to maintain
calcium balance and stabilize bone mass. For postmenopausal women who do not
take estrogen, it is estimated that a calcium intake of 1,500 mg/day may limit
loss of bone mass, but should not be considered a replacement for estrogen.
Therefore, recommended calcium intake for postmenopausal women up to 65 years of
age is 1,000 mg/day in conjunction with hormonal replacement and 1,500 mg/day in
the absence of estrogen replacement. Adult men also sustain fractures of the hip
and vertebrae, although at a lower frequency than women. In several prospective
and cross-sectional studies, hip fracture risk in men has been found to be
inversely correlated with calcium intake. Although the data are less extensive
in men than in women, the evidence in men suggests that inadequate calcium
intake is associated with reduced bone mass and increased fracture risk.
Available data, although sparse, indicate an optimal calcium intake among adult
men similar to women, namely 1,000 mg/day.
Calcium Intake in Adults (Older Than 65 years)
In men and women 65 years of age and older, calcium intake of less than 600
mg/day is common. Furthermore, intestinal calcium absorption is often reduced
because of the effects of estrogen deficiency in women and the age-related
reduction in renal 1,25-dihydroxy vitamin D production. Calcium insufficiency
due to low calcium intake and reduced absorption can translate into an
accelerated rate of age-related bone loss in older individuals. Among the
homebound elderly and persons residing in long-term care facilities, vitamin D
insufficiency has been detected and may contribute to reduced calcium
absorption. Calcium intake among women later in the menopause, in the range of
1,500 mg/day, may reduce the rates of bone loss in selected sites of the
skeleton such as the femoral neck. (These findings also indicate that the
calcium threshold for reducing bone loss may vary for different regions of the
skeleton.) The physiology of calcium homeostasis in aging men over 65 is similar
to that of women with respect to the rate of bone loss, calcium absorption
efficiency, declining vitamin D levels, and changes in markers of bone
metabolism. It seems reasonable, therefore, to conclude that in aging men, as in
aging women, prevailing calcium intakes are insufficient to prevent
calcium-related erosion of bone mass. Thus, in women and in men over 65, calcium
intake of 1,500 mg/day seems prudent.
Pregnant and Lactating Women
The current RDA for calcium intake during pregnancy and lactation is 1,200
mg/day. Pregnancy represents a significant physiological stress on maternal
skeletal homeostasis. A full-term infant accumulates approximately 30 grams of
calcium during gestation, most of which is assimilated into the fetal skeleton
during the third trimester. Available data suggest that, with pregnancy, no
permanent decline in body calcium occurs if recommended levels of dietary
calcium intake are maintained. There is no association between parity and bone
mass. Furthermore, there is no evidence to support changing the current
recommendation of calcium intake for well-nourished pregnant women. There is,
however, a large population of pregnant women who are not ingesting sufficient
calcium, especially those who are undernourished. These women need to be
identified, and appropriate adjustments in their calcium intake should be made.
Data are not available regarding the calcium requirement for pregnant women at
the extremes of reproductive years, for those who experience non-singleton
births, and for those with closely spaced pregnancies. During lactation, 160-300
mg/day of maternal calcium is lost through production of breast milk.
Longitudinal studies in otherwise healthy women demonstrate acute bone loss
during lactation that is followed by rapid restoration of bone mass with weaning
and the resumption of menses. Women who are lactating should ingest at least
1,200 mg of calcium per day. Lactating adolescents and young adults should
ingest up to 1,500 mg of calcium per day.
Health Tip:
Calcium is the most common mineral in the human body and is directly related
to bone health and osteoporosis.
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Did
You Know? There are approximately 60 to 84 minerals your
body must have and farmers are only replacing 3 back into the soil.