Calcium's role in health and disease prevention
Calcium and bone healthYour 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.
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.
Although osteoporosis affects people of different races, genders and ethnicities, women are at highest risk because their skeletons are smaller to start with and because of the accelerated bone loss that accompanies menopause. Adequate calcium and vitamin D intakes, as well as weight bearing exercise are critical to the development and maintenance of healthy bone throughout the lifecycle. Older adults should strive to maintain recommended daily calcium intakes as well as an adequate vitamin D intake.
Calcium and high blood pressure
Some observational studies (type of research study in which the treatment/intervention is observed and not controlled by the researchers) and experimental studies (type of research study in which the researchers control the treatments/interventions and that are assigned to participants) indicate that individuals who eat a vegetarian diet high in minerals (including calcium, magnesium and potassium) and fiber, and low in fat, tend to have reduced blood pressure.
Findings from some clinical trials (a specific type of experimental study) used to evaluate the effects of one or more treatments/interventions in humans) indicate that an increased calcium intake lowers blood pressure and the risk of hypertension (high blood pressure). However, the results of some studies produced small and inconsistent reductions in blood pressure. One reason for these results is because these research studies tended to test the effect of single nutrients rather than foods on blood pressure.
Calcium and cancer
Colorectal cancerThe relationship between calcium intake and the risk of colon cancer has not been conclusively determined. Observational and experimental research studies investigating the role calcium plays in the prevention of colon cancer show mixed results. Some studies suggest that increased intakes of dietary (low fat dairy sources) and supplemental calcium are associated with a decreased risk of colon cancer. Supplementation with calcium carbonate is reported to lead to reduced risk of adenomas (nonmalignant tumors) in the colon, a precursor to colon cancer, but it is not known if this will ultimately translate into reduced cancer risk. Another study reported on the association between diet and colon cancer history in 135,000 men and women participating in two large health surveys, the Nurses' Health Study and the Physicians' Health Study. The authors found that those who consumed 700 to 800 mg calcium per day had a 40 to 50% lower risk of developing left side colon cancer. However, a few other observational studies found inconclusive evidence regarding any association of calcium intake with colon cancer. Although some research findings indicate a protective effect of calcium or low fat dairy foods against colon cancer, further studies are necessary to confirm this role for calcium.
Prostate cancer
There is some evidence to suggest that higher calcium (ranging from 600 mg to >2000 mg of calcium) and/or dairy intakes (>2.5 servings) may be associated with the development of prostate cancer. However, these studies are observational in nature rather than clinical trials and cannot establish a definite causal relationship between calcium and prostate cancer. Other findings only show a weak relationship, no relationship at all or the opposite relationship between calcium and prostate cancer. Thus, the relationship between calcium intake, dairy intake and prostate cancer risk remains unclear. At the present time, it is recommended that men ages 19 and over consume a "modest" intake of calcium ranging from 1000-1200 mg per day and maintain an intake below the upper tolerable limit (2500 mg).
Calcium and kidney stones
Kidney stones are crystallized deposits of calcium and other minerals in the urinary tract. Calcium oxalate stones are the most common form of kidney stones in the US. High calcium intakes or high calcium absorption were previously thought to contribute to the development of kidney stones. However, more recent studies show that high dietary calcium intakes actually decrease the risk for kidney stones. Other factors such as high oxalate intake and reduced fluid consumption appear to be more of a risk factor in the formation of kidney stones than calcium in most individuals.
Calcium and weight management
Several studies, primarily observational in nature, have linked higher calcium intakes to lower body weights or less weight gain over time. Two explanations have been proposed for how calcium may help to regulate body weight. First, high-calcium intakes may reduce calcium concentrations in fat cells by lowering the production of two hormones (parathyroid hormone and an active form of vitamin D), which in turn increases fat breakdown in these cells and discourages its accumulation. In addition, calcium from food or supplements may bind to small amounts of dietary fat in the digestive tract and prevent its absorption, carrying the fat (and the calories it would otherwise provide) out in the feces.
Dairy products in particular may contain additional components that have even greater effects on body weight than their calcium content alone would suggest. Three small, recently published clinical trials show that calcium-rich dairy products may help obese individuals following reduced-calorie diets to lose some excess weight and fat. In one trial, 32 obese adults were randomized to one of three groups: eating a standard diet providing 400-500 mg calcium, eating a standard diet supplemented with 800 mg calcium, and eating a diet with 3 servings/day of dairy products to provide 1,200-1,300 mg calcium. The subjects ate 500 fewer calories a day over the 24 weeks of the study. All lost weight and body fat, but those taking the calcium supplements lost significantly more than subjects eating the unsupplemented standard diet, and those on the high-dairy diet lost by far the most. Dairy products also favorably affected body composition in a small group of obese African-American adults who followed a weight-maintenance program for 24 weeks. Subjects who ate 3 servings/day of dairy products, which increased calcium intakes to 1,200 mg/day, lost significantly more fat (both total body and abdominal) and preserved lean body mass as compared to those who consumed less than one daily serving of these foods and 500 mg/day total calcium.
Despite the hopeful results of these studies, other recent clinical trials make it clear that the involvement of calcium and dairy products in weight regulation and body composition is complex, inconsistent, and not well understood. For example, one study in young women of normal body weight found that higher intakes of dairy products had no effect on weight or fat mass over the course of one year. Another study in which 100 overweight and obese pre- and post-menopausal women on reduced-calorie diets received either 1,000 mg/day calcium or a placebo for 25 weeks found no significant differences in weight or fat loss between the groups. Similar results were obtained in a study of 1,471 postmenopausal women (somewhat overweight on average) who were randomly assigned to take 1,000 mg/day calcium or a placebo for 30 months, though there was a trend toward greater weight loss in those who took the calcium supplement and whose calcium intakes from food averaged less than 600 mg/day. Clearly, larger clinical trials are needed to better assess the effects of calcium and dairy products on body weight, composition, and fat distribution.
When can a calcium deficiency occur?
Inadequate calcium intake, decreased calcium absorption, and increased calcium loss in urine can decrease total calcium in the body, with the potential of producing osteoporosis and the other consequences of chronically low calcium intake. If an individual does not consume enough dietary calcium or experiences rapid losses of calcium from the body, calcium is withdrawn from their bones in order to maintain calcium levels in the blood.
Signs of calcium deficiency
Because circulating blood calcium levels are tightly regulated in the bloodstream, hypocalcemia (low blood calcium) does not usually occur due to low calcium intake, but rather results from a medical problem or treatment such as renal failure, surgical removal of the stomach (which significantly decreases calcium absorption), and use of certain types of diuretics (which result in increased loss of calcium and fluid through urine). Simple dietary calcium deficiency produces no signs at all. Hypocalcemia can cause numbness and tingling in fingers, muscle cramps, convulsions, lethargy, poor appetite, and mental confusion. It can also result in abnormal heart rhythms and even death. Individuals with medical problems that result in hypocalcemia should be under a medical doctor's care and receive specific treatment aimed at normalizing calcium levels in the blood. [Please note that the symptoms described here may be due to a medical condition other than hypocalcemia.] It is important to consult a health professional if you experience any of these symptoms.
Who may need extra calcium to prevent a deficiency?
Post-Menopausal Women, menopause often leads to increases in bone loss with the most rapid rates of bone loss occurring during the first five years after menopause. Drops in estrogen production after menopause result in increased bone resorption, and decreased calcium absorption. Annual decreases in bone mass of 3-5% per year are often seen during the years immediately following menopause, with decreases less than 1% per year seen after age 65. Two studies are in agreement that increased calcium intakes during menopause will not completely offset menopause bone loss.
source : http://dietary-supplements.info.nih.gov/
Calcium and bone healthYour 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.
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.
Although osteoporosis affects people of different races, genders and ethnicities, women are at highest risk because their skeletons are smaller to start with and because of the accelerated bone loss that accompanies menopause. Adequate calcium and vitamin D intakes, as well as weight bearing exercise are critical to the development and maintenance of healthy bone throughout the lifecycle. Older adults should strive to maintain recommended daily calcium intakes as well as an adequate vitamin D intake.
Calcium and high blood pressure
Some observational studies (type of research study in which the treatment/intervention is observed and not controlled by the researchers) and experimental studies (type of research study in which the researchers control the treatments/interventions and that are assigned to participants) indicate that individuals who eat a vegetarian diet high in minerals (including calcium, magnesium and potassium) and fiber, and low in fat, tend to have reduced blood pressure.
Findings from some clinical trials (a specific type of experimental study) used to evaluate the effects of one or more treatments/interventions in humans) indicate that an increased calcium intake lowers blood pressure and the risk of hypertension (high blood pressure). However, the results of some studies produced small and inconsistent reductions in blood pressure. One reason for these results is because these research studies tended to test the effect of single nutrients rather than foods on blood pressure.
Calcium and cancer
Colorectal cancerThe relationship between calcium intake and the risk of colon cancer has not been conclusively determined. Observational and experimental research studies investigating the role calcium plays in the prevention of colon cancer show mixed results. Some studies suggest that increased intakes of dietary (low fat dairy sources) and supplemental calcium are associated with a decreased risk of colon cancer. Supplementation with calcium carbonate is reported to lead to reduced risk of adenomas (nonmalignant tumors) in the colon, a precursor to colon cancer, but it is not known if this will ultimately translate into reduced cancer risk. Another study reported on the association between diet and colon cancer history in 135,000 men and women participating in two large health surveys, the Nurses' Health Study and the Physicians' Health Study. The authors found that those who consumed 700 to 800 mg calcium per day had a 40 to 50% lower risk of developing left side colon cancer. However, a few other observational studies found inconclusive evidence regarding any association of calcium intake with colon cancer. Although some research findings indicate a protective effect of calcium or low fat dairy foods against colon cancer, further studies are necessary to confirm this role for calcium.
Prostate cancer
There is some evidence to suggest that higher calcium (ranging from 600 mg to >2000 mg of calcium) and/or dairy intakes (>2.5 servings) may be associated with the development of prostate cancer. However, these studies are observational in nature rather than clinical trials and cannot establish a definite causal relationship between calcium and prostate cancer. Other findings only show a weak relationship, no relationship at all or the opposite relationship between calcium and prostate cancer. Thus, the relationship between calcium intake, dairy intake and prostate cancer risk remains unclear. At the present time, it is recommended that men ages 19 and over consume a "modest" intake of calcium ranging from 1000-1200 mg per day and maintain an intake below the upper tolerable limit (2500 mg).
Calcium and kidney stones
Kidney stones are crystallized deposits of calcium and other minerals in the urinary tract. Calcium oxalate stones are the most common form of kidney stones in the US. High calcium intakes or high calcium absorption were previously thought to contribute to the development of kidney stones. However, more recent studies show that high dietary calcium intakes actually decrease the risk for kidney stones. Other factors such as high oxalate intake and reduced fluid consumption appear to be more of a risk factor in the formation of kidney stones than calcium in most individuals.
Calcium and weight management
Several studies, primarily observational in nature, have linked higher calcium intakes to lower body weights or less weight gain over time. Two explanations have been proposed for how calcium may help to regulate body weight. First, high-calcium intakes may reduce calcium concentrations in fat cells by lowering the production of two hormones (parathyroid hormone and an active form of vitamin D), which in turn increases fat breakdown in these cells and discourages its accumulation. In addition, calcium from food or supplements may bind to small amounts of dietary fat in the digestive tract and prevent its absorption, carrying the fat (and the calories it would otherwise provide) out in the feces.
Dairy products in particular may contain additional components that have even greater effects on body weight than their calcium content alone would suggest. Three small, recently published clinical trials show that calcium-rich dairy products may help obese individuals following reduced-calorie diets to lose some excess weight and fat. In one trial, 32 obese adults were randomized to one of three groups: eating a standard diet providing 400-500 mg calcium, eating a standard diet supplemented with 800 mg calcium, and eating a diet with 3 servings/day of dairy products to provide 1,200-1,300 mg calcium. The subjects ate 500 fewer calories a day over the 24 weeks of the study. All lost weight and body fat, but those taking the calcium supplements lost significantly more than subjects eating the unsupplemented standard diet, and those on the high-dairy diet lost by far the most. Dairy products also favorably affected body composition in a small group of obese African-American adults who followed a weight-maintenance program for 24 weeks. Subjects who ate 3 servings/day of dairy products, which increased calcium intakes to 1,200 mg/day, lost significantly more fat (both total body and abdominal) and preserved lean body mass as compared to those who consumed less than one daily serving of these foods and 500 mg/day total calcium.
Despite the hopeful results of these studies, other recent clinical trials make it clear that the involvement of calcium and dairy products in weight regulation and body composition is complex, inconsistent, and not well understood. For example, one study in young women of normal body weight found that higher intakes of dairy products had no effect on weight or fat mass over the course of one year. Another study in which 100 overweight and obese pre- and post-menopausal women on reduced-calorie diets received either 1,000 mg/day calcium or a placebo for 25 weeks found no significant differences in weight or fat loss between the groups. Similar results were obtained in a study of 1,471 postmenopausal women (somewhat overweight on average) who were randomly assigned to take 1,000 mg/day calcium or a placebo for 30 months, though there was a trend toward greater weight loss in those who took the calcium supplement and whose calcium intakes from food averaged less than 600 mg/day. Clearly, larger clinical trials are needed to better assess the effects of calcium and dairy products on body weight, composition, and fat distribution.
When can a calcium deficiency occur?
Inadequate calcium intake, decreased calcium absorption, and increased calcium loss in urine can decrease total calcium in the body, with the potential of producing osteoporosis and the other consequences of chronically low calcium intake. If an individual does not consume enough dietary calcium or experiences rapid losses of calcium from the body, calcium is withdrawn from their bones in order to maintain calcium levels in the blood.
Signs of calcium deficiency
Because circulating blood calcium levels are tightly regulated in the bloodstream, hypocalcemia (low blood calcium) does not usually occur due to low calcium intake, but rather results from a medical problem or treatment such as renal failure, surgical removal of the stomach (which significantly decreases calcium absorption), and use of certain types of diuretics (which result in increased loss of calcium and fluid through urine). Simple dietary calcium deficiency produces no signs at all. Hypocalcemia can cause numbness and tingling in fingers, muscle cramps, convulsions, lethargy, poor appetite, and mental confusion. It can also result in abnormal heart rhythms and even death. Individuals with medical problems that result in hypocalcemia should be under a medical doctor's care and receive specific treatment aimed at normalizing calcium levels in the blood. [Please note that the symptoms described here may be due to a medical condition other than hypocalcemia.] It is important to consult a health professional if you experience any of these symptoms.
Who may need extra calcium to prevent a deficiency?
Post-Menopausal Women, menopause often leads to increases in bone loss with the most rapid rates of bone loss occurring during the first five years after menopause. Drops in estrogen production after menopause result in increased bone resorption, and decreased calcium absorption. Annual decreases in bone mass of 3-5% per year are often seen during the years immediately following menopause, with decreases less than 1% per year seen after age 65. Two studies are in agreement that increased calcium intakes during menopause will not completely offset menopause bone loss.
source : http://dietary-supplements.info.nih.gov/
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