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 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 thisarticle said no to each of those questions! The most recent national survey conducted by the Australian Bureau of Statistics (ABS) found that on average the calcium consumption of each age group of women was significantly lower than the recommended daily intake (RDI)
(i).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 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 older women are at even greater risk. But why should a young healthy 20-year old female be worried about the effect of menopause, which is approximately another 30 years away? Because their physiological clock for building bone 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
- Bones are made from calcium so to ensure good bone health young women should be aiming for 1000mg per day. 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 increasesix. 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 forcesix. 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 personand 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?
PIC: Dexa Scan
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 increaseyour 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 consideredxiii.
Some recent studies have also found that resistance training with rapid rates of force development is of greater value than conventional lifting (i.e. powertraining)xiii (xiv). This opens the door for developing a program, which has a combination of strength and power exercisesxiv. Lifting weights are stereo typically seen as a ‘male activity' but young women need to participate in full body resistance training programs. 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 do 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 than you are used to. 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 impactix. Conversely, calcium is a required component ofbone - in the absence of calcium, additional bone cannot be formed, regardless of the level of activityix. 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. Fitnance resistance training sessions are a great way of improving bone density. Refer to our fitness class timetable,
If you are concerned about bone density, a DEXA scan will accurately tell you your bone density. see your GP for a referral.
(i) Australian Bureau of Statistics (1997, December 22). NationalNutrition Survey: Selected Highlights, Australia, 1995. Australian Bureau ofStatistics. 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: anEmerging World-Wide Public Health Problem. International Journal ofEnvironmental Research and Public Health, 6(10), 2593.doi:10.3390/ijerph6102585 Retrieved fromhttp://www.mdpi.com/1660-4601/6/10/2585/
(iii) Australian Bureau of Statistics (2006, September 28). MusculoskeletalConditions in Australia: A snapshot, 2004-2005. Australian Bureau ofStatistics. Retrieved October 19, 2011, fromhttp://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. Journalof the American Medical Association, 285(6), 788-789.doi:10.1001/jama.285.6.785 Retrieved fromhttp://jama.ama-assn.org.ezp01.library.qut.edu.au/content/285/6/785.full.pdf+html
(v) Dieitians Association of Australia (2010). Calcium Supplements andHeart Disease Risk. Dietians Association of Australia. Retrieved October21, 2011, fromhttp://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, September09). Nutrient Reference Values for Australia and New Zealand IncludingRecommended Dietary Intakes. National Health and Medical Research Council.Retrieved October 21, 2011, fromhttp://www.nhmrc.gov.au/_files_nhmrc/publications/attachments/n35.pdf
(vii) Stewart, R. (2009). Nutrient Requirements. In Griffith Handbook ofClinical Nutrition and Dietetics. (3rd ed.). Southport, Queensland.
(viii) American College of Sports Medicine (2007). Guidelines for healthyadults under age 65. American College of Sports Medicine. RetrievedOctober 21, 2011, fromhttp://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 movefrom a casual acquaintance to a lifelong partnership. Canadian Journal ofDietetic Practice and Research , 62(3), Retrieved fromhttp://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-IntensityResistance Training on Bone Mineral Density in Young Male Powerlifters. CalcifiedTissue Internation, 63(4), 284-285. doi:10.1007/s002239900527Retrieved fromhttp://www.springerlink.com.ezp01.library.qut.edu.au/content/hafnnr2v1c948haf/fulltext.pdf
(xi) Maddalozzo, G. F., & Snow, C. M. (2000). High Intensity ResistanceTraining: Effects on Bone in Older Men and Women. Calcified TissueInternational, 66(6), 401-404. doi:10.1007/s002230010081 Retrievedfrom http://www.springerlink.com.ezp01.library.qut.edu.au/content/1cdcvna0wm70n0dy/fulltext.pdf
(xii) Vincent, K. R., & Braith, R. W. (2002). Resistance exercise andbone turnover in elderly men and women. Medicine and Science in Sports andExercise, 34(1), 17-23.
(xiii) Shield, A.(2010). HMB282 Resistance Training: Adaptations to Resistance Training (LectureNotes). Retrieved fromhttp://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 PredictsBone Mineral Density and Balance in Premenopausal Women. Journal of Women'sHealth and Gender-Based Medicine, 9(8), 866. Retrieved fromhttp://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
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