Building Better Bone Density
by Mary Sowa
Osteoporosis, known as the
silent epidemic, is a metabolic disease characterized by an excessive
loss of bone mineral mass. Osteoporosis most commonly effects elderly
women. It is estimated that 1.5 million fractures occur each year resulting
in over $10 billion in medical costs. Why is this important? There is
no cure for osteoporosis; prevention is crucial.
Bone mineral mass is continually
formed from infancy to young adulthood. Peak bone mass, the highest
level of bone mineral density accumulated, is achieved by the age of
30. However, most bone density accumulation occurs during the adolescent
growth spurt. Optimizing bone mass accretion will help lessen the risk
of fractures as women age.
There are a number of factors
that influence the attainment of peak bone mass. Heredity accounts for
60 to 80 percent of bone mineral accretion. Nutrition and exercise habits
can be modified to enhance bone mineral density.
The Food and Nutrition Board
of the National Academy of Science released new Dietary Reference Intakes
(DRI) for calcium, phosphorus and vitamin D in August of 1997. All of
these nutrients are important in bone health. Ninety-nine percent of
body calcium is found in the skeleton. Phosphorus is an equally important
mineral in bone density. Vitamin D is a precursor to calcitriol, a hormone
that stimulates calcium absorption and bone remodeling. These new recommendations
reflect the latest research in relation to optimizing bone density.
Calcium is of particular concern because of the diminished intake seen
in adolescents. Recent studies have revealed that teens are only consuming
~800 mg calcium/day compared to the new recommendation of 1300 mg/day.
Teens, especially females, start to shy away from dairy products at
this time as they tend to choose more empty calorie beverages.
Another modifiable factor
that enhances bone density is weight bearing exercise. Weight bearing
exercise provides mechanical loads to the skeleton that helps stimulate
bone mineralization. Gymnastics is an example of a weight bearing exercise
that can improve bone mineral density.
There are a number of published
studies that demonstrate this effect. Investigators from Children's
Hospital Medical Center, Cincinnati, Ohio, examined bone mineral density
(BMD) in females 7-9 years of age. The investigators compared BMD of
14 gymnasts, 14 swimmers and 17 control subjects. The gymnasts were
either level 5 or 6 competitors and the swimmers were either synchronized
or speed swimmers. The control subjects were not involved in sports
on a year around basis. Total body BMD was significantly greater in
the gymnasts than the other two groups.
Investigators from the Department
of Kinesiology and the Department of Nutrition and Food Sciences from
Texas Woman's University examined BMD in college-aged females. Bone
mineral density was measured in 11 gymnasts and 11 control subjects.
Bone mineral density (lumbar and femoral neck regions) was found to
be significantly higher in the gymnasts than the controls. These are
only two examples of a number of studies that show the positive effects
of gymnastics. The mechanical loads of gymnastics, result in higher
BMD in females at a variety of ages.
The nutrition and exercise
habits of pre-adolescent and adolescent females can affect their ability
to achieve peak bone mass. Gymnasts are involved in a sport that enhances
BMD. Emphasizing the importance of a diet adequate in calcium, along
with other nutrients, will help optimize the accretion of bone mineral
density. The following is provided as a handout for your gymnasts to
assess their calcium intake. If you do not cover nutrition on a regular
basis at your gym, consult the USA Gymnastics Referral Network (list
can be found on www.usa-gymnastics.org/wellness/) for a Registered Dietitian
in your area or contact the American Dietetic Association for an appropriate
referral.
References:
- Nutrition & the M.D., Vol. 22, No. 7, July 1996.
- Nichols, et al., The effects of gymnasts training on bone mineral
density. Medicine and Science in Sports and Exercise, Vol.
26, No. 10, pp. 1220- 1225, 1994.
- Cassell, et al., Bone mineral density in elite 7- to 9-yr-old female
gymnasts and swimmers. Medicine and Science in Sports and Exercise,
Vol. 28, No. 10 pp. 1243-1246, 1996.
- Food and Nutrition board, Institute of Medicine, (1997). Dietary
reference intakes: Calcium, phosphorus, magnesium, vitamin D and fluoride.
Washington DC: National Academy Press.
Why should calcium be important
to you?
FUNCTIONS:
- Essential for building
strong bones and teeth.
- Helps muscles contract
and relax during gymnastics practice and other activities.
- Helps cuts and scrapes
to stop bleeding.
CALCIUM CONTENT IN FOODS:
| High Calcium Foods
|
Medium Calcium Foods |
300 mg/serving
1 cup milk
1 cup yogurt
1 cup reduced lactose milk
(ex. Lactaid milk)
1 cup pudding |
200 mg/serving
1 cup lactose free drink (ex. Vitamite or Edensoy Extra)
1 cup calcium fortified orange juice
2 slices American cheese
1 cup cottage cheese
1 cup ice cream
4 oz. salmon
1 cup kidney beans
1cup tofu with calcium |
* Note: 2 cups cooked
broccoli or 1-1/2 cups cooked spinach has about 200 mg of calcium, so
it takes a lot of vegetables to get enough calcium. (Vegetables also
have substances called oxalates and phytates which bind calcium, so
it isn't absorbed as well.)
* Calcium is better absorbed
with vitamin C, which is found in citrus fruits, (ex. oranges, grapefruits,
strawberries, lemons and tomatoes.)
How much calcium do you need
each day?
DRIs (Dietary Reference Intakes)
are:
- Ages 4-8 - 800 mg/day
- Ages 9-13 - 13000 mg/day
- Ages 14-18 - 13000 mg/day
- Ages 19-30 - 1000 mg/day
Take a minute to write down what
you ate for breakfast, lunch, dinner and snacks yesterday. Add up the
amount of calcium you consumed. Are you reaching your target? If you do
not reach your target on a daily basis, talk to you doctor or registered
dietitian to see if a calcium suppliment is rignt for you. Calcium
supplements:* The amount of calcium varies in each tablet so check
the labels. Calcium citrate is a fairly common form of calcium and is
likely better absorbed than calcium carbonate suppliments.
Here are a few sports nutrition
websites:
American College of Sports Medicine
www.ascm.org
American Dietetic Association www.eatright.org
Gatorade Sports Science Institute http://gssiweb.com
National Strength & Conditioning Association www.ncsa-lift.org
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