The Essentials of Bone Health
Beyond the formative structure, the skeleton serves, bone is dynamic and metabolically active.1 It provides support for the movement, muscles of varying length and strength are attached to this, and it provides a framework of protection for the internal organs. Bone is under constant regulation by hormones ( Parathyroid hormone, calcitriol, and estradiol ) and undergoes constant remodeling, where the old or damaged bone is replaced by new bones formed by special cells called osteoblasts.2 Among its physiologically important functions include the production of bone marrow and cells essential for hematopoiesis and it acts as a reservoir for the storage of calcium and phosphate.1 It’s interesting to know that as adults, we have less of the number of bones that were being born with. An adult human skeleton has 206 bones while a newborn has 270 bones!
Recognizing these important characteristics leads us to consider bone health with better focus. The attainment of peak bone mass in the second decade of life is the key to ensuring that throughout the life stages, the inevitable loss of bone mass with aging does not lead to the risk of early onset of osteoporosis. This structural deterioration called osteoporosis causes the bones to be fragile and puts an individual at an increased risk of fractures. Inadequate dietary intake, lack of exercise and sun exposure, and intake of certain medications like glucocorticoids increase bone fragility. The risk of osteoporotic fractures increases with age. Women > 50 years old are an especially vulnerable cohort.3 A 0.13% per year bone loss in a premenopausal woman increases to 2.5% per year after menopause, particularly spine bone mineral density.3. Understanding this natural progression calls for fortifying and preventive measures to begin as early as the second decade of life, the period where there is a window for maximal bone mass accrual. The strategy towards achieving this peak bone accrual is largely influenced by diet and exercise.
The calcium needs for the different age groups is a requirement that must be fulfilled to enhance bone mineral deposition. Maintaining adequate calcium intake during childhood is necessary for the development of maximal peak bone mass and the reduction of the risk of osteoporosis in later adulthood.4,5 It has been reported that about 40-60% of adult bone mass is obtained during adolescence.6
The Calcium RDA for pre-adolescents and adolescents aged 9 through 18 years is 1300 mg/d.6 It is of importance to consistently promote dietary preferences that would approximate adequate calcium intake in this age group. 7
Establishing dietary patterns that are rich in Calcium necessitate knowledge of Calcium-rich foods. 15
Exercise strengthens muscles and reinforces bone strength. Strategies to maximize benefit from exercise would be to plan for a high impact, low-frequency exercise like walking, dancing, running, jumping, skipping, and hopping for 10 minutes, 3x a week.6 Welten et al showed in a large Dutch cohort of children that regular weight-bearing activity had a greater influence on peak bone mass than dietary calcium.8 Thereby, promoting a calcium-rich diet and encouraging regular exercise are complementary strategies for laying down a strong foundation of bone health.
Exposure to UVB radiation in the range of 290-315 nm from sunlight is the major source of Vitamin D. Exposure of arms and legs to 0.5 minimal erythemal doses of sunlight for 5 to 15 mins, 2-3 x a week, produces approximately 3000 IU of Vitamin D. Natural dietary sources are limited but include cod liver oil, fatty fish (eg. salmon, sardines and tuna) and fortified foods.6
After achieving this peak bone mass at the second decade of life, and as the individual ages subsequently there is a slow progression towards increasing fracture risk. Particularly for women, estrogen deficiency has been well established as a cause of bone loss. 3. Even after peak bone mass has been achieved, the bone undergoes constant remodeling. Thereby the need to maintain normal calcium and Vitamin D homeostasis is necessary throughout adulthood.
The Calcium and Vitamin D RDA for adults are as follows:5,9,10
The need for Calcium and Vitamin D supplementation arises when there is limited availability of calcium-rich foods or whereby cultural preference influences dietary habits, resulting in limitation of choices. Calcium and Vitamin D are under-consumed dietary nutrients.5 Weaver et al reports that if only relying on food intake, 38% consume inadequate levels of Calcium and 98% consume inadequate levels of Vitamin D. It may be easier to circumvent the reported inadequacy for Vitamin D as this is naturally produced in the skin in response to sunlight but this may be limited by climate, time spent outdoors, choice of clothing, skin pigmentation and use of sunscreen.11
For both adolescents and adults, there is a consensus that maximizing dietary sources to achieve the recommended dietary requirements for Calcium and Vitamin D is the most appropriate strategy.11 However, it must be recognized that a gap may exist for individuals who are:
- Following a vegan diet
- Lactose intolerant
- Consuming large amounts of protein or sodium, which causes the body to excrete more calcium
- Receiving long-term treatment with corticosteroids
- Suffering from certain bowel or digestive diseases that decrease your ability to absorb calcium, such as inflammatory bowel disease or celiac disease
The value of Calcium and Vitamin D supplementation needs to be identified by a health provider who will evaluate, advise and provide the necessary dosage and formulation. Supplements bridge the identified gap in dietary intake. However, care must be made in ensuring that intake should not exceed 2000 mg of Calcium per day and 4000 IU of Vitamin D day.5,12 Recognizing the interlinked role of Calcium and Vitamin D, available supplements in combination allow ease of intake and better compliance. Especially for those populations at high risk for Osteoporosis ( Postmenopause, history of Glucocorticoid intake, history of fall )13, a decision for Calcium and Vitamin D supplementation may be prudent and should be made with the guidance of a health care professional.14
Across the life stages, a well-balanced diet that includes calcium-rich sources to the approximate dietary requirement is recommended. Together with an exercise regimen that befits the age, maintenance of adequate sun exposure, avoidance of smoking, caffeine, and alcohol intake constitutes lifelong healthy habits that support bone health.
REFERENCES:
1 Graboski, P. Physiology of Bone. Endocr Dev.2015
2 El Sayed, SA et al. Physiology, Bone.In:StatPearls.2020
3 Lentz et al. Comprehensive Gynecology, 6th ed
4 National Institutes of Health Consensus Conference. NIH consensus development panel on optimal calcium intake. JAMA. 1994
5 Weaver CM and Miller GD, Required versus optimal intakes: a look at calcium. J Nutr. 1994
6 Golden NH, Abrams SA. Committee on nutrition optimizing bone health in children and adolescents. Pediatrics. 2014.
7 American Academy of Pediatrics.Calcium requirements of Infants, Children, and Adolescents. Pediatrics, 1999.
8 Welten et al.Weight-bearing activity during youth is a more important factor for peak bone mass than calcium intake. J Bone Miner Res.1994.
9 Rosen, H. Patient education: Calcium and Vitamin D for Bone Health. Beyond the Basics.UpToDate.2019
10 Li, K et al. The Good, the bad and the ugly of calcium supplementation: a review of calcium intake on human health.Clinical Interventions in aging. 2018.
11 Heravi, A and Michos, E. Vitamin D and Calcium Supplements: Helpful, Harmful or Neutral for Cardiovascular Risk. Methodist Debakey Cardiovasc. 2019
12 Jennings, K.Healthline.2018
13 Reid, I and Bolland, M.Calcium and/or Vitamin D supplementation for the Prevention of Fragility Fractures: Who Needs It? Nutrients.2020
14 Grossman, D et al. Vitamin D, Calcium or Combined Supplementation for the Primary Prevention of Fractures in Community-Dwelling Adults. JAMA.2018
15 A guide to Calcium rich food. National Osteoporosis Foundation. 2021