Ever since we were kids, we've known that calcium was a very important nutrient, with a wide range of activity in virtually all body systems. Even the FDA, in its wisdom, has seen fit to allow efficacy claims for only three nutrient supplements, of which calcium as the first — for reducing the risk of osteoporosis.*

Of course, those of us living in the real world know that calcium does a lot more than just help build strong bones. Outside the FDA bubble, it is widely recognized that calcium can be an important factor in helping to prevent colon cancer, control blood pressure, and prevent periodontal (gum) disease.

Now, new research from Germany¹ suggests that calcium supplements may also help control cholesterol metabolism. But not just any calcium supplement. The most common calcium supplements usually consist of calcium carbonate, calcium citrate, or calcium citrate malate. These calcium salts are preferred for building bone strength and other uses because of their relatively high bioavailability, but it is not clear they have any beneficial effects on lipid levels.

On the other hand, supplements containing calcium phosphate (CaP) have relatively low bioavailability, but they also have the ability to bind to cholesterol-carrying bile acids in the gastrointestinal tract and sweep them out of the body in the feces. CaP's activity on bile acids may contribute to a lower risk of colon cancer. At the same time, by lowering cholesterol levels, CaP may also protect against heart disease.

In the German study, healthy men and women were randomly divided into two groups: One group consumed bread containing CaP for 4 weeks, followed by 4 weeks on a "placebo bread." The second group consumed both types of bread in the opposite order. The remainder of the participants' diet was also carefully controlled. At various times during the 8-week trial, the investigators collected samples of blood, urine, and feces. The study was double-blinded, so neither the participants nor the investigators knew who was getting which type of bread until the study concluded.

The results showed that most of the ingested calcium was excreted in the feces, confirming that you would not want to take supplemental CaP if your only concern was building bone strength. However, total cholesterol levels and LDL-cholesterol ("bad cholesterol") levels decreased significantly (~5.6%) during the 4 weeks when the participants consumed the Ca-enriched bread compared with placebo (Figure 1). The ratio of LDL-cholesterol:HDL-cholesterol also decreased significantly (~5.4%) following CaP supplementation (P < 0.05). The lower this ratio, the lower the risk of heart disease.

The mechanism by which CaP lowers cholesterol is not completely understood. However, it is known that calcium phosphates are insoluble in water at a neutral pH. Thus, when ingested, the stomach's acidic environment dissolves the CaP and passes it along in solution until it reaches the small intestine, where the pH rises to about 5.6 to 7.0. In this less acidic environment, the CaP precipitates out of solution to form amorphous calcium phosphates, which can bind and precipitate cholesterol-carrying bile acids in the colon, effectively removing them from the body. The authors speculate that the small amount of calcium that is absorbed from CaP could also help prevent age-related bone loss.

Sequestration of bile acids is a well-known mechanism for reducing cholesterol levels. For many years, drugs called bile acid sequestrants were used to help control blood lipids. CaP increased bile acid secretion by 11% in this study and has been shown in other studies to lower cholesterol levels by about 5% to 6% in people with high cholesterol levels. While CaP reduced cholesterol less than the drugs do, capsules containing CaP are far easier to take (the drugs have to be dissolved in water before drinking), and the drugs have far more serious side effects.

Although calcium excretion is markedly increased when taking CaP, recent research indicates that this does not increase risk of kidney or urinary stones, as once thought. In fact, a higher intake of dietary calcium is now associated with a decreased risk of kidney stones.

Because the risk of coronary heart disease increases sharply as total cholesterol levels rise, the authors speculate that by helping to lower serum cholesterol levels, taking supplementary CaP, either from sources like bread mixes, cereal, and supplements might contribute to a reduction in the long-term risk for coronary heart disease.

References

1. Ditscheid B, Keller S, Jahreis G. Cholesterol metabolism is affected by calcium phosphate supplementation in humans. J Nutr. 2005 Jul;135(7):1678-82.