By Felicity Curtain, Accredited Practising
Dietitian
With 99 percent of the body’s calcium found within our
bones, the well-known link between calcium-rich foods and strong bones is
understandable. But calcium does not act alone to strengthen and maintain our
bones, and emerging evidence supports the important role of a balanced diet containing
adequate dietary protein, phosphorus, potassium, magnesium, and zinc, in
promoting strong bones. We delve into the latest evidence on dietary patterns
linked with strong bones in children and adolescents, a critical time for
building bone density.
Healthy bones –
the foundation for a healthy body
Strong bones are vital for protecting internal organs,
providing structural support for daily activities. Failing to achieve peak bone
mass early in life leaves an individual with less reserve to endure the normal
losses that occur with advancing age.
Traditionally, the nutrition focus for bone health has
centred on calcium and calcium-rich dairy products. While calcium does take
centre stage, other individual factors also play essential roles in the
production of healthy bones. These include vitamin D (mostly from sunlight) for
its role in the absorption and utilisation of calcium(1); protein which is a key
constituent of bone tissue and assists in the repair and maintenance of the
skeleton(2); minerals such as zinc,
magnesium, and phosphorus which are important for bone mineralisation, as well
as potassium which promotes an alkaline environment and prevents skeletal
calcium from being mobilised to maintain normal pH levels(3).
With a deeper understanding of the essential role of a
range of nutrients for bone formation and maintenance, the importance of a
balanced diet for optimal bone health is apparent. Indeed, the latest research
on bone health has looked beyond any single food or nutrient to total dietary
patterns that are linked with strong bones.
What does the
latest research say?
Adolescence is a crucial period for bone health and
development, with as much as one-quarter of adult bone mass built over roughly
two years (ages 12-14 for girls, and 13-15 for boys)(4). A recently published longitudinal
study of 1,024 Australians aged 14 and 17 at baseline investigated dietary
patterns during adolescence, and their associations with later bone density.
Through dietary analysis two types of dietary patterns
emerged. Pattern one was considered high-protein,
high-calcium, high-potassium, and was characterised by high intakes of dairy
products, whole grains, legumes; yellow, red, leafy green, and cruciferous
vegetables; steamed, grilled, or canned fish; fresh and dried fruit, and plain
mineral water – reflective of the dietary guidelines. Pattern one was low in soft drinks, chips,
takeaway foods, processed meats, and other discretionary foods.
Conversely, pattern two was high-protein, low-calcium,
and low-potassium, and included high intakes of red meat, poultry, processed
meats; steamed, grilled, canned or fried fish; eggs, and takeaway foods. Pattern two was low in dairy products, fruit,
cake and cookies, whole grains and legumes.
Higher consumption of dietary pattern one, the diet which
reflected a balanced diet at age 14 was associated with higher bone mineral
density at the age of 20, though no observable difference was noted with the
dietary pattern at age 17(5). This suggests that adequate
nutrition through the consumption of a balanced diet during early adolescence
may be more important for bone development, than in late adolescence.
Similarly, a Korean study of school girls aged 9-11 years
compared dietary patterns with subsequent changes in anthropometric measures and
bone mineral density. One hundred and ninety eight girls were included, and
dietary data was categorised into two patterns: ‘egg and rice’ and a more
varied dietary pattern including ‘fruit, nuts, milk beverage, egg and grains’. While the two patterns showed similar results
for change in body mass index and percentage body fat, subjects adhering to the
latter, more balanced dietary pattern, which included a higher intake of dairy
products and grains, had a greater increase in bone mineral density(6).
In both of these studies, it is evident that the dietary
pattern associated with greater bone health, was also linked to higher intake
of calcium rich dairy products. This is not surprising as we know from previous
research that dairy foods themselves (i.e. milk) have a favourable effect on
bone mass(7). However, more recent research
on dietary patterns shows that higher intakes of calcium, as well as other key
nutrients including protein, potassium, magnesium, phosphorous and zinc, found
in foods such as grains and legumes, are also important for bone health(5). To further
substantiate this claim future research should aim to assess the independent effect
of non-dairy based foods, rich in protein, potassium, magnesium, phosphorous
and zinc on bone formation, maintenance and strength.
The take-home
message
These findings re-iterate that it is not single nutrients
or food groups in isolation that promote health and wellbeing, but rather the
complex action and interaction of nutrients and foods obtained through a
balanced diet as a whole.
Given the importance of a balanced diet in early
adolescence for long-term bone health, it is particularly concerning that
adolescents tend to have the least balanced diets, with the highest proportion
of energy intake from nutrient poor discretionary choices (i.e. pizza, pies,
muffins)(8), and the lowest intakes
of nutrient rich whole grains(9). When it comes to grain foods, teenagers should
be encouraged to swap nutrient-poor discretionary foods for healthier core grains,
choosing whole grain more often, as well as a variety of dairy products, fruit,
vegetables (which includes legumes) and lean meat/alternatives, as part of a
balanced diet. Practically, this could be as easy as choosing a whole grain
breakfast cereal with fruit and yoghurt in the morning, opting for whole grain
crackers with cheese for morning tea, and adding legumes into the families
favourite spaghetti Bolognese recipe.
References
1. Bone
Health and Osteoporosis: A Report of the Surgeon General: Office of Surgeon
General; 2004.
2. Peters BS, Martini LA. Nutritional aspects of the prevention
and treatment of osteoporosis. Arq Bras Endocrinol Metabol. 2010;54(2):179-85.
3. Palacios C. The role of nutrients in bone health, from A to
Z. Critical reviews in food science and nutrition. 2006;46(8):621-8.
4. Teens: Healthy Bones Action Week; 2015. Available from: http://www.healthybones.com.au/why-strong-bones/teens.
5. van den Hooven EH, Ambrosini GL, Huang R-C, Mountain J,
Straker L, Walsh JP, et al. Identification of a dietary pattern prospectively
associated with bone mass in Australian young adults. The American journal of
clinical nutrition. 2015.
6. Noh HY, Song YJ, Lee JE, Joung H, Park MK, Li SJ, et al.
Dietary patterns are associated with physical growth among school girls aged
9-11 years. Nutr Res Pract. 2011;5(6):569-77.
7. Du XQ, Greenfield H, Fraser DR, Ge KY, Liu ZH, He W. Milk
consumption and bone mineral content in Chinese adolescent girls. Bone.
2002;30(3):521-8.
8. ABS. Australian Health Survey: Nutrition First Results -
Foods and Nutrients, 2011-12. Australian Bureau of Statistics, 2014.
9. GLNC. 2014 Australian Grains and Legumes Consumption and
Attitudinal Report. Unpublished: 2014.
