December 21, 2011
By Marie Spano, M.S., R.D., Contributing Editor
From osteoporosis to osteoarthritis, many people suffer from problems with their bones or joints. One way to maintain strong bones and flexible joints is through proper nutrition, according to the latest research.
Calcium is the top functional ingredient for bone health. When calcium intake drops, the mineral is pulled from the bodys reservoir in bone tissue to maintain normal blood levels of calcium used for heart, muscle and nerve functioning. Over time, this process can lead to porous bone, setting the stage for the brittle bone disease osteoporosis. Though studies have varying results depending on the population examined and baseline calcium intake, a meta-analysis of 29 randomized studies found that calcium only or calcium plus vitamin D supplementation helped prevent bone loss and fracture in adults over age 50 (Lancet, 2007; 370:657-666). In addition, a review of 32 controlled trials found an average supplemental calcium intake of 1,000 mg prevented bone loss in postmenopausal women (Osteoporosis International, 2009;20:2,135-2,143).
Many people, especially females, are falling short on dietary calcium intake. NHANES 2005-2006 data found 28% and 33% of females ages 19 to 30 and ages 31 to 50, respectively, consumed above Adequate Intake (AI) levels set to ensure nutrition adequacy. And, only 8% of women ages 51 to 70 consumed above the AI. Further, NHANES 2007-2008 data reveals average intake for all groups of girls and women over age 6 are falling short on calcium, and males ages 12 to 19 and over 70 are falling slightly short (USDA, Agricultural Research Service (ARS)).
Vitamin D facilitates intestinal absorption of calcium, maintaining adequate blood concentrations of calcium and phosphate, and promoting bone formation and mineralization. Over time, low vitamin D levels can lead to softening of the bones and skeletal deformities. According to the Institute of Medicine (IOM), Washington, D.C., most individuals can meet their vitamin D needs for bone health through food, modest supplemental intake and sunlight, though it is debatable if higher doses of vitamin D are necessary to treat those with osteoporosis (Journal of Clinical Densitometry, 2011; 14(2):79-84). NHANES 2007-2008 data shows many Americans are not meeting their vitamin D needs through food alone, although average blood levels are above the minimum of 20 ng/ml necessary for bone health, indicating that sun exposure may be contributing meaningful amounts of vitamin D. Groups at risk for getting too little vitamin D include older individuals, those living in institutions and not exposed to sunlight, as well as people with dark skin, according to USDA/ARS.
Studies examining supplemental vitamin D and fracture risk are conflicting. However, many studies didnt measure baseline serum vitamin D levels, or only measured these in small subgroups. A meta-analysis of seven randomized trials, with mean ages ranging from 62.4 to 84.7 years, examined vitamin D supplementation with or without calcium and found that 10 and 20 mcg (400 to 800 IU) doses of vitamin D showed no effect on fracture risk, whereas 10 or 20 mcg doses of vitamin D combined with 1,000 mg calcium reduced hip fractures and total fractures (British Medical Journal, 2010; 340:1-8). In children, a meta-analysis of six studies found vitamin D supplementation may be important for raising bone mineral density in children who are deficient in the vitamin, but supplementation wasnt beneficial for children with normal vitamin D levels (British Medical Journal, 2011; 342:1-9).
Two other important minerals for bone health are magnesium and phosphorus, which contribute to the structural components of bone. Though the majority of Americans are meeting their phosphorus needs, USDA/ARS says the average intake of magnesium is low in teens and adults, which may interfere with bone mineralization and increase ones risk of osteoporosis (Journal of the American College of Nutrition, 2009; 28:131-141).
Vitamin K functions as a coenzyme during the synthesis of a number of proteins involved in bone metabolism. However, vitamin K1 and K2 may have different functions in bone tissue according to the Food and Nutrition Board, IOM. Few randomized controlled trials have examined vitamin K2 and bone loss or fracture risk. However, more recent studies show 360 mcg of K2 given to postmenopausal women for 12 months didnt slow bone loss compared to placebo (Osteoporosis International, 2010; 21:1,731-1,740), and 45 mg per day of vitamin K2 given to 325 postmenopausal women for three years had no effect on bone mineral density but increased femoral neck width and attenuated loss of hip bone strength, which decreased significantly in the placebo group (Osteoporosis International, 2007; 18:963-972). A systematic review of randomized controlled trials also found vitamin K1 was associated with a significant reduction in fractures compared to placebo in postmenopausal women with osteoporosis or osteopenia (Health Technology Assessment, 2009; 13(45)).
Inulin may improve bone health by increasing calcium absorption in some, but not all, subjects, indicating that some may be responders" and others non-responders." Eight grams of inulin-type fructans led to significant increases in calcium absorption in 9 to 13 year olds who were responders (identified as having more than 3% increase in calcium absorption), compared to placebo (Journal of Nutrition, 2007; 137:2,524S-2,526S).
In addition to the nutrients mentioned above, several other nutrients are also important for bone mineralization, including zinc, boron, copper, fluoride, manganese, silicon and vitamins C and K, according to NIH Osteoporosis and Related Bone Diseases National Resource Center.
By age 70, almost everyone has some symptoms of osteoarthritis, a joint disorder caused by wear and tear, leading to pain and stiffness. Two compounds, glucosamine and chondroitin sulfate, have been shown to have a protective effect. Both have GRAS status for foods and beverages. A meta analysis of six studies (two on glucosamine and four on chondroitin sulfate) found glucosamine sulfate had a small to moderate protective effect on joint space after three years of treatment, and chondroitin sulfate had a small but significant protective effect on minimum joint space after two years (Rheumatology International, 2010; 30:357-363). The Glucosamine, Arthritis Intervention Trial found 1,500 mg glucosamine combined with 1,200 mg chondroitin sulfate taken daily over 24 weeks was significantly more effective than placebo for decreasing knee pain measured by WOMAC (in addition to secondary outcome measures), whereas celecoxib, glucosamine only and chondroitin sulfate only were not significantly different than placebo in patients with moderate to severe pain (The New England Journal of Medicine, 2006; 354:795808).
In addition to glucosamine and chondroitin sulfate, the omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid have been shown to decrease both inflammation and cartilage degradation in vitro, though clinical trial data is lacking (Arthritis Research & Therapy, 2010; 12:R207). Additional, potentially promising joint-health ingredients on the horizon include tart cherry juice and antioxidants.
Marie Spano, M.S., R.D., CSCS, is a nutrition communications expert whose work has appeared in popular press magazines, e-zines and nutrition-industry trade publications. She has been an expert guest on NBC, ABC and CBS affiliates on the East Coast. For more information, visit mariespano.com.
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