New Reports Bolster Bone-Building Benefits of Green Tea and Foods Rich in Vitamin D, Calcium, and Protein
Findings point toward a multi-faceted approach to bone strength, and dispel some common misconceptions
by Craig Weatherby
Talk about “boning up” on a subject! Earlier this month, Toronto, Canada played host to the International Osteoporosis Foundation’s World Congress: the largest medical conference focused specifically on bone health. (That's Olympic figure-skating gold medalist Peggy Fleming at left, speaking to the assembly.)
This year’s bone-health summit meeting featured more than 700 oral and poster presentations on the latest research. We'll review the five that offered the most significant new information on nutritional prevention of osteoporosis and fractures.
The term “osteoporosis” defines a condition in which the bones become porous and break easily. Osteoporosis ranks among the most common and debilitating diseases, as one out of three women and one out of five men over 50 will suffer osteoporotic fractures.
Osteoporosis is easily diagnosed and can be treated with bisphosphonate-class drugs such as alendronate (Fosamax) and etidronate (Didronel), which increase bone density and decrease the rate of bone fractures by preventing breakdown of bone tissue.
|The Five Studies, in Brief|
- #1: Food sources of calcium beat pills for reducing fracture risks
- #2: Together, supplemental vitamin D and calcium prevent fractures better than either alone
- #3: Protein-rich diets do not raise fracture risks
- #4: Vitamin D shortage strikes European women from Spain to Sweden
- #5: Women who drink green tea five times a week enjoy better bone health than those who drink very little tea
However, these drugs are associated with significant adverse effects, and osteoporosis can be prevented or reduced to a very significant extent with diet, supplements, and weight-bearing exercise.
There is also substantial disagreement among experts concerning the new diagnosis of “osteopenia”, or low bone density, and the use of bisphosphonate-class drugs as agents to prevent progression to full blown osteoporosis (See “Diseased by Definition: Drug Profits Distort Medical Decisions," in our July 18, 2005 edition.).
The five studies reviewed here illuminated the roles of green tea, calcium, vitamin D, and protein in reducing the risk of fractures related to osteoporosis.
Study #1: Calcium from food beats calcium supplements
When health authorities discuss essential nutrients like calcium they often recommend getting them from foods rather than pills. This advice makes sense in some cases, but is hard to follow in others. Such is the case with the US recommended daily allowances (RDAs) for calcium of 1,000 mg for men and women, as these calcium intake targets are near impossible to meet without supplemental amounts from pills.
In addition, the link between calcium intake alone and osteoporosis is weak, with most population studies showing no strong correlation between higher calcium intake and lower fracture rates.
As Harvard nutrition research chief Walter Willett, M.D. reported at Dr. Andrew Weil’s 2006 Nutrition & Health conference (see “Vital Choice Visits Dr. Weil’s Nutrition Conference”), the current evidence indicates that people can maintain strong bones on levels of calcium far lower than the US RDAs, and that dietary vitamin D is more important than dietary calcium.
(The results of another study presented in Toronto this month suggest that the stronger effect of vitamin D holds true only up to a point: see “Study #2”, below.)
The results of a study presented at the Toronto bone-health congress (Thompson JN 2006) supports the suspicions that high calcium intake does not by itself ensure stronger bones. Estrogen and bone-health expert Reina
Armamento-Villareal, M.D. of the Washington University School of Medicine led a team that examined calcium intake in three groups of women, the members of which got their calcium in one of three different ways:
The women in the “food only” group enjoyed the greatest bone benefits. They also showed signs of higher body levels of estrogen, which promotes bone building in childhood and adolescence and inhibits post-menopausal osteoporosis.
- Calcium from supplements only
- Calcium from food only
- Calcium from supplements and food.
The study needs to be repeated for a longer duration, and Dr. Armamento-Villareal plans a longer-term, two-to-three year study.
Study #2: Supplemental vitamin D prevents fractures better when taken with calcium
Last November, we related the findings of an Icelandic research team, whose study found that high blood levels of vitamin D inhibit secretion of parathyroid hormone (PTH): a body chemical that prompts the body to draw calcium from bones. In other words, low vitamin D levels prompt loss of calcium from bones, and raise the risks of osteoporosis and fractures (See “Vitamin D Called More Critical for Bones than High-Dose Calcium”).
The Icelandic team's key finding was that high calcium intake did nothing to prevent high blood levels of bone-weakening PTH, and that vitamin D intake levels were more important than calcium intake levels.
The Icelandic group's report was preceded by the findings of a joint Canadian/American team (including Harvard's Walter Willett), which confirmed that post-menopausal women who have osteoporosis or are at risk of developing it do not have enough vitamin D in their bodies (See “Women Need to Bone Up on Vitamin D”).
And in May of last year, a joint Swiss-American team published an analysis of prior clinical research, which indicated that taking supplemental vitamin D in amounts double the US RDA of 400 international units (IU)—i.e., 700-800 IU or more—reduces the risk of bone fractures substantially. However, the data analyzed in that study (Bischoff-Ferrari 2005) did not reveal the role of calcium in that level of protection.
The Toronto bone congress included a paper from a Belgian-Dutch research team (Boonen S 2006) that followed up the 2005 Swiss-American report with a broad literature search that sought to reveal the interactive roles of calcium and vitamin D in reducing hip fracture risks.
The investigation showed that, in the absence of supplemental calcium, even a daily supplement regimen that provides 800 IU or more of vitamin D per day affords no added protection against hip fractures, versus taking supplements that provide only the RDA (400 IU). The IOF press release quoted team leader Dr. Steven Boonen as saying, "Our meta-analysis shows there are two requirements for vitamin D to be effective. First, you need the appropriate dose of vitamin D, as indicated by… [the 2005 Bischoff-Ferrari meta-analysis] and second you have to combine that dose with calcium."
This isn’t much of a surprise, since the ability of vitamin D to reduce osteoporosis and fractures relates directly to its role in enabling efficient uptake of dietary calcium into bones.
In light of the “food-versus-pills” calcium/fractures study described above (Thompson JN 2006), it is unfortunate that the new Belgian-Dutch meta-analysis presented in Toronto didn’t determine whether varying levels of calcium intake from foods, rather than supplements, affect the efficacy of high-doses of supplemental vitamin D.
Study #3: Protein-rich diets do not raise fracture risks
For several decades, researchers had assumed that diets high in protein promote osteoporosis. This hypothesis flowed from two observations:
But many other factors affect osteoporosis, and new findings from Toronto undermine this old anti-protein proposition: at least with regard to women.
- High protein intake lowers the pH of blood (i.e., makes it more acidic), and the body seeks to re-balance blood pH by transferring calcium—an alkaline, high-pH mineral—from bones to blood
- Countries with high protein intakes—mostly in Europe and North America—suffer high rates of osteoporosis, compared with low-protein-intake countries in Asia and Africa.
The Toronto congress featured findings by Donna Thorpe, MPH and her colleagues from California’s Loma Linda University. Professor Thorpe’s team reported that, regardless of the source, higher levels of protein intake appear to protect against wrist fracture in post-menopausal women (Thorpe DL 2006).
The Loma Linda group examined data from 1,865 peri- and postmenopausal women, who completed two lifestyle questionnaires. The first questionnaire, from 1976–77, concerned diet, while the second survey, conducted in 2001, gathered information on the number of “low-trauma” fractures the women experienced during the intervening 25 years.
The data analysis revealed two key findings that seem to allay fears that protein-rich diets undermine bone strength:
Professor Thorpe made this cogent comment: "As women age, they tend to eat less protein, so this study tells me we that we have to get sufficient dietary protein to those who are at high risk for fracture.”
- Vegetarian women who ate the highest amounts of protein-rich plant foods—nuts, beans, soybean foods, etc.—enjoyed a 66 percent reduction in the risk of wrist fractures, compared with those who ate the lowest amounts. Those who ate cheese as well (so-called lacto-ovo vegetarians) enjoyed similar protection.
- Women who consumed cheese three or more times a week or meat four or more times a week enjoyed fracture rates less than half those of women who ate these protein-rich animal foods less often. (It seems very safe to assume that protein from fish would produce comparable bone-strength gains, especially since prior research results suggest that omega-3s may promote bone strength to a minor extent.)
We should note that this is not the first study to demonstrate that higher fruit and vegetable consumption yields higher bone density in people of all ages and both genders.
Coincidentally, a very well-controlled study published in the in the June issue of the American Journal of Clinical Nutrition (Prynne CJ 2006) offers further support for the bone-building powers of fruits and vegetables. The British research team reported the findings of their study designed to determine the association between fruit and vegetable consumption and bone-mineral status in five groups of people, each representing a different age and sex profile (e.g., teenage boys, older women).
The results show that higher fruit and vegetable intakes enhance both spinal bone-mineral content and whole body bone-mineral content.
|Food sources of vitamin D: sockeye rules “D” roost|
Sockeye salmon appears to be the richest food source, by far, beating all comers by a wide margin. This distinction is probably a function of its unusual diet, which features more vitamin D-rich plankton than other salmon and most other fish.
Independent lab tests indicate that Vital Choice wild sockeye salmon average 687 IU of vitamin D per 3.5-ounce serving, and that a single 6-oz portion contains more than 1,100 IU: a proven-safe amount just above the daily intake (1,000 IU) recommended by bone-health and cancer researchers worldwide. (Note: the vitamin D content of sockeye salmon will vary seasonally. When it is time to spawn, they eat more to store energy for the strenuous journey upriver.)
After sockeye, the best vitamin D sources among our seafood selection are albacore tuna (544 IU), silver salmon (430 IU), halibut (276 IU), king salmon (236 IU), sardines (222 IU), and sablefish (182 IU). For a graph showing the vitamin D content of all our fish, click here.
And, each 1,000 mg capsule of our Sockeye Salmon Oil dietary supplement contains 53 IU of vitamin D.
mineral density in adolescent boys and girls aged 16 to 18. In women aged 60 to 83, higher fruit intake was associated with better spinal bone-mineral content, with a doubling of fruit intake resulting in a large, five-percent increase in spinal bone-mineral content.
There are several possible mechanisms that might explain the bone-building effects of fruits and vegetables, such as a direct blood-alkalizing effect and the dietary influence of vitamin K and estrogenic flavonoids.
Study #4: Vitamin D shortages found regardless of latitude and age
The body makes vitamin D in large amounts when sunlight strikes the skin. So it surprised one group of researchers presenting in Toronto that they found low vitamin D levels among postmenopausal European women with osteoporosis, regardless of whether they lived in sunny southern countries like Spain or in nations with much darker skies, like Britain and Denmark (Bruyere O 2006).
Dr. Olivier Bruyere of the University of Liege, Belgium led a research team whose analysis of vitamin D levels in 8,532 women— from France, Belgium, Denmark, Italy, Holland, Hungary, Spain, the UK, and Germany—showed that most are deficient in vitamin D.
Normal adult vitamin D blood levels range from 50 to 140 nmol/liter (nano-moles per liter), but leading vitamin D researcher Michael Holick, M.D. of Boston University says that optimal fracture-prevention blood levels start at 115 nmol/liter: a concentration that most older women don't reach.
Almost 80 percent of the European women in the new study had blood vitamin D levels below 80 nmol/liter: a concentration that puts them at risk of osteoporotic fractures. Worse yet, about one third of the women had blood vitamin D levels below 50 nmol/liter.
Because the women who lived in the sunniest, southernmost countries did not have substantially higher vitamin D levels, it may be that women in all these countries spend little time outdoors, or that sun exposure isn’t keeping vitamin D levels high with sufficient consistency. Thus, it seems smart to favor foods high in vitamin D, such as sockeye salmon (see our “Food sources of vitamin D” sidebar) and supplement your diet with 800-1,000 IU of vitamin D-3 (the best form) every day.
The researchers’ findings also indicate that a woman’s age had little bearing on her degree of vitamin D deficiency, which led Dr. Bruyere to make this recommendation: “Supplements should not be restricted just to the elderly. Even young post-menopausal women should take some form of vitamin D supplementation.”
Study #5: Green tea builds bone strength
Researchers at the University of Tokyo knew that previous population studies have shown an association between drinking black (heavily fermented) tea and increased bone mineral density. Their presentation at the Toronto congress (Muraki S 2006) reported success in extending those findings to green (lightly fermented) tea.
This study included 655 women aged 60 years and above who visited the Osteoporosis Outpatient Clinic in Tokyo Metropolitan Geriatric Medical Center. The volunteers completed a questionnaire about their consumption of 10 dietary items such as green tea, milk, cheese, yogurt, fish, vegetable, tofu, natto (a soy food), meat and coffee, smoking, consumption of alcohol, physical activity and use of anti-osteoporosis bisphosphonate drugs like Fosamax.
For each dietary item, subjects were divided into two groups: 1) those who consumed the item five or more days per week, and 2) those who consumed the item fewer than five days per week. The researchers then measured the bone mineral density (BMD) of the women's lumbar spines, as well as blood markers for osteoporosis risk, including levels of calcium, phosphorus, parathyroid hormone, alkaline phosphatase, osteocalcin, and vitamin D.
Among the 655 subjects, 600 drank green tea five days or more per week, and their average BMD was significantly higher (0.808 grams of hydroxyapatite-form calcium per square centimeter) than that of the 55 women who reported drinking green tea less than five days per week (0.738 grams per square centimeter).
The tea drinkers’ bone-density advantage persisted after the results were adjusted for age, body mass index, other dietary items, smoking, alcohol, physical activity and use of osteoporosis drugs.
As the Tokyo team reported, “We conclude that green tea drinking is associated with increased BMD among elderly women.”
They hypothesized that the catechin-class flavonoids in green tea provided the benefits, via estrogenic effects known to build bone strength and/or induce “suicide” (apoptosis) among the bone-destroying cells called osteoclasts.
These proposed mechanisms would be similar to the ways in which bisphosphonate drugs like Fosamax are believed to prevent bone loss. But, unlike eminently safe, healthful green tea, these potent drugs can cause inflammatory eye disorders, abdominal pain, nausea, vomiting, dyspepsia and diarrhea, as well as other, rarer side effects.
If the statistical association seen in this study is confirmed as a cause-effect relationship in clinical trials, the higher bone mineral density that green tea appears to have produced among the Japanese women might be sufficient to give Fosamax and company serious—and infinitely safer—competition.
- Thompson JN, Napoli N, Civitelli R, Armamento-Villareal RC. P696MO. Effects of dietary calcium vs. calcium supplements on estrogen metabolism and bone density. IOF World Congress on Osteoporosis, Toronto, Canada. June 5, 2006. Accessed online June 15, 2006 at http://www.osteofound.org/wco/2006/downloads/abstracts_iof_wco_2006.pdf
- Boonen S, Haentjens P, Vanderschueren D, Lips P. OC21. Fracture risk reduction with vitamin D supplementation requires additional calcium: evidence from a comparative metaanalysis. IOF World Congress on Osteoporosis, Toronto, Canada. June 5, 2006. Accessed online June 15, 2006 at http://www.osteofound.org/wco/2006/downloads/abstracts_iof_wco_2006.pdf
- Boonen S, Malaise O, Neuprez A, Reginster J-Y. P142SA. High prevalence of inadequate serum vitamin D levels in osteoporotic European postmenopausal women. IOF World Congress on Osteoporosis, Toronto, Canada. June 5, 2006. Accessed online June 15, 2006 at http://www.osteofound.org/wco/2006/downloads/abstracts_iof_wco_2006.pdf
- Thorpe DL, Knutsen SF, Rajaram S, Beeson WL, Fraser GE. P111MO. Effects of foods high in protein on risk of wrist fracture over 25 years among peri- and postmenopausal women. IOF World Congress on Osteoporosis, Toronto, Canada. June 5, 2006. Accessed online June 15, 2006 at http://www.osteofound.org/wco/2006/downloads/abstracts_iof_wco_2006.pdf
- Muraki S, Yamamoto S, Oka H, Yoshimura N, Kawaguchi, H, Orimo H, Nakamura K. P187SA. Green tea drinking is associated with increased bone mineral density in elderly women. IOF World Congress on Osteoporosis, Toronto, Canada. June 5, 2006. Accessed online June 15, 2006 at http://www.osteofound.org/wco/2006/downloads/abstracts_iof_wco_2006.pdf.
- IOF World Congress on Osteoporosis. New research clarifies nutritional roles of calcium, vitamin D, and protein in bone health and fracture risk. Toronto, Canada June 5, 2006. Accessed online June 15, 2006 at http://www.osteofound.org/wco/2006/media_centre/20060605_nutrition/20060605_nutrition.doc
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