Fight Crime - Eat Chalk
by Dr. Joe Schwarcz
an excerpt from the book Radar, Hula Hoops and Playful Pigs
One of the most memorable demonstrations I perform in a lecture room, or so students tell me, is to simply eat a piece of chalk. I normally do this when we discuss the chemistry of calcium supplements, pointing out that the source of calcium carbonate is irrelevant. Of course I am not the first person to take an unusual calcium supplement, that honor belongs to Cleopatra.
Sometime during the first century B.C., the Egyptian queen wagered her lover, Marc Antony, that she could invite him to the most expensive dinner in history. Now, Marc had had some pretty elaborate meals, so he agreed to the bet. When the appointed moment came, Antony saw a table set with nothing but a goblet filled with a clear liquid. He undoubtedly sensed victory and the spoils that would surely follow.
As the Roman's anticipation grew, Cleopatra carefully removed one of her huge pearl earrings, crushed it, and dropped the powder into the goblet. The liquid, which actually was vinegar, fizzed impressively as the bits of pearl dissolved. The Queen picked up the goblet and triumphantly drank the potion. She had indeed consumed the most expensive dinner in history: the pearl was worth as much as two million ounces of silver! By this act, Cleopatra may also have been the first woman to make use of dietary calcium supplements.
Pearls are essentially composed of calcium carbonate, the substance which is the active ingredient in most calcium tablets used today with the hope of preventing the bone-brittling disease known as osteoporosis. But increased intake of calcium may have even more wide reaching effects. It may offer protection against kidney and colon cancer. Furthermore, calcium increases the rate at which the body produces nitric oxide, a chemical instrumental in relaxing the walls of blood vessels, thereby lowering blood pressure.
And, believe it or not, calcium consumption may even reduce the crime rate! At least one study has linked high blood levels of lead and manganese with murder, assault and robbery. The researchers suggest that these minerals are absorbed into the brain far more readily if there is an inadequate calcium intake. Make those criminals drink milk!
Osteoporosis is a serious disease, striking about one quarter of all women over the age of fifty, and causing about 350,000 hip fractures a year in North America. Roughly 15% of these cases eventually result in death from circulatory problems, blood clots or pneumonia, all well-established complications of such fractures. Broken wrists and loss of height due to fractures of the vertebrae in the spine can also be direct results of osteoporosis.
Of course, low calcium intake is not the only predisposing factor for the disease. Too much protein and salt in the diet, too little vitamin D, too little exercise, early menopause, long term cortisone therapy and smoking are just some of the other risk factors. But increased calcium intake is something that most people can readily and safely accommodate to increase bone strength.
Bones get their strength from a matrix of flexible protein fibers combined with hard calcium phosphate crystals. These crystals however are not static; bone is living tissue which is constantly being "remodeled." This term simply means that there is a constant turnover of bone, with some minerals being deposited to form bone and some dissolving from bone into the blood. This latter process is known as "resorption."
Calcium, the most abundant mineral in the human body, serves a variety of functions in addition to its role in bone formation. It is essential for blood clotting, for the normal functioning of nerve tissue and for contractions of smooth muscle. Even the very beating of our heart is regulated by calcium levels.
Since blood calcium is obviously essential to life, the body will attempt to maintain adequate levels even at the expense of bone resorption. If the bones are well formed and contain enough calcium, there is no problem. On the other hand, insufficient bone mass can result in osteoporosis and all of its consequences.
How do we know what the ideal calcium intake is? An important clue comes from measuring calcium output in the urine. When the intake is greater than about a gram (1000mg), the calcium concentration in the urine increases, meaning the body has retained as much as it needs. It seems that 1000 mg of calcium a day for premenopausal women and men below the age of 65 is appropriate to achieve calcium balance, but about 1500 mg are needed by men over the age of 65 and women after menopause who are not taking estrogen supplements. Taking estrogen reduces the requirement to around 1000 mg.
The best sources of calcium in the diet are dairy products. Indeed, it is difficult to meet the daily calcium needs if these are not consumed. A glass of milk has around 300 mg, a cup of yogurt 400. By comparison, the best vegetable source is broccoli, with about 100 mg per cup. Unfortunately some people have been frightened away from milk products because of concerns about increased blood cholesterol and unfounded allegations by some activists that "cow's milk is for calves not humans."
Yes, full fat dairy products can increase blood cholesterol levels, but these are easily avoided. Today a wide variety of low fat and fat-free products which contain the same amount of calcium as their higher fat cousins are available. Fluid milk also contains vitamin D which is essential for proper calcium absorption; alternatively a 15 minute exposure to sunlight daily can generate enough of this vitamin. Calcium fortified orange juice containing 350 mg per cup has also appeared, making it easier to achieve the dietary calcium goals.
Still, many people find it difficult to consume 1000 mg. of calcium a day and resort to supplements. Then comes the question about which one? Actually, the form in which calcium is made available appears to be of little significance, but for maximum benefit, it is important to couple the supplements with exercise.
Calcium lactate, calcium gluconate, calcium citrate and calcium carbonate are all suitable, best taken with meals. Calcium citrate may be somewhat more readily absorbed, but contains less calcium than calcium carbonate, 24% by weight compared with 40%. Remember that dietary recommendations are always in terms of calcium, which makes up only part of the weight of a supplement! Calcium carbonate is therefore the most efficient source, although it may have a slight constipating effect.
As far as the body is concerned, it makes no difference whether the calcium carbonate is manufactured in a laboratory or comes from pearls. Whether one chews on "Tums," grazes on the White Cliffs of Dover or dines on chalk is a question of purely personal preference.
I usually end my "chalk eating" lecture by asking the students to estimate their daily calcium intake. The results are almost always frightening. Many have intakes below 400 mg! Still, they are very hesitant when I offer them a bite of chalk. But I know they've bought my arguments when they happily drink the skim milk I pass around. Maybe it doesn't have the greatest taste, but it will go a long way towards reducing the risk of osteoporosis and perhaps even heart disease. And it sure beats eating chalk!
© 2002 Dr. J. Schwarcz.. This information is published and may not be reprinted.