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Bone Health in Young Women

Concern for Bone Health in Young Women: A synergy between nutrition and exercise.

By Jacinta King

On a daily basis do you drink 3.5 cups of milk? Eat 7 slices of cheddar
cheese or 2 tubs of yoghurt? What about if you do not like dairy products? If
this is the case do you consume 333 almonds, 300g of canned sardines or 1kg of
bok choy in an average day? Chances are that majority of women reading this
article said no to each of those questions! The most recent national nutrition
survey conducted by the Australian Bureau of Statistics (ABS) found that on
average the calcium consumption of each age group of women fell significantly
below the recommended daily intake (RDI).
On average, young women (19-30 years of age) are only consuming 643mg of
calcium/day when the RDI for this age group is 1000mg/day[ii].
Therefore most young women are falling short of approximately 400mg of calcium
each day! So why is this a problem? Well, it is fairly common knowledge now
that low levels of calcium lead to a much greater risk of developing
osteoporosis, with women being at an even greater risk (approximately five
times higher than men[iii]) due to a decrease in the hormone oestrogen with menopause. But why should a young healthy 20-year old female be worried about the effect of menopause,
which is approximately another 30 years down the track for them? Because their
physiological clock for building bone is ticking faster and faster as time is
running out each day! Research has shown that men and women have up until approximately the age of 30 to maximise bone mass, as from this age onwards our bone density naturally begins to decline at a rate faster than we can increase it[iv]. Therefore ideally all young adults, especially young women, should be spending
their younger years working towards reaching this peak bone mass so when it
starts to decline with age and menopause, they would have started with a lot
more ‘bone in the bank' and therefore delay musculoskeletal disease such
as osteoporosis. Multiple research studies have shown that the best way of achieving a high peak bone mass is through an adequate intake of calcium and vitamin D, in conjunction with participation in weight bearing exercise ^{ii, iv, [v]:}

• Bones are made from calcium so to ensure good bone health young women should be aiming for 1000mg per day[vi]. The richest sources of calcium come from dairy products. Clearly young women are struggling with obtaining 1000mg/day so trying out some of the
       advice below may benefit you: 
  • Try making a Smoothie - use reduced fat milk + a tub of reduced fat yoghurt and add
          your favourite fruits such as berries. This is an easy way of obtaining up
          to nearly ½ your daily intake at one meal, and is great for people who
          struggle with drinking plain milk or getting through a tub of yoghurt.  
  • For a mid meal snack try having crackers with reduced fat cheese teamed with other
          nutritious toppings such as tomato and avocado. 
  • Try swapping from toast for breakfast to a calcium fortified breakfast cereal,
          in which you can add reduced fat milk. Or for a more convenient breakfast
          try a sanitarium ‘up and go' popper. 
  • Try eating your daily fruit serves mixed in with a reduced fat yogurt, or try
          yoghurt and muesli as a filling mid meal snack. 
  • Where possible, choose calcium-fortified products. 
  • Add spinach and tofu to main meals where possible e.g. in a salad or stir-fry
          etc.
     

Obtaining calcium through food sources rather than supplements is better, as food
provides other nutrients that keep you healthy. Relying 100% on calcium
supplements should be avoided. If you are lactose intolerant try lactose free
versions of dairy products such as lactose free milk, yoghurt, cheese and
ice-cream. Or if you do not like dairy products try a combination of
supplementation with non-dairy calcium sources such as canned salmon with
bones, bok choy, broccoli, sardines and calcium fortified juices and cereals.
Another thing to remember: many young women fail to get enough calcium due to
chronic dieting. As mentioned above the best sources of
calcium come from dairy products which are typically associated as being ‘high
fat' products and therefore usually some of the first foods to be cut out of
the diet. Young women should be reminded that you can buy reduced fat dairy
products such as skim milk, extra light cheese and reduced fat yoghurts that
are low in energy whilst also containing protein which will help to keep you
fuller for longer, and therefore actually a good option for people trying to
lose weight.
 

• Ensure adequate vitamin D intake, which helps the body absorb the calcium from the food
       you eat. Vitamin D is produced in your skin when it is exposed to
       sunlight. You need 10-15 minutes of sunlight to the hands, arms and face,
       two to three times a week to make enough vitamin D[vii].
  
• Participate in weight bearing activity on a regular basis (at least 2-3 times per week
       for 30 minutes)[viii]. Our bones are constantly remodelling themselves to adapt to the forces they experiences[ix]. If the bone is not used i.e. the forces it experiences decrease (e.g. in extended bed rest), bone breakdown increases^ix. If bone is
       exposed to forces stronger than those experienced in normal daily living
       they will adapt by taking up more calcium and building more bone, so that
       it can withstand the increased forces^ix. Therefore, to build
       bone and subsequently increase your bone mineral density (BMD), you need
       to expose your bone to stronger loads than that experienced in normal
       daily living.
  

Many government websites claim that weight bearing activities such as walking,
running and dancing are good for bone health. This is where some controversy
lies. Yes, these activities are good for increasing BMD in a sedentary person
and maintaining BMD in more active people, because they are weight-bearing
activities. However, these activities are not necessarily exposing your bones
to loads greater than that experienced in activities of daily living, which we
know from research are required to stimulate bone growth. For example, if you
were to go for a run everyday, how are the forces experienced on one day any
larger to the forces experienced on another day?

Research has shown that the stronger you are (i.e. the bigger your 1RM), the stronger
your bones are[x], which is why resistance training is one of the best ways to increase
your BMD. As strength has been proven to be correlated with a higher BMD, you
can tailor a resistance training program designed for bone strength to increase
1RM strength as much as if safely possible. Studies have shown that
light loads less than 60%1RM performed at slow to moderate movement speeds are
not sufficient enough to increase BMD[xi]. Rather, loads of at least 70%1RM appear to be required for an increase in BMD to occur[xii]. Remember that the whole idea of a bone health program is to prevent osteoporotic fractures etc in the future, so a key part of any bone health exercise program should be to load the bones most prone to osteoporotic fractures in old age[xiii]! This includes the spine, femur, radius, ulna, humerus, clavicle and hip. Therefore exercises such as the squat, deadlift, bench press, dips and push ups should all be considered^xiii.

Some recent studies have also found that resistance training with rapid rates of
force development is of greater value than conventional lifting (i.e. power
training)^{xiii [xiv]}. This opens the door for developing a program, which has a
combination of strength and power exercises^xiv. Lifting weights are stereotypically seen as a ‘male activity' but young women should be heavily encouraged to participate in a full
body resistance training program as this will also have great benefits on
muscle development as well.

Still not into weight lifting? Some studies have shown plyometric programs to have an
even more positive effect than conventional resistance training. This fits with
the research showing that bones respond to rapid changes in load more so than
to large constant loads. However, some studies have found no impact with
plyometrics, and the research is still limited. The key most important thing to
remember here is that to build bone you have to expose yourself to
stronger forces. If you do the same thing every day chances are you are not
causing enough of a stimulus for bone growth!

• For those women who may already been participating in a full body resistance training program, and religiously consume protein to enhance muscle mass, it is important to
       keep in mind that high dietary protein has been positively associated with
       an increase in calcium excretion via urination. For every 50g increase in
       dietary protein, a 150mg increase in urinary calcium excretion is possible[xv].
       Therefore high protein eaters need to be especially careful about
       consuming the recommended calcium intake.
   

Therefore, the importance of the combination between calcium
and weight bearing exercise is obvious. Weight bearing exercise is required as a
stimulus to build bone - in the absence of activity, extra calcium has a
limited impact^ix. Conversely, calcium is a required component of
bone - in the absence of calcium, additional bone cannot be formed, regardless
of the level of activity^ix. Young women must realise this synergy between
nutrition and exercise and that what they do now can have serious
effects on their health long term. Just because we cannot see our bones
does not mean they are not suffering. Nutrition and exercise are key to
achieving optimal peak bone mass; without this combination optimal peak bone
mass is severely compromised and will no doubt result in osteoporotic related
problems later in life. It is time to start being actively aware of your
calcium intake and start moving sooner rather than later, because remember...time
is ticking!!

Australian Bureau of Statistics (1997, December 22). National
Nutrition Survey: Selected Highlights, Australia, 1995. Australian Bureau of
Statistics. Retrieved October 19, 2011, from http://www.abs.gov.au/ausstats/abs@.nsf/mf/4802.0

[ii] Peterlik, M., Boonen, S., Cross, H. S., & Lamberg-Allardt, C.
(2009). Vitamin D and Calcium Insufficiency-Related Chronic Diseases: an
Emerging World-Wide Public Health Problem. International Journal of
Environmental Research and Public Health, 6(10), 2593.
doi:10.3390/ijerph6102585 Retrieved from
http://www.mdpi.com/1660-4601/6/10/2585/

[iii] Australian Bureau of Statistics (2006, September 28). Musculoskeletal
Conditions in Australia: A snapshot, 2004-2005. Australian Bureau of
Statistics. Retrieved October 19, 2011, from
http://www.abs.gov.au/ausstats/abs@.nsf/mf/4823.0.5

[iv] NIH Consensus Development Panel on Osteoporosis Prevention, Diagnosis,
and Therapy (2001). Osteoporosis Prevention, Diagnosis, and Therapy. Journal
of the American Medical Association, 285(6), 788-789.
doi:10.1001/jama.285.6.785 Retrieved from
http://jama.ama-assn.org.ezp01.library.qut.edu.au/content/285/6/785.full.pdf+html

[v] Dieitians Association of Australia (2010). Calcium Supplements and
Heart Disease Risk. Dietians Association of Australia. Retrieved October
21, 2011, from
http://daa.asn.au/for-the-media/hot-topics-in-nutrition/calcium-supplements-and-heart-disease-risk/

[vi] National Health and Medical Research Council (NHMRC) (2005, September
09). Nutrient Reference Values for Australia and New Zealand Including
Recommended Dietary Intakes. National Health and Medical Research Council.
Retrieved October 21, 2011, from
http://www.nhmrc.gov.au/_files_nhmrc/publications/attachments/n35.pdf

[vii] Stewart, R. (2009). Nutrient Requirements. In Griffith Handbook of
Clinical Nutrition and Dietetics. (3rd ed.). Southport, Queensland.

[viii] American College of Sports Medicine (2007). Guidelines for healthy
adults under age 65. American College of Sports Medicine. Retrieved
October 21, 2011, from
http://www.acsm.org/AM/Template.cfm?Section=Home_Page&TEMPLATE=/CM/HTMLDisplay.cfm&CONTENTID=7764

[ix] Barr, S. I. (2001). Nutrition and physical activity: Why we must move
from a casual acquaintance to a lifelong partnership. Canadian Journal of
Dietetic Practice and Research , 62(3), Retrieved from
http://search.proquest.com.ezp01.library.qut.edu.au/docview/220818964/fulltext/1328106CE311046525E/1?accountid=13380

[x] Tsuzuku, S., Ikegami, Y., & Yabe, K. (1998). Effects of High-Intensity
Resistance Training on Bone Mineral Density in Young Male Powerlifters. Calcified
Tissue Internation, 63(4), 284-285. doi:10.1007/s002239900527
Retrieved from
http://www.springerlink.com.ezp01.library.qut.edu.au/content/hafnnr2v1c948haf/fulltext.pdf

[xi] Maddalozzo, G. F., & Snow, C. M. (2000). High Intensity Resistance
Training: Effects on Bone in Older Men and Women. Calcified Tissue
International, 66(6), 401-404. doi:10.1007/s002230010081 Retrieved
from http://www.springerlink.com.ezp01.library.qut.edu.au/content/1cdcvna0wm70n0dy/fulltext.pdf

[xii] Vincent, K. R., & Braith, R. W. (2002). Resistance exercise and
bone turnover in elderly men and women. Medicine and Science in Sports and
Exercise, 34(1), 17-23.

[xiii] Shield, A.
(2010). HMB282 Resistance Training: Adaptations to Resistance Training [Lecture
Notes]. Retrieved from
http://blackboard.qut.edu.au/webapps/portal/frameset.jsp?tab_tab_group_id=_2_1&url=%2Fwebapps%2Fblackboard%2Fexecute%2Flauncher%3Ftype%3DCourse%26id%3D_63214_1%26url%3D

[xiv] Kerri, W. M., & Christine, S. M. (2000). Body Composition Predicts
Bone Mineral Density and Balance in Premenopausal Women. Journal of Women's
Health and Gender-Based Medicine, 9(8), 866. Retrieved from
http://www.liebertonline.com/doi/pdf/10.1089/152460900750020892

[xv] Giskes, K.
(2009). PUB405 Nutrition Science: Calcium (macromineral) [Lecture Notes].
Retrieved from:
http://blackboard.qut.edu.au/webapps/portal/frameset.jsp?tab_tab_group_id=_2_1&url=%2Fwebapps%2Fblackboard%2Fexecute%2Flauncher%3Ftype%3DCourse%26id%3D_43660_1%26url%3D