Title: Peak Bone Mass.

Key words: osteoclasts, osteoblasts, osteocytes, mineralisation, calcium, Vitamin D, calciferol, menopause, bone loss, fractures, Vitamin K, caffeine, hypercalciuria, bone mineral density, osteoporosis, oestrogen deficiency,

Date: Sept 2000

Category: The Body

Type: Article

Author: Dr Van Rhijn

Peak Bone Mass.

Introduction

Adult bone health is governed by maximum attainment of peak bone mass (PBM), and bone loss rate with ageing. Skeleton is dynamic, constantly resorbed (osteoclasts) and replaced (osteoblasts), coupled by locally acting communicating cells (osteocytes), under careful control by genetic, hormonal and mechanical factors. Bone ossification (osteoblasts) and mineralisation (Ca) is an extremely complex process where PBM, usually attained during the first 25-30 years, entirely replaced every 7 years, starts to decline between 3-5 years after menopause. This paper reviews the role of nutrition and physical activity in this process of constant remodelling¹, required to maintain the integrity and maximum mechanical skeleton strength (PBM).

Role of Nutrition

Skeleton calcium (Ca=1Kg)², is in equilibrium with plasma Ca (2.25-2.6 mmol/L), and gut absorption (active & passive), enhanced by vitamin D metabolite, calciferol (1.25(OH)₂D₃), in balance with faecal and urine losses³. Numerous factors (intake, absorption, hormones and physiological states) finely regulate Ca plasma pool making it difficult to verify each individual contribution. Various Ca supplementation trials, show positive effects on bone mass^4,5,6,7,8 and skeletal growth^9,10, with a threshold evident above which additional Ca has no further bone gain effects¹¹, although effects may be temporary¹². Postmenopausal Ca supplementation has little effect^13,14, or some effect^15,16 in reducing bone loss, but prevents hip fractures in presence of vitamin D^{17,18,19,20,21}. Vitamin K may have a positive effect on bone development and maintenance through its role in promoting carboxylations of the matrix protein, osteocalcin^22,23.

Caffeine²⁴ and dairy protein (acid producing) has negative effects on bone mineral density by increasing calcium excretion, resulting in more hip fractures^25,26, but does not ally to dairy products^27,28, as phosphorus negates protein induced hypercalciuria²⁹. Potassium bicarbonate benefits skeletal metabolism^30,31 by improving acid-base homeostasis and explaining Ca mobilisation and loss in the elderly. Bone contains magnesium (65% of total body amount)³² and phosphorus (80% of total body amount)³³ which are closely associated with calcium absorption, metabolism and bone density. Other elements such as boron, fluoride, manganese, copper, lithium, molybdenum, silicon and vanadium are concentrated in bone, and although their role is as yet unknown deficiency contributes to osteoporosis. Increased sodium intake may contribute to increased Ca excretion^34,45 and promote bone demineralisation³⁶.

Role of Physical activity

Bone mass regulation (mechanostat model)³⁷ responds to regular weight bearing exercise^38,39,40,41, (increased PBM) and skeletal bone loss occurs in its absence⁴². This positive relationship exists in all ages⁴³, though youth^44,45,46 onset, high impact exercise is more important than Ca intake^47,48 and debatably⁴⁹ provides protection against risk of osteoporosis in later life - as is the case in sports women who have increased bone density⁵⁰.

However, women involved in high intensity physical training risk low bone mineral density. Factors contributing to the failure achieving maximum PBM^51,52 are low body weight (stress / negative energy balance) related amenorrhoea and subsequent hypothalamic ovarian suppression. This oestrogen deficiency suppresses the osteoblasts⁵³, as opposed to osteoclast over activity seen in menopausal women. There is a correlation between energy deficit and reduced bone formation serum markers⁵⁴, making these athletes prone to premature bone loss and stress fractures⁵⁵. The American College of Sports Medicine encourages recognition, prevention and management of this ‘female athletic triad’ of under-nutrition, amenorrhoea and osteoporosis⁵⁶. In contrast, age matched, low body weight gymnasts have a significantly higher bone mass⁵⁷ and further studies are underway to elucidate this observation⁵⁸.

Conclusion

Nutrient intake role on bone health remains undelineated⁵⁹ due to difficulty isolating individual nutrient contributions amongst multi-factorial control on PBM, and requires more research⁶⁰. The COMA Subgroup on Nutrition and Bone Health recommends a healthy lifestyle, with varied, adequate diet and regular weight-bearing activity to achieve PBM and maintain bone health.

Prevention of osteoporosis should begin during pre-pubertal years⁶¹and continue throughout life, but caution against strenuous physical activity in under-nourished sports women, as this could be detrimental to their bone health.

References

1. Ralston, S.H. What determines peak bone mass and bone loss? Baillieres Clin. Rheumatol. 1997; 11, 3: 479 - 494.

2. Smith, R. Clinical Nutrition and bone disease. In: Garrow, J.S & James, W.P. 1996. Human nutrition and Dietetics. Ninth Edition. Churchill Livingstone. Ch. 37. pp. 556 - 566.

3. Fraser, D.R. Vitamin D. Lancet. 1995; 345, 104 – 107.

4. Lloyd, T. et al. Calcium supplementation and bone mineral density in adolescent girls. JAMA. 1993; 270: 814 – 844.

5. Ho, S.C. et al. Determinants of bone mass in Chinese women aged 21-40 years. Patterns of dietary calcium intake and association with bone mineral density. Osteopor. Intern. 1994; 4: 167 – 175.

6. Ramsdale, S.J. Dietary calcium intake relates to bone mineral density in premenopausal women. Br. J. Nutr. 1994; 71: 77 – 84.

7. Matkovic, V. et al. Factors that influence peak bone mass formation: a study of calcium balance and the inheritance of bone mass in adolescent females. Am. J. Clin. Nutr. 1990; 52: 878 – 888.

8. Anderson, J.J. & Rondano, P.A.. Peak bone mass development of females: can young adult women improve their peak bone mass? J. Am. Coll. Nutr. 1996; 15, 6: 570 - 574.

9. Johnston, C.C. et al. Calcium supplementation and increased bone mineral density in children. 1992; 327: 82 – 87.

10. New, S.A. et al. Nutritional influences on bone mineral density: a cross-sectional study in pre-menopausal women. Am. J. Clin. Nutr. 1997; 65: 1831 – 1839.

11. Matkovic, V. & Heaney, R.P. Calcium balance during human growth: evidence for threshold behaviour. Am. J. Clin. Nutr. 1992; 55: 992 – 996.

12. Slemenda, C.W. et al. Bone growth in children following the cessation of calcium supplementation. J. Bone Miner. Res. 1993b; 8 (Suppl.) 1: S154.

13. Dawson-Hughes, B. et al. A controlled trial of the effect of calcium supplementation on bone density in postmenopausal women. N. E. J. Med. 1990; 323: 878 – 883.

14. van Berestein, E.C.H. et al. Relation of axial bone mass to habitual calcium intake and to cortical bone loss in healthy early postmenopausal women. Bone. 1990a; 11: 7 – 13.

15. Reid, I.R. et al. Long-term effects of calcium supplementation on bone loss and fractures in post menopausal women: a randomised controlled trial. Am. J. Med. 1995; 98: 331 – 335.

16. Fardellone, P. Biochemical effects of calcium supplementation in postmenopausal women: Influence of dietary calcium intake. Am. J. Clin. Nutr. 1998; 67, 1273 – 1278.

17. Chapuy, M.C. et al. Vitamin D and calcium to prevent hip fractures in elderly women. N .E. J. Med. 1992; 327, 23: 1637 – 1642.

18. Heikinheimo, R.J. Annual injection of vitamin D and fractures of aged bone. Calcified Tissue Intern. 1992; 51,2: 105 – 110.

19. New, S.A. Bone health: the role of micronutrients. Br. Med. Bull. 1999; 55, 3: 619 - 633.

20. Ooms, M.E. et al. Prevention of bone loss by vitamin D supplementation in elderly women: a randomised double-blind trial. J. Clin. Endocr. Metab. 1995; 80: 1052 – 1058.

21. Dawson-Hughes, B. et al. Effect of calcium and vitamin D supplementation on bone density in men and women 65 years of age or older. New Eng. J. Med. 1997; 337: 670 – 676.

22. Anderson, J.J. et al. Roles of diet and physical activity in the prevention of osteoporosis. Scand. J. Rheumatol. Suppl. 1996; 103: 65 – 74.

23. Shearer, M.J. Vitamin K. Lancet. 1995; 345, 229 – 234.

24. Harris, S.S. et al. Caffeine and bone loss in healthy postmenopausal women. A. J. Clin. Nutr. 1994; 60: 573 – 578.

25. Abelow, B.J. Cross-cultural association between dietary animal protein and hip fracture: a hypothesis. Calcified Tissue Intern. 1992; 51,1: 14 – 18.

26. Hegstead, M. Calcium and osteoporosis. J. Nutr. 1986; 116: 2316 – 2319.

27. Chan, G.M. et al. Effects of dairy products on bone and body composition in pubertal girls. J. Paediatrics. 1995; 126: 551 – 556.

28. Teegarden, D. et al. Previous milk consumption is associated with greater bone density in young women. Am. J. Clin. Nutr. 1999; 69, 5: 1014 - 1017.

29. Heaney, R.P. Nutritional factors in osteoporosis. Ann. Rev. Nutr. 1993; 13: 287 – 316.

30. Lehman, J. et al. Potassium causes calcium retention in healthy adults. J. Nutr. 1993; 123: 1623 – 1626.

31. New, S.A. et al. Association between dietary intake and bone health in post-menopausal and elderly Scottish women. Proc. Nutr. Soc. 1998b; 57: 37A

32. Vitamins, Minerals and Health: Fact File No 3: 1997; National Dairy Council. London.

33. Swaminathan, R. Nutritional factors in osteoporosis. Int. J. Clin. Pract. 1999; 53, 7: 540 - 548.

34. MacGregor, G. A. Salt: blood pressure, the kidney, and other harmful effects. Tony Raine Memorial Lecture. Nephrol. Dial. Trans. 1998; 13: 2471 – 2479.

35. Massey, L.K. & Whiting, S.J. Dietary salt, urinary calcium and bone loss. J. Bone and Mineral Res. 1995; 11, 731 – 736.

36. Devine, A. A longitudinal study of the effect of sodium and calcium intakes on regional bone density in postmenopausal women. Am. J. Clin. Nutr. 1995; 62, 740 – 745.

37. Frost, H.M. The mechanostat: a proposed pathogenic mechanism of osteoporosis and the bone mass effects of mechanical and non-mechanical agents. J. Bone Min. Res. 1987; 2: 73 – 85.

38. Pocock N.A. et al. Mechanical load and the skeleton: the interaction of regional muscle strength, physical fitness and weight with bone mass. J. Bone Min. Res. 1989; 4: 441 – 448.

39. Recker, R.R. et al. Bone gain in young adult women. JAMA. 1992; 268,17: 2403 – 2408.

40. Wolman R.L. et al. Different training patterns and bone mineral density of the femoral shaft in elite female athletes. Ann. Rheum. Dis. 1991; 50: 487 – 489.

41. Krall, E.A. & Dawson-Hughes, B. Walking is related to bone density and rates of bone loss. Am. J. Med. 1994; 96: 20 – 26.

42. Wilmet, E. et al. Longitudinal study of the bone mineral content and of soft tissue composition after spinal chord section. Paraplegia. 1995; 33: 674 – 677.

43. Jonsson, B. et al. Effects of physical activity on bone mineral content and muscle strength in women: a cross sectional study. Bone. 1992; 13: 191 – 195.

44. Ho, S.C. et al. Determinants of peak bone mass in Chinese women aged 21-40 years. III. Physical activity and bone mineral density. J. Bone Miner. Res. 1997; 12, 8: 1262 – 1271.

45. Barr, S.I. & McKay, H.A.. Nutrition, exercise, and bone status in youth. Int. J. Sport Nutr. 1998; 8, 2: 124 – 142.

46. Cooper, C. Childhood growth, physical activity, and peak bone mass in women. J. Bone Miner. Res. 1995; 10, 6: 940 – 947.

47. Welten, D.C. et al. weight-bearing activity during youth is a more important factor for peak bone mass than calcium intake. J. Bone Min. Res. 1994; 9: 1089 - 1096.

48. Friedlander, A.L. et al. A two-year program of aerobics and weight training enhances bone mineral density of young women. J. Bone Miner. Res. 1995; 10, 4: 574 –585.

49. Courteix, D. et al. Effect of physical training on bone mineral density in pre-pubertal girls: a comparative study between impact-loading and non-impact-loading sports. Osteoporos. Int. 1998; 8, 2: 152 – 158.

50. Slemenda, C.W. & Johnston, C.C. High intensity activities in young women: site specific bone mass effects among female figure skaters. J. Bone Min. Res. 1993; 20: 125 – 132.

51. Keay, N. et al. Bone mineral density in professional female dancers. Br. J. Sports Med. 1997; 31, 2: 143 – 147.

52. Bennell, K.L. et al. Skeletal effects of menstrual disturbances in athletes. Scan. J. Med. Sci. Sport. 1997; 7: 261 – 273.

53. Zanker, C.L. & Swaine, I.L. Bone turnover in amenorrhoeic and eumenorrhoeic women distance runners. Scan. J. Med. Sci. Sport. 1998; 8: 20 – 26.

54. Zanker, C.L. & Swaine, I.L. The relationship between biochemical markers of bone turnover and energy balance in young athletic women. Br. J. Sports Med. 1998; 32: 167 – 171.

55. Branca, F. Physical activity, diet and skeletal health. Public Health Nutrition. 1999; 391 – 396.

56. American College of Sports Medicine. Position stand on the female athletic triad. Med. Sci. Sport Exerc. 1997; 29: i-ix.

57. Robinson, T.L. et al. Gymnasts exhibit higher bone mass than runners despite similar prevalence of amenorrhoea and oligomenorrhoea. J. Bone Min. Res. 1995; 10: 26 – 35.

58. New, S. ‘Fit but Fragile’ Are elite sports women at an increased risk of osteoporosis? BNF Nutr. Bullit. 1998; 23, 211 – 214.

59. Rubin, L.A. et al. Determinants of peak bone mass: clinical and genetic analyses in a young female Canadian cohort. J. Bone Miner. Res. 1999; 14,4: 633 – 643.

60. Reid, D.M. & New, S.A. Nutritional influences on bone mass. Proc. Nutr. Soc. 1997a; 56: 977 – 987.

61. Tsukahara, N. et al. Effects of physical characteristics and dietary habits on bone mineral density in adolescent girls. J. Nutr. Sci. Vitaminol. (Tokyo) 1997; 43, 6: 643 - 655.