Dairy calcium, proteins and dietary minerals: All important for maintaining bone health

The association between calcium intake and bone health is well established.1 New evidence supports this association, but also highlights the important role of dairy calcium, as opposed to calcium derived from supplements and other sources, in growing and maintaining healthy bones. This evidence suggests that the consumption of other macro and micro nutrients found in dairy products also plays an important role in the development and maintenance of healthy bones.3-5

In Australia, many patients, particularly adolescent patients, consume less than their average daily calcium requirements.⁶ New evidence suggests some avoid dairy products because they perceive them to be high in fat.^7,8 In avoiding dairy, they are also avoiding the best available source of calcium and increasing their risk of bone problems now and in the future.¹ Thus the new evidence is of great importance to Australian clinicians, as they are now better equipped to proactively educate their patients about the importance of consuming dairy to maintain bone health.

The results of a number of rigorous studies examining the associations between calcium and bone mineral density were published in major journals the last two years. The studies examined a wide range of issues related to calcium and bone health, such as the efficiency of various types of calcium in growing and maintaining bone density,^5,9 the importance of calcium at different points in the lifecycle,^10-12 the role of other micronutrients and proteins in promoting healthy bones^2-5 and the dietary habits of children and adolescents, as well as the factors influencing their consumption of dairy products.^6-8

Higher dairy and protein intake results in higher BMD in kids

A British cohort study assessed the eating patterns of 84 children annually, over a 12 year period, using three day diet records. The children were all 15–17 years old at the end of the study period when their bone mineral content was assessed. Data analysis revealed that children in the high dairy intake group (average of two or more serves per day) had 6% greater bone mineral density than children in the low dairy intake group (less than two serves per day), confirming a long-standing association between adequate dairy intake and healthy bones.⁵

The study also analysed other dietary factors and their association with bone health, finding that high protein intake (i.e. more than 4 serves per day) had an independent positive effect on bone health. Children with the healthiest bones were those with high intakes of both calcium and protein.⁵ The protective effect of protein vis-à-vis bone density was also noted in two Dutch studies. These further suggested that protein derived from dairy products, contributes more bone mineral density than protein derived from other sources (e.g. meat). The authors of these studies suggest that dairy protein better promotes bone mineralisation.^3,4

Potassium from dairy important for bones

There is also evidence that many of the micronutrients found in dairy products (e.g. potassium) play a role in building healthy bones, by aiding the retention of calcium in the body. Potassium has been shown to play an important role in calcium retention and bone growth.² A recent national nutrition survey from the United States showed an association between low dairy and inadequate potassium intake.¹³ Taken together, the results of these two studies indicate that amongst individuals with low dairy intake, calcium is absorbed less efficiently, as their potassium intake is insufficient to facilitate its retention.

Use of calcium supplements

This new evidence demonstrates the additional benefits of dairy sources of calcium. Further study results show that calcium supplements can also play a role in building bones in individuals with low baseline calcium intake.^9,10 The results of a meta-analysis of 21 experimental studies showed that calcium supplements significantly improved bone density in children with low baseline calcium intake, but resulted in no improvement in individuals who already consumed adequate amounts of calcium.⁹

Results of a further experimental study suggest that improvements in bone mineral density from calcium supplementation are short term and do not persist following the withdrawal of supplements. That study noted a significant improvement in bone mineral density after eighteen months treatment in the calcium supplement arm of the trial compared to the placebo arm. Follow-up two years after the withdrawal of calcium supplements revealed no ongoing differences in bone mineral density between the two groups.¹⁰

Aussie adolescents only consume 10–50% calcium RDI

Data for the above-mentioned studies were derived from a number of developed countries. The results are highly applicable to Australia, where significant proportions of the adolescent population consume insufficient calcium. A 2007 national nutrition survey revealed that only half of Australians aged 12–16 consume their estimated average requirement for calcium.⁶ Young Australian girls are even less likely than their male counterparts to consume sufficient calcium.⁶ This is a major health issue – because most bone mass growth occurs in the adolescent years, calcium consumption during adolescence largely determines bone health later in life.¹

The 2007 survey revealed that only 11% of girls aged 12–13 and 18% of girls aged 14–16 consumed adequate calcium, compared to 50% and 56% of boys in the same age groups.⁶ Teenaged girls are under particular pressure to lose weight, as thinness is considered fashionable and many girls are conscious of their body image. Evidence from two Canadian studies suggest that adolescent girls who diet may avoid dairy products because they perceive them to be high in fat, and girls who diet more regularly eat less calcium and dairy.^7,8

Women’s reproductive functions further exacerbate bone health risks. Calcium requirements increase during pregnancy,¹⁴ and the use of hormonal contraceptive pills impacts negatively on bone mineral density.¹¹

Insufficient calcium intake contributes to significant bone health problems. However, consuming adequate calcium is a realistic goal for all Australians, even those who are dieting. Research has demonstrated that weight loss and consuming adequate calcium are not mutually exclusive goals.¹² A large range of low fat dairy products are now available, so consumers can receive their calcium without consuming the fat traditionally found in dairy.

Bone health is a growing public health concern in Australia. Correcting the problem is as easy as eating three serves of dairy per day.

Calcium Intake Calculator

How much calcium do you consume?

Calcium is found in many foods, in particular dairy products and to a lesser degree bony fish, nuts and legumes, fruit and vegetables. It plays an important role in building and maintaining healthy bones and teeth. Individuals need to consume sufficient amounts of calcium throughout their lifespan.  Calcium requirements increase throughout childhood, peak during puberty, then stabilise until an individual is approximately 50 years old, when bone mass deteriorates and more calcium is required.

Click here to calculate your required calcium intake

For more information, see the Dairy Nutrition News March 2009.

Visit the Dairy Australia website for health professionals.

References

1. Weaver CM The role of nutrition in optimizing peak bone mass. Asia Pac J Clin Nut. 2008; 17(Supp 1): 135-7.
2. Lanham-New SA. The balance of bone health: Tipping the scales in favor of potassium-rich, bicarbonate-rich foods. J Nutr. 2008; 138(1): 172-7S.
3. Budek AZ, Hoppe C, Ingstrup H, Michaelsen KF, Bügel S, Mølgaard C. Dietary protein intake and bone mineral content in adolescents – The Copenhagen Cohort Study. Osteoporos Int. 2007; 18(12): 1661-7.
4. Budek AZ, Hoppe C, Michaelson KF, Mølgaard C. High intake of milk, but not meat, decreases bone turnover in prepubertal boys after 7 days. Eur J Clin Nutr. 2007; 61(8): 957-62.
5. Moore LL, Bradlee ML, Gao D, Singer MR. Effects of average childhood dairy intake on adolescent bone health. J Pediatr. 2008; 153(5): 667-73.
6. Commonwealth Scientific and Industrial Research Organisation (CSIRO). 2007 Australian National Children’s Nutrition and Physical Activity Survey: Main Findings [online]. Commonwealth of Australia. 21 October 2008 [cited 7 May 2009]. Available from URL: http://www.health.gov.au/ internet/ main/ publishing.nsf/ Content/ 66596E8FC68FD1A3CA2574D50027DB86/ $File/ childrens-nut-phys-survey.pdf
7. Barr SI. Calcium and body fat in peripubertal girls: Cross-sectional and longitudinal observations. Obesity. 2007; 15(5): 1302-10.
8. Barr SI, Petit MA, Vigna YM, Prior LC. Eating attitudes and habitual calcium intake in peri pubertal girls are associated with initial bone mineral content and its change over 2 years. J Bone Miner Res. 2001; 16(5): 940-7.
9. Huncharek M, Muscat J, Kupelnick B. Impact of dairy products and dietary calcium on bone mineral content in children: Results of a meta-analysis. Bone. 2008; 43(2): 312-21.
10. Lambert HL, Eastell R, Karnik K, Russell JM, Barker ME. Calcium supplementation and bone mineral accretion in adolescent girls: An 18-mo randomized controlled trial with 2-y follow-up. Am J Clin Nutr. 2008; 87(2): 455-62.
11. Teegarden D, Legowski P, Gunther CW, McGabe GP, Peacock M, Lyle RM. Dietary calcium intake protects women consuming oral contraceptives from spine and hip bone loss. J Clin Endocrinol Metab. 2005; 90(9): 5127-33.
12. Thorpe MP, Jacobson EH, Layman DK, He X, Kris-Etherton PM, Evans EM. A diet high in protein, dairy, and calcium attenuates bone loss over twelve months of weight loss and maintenance relative to a conventional highcarbohydrate diet in adults. J Nutr. 2008; 138(6): 1096-100.
13. McGill CR, Fulgoni VL 3rd, DiRienzo D, Huth PJ, Kurilich AC, Miller GD. Contribution of dairy products to dietary potassium intake in the United States population. J Am Coll Nutr. 2008; 27(1): 44-50.
14. National Health and Medical Research Council (NHMRC). Nutrient Reference Values for Australia and New Zealand including recommended dietary intakes [online]. National Health and Medical Research Council, Department of Health and Ageing, Australian Government and Manatu Hauora Ministry of Health, New Zealand. 13 December 2006 [cited 7 May 2009]. Available from URL: http://www.nhmrc.gov.au/ publications/ synopses/ _files/ n35.pdf