There are a lot of calcium products on the market, so many that it is quite confusing. What is your take on the products out there?
SANDY: We weren't satisfied with the calcium supplements that were available on the market, which often contain types of calcium that may not be absorbed by the body very efficiently.
DURK: Calcium carbonate, for example, is difficult to absorb in the absence of adequate amounts of stomach acid. On the other hand, calcium citrate (a chelate) and calcium ascorbate (a complex) do not require any stomach acid; they are thus quite bioavailable. A third calcium, tricalcium phosphate, is closely related to the type that you have in your bones. Tricalcium phosphate is also called "bone ash," and differs from the calcium in your bones by having a different crystal structure and by being dehydroxylated, which results in lower acid requirements for dissolution and absorption. Other than the lower stomach acid requirement, it is absorbed and transported by the same mechanisms as bone calcium, a form of calcium that omnivores and carnivores have been consuming for hundreds of millions of years, unlike calcium carbonate. (Calcium carbonate is a good antacid because it uses up so much stomach acid; if you are not producing excess stomach acid, calcium carbonate - such as oyster shells or limestone - is not your best choice.)
Calcium citrate is a calcium/citric acid complex. Your stomach lining has pumps, which pull the citric acid from the lumen of your intestines, in order to transport the calcium/citric acid complex across the intestinal tissue and into your blood stream. Your gut also has very active pumps for vitamin C. These pumps drive vitamin C from the lumen of the intestine across the intestinal tissue into the blood stream. And since vitamin C is bound with calcium (calcium ascorbate is a calcium/vitamin C complex), calcium is carried along with it. In fact, there is a significant amount of evidence that suggests that calcium metabolism and your ability to absorb calcium declines very substantially if you don't have enough vitamin C, which is another good reason for including vitamin C.
Also, vitamin D is necessary for proper calcium transport and metabolism and a lot of people simply aren't getting enough. Now if you were running around naked all summer long, you'd get plenty of vitamin D, but you'd also probably end up getting skin cancer, because you'd live long enough to get it.
SANDY: (Laughs) Eventually, yes.
DURK: Of course, back in the bad old days, you'd die of pneumonia before you died of skin cancer. However, nowadays, people tend to be covered up, or if they're not covered up, they're wearing sunscreen. And of course, during the winter, you don't get much sun, no matter how you slice it.
SANDY: Unless you're drinking adequate amounts of vitamin-D-fortified milk, you're not likely to be getting enough vitamin D. And in fact, it's been found that for elderly people, vitamin D deficiency is a very serious problem.
DURK: Beta-carotene is also important. If you don't have enough vitamin A, your body can convert beta-carotene to vitamin A; but if you have enough vitamin A, your body will leave the beta-carotene alone. You must be careful about taking too much vitamin A. In some elderly people who have liver damage, toxic effects have been seen at as little as 15,000 IU a day. But that doesn't happen with beta-carotene, because your body shuts off the conversion of beta-carotene to vitamin A when you have adequate amounts.
SANDY: Vitamin A is important for the regulation of vitamin D receptors.
WILL: There are a lot of reasons to take calcium. It seems there are more studies coming along all the time. And one of the things I've noticed is that, generally, the recommended amounts have continued to increase for both men and women. Would you care to comment on both of those things?
DURK: Yes, that's true. Not only is calcium important for preventing osteoporosis - and I might add that osteoporosis is not just a problem of post-menopausal women; it's a problem that happens to men too, though not as severely - but taking additional calcium supplements can reduce the rate of calcium loss and bone strength loss in both men and women. For best results, a woman ought to consider hormone replacement therapy, if she is postmenopausal, unless she has some condition which is contraindicative, such as having had breast cancer or uterine cancer.
SANDY: Hormone replacement is vital for the regulation of calcium metabolism in women. Without it, women will lose calcium and experience bone loss. This loss can be slowed by hormones, exercise and by calcium supplements. But nevertheless, hormones are really important in terms of maintaining or even increasing bone density.
DURK: Whether or not you're taking a hormone replacement therapy, whether you're a man or woman, you really ought to be taking a calcium supplement. In addition, calcium does a lot more in your body than just keeping your bones strong. Calcium is important in a process called apoptosis, which is a very carefully controlled programmed cell suicide. Every time a cell divides, the cell is supposed to stop at a checkpoint and check the integrity of its DNA. If the DNA is damaged, it tries to repair it. And if it's a type of damage that can't be repaired, at that point apoptosis is triggered. At first there is an in-rush of calcium ions, triggering off a bunch of other enzymes which - among other things - literally shred the entire genome of the cell. If you've got a cancer virus in your cell, you don't want to let it loose. By letting the cell die, the cancer virus might get out and affect other cells. So what apoptosis does is run the DNA and the nucleus completely through a shredder, chopping it into pieces so short it can't carry any dangerous information. Thus, adequate calcium levels help make apoptosis more efficient and that in turn can help disarm certain cancer cells before they run amok.
SANDY: The inflow and outflow of calcium ions is an almost universal signal in the regulation of cellular activity.
DURK: Very interestingly, they've found that increased amounts of calcium in the diet correlate epidemiologically with a lower incidence of colon and rectal cancer in human beings.2 In experiments in animals, giving them calcium supplements can reduce the incidence of colon and rectal cancer.
WILL: Is apoptosis the explanation for these benefits?
DURK: Perhaps, at least in part. (Calcium also binds potentially carcinogenic fatty acids and bile acids in the colon, reducing their bioavailability). Calcium influx is an essential and early part of the apoptotic process. It triggers off a system of calcium activated enzymes inside of the cells that chew everything up.
WILL: So if you don't get genetically damaged cells chewed up, then basically you have a lack of fidelity in the replication process of cell division.
DURK: That's right. If the part of the cell that tells it when to divide and when not to divide is damaged and that cell goes on dividing, you can end up with cancer or a precancerous hyperplasia.
WILL: What about calcium for men? Men don't have the problems with the falloff of estrogen that women do.
DURK: No they don't. But they do have a problem with the falloff of testosterone. Testosterone is also linked with calcium deposition in the bones. Men do lose bone density and bone strength. This reduction in bone density and calcium loss can be reduced substantially by taking a calcium supplement.
WILL: There is one other item that you didn't mention, and that is the mineral, boron.
DURK: Yes. Boron is necessary for proper use of calcium in the body, probably because of an involvement in your steroid hormone synthesis metabolism.
WILL: I remember reading Forest Nielson on the impact of taking adequate levels of boron. With boron you can obtain the benefits of higher levels of supplemental estrogen (if you're a woman) or greater testosterone (if you're a man).
DURK: Apparently, synthesis of the steroid hormones in your body, including both testosterone and estrogen, requires boron. Boron is an essential nutrient not just in plants, but in animals as well. In the diet there's not a whole lot of ways to get it, so the best thing to do is to take a reasonable amount as a supplement.
WILL: Any new studies, large-scale studies, on calcium that have been drawn to your attention? I've seen quite a few, but any that you care to mention?
DURK: No. But I do encourage people who are hooked up to the web to do a search for calcium supplementation in the National Library of Medicine database, which is now available free.
WILL: Through PubMed. What about amounts? What do you think should be the appropriate amounts of total calcium for men and for women?
DURK: The FDA official amount is about 1 gram a day for men and 1.2 grams for women, as my memory serves me. For once we agree. Sandy and I take 4 capsules a day which, in conjunction with our meals, gives us more than that.
SANDY: We get calcium from the supplements and then of course we drink a lot of milk, too.
DURK: That, incidentally, is a really interesting trick. You can increase your calcium absorption from the supplement even further if you drink some milk along with it.
WILL: Why is that?
DURK: Each glass of milk doesn't have all that much calcium. The amount of calcium in milk is, shall we say, surprisingly low. What happens though, is that the cows make a protein which is resistant to being processed by digestive enzymes, which assists in the transport of calcium across the wall of your gut and into your blood stream. It turns out that, unlike a lot of animal hormones, this one works in human beings as well as in calves.