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TOPIC: Latest Findings on Best Calcium Sources

Latest Findings on Best Calcium Sources 04 Feb 2008 12:41 #3736

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Latest Findings on Best Calcium Sources

Too often the media sound bite is the only thing people remember from a news story, which can be a problem when important pieces of information get left out. This happened not long ago when headlines proclaimed that "dietary calcium is better than supplements at protecting bones." There's a whole lot more to that story than can be learned from the nibble of news delivered in the headline.

Most people already know that maintaining bone density is a challenge as we age. This study saying that it is better to get calcium from food sources than supplements seems easy enough to digest -- but actually, it's not quite so simple. Calcium doesn't do the work on its own. Researchers have long been aware that estrogen plays an important protective role in bone health. In fact, this was an often-cited benefit of HRT for post-menopausal women. In the body, estrogen has two primary fates -- it can metabolize into one of two different metabolites, each with a different effect on bone health. One metabolite, the 16 alpha-hydroxyestrone, is believed to be more "active" (or estrogenic) and protective against bones, while another -- the 2-hydroxyestrone -- has less estrogenic activity, and may be associated with bone loss in vulnerable individuals.


I spoke with Reina Armamento-Villareal, MD, an assistant professor of medicine in the Division of Bone and Mineral Diseases at Washington University School of Medicine in St. Louis, and an author of this latest study on calcium intake and bone health. She told me that the point of the research was to learn more about calcium's role on the metabolism of estrogen in the body, specifically its effect on bone density. Did it act as a traffic cop, sending estrogen down certain pathways and not others? And if so, what forms of calcium were most effective at this task?

In the study, 168 healthy post-menopausal women were given detailed questionnaires about their dietary habits over the course of seven days so researchers could then calculate the calcium intake for each, along with where it was coming from -- diet, supplements or a combination of both. Based on the results, the women were divided into three groups -- those who got 70% or more of their calcium from diet... those who got 70% or more of their calcium from supplements... and an in-between group, whose calcium intake derived somewhat equally from both diet and supplements. Urine samples were used to measure the estrogen metabolites of the subjects. Their bone mineral density was also measured with a Dual Energy X-ray Absorptiometry (DEXA) scan.

The results indicated that the "diet plus supplement" group had the highest calcium intake, with more than 1,600 mg/day, along with the highest bone density of all three groups. Versus the supplement-only group, those women who got the majority of their calcium from dietary sources alone had higher amounts of the highly estrogenic metabolite 16 alpha-hydroxyestrone -- and higher bone density readings as well, both of which help to provide greater protection against osteoporosis as this study suggests.


But, as noted above, it's not a straight line to the conclusion that "it's better to get your calcium from dietary sources." Here's why: The 16 alpha-hydroxyestrone metabolite that measured higher in both the "diet" group and the "diet-plus-supplements" group and which appears to be so protective to bone health is also probably carcinogenic, implicated in hormone-dependent cancers for both men and women. It is exactly the metabolite you don't want to elevate. The health-promoting anti-cancer compounds in vegetables like broccoli are helpful precisely because they do act as traffic cops, directing estrogen metabolism into the "2" pathway instead of the "16," thus supporting a less cancer-prone estrogen environment. "Unfortunately, the ratio of 2:16 metabolites that's most protective for bones is also the least desirable from a breast cancer point of view," said Dr. Armamento-Villareal.


So which one is the villain? The supplements? The 16 alpha-hydroxyestrone? Actually it's more likely the source of dietary calcium. For both the "diet" and "diet plus supplement" groups, more than 90% of the dietary calcium came from dairy products. The additional hormones in the dairy products could be a mitigating factor: "Because the main source of dietary calcium in our subjects was indeed dairy, the increase in the 16 alpha-hydroxyestrone metabolites might have been related to the presence of active estrogen metabolites in milk products, rather than from the dietary calcium in general," Dr. Armamento-Villareal acknowledges. Another factor could be that different supplements are digested differently.

So it turns out that the take-away from this research is more nuanced than merely getting your calcium from food, not supplements. "The prudent course is to get your calcium from a combination of foods and supplements, while also reducing your reliance on dairy as a calcium source," says Jonny Bowden, author of The 150 Healthiest Foods on Earth (Fair Winds). He suggests eating foods like sardines canned with the bones (325 mg per 3 ounces)... fermented soy products like natto (380 mg per cup), miso (157 mg per cup) and tempeh (184 mg per cup)... dried uncooked figs (241 mg per cup)... rhubarb (348 mg per cup)... pinto beans (172 mg per cup)... turnip greens (249 mg per cup)... swiss cheese (224 mg per ounce)... blackstrap molasses (172 mg per tablespoon)... cooked kale (94 mg per cup)... canned pumpkin (64 mg per cup)... and cooked broccoli (62 mg per cup).

Add to that well-known bone building activity like strength-training, he advises. "The supplement-plus-diet regimen protects bones, especially if you avoid the possible estrogenic dairy products, and most especially if you add weight training to the mix." It's a matter of balance, once again.


Reina Armamento-Villareal, MD, a bone specialist and assistant professor of medicine in the Division of Bone and Mineral Diseases at Washington University School of Medicine in St. Louis.

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