Ms. Colberg is an exercise physiologist and associate professor of exercise science at Old Dominion University in Norfolk, Virginia. A diabetes researcher with almost four decades of practical experience as a type 1 diabetic exerciser, she is a Fellow of the American College of Sports Medicine, a professional member of the American Diabetes Association, and the author of three books on diabetes.
Editor's Note: You wouldn't buy a house without checking the foundation and support structures to make sure they are sound, so you already know why keeping your bones healthy is so important. As you age, you have to do more to offset the bone loss that begins as early as age 25.
The following is an excerpt from a new book by The Doctor's Senior Living specialist, gerontologist, Dr. John Morley: The Science of Staying Young, 10 Simple Steps to Feeling Younger than You Are in 6 Months or Less, written with Sheri R. Colberg, Ph.D. (McGraw-Hill, 2008). Used by permission.
Healthy bones and joints are crucial to your mobility and extended youthfulness, as well as living a pain-free life as you move around. Some largely effective strategies exist to prevent and limit potential bone problems, no matter what your age is, including adequate calcium and vitamin D intake, regular weight-bearing exercises, avoidance of phosphorus-filled sodas, moderation of protein intake, and in some cases hormone replacement therapies. All of these options for improving bone health will be addressed in this [article], along with how to maintain healthy joints in order to reduce and minimize pain from any arthritis you may develop to help you stay feeling younger than your chronological age.
The term "osteoporosis" was originally coined in the early 19th century, but it wasn't until 1940 that the loss of estrogen in women at menopause was identified as playing a role in its development. It has often been asserted that osteoporosis is actually a pediatric disease because the amount of calcium you ingest during your childhood likely is a major determinant of your bone mineral density later in life. Regardless of when it actually starts, it's undeniably a chronic condition that causes bones to gradually lose their stored calcium, leaving them porous and brittle. Over time, this process of demineralization causes the skeleton to become weaker, and when it reaches a critically low level, bone fractures can occur and recur from seemingly minor impacts.
[O]steoporosis is actually a pediatric disease because the amount of calcium you ingest during your childhood likely is a major determinant of your bone mineral density later in life.
Whereas bone loss occurs over many years, you will likely only become aware of having this condition when fractures are blatant or postural changes are well advanced. For example, repeated, undetected compression fractures in the vertebrae of the spine can lead to stooped posture and backaches, both of which are common characteristics of older women (and some men). Hip fractures resulting from this disease can be immensely debilitating, often signaling the start of a downward trend of reduced strength and a lower quality of life.
All women reaching the age of menopause should have their bone mineral density measured, along with at least one more check at 65 years of age. Since they lag behind, men should ideally have testing done when they reach 65 to 70 years old. The actual diagnosis of osteoporosis is made when you have a bone mineral density that is more than 2.5 standard deviations below the young adult average (a T-score of 1.0 to 2.5). Your bone mineral density should be repeated after two years to determine your rate of bone loss, and the testing should always be repeated at the same time of year, as seasonal changes in bone density are common.
If you avoid milk because of lactose intolerance, the most reliable way to get calcium is to choose lactose-reduced or low-lactose alternative dairy products.
Calcium supplements are certainly one way to ensure adequate intake, but it can also be accomplished through intake of calcium-rich foods (Table 1), which is the preferred method as it can convey other health benefits as well. According to most nutritionists, the best choices are low- or non-fat dairy products. If you avoid milk because of lactose intolerance, the most reliable way to get calcium is to choose lactose-reduced or low-lactose alternative dairy products, such as cheese, yogurt, or lactase-treated milk, or to consume the enzyme lactase before consuming milk products to aid digestion.
On the other hand, others and particularly vegans (complete vegetarians) would argue that many green vegetables have calcium absorption rates of more than 50 percent, compared with about 32 percent for milk, making vegetables a potentially better source. A recent article in the American Journal of Clinical Nutrition reported calcium absorption to be about 53 percent for broccoli, 64 percent for Brussels sprouts, 58 percent for mustard greens, 52 percent for turnip greens, and 40 to 59 percent for kale. Likewise, beans (e.g., pinto beans, black-eyed peas, and navy beans) and bean products, such as tofu, are rich in calcium. About 36 to 38 percent of the calcium in calcium-fortified orange juice is absorbed (as reported by manufacturer's data). Even most fruits contain some calcium, albeit relatively small amounts, as do most nuts and seeds. However, the amount of calcium that can be absorbed from these foods varies, so both calcium content and its bioavailability, shown in Table 1, should be considered. Some plant foods have calcium that is well absorbed, but low in total content per serving.
|Food Source||Calcium Content (milligrams)||Fractional Absorption (%)|
|Cow's milk, 1 cup||250-300||32|
|Most cheeses, 1.5 ounces||305-336||32|
|Yogurt, low-fat, 8-oz container||338-448||32|
|Soymilk, calcium fortified, 1 cup||75-300||24|
|Tofu, medium or firm, 1/2 cup||130 (medium), 258 (firm)||31|
|Pink salmon, canned, with bone, 3 oz||181||27|
|Sardines, Atlantic, in oil, drained, 3 oz||325||27|
|Rainbow trout, farmed, cooked, 3 oz||173||27|
|Ocean perch, Atlantic, cooked, 3 oz||116||27|
|Most canned beans, 1 cup||69-161||17|
|Turnip greens, boiled, 1 cup||198||52|
|Chinese cabbage (bok choy), boiled, 1 cup||158||54|
|Spinach, boiled, 1 cup||244||5|
|Kale, boiled, 1 cup||94||59|
|Mustard greens, boiled, 1 cup||82||58|
|Broccoli, boiled, 1 cup||178||53|
|Brussels sprouts, boiled, 1 cup||56||64|
|Cauliflower, boiled, 1 cup||34||69|
|Navel orange, 1 medium||56||N/A|
|Orange juice, calcium fortified, 1 cup||300||25|
|Almonds, dry roasted, 1 cup||80||21|
Thus, many green leafy vegetables, beans, calcium-fortified soymilk, and calcium-fortified 100-percent juices are equally good (and some are likely superior) calcium sources with advantages that dairy products lack. These alternate foods are excellent sources of phytochemicals and antioxidants, while containing little fat, no cholesterol, and no animal proteins that in excess can actually cause the loss of calcium from bones.
- they contain high amounts of phosphoric acid, which can cause an imbalance between blood levels of calcium and phosphorus, resulting in calcium loss from bones;
- caffeine added in most sodas can additionally mobilize bone calcium.
Ideally, your dietary intake of calcium and phosphate should be balanced equally (1:1), but many people consume up to 15 times more phosphate as it is widely distributed in foods and beverages.
High phosphorus intake may also accelerate the ability of elevated blood glucose levels to damage your body... Thus, there are many good reasons for drinking very limited amounts of phosphate-containing sodas.
The real issue is that a calcium-phosphate imbalance triggers the release of parathyroid, a hormone that causes your bones to release more calcium into your bloodstream, causing loss of this mineral when excess phosphates are consumed over a lifetime. High phosphorus intake may also accelerate the ability of elevated blood glucose levels to damage your body through the formation of advanced glycation endproducts (AGEs) that cause premature aging. Thus, there are many good reasons for drinking very limited amounts of phosphate-containing sodas.
Even higher intakes of protein may increase your bone mineral loss. The effect of excess protein intake on bone health remains unclear, but some studies show that diets that are high especially in animal protein do cause increased losses of calcium in the urine and may even increase fracture risk. These effects may be especially important if your calcium intake is marginal or low. Other studies, however, suggest that a higher protein intake is needed to promote calcium absorption, reduce the risk of fracture, and increase bone density. Until further evidence is available, it would be best for you to meet recommended calcium intakes and to consume adequate (at least 1.2 grams of protein per kilogram of body weight daily to maintain muscle mass), but not excessive, amounts of protein from non-plant sources.
Finally, a final dietary factor in bone health is total sodium intake. Sodium increases calcium losses, with an estimated five to ten mg of calcium lost with each gram of salt eaten. Thus, it is likely that reducing your sodium intake can positively impact your bone mineral content. In general, diets like Atkins that are high in protein and often sodium actually contribute to osteoporosis and are best avoided long-term for this reason, if no other.
Since it's still unlikely that sunlight and food alone will provide sufficient amounts as you get older, you will likely need to supplement with vitamin D. For adults under 50, the usual recommended daily intake is 200 IU, which doubles to 400 IU once you reach 50. The potential youthful effects of having enough of this vitamin are usually underestimated, so we (and others) recommend 800 IU as an optimal daily dose for anyone 50 years of age and older.
Read more in The Science of Staying Young, 10 Simple Steps to Feeling Younger than You Are in 6 Months or Less © 2008 by John E. Morley and Sheri R. Colberg. Reprinted by permission of the authors.