|Bone Loss Prevention|
Physical activity that provides some strain or stress on bones provokes the bones to retain and possibly even gain density all the way through your life. Cells within the bone feel this stress and react by making the bone stronger and denser. These “weight-bearing” exercises include walking, dancing, jogging, weightlifting, stair-climbing, racquet sports, and hiking.
As for the swimming, it is a useful form of exercise for the heart and cardiovascular system. But as water supports the bones, rather than putting stress on them, it's not considered a good "weight-bearing" exercise for bone strength. Besides, physical activity doesn't make stronger all bones, just those that are stressed, so you need a variety of exercises or activities to keep all your bones healthy.
One more function of physical activity, almost certainly at least as important as its straight effect on bone mass, is its role in increasing muscle strength and coordination. With greater muscle strength, one can often avoid falls and situations that lead to fractures. Making physical activity a habit can help keep up balance and avoid falls.
In spite of the discussions nearby milk and calcium, one thing is obvious: adequate calcium - both for bone development and for non-bone functions - is key to lowering the risk of osteoporosis. On the other hand, the healthiest or safest amount of dietary calcium hasn't yet been established. Different scientific approaches have yielded different estimates, so it's important to consider all the evidence.
Balance studies suggest that a sufficient intake is 550 mg/day. To make sure that 95% of the population gets this much calcium, the National Academy of Sciences established the following recommended intake levels:
- 1,000 mg/day for those age 19-50;
- 1,200 mg/day for those age 50 or over;
- 1,000 mg/day for pregnant or lactating adult women.
But for the most part balance studies are short-term and for that reason have significant limitations. To distinguish how the body adapts to different calcium intakes over a long period of time requires studies of longer duration.
The results from such long-term studies may be astonishing to some. While they do not question the importance of calcium in maximizing bone strength, they cast doubt on the value of consuming the large amounts presently recommended for adults.
These studies suggest that high calcium intake doesn't really come out to lower a person's risk for osteoporosis. For instance, in the large Harvard studies of male health professionals and female nurses, individuals who drank one glass of milk (or less) per week were at no greater risk of breaking a hip or forearm than were those who drank two or more glasses per week. Other studies have found similar outcome.