Osteoporosis, the bone-loss disease that causes dowager's hump and brittle bones, has become a public health problem of epidemic proportions, affecting 25% of the Caucasian female population over 60 years old at a cost to society of $3.8 billion a year.
That's old news.
The new news is that today's female teen-agers who do not consume at least 1,000 to 1,500 milligrams of calcium per day (equivalent to a normal, balanced diet including three servings of calcium-rich foods) are setting the stage for bone fractures, curvature of the spine, loss of height and dowager's hump by age 55.
"Teen-agers are in greatest jeopardy for late osteoporosis because they are not consuming enough calcium during the years when they are building bones. If sufficient bone mass is not built at an early age, the teen-ager may be setting herself up at risk for osteoporosis in the later years when the ability of body to absorb calcium is greatly reduced," said Dr. Charles H. Chesnut III, professor of medicine and radiology at the University of Washington School of Medicine. Chesnut spoke to food writers at the Dairy Council of California's 15th annual nutrition conference at the Highland's Inn here.
"Bone mass at 55 is determined by how much bone was developed at skeletal maturity between ages 12 and 15. We can build more skeletal mass if we take in more calcium during the teen-age years. Large enough bone mass will prevent osteoporosis at menopause time," Chesnut said.
Today's teen-agers may be at risk of osteoporosis because of poor eating habits and lax attitudes toward health, Chesnut said.
Displaced by Soft Drinks
"Many teen-age girls consume soft drinks or diet drinks, which could displace calcium-rich foods. They are also worried about their weight, which further reduces chances of consuming enough foods rich in calcium," Chesnut said.
The current Recommended Daily Allowance of calcium for teen-age girls is 1,200 milligrams. The RDA for women ages 20 through menopause is 800 milligrams daily, an amount that leading researchers now think is too low for good bone health, especially for the elderly population. Chesnut recommends that the calcium RDA be raised to at least 1,000 milligrams a day for premenopausal women and 1,500 milligrams for post-menopausal women not taking estrogen.
Remedial treatment with added intake of calcium-rich foods can at least retard the further loss of bone but not replace it. "Early prevention can mean the difference between osteoporosis or not," Chesnut said.
Meanwhile, studies show that the intake of calcium of elderly women is only half the RDA--400 to 500 milligrams. Studies also show that from age 11 on, American women consistently fail to consume enough calcium, even at current recommended levels.
Why so low?
Chesnut thinks that the American female population consumes too little calcium because they are eating fewer dairy products, which supply about 75% of the calcium in the American diet. Dairy products are considered primary sources of calcium, providing 300 milligrams per serving. Other foods such as tofu, salmon (with bones), baked beans, sardines, dark-green leafy vegetables and waffles or pancakes are considered secondary sources of calcium and provide about 150 milligrams of calcium per serving.
Chesnut cited a study performed in Yugoslavia that reported that those living in an area of the country with high dairy consumption had more bone mass than those living in a low-calcium-consuming area. Fewer bone fractures were reported among the high-calcium-consuming group.
Concern about obesity also may be one of many answers as to why women do not consume enough dairy products. "Interestingly, leanness is a risk factor in osteoporosis. If you have a little extra weight you probably are at less risk for osteoporosis. Why? It appears that the fat cells in the obese individuals continue to put out some female sex hormones (estrogen) even after the ovaries, the organ normally responsible for estrogen production, fail at menopause," Chesnut said. If milk is not a favorite, there is low-fat yogurt or cheese to fill in, he said.
Gastrointestinal problems related to lactase deficiency (the inability of the intestinal tract to break down lactose, a sugar in milk, because individuals lack the enzyme necessary for the function) is yet another factor often blamed on calcium depletion problems in some groups of people. However, blacks, who also are prone to lactose intolerance, seem to have been provided by nature with compensatory large bone mass, offsetting the effects of low calcium absorption among the lactose-intolerant.
"We rarely see osteoporosis in black individuals because they simply have more bone. They begin bone loss about the same time after menopause as other women, but since they have more bone to start with, they do not run into problems as soon," Chesnut said.
Males Escape Problem
Osteoporosis is primarily a disease of Caucasians and Asians, according to Chesnut. Nor do males have the accelerated bone loss seen in osteoporotic women, he said. "Males have more bone mass, and they undoubtedly get enough calcium in their diet. Males also tend not to diet as much as females and presumably their calcium intake is reasonable," Chesnut said. Studies show that calcium intake in males at any age appears to be at the RDA.
Other reasons for calcium depletion? Alcohol problems. "Alcohol does nothing good to bones. It blocks absorption of calcium, turns on a process called resorption, causing loss of bone and blocks new bone formation," Chesnut said.
But perhaps the most prevalent cause of bone loss in older women is postmenstrual estrogen deficiency caused by menopause.
"The first risk factor of osteoporosis is the loss of female sex hormones or estrogens after the menopause. This probably leads, at least to a certain extent, to some of the deficiency of calcium that we see in the elderly population," Chesnut said.
Chesnut explained that estrogens prevent a process called bone resorption, or the depleting of bone by a hormone secreted by the parathyroid gland. "Estrogens protect against the action of parathyroid hormone on bone, and after the menopause or any particular physiologic state in which there is a deficiency of estrogens, one can anticipate bone loss."
Chesnut pointed out that loss of estrogens occurs after a normal menopause or after a hysterectomy or oophorectomy (removal of the ovaries). "It also can occur in individuals who simply never put out enough estrogen, and it can also happen to women who exercise to the extreme or who no longer menstruate," Chesnut said.
Chesnut cited a study in which osteoporosis had been detected in young female marathon runners, even though these women produce estrogen and have normal menstrual cycles. "Since two of the three major osteoporosis-prevention factors are present--regular weight-bearing exercise and estrogen production--indications are that inadequate calcium intake may be a factor in their bone loss," Chesnut said.
Dieting by the female athlete may also be one of the high-risk factors for her calcium-deficiency problems, according to Chesnut. The women in the runners' study consumed an average of 350 milligrams of calcium daily, about half the amount prescribed by the RDA and only a third the amount recommended by concerned scientists.
Many of the marathoners also had amenorrhea--that is, they no longer menstruated. "This means that they don't produce estrogen, and as we have seen, this can lead to bone loss," Chesnut said.
What can one do to help retard the onslaught of calcium depletion and osteoporosis?
According to Chesnut, moderate exercise not only is necessary for good bone health, it can act as a stimulant for the body to continue bone remodeling, which retards bone depletion. Adding exercise to one's daily routine can help retard bone depletion, especially during menopause years, and even before.
"The best thing to do is to try to prevent osteoporosis by exercising daily and consuming adequate amounts of calcium through the diet," Chesnut said. Chesnut encourages his patients to consume a normal, balanced diet, which includes two to three servings of calcium-rich foods, such as nonfat milk, buttermilk, mozzarella cheese, low-fat milk, plain yogurt, whole milk, chocolate milk, cheese, cocoa, fruit-flavored yogurt, milkshake, pudding and custard among the dairy group and sardines among the meat-fish group.
However, if one cannot tolerate or get enough of these calcium sources in the diet, calcium supplementation in form of pills is a good alternative. Calcium supplements provide the same calcium value as milk. Any generic calcium supplement can be used. "They're cheaper and just as good as the more expensive brand names," Chesnut said.
Chesnut advises that people who are not taking estrogen or are in the postmenopausal period of life (55 to 60) start consuming 1,500 milligrams of calcium daily. Girls and women between 12 and 25 and women over 25 years of age who are taking estrogen or are menstruating should take 1,000 milligrams of calcium.
"Increasing calcium intake is safe. However, too much of a good thing can be bad. I would say that an intake of 2,000 milligrams or more may no longer be beneficial and could cause calcium deposits to develop," Chesnut said.