Aging Bones
By Rebecca Kirby, M.D., M.S., R.D.
As we get older, a normal part of aging is bone loss. Aging begins after growth stops. For the skeleton, peak bone mass is usually achieved in the middle of the third decade and plateaus for about 10 years. After this point, more bone tissue will be broken down or dissolved than will be rebuilt due to the dynamic nature of bone metabolism. In about 30 minutes of sun on the skin, the body can make approximately 20,000 IU of vitamin D. Healthy bones are constantly remodeling to repair minor injuries and maintain strength. Within the bone, a protein matrix made up of collagen and connective tissue acts like scaffolding on which mineralization takes place. A team of cells called osteoclasts (which dissolve and reabsorb bone) and osteoblasts (which build bone) move along the bone, dissolving and rebuilding. After about our mid-30’s, the balance shifts to more osteoclast activity than osteoblast activity.
There are many factors that influence bone remodeling. Nutritional, genetic, hormonal, metabolic, and structural factors are all involved in the orchestration of bone building and resorption.
The importance of gravity was brought home by the observation that astronauts lost 1 % of bone mass in one week of weightlessness. Muscle contractions and pounding the ground with running or walking stimulate the bone building osteoblasts. In addition, inactivity results in a loss of calcium through excretion from the body.
More than just calcium is needed for bone building; there is whole team of nutrients involved in bone metabolism. Adequate dietary protein is needed for the protein matrix. Vitamin K is required for protein production in the bone, as well as vitamin C, which enhances the synthesis of collagen protein. In a study of 994 women on estrogen and calcium therapy, those who consumed an average of7 50 mg of vitamin C daily had a higher bone mineral density. Good sources of vitamin C are peppers, melons, citrus fruits, papayas, strawberries, and broccoli. Vitamin K comes from dark green leafy vegetables like spinach and Brussels sprouts. A low vitamin K intake is associated with increased incidence of hip fractures. Vitamin K helps to maintain the bone building osteoblasts and works with vitamin D.
Vitamin D has a well-recognized role with calcium in bone mineralization. However, vitamin D has also been associated with better muscle strength and balance. A study found that vitamin D supplementation increased protein synthesis and muscle growth in older women. Although the current RDA for vitamin D is 400 IU daily, an investigation of study results found that people who took 700 to 800 IU daily had a 26% lower risk of hip fractures. Vitamin D is known as the sunshine vitamin; in about 30 minutes of sun on the skin, the body can make approximately 20,000 IU of vitamin D. Other sources are cod liver oil, salmon, sardines, tuna, liver, eggs, and fortified foods like milk and orange juice.
Other vitamins, such as BI2 and folic acid, are necessary for good bone health, and a long list of minerals are all part of healthy bone metabolism. Not only is calcium important but mineralization of the bone also requires phosphorus, magnesium, zinc, copper, manganese, boron, silicon, and strontium.
Strontium may play a role in drawing calcium into the bone. It was found in studies from the 1950’s to relieve bone pain. More recent studies are finding increased bone mineral density and reduced incidence of fractures using strontium ranelate. This form of strontium has a patent pending; however, strontium is available in other forms such as carbonate and citrate.
Being exposed to heavy metals such as aluminum, lead, and cadrnium (in cigarette smoke) can impair good bone mineralization. Other risks for poor bone metabolism include cigarette smoking
and long-term use of many medications, including corticosteroids, dilantin, tranquilizers, furosemide diuretics, antacids, and calcium channel blockers, just to name a few. Recent investigations have revealed that the use of proton pump inhibitors (for acid reflux) and certain antidepressants increase fracture risk. Also, recently published is a study showing that cola consumption (with or
without caffeine) can contribute to low bone mineral density. There are sustained illnesses such as chronic renal failure and chronic obstructive lung disease, celiac disease, liver disease, and rheumatoid arthritis that are causes of osteoporosis.
Many people, primarily women, are confronted with the diagnosis of osteoporosis or osteopenia. These diagnoses are being made in epidemic proportions. Prior to the 1980’s, osteoporosis was considered rare and seen in extreme old age. However, since that time bone mineral density measurements using DEXA scans has become widely accepted.
Why is bone mass important? Osteoporosis is defined as a progressive bone disease with a decrease in the amount of bone required for mechanical support. In other words osteoporosis is about skeletal strength and being at risk of breaking a bone. However, to say that the risk of breaking a bone is associated with bone mineral density is not clear cut. A recent study from The Netherlands
shows that bone mineral density identified only one sixth of fracture risk in women 60 to 80 years of age.
It is critically important to assess other risks to prevent fracture. The goal is not to prevent normal bone loss with aging; the goal is to prevent breaking a bone. The risk of fracture increases with
advancing age, especially with dementia, frail health, and impaired vision, all of which increase the likelihood of falling. Ninety percent of hip fractures are a result of falling. The risk of falling is also increased with heavy alcohol consumption and certain medications which affect balance.
Preventing fractures means preventing falling. To prevent falling, improve strength, balance, and coordination. Avoid medications that affect balance, cause postural hypotension, or alter alertness. Taking more than four medications increases fracture risk. To prevent falling, correct poor vision and improve lighting around the home. Wear shoes; a study found that elderly who walked around in their stocking feet at home were more likely to fall. Get rid of scatter rugs and other trip hazards like lamp wires, and make sure any uneven surfaces such as steps are well marked and lighted. One study reported walking on irregular surfaces, especially uneven sidewalks, is a hazard for tripping and falling. Another study found that sleeping too much increased fracture risk in elderly who sleep more than 10 hours a day.
Minimize your risks not just environmentally but also with what you ingest. Remember the nutrient teamwork approach to bone health with calcium and vitamins D, K, C, B12, folic acid, and minerals phosphorus, strontium, magnesium, zinc, copper, manganese, boron, and silicon. Eat adequate protein and avoid refined foods. Engage in gravity-bearing exercise; improve balance, posture, and strength. Exercise has been statistically proven to prevent hip fractures with twice the reduction rate than that achieved with medication. And while you are out walking, enjoy a little bit of sunshine.
