Mild calcium deficiency can cause nerve sensitivity, muscle twitching, brittle
nails, irritability, palpitations and insomnia. Signs of severe deficiency include
abnormal heartbeat, muscle pains and cramps, numbness, stiffness and tingling
of the hands and feet, and depression. Children can suffer from rickets, a disease
characterized by excessive sweating of the head; slowness in sitting, crawling
and walking; insomnia; bone deformities; and growth retardation. In adults,
deficiency can lead to osteomalacia with symptoms of bone pain, muscle weakness and delayed healing of fractures.
Those at risk of calcium deficiency include the elderly, people who don't can dairy products or other high calcium foods, athletes, those on high protein or high fiber diets, and those who drink a lot of alcohol. High dietary levels of phosphorus cause calcium to be removed from bone and excreted. Phosphorus is found in many common foods such as meat, cheese, processed foods and soda drinks, and people who consume large amount of these foods are at increased risk of calcium deficiency. People on weight-reducing diets are also at risk as they may avoid high calorie foods, which are often good sources of calcium.
Studies have shown that calcium is deficient in the diets of many women.
The National Osteoporosis Foundation estimates that the average adult in the US gets only 500 to 700 mg per day. Calcium deficiency is relatively common in many countries.
Calcium deficiency contributes to osteoporosis, which literally means "porous bones" and in some cases, can be so severe as to cause the bones to break under the weight of the body. Particularly badly affected bones include the spinal vertebrae, the thigh bone and the radius (shorter arm bone). The symptoms of osteoporosis may be absent until fractures occur, although in some cases there may be back pain.
Osteoporosis is most common in elderly white women with a history of borderline calcium intake. Around 3 5 per cent of women suffer from osteoporosis after menopause and, although it is less common, the problem occurs in a similar way in men. Most of the bone loss seen in osteoporosis occurs in the first five to six years after menopause due to a decline in circulating estrogens and an age-related reduction in vitamin D production.
Good nutrition plays a role in reducing the incidence of osteoporosis by
promoting the development of favorable peak bone mass during the first 30 to
40 years of life. Getting enough calcium in early adolescence and early adulthood
is vital for bones to reach their maximum density so that they are strong enough
to support the body even when they lose density later in life. Studies suggest
that calcium intake in adolescence is often below the recommended levels.
Researchers involved in a 1994 USD A study measured calcium intake in 51 girls aged 5 to 16 years old. They found calcium intake to be below the recommended dietary allowance for 21 out of 25 girls aged 11 or over. These studies suggest that the current calcium intake of American girls during the puberty is not enough to enable bones to develop maximum strength and that increased intakes may be necessary.
However, it is never too late to slow the bone-loss seen in osteoporosis,
and early postmenopausal years are also an important time to ensure optimal
intake. A 1997 study done at King's College Hospital in London suggests that
high calcium intakes are linked to bone mineral density in elderly women.
Researchers assessed calcium intake in 124 women aged from 52 to 62 and also measured bone mineral density at the spine, hip and foot (os calcis). Results showed that women with high calcium intakes had higher bone mineral density.
Results from the Rotterdam Study, which involves 1,856 men and 2,452 women aged 55 years and over also show that high calcium intakes also protect against bone loss in men.
Calcium deficiency is only one factor in osteoporosis. There is likely to be
a genetic component and other dietary, behavioral and hormonal factors also
play a major part. Adequate intakes of vitamin D, magnesium and boron are
also necessary to build healthy bones. Body weight is the factor most linked to
bone mineral density and, in women, body fat may be at least as important as
muscle in maintaining bone mineral content. Weight-bearing exercise, adequate
lifelong calcium intake, and moderate alcohol intake all play important roles in preventing osteoporosis. Estrogen replacement therapy is often used to treat osteoporosis.
Bone loss is found to be up to 11 per cent greater during the night. Calcium levels are also lowest during the night and may be affected by the concentration of the hormone, Cortisol. These findings may lead to new hormone treatments for osteoporosis.
Calcium deficiency may be linked to an increased risk of colon cancer. Research on animals and some epidemiological studies suggest that people with high calcium intakes are less likely to develop colon cancer. Research findings in humans are inconclusive, with some studies showing protective effects while others have not. The overall results seem to suggest that the protective effect of high calcium intake does exist but that it is not very marked.
The association between calcium intake and deaths from gastrointestinal cancer was assessed in a 28-year follow-up study of 2 591 Dutch civil servants and their spouses, aged 40 to 65 years. The researchers found that men and women who died of colorectal cancer had a lower average calcium intake compared to the rest of the population.
Results from the Iowa Women's Health Study published in 1998 showed that calcium can decrease the risk of rectal cancer. Researchers analyzed information from 34 702 postmenopausal women who responded to a mailed survey in 1986. After nine years of follow-up, 144 rectal cancer cases were identified. The results showed that high total calcium intake reduced the risk of rectal cancer. Other results from this study show a reduced risk of colon cancer in women with high intakes of calcium and vitamin D.
In a 1996 study, Harvard University researchers working on the Health Professionals Study assessed the links between calcium intake and colon cancer in almost 48,000 men aged from 40 to 75. They found that higher intake of calcium from foods and supplements was associated with a lower cancer risk until they adjusted their results to take other factors into account. They concluded that calcium may possibly mildly lower the risk of colon cancer. Data from the Nurses Health Study, which involved over 89,000 nurses, also showed a small reduced risk.
Calcium may exert its protective effects by binding to toxic substances such as bile acids and fats and reduce the chance that these will cause cancerous changes in the gut. Calcium may also normalize the growth of cells in the intestinal wall, thus protecting against cancerous changes. Limited evidence suggests that low calcium intake may also increase the risk of breast, cervical and esophageal cancers.
Taiwanese studies done in 1997 and 1998 showed a protective effect both against gastric and colorectal cancers from high levels of calcium in drinking water.
Calcium metabolism seems to be altered in people with hypertension. Several studies suggest that low dietary intake of calcium is associated with an increased risk of developing hypertension and cardiovascular disease. Some research suggests studies show that restriction of calcium increases, and supplementation with calcium lowers, blood pressure. Data from the US Health and Nutrition Examination Survey (NHANES I) showed that hypertensive people consumed 18 per cent less dietary calcium than those with normal blood pressure.
A review published in 1997 in the American Journal of Clinical Nutrition showed that experimental data support the view that when adults meet or exceed the recommended dietary allowances of calcium, potassium, and magnesium, high sodium intakes are not associated with high blood pressure. Thus adequate mineral intake may protect against salt sensitivity.
Some evidence suggests that a woman who eats a low calcium diet in pregnancy may also increase the chances of her child suffering from high blood pressure.
When blood calcium levels drop below normal, the sensitivity of the nerves can increase, leading to muscle cramps. Pregnant women whose diets are deficient in calcium are at greatest risk of muscle cramps.
Severe calcium deficiency can lead to periodontal disease (inflammation and degeneration of the bone and gum structures that support the teeth).
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