Optimizing Bone Health in Children: Endocrinology and Micronutrient influences

Introduction

A good bone health is essential for people of all age group as it provides structural and mechanical support to our body and helps us stay healthy and independent in long term.1  As childhood and young adulthood are the bone building years, promoting good bone health in the early life ensures good skeletal health in advancing age also. Establishing bone health in childhood reduces the likelihood of fractures and prevents development of mineral deficiency disease such as osteoporosis in adulthood.2,3

Bone is a structural unit of the skeletal system which forms the framework of our body. Bone is composed of the following3:

  • Collagen fibers3
  • Bone cells: osteoblasts, osteocytes, osteoclasts, stromal, and hematopoietic cells1
  • Bone minerals: calcium (mostly as hydroxyapatite) and phosphates4

Eighty percentage of adult skeleton is formed of dense outer part called cortical bone while 20% is made of network of trabecular bone enveloped by cortical bone. Factors responsible for the bone loss mostly affect trabecular bone.4

Bone Development, modeling and remodeling

The basic skeletal formation, development and mineralization occur during embryonic age only. After the birth subsequent changes in bone shape, size and mass occurs during bone modeling process. The process is associated with increase bone mass.1There is 40-times increase in bone mineral content (BMC) from birth to adulthood. About 90% of peak bone mass is achieved at the age of 18 years.3 The human skeleton is renewed throughout life by the process called bone remodeling or bone metabolism.1

The process of bone modeling and remodeling is accomplished by the action of osteoblasts (bone forming cells) and osteoclasts (bone resorbing cells).1,4   Genes, hormones, nutrition, and physical activity play an important role in achieving peak bone mass.5

Factors affecting bone health

There are several factors which affect bone health where some are non-modifiable like genetics, gender and ethnicity while others are modifiable such as hormonal status, nutrition, mineral deficiency, physical activity, and other lifestyle related factors.3

Various factors that influences bone health are:

Non-modifiable factors:

Genetics: Bone mineral density (BMD) has some hereditary link although no particular gene contributing in bone health has been determined. BMD varies with population where black women demonstrate higher bone mass compare to their white or Asian counterpart.3

Gender: The influence of gender on BMD has also been noticed in several studies. Women have lower bone mass as compare to Men, also many mother–child studies demonstrated close relation between mother–daughter BMD than mother–son BMD.2,3

Modifiable factors:

Hormones:

Many hormones such as estrogen, testosterones, glucocorticoids, growth hormones and IGF-1 have key role in bone health. Estrogen helps in maintain BMD in female. Its deficiency can cause increased bone resorption and increases the risk of fracture in women. Growth hormone, testosterone and IGF-1 stimulate bone formation while opposite is promoted by glucocorticoids.3

Nutrition: The qualitative and quantitative nutritional supply at all stages right from fetal life to adolescence determines the bone health in children.2

Prenatal:

During fetal stage nutritional requirement like vitamin D and calcium are meet through only maternal source. Thus nutritional deficiency in mother affects the health of her baby. As in case of deficiency of Vitamin D in mother during pregnancy, her baby is born with vitamin D deficiency and poor bone health. However Deficiency of calcium during pregnancy has little or no effect on child bone health.2

Early childhood:

Suboptimal level of calcium and vitamin D intake results in lower bone mass in children. Calcium is the major component of bone mineral. It is essential for achieving peak bone mass.2 Vitamin D is essential for the absorption and utilization of calcium by the body. Only 10% to 15% of calcium is absorbed in absence of vitamin D.3 Deficiency of vitamin D leads to the development of rickets in young children whereas increases the risk of fracture in older children, teenagers and adults.3

Risk of Vitamin D deficiency is also high in children with liver or renal insufficiency and diseases, on certain medications like anticonvulsant, antifungal, antiretroviral and glucocorticoid.3

 

Late childhood and adolescence:

Undernourishment during childhood and teenage results in reduced bone formation and growth and affects overall health. Its deficiency can cause osteomalacia in the children of this age group.3

Physical activity or exercise

Some kind of physical activity increases bone formation, growth and augments bone strength in children and teenagers.2  Activities like such as jogging, walking, jumping, running, basketball, gymnastic, and dancing are good for bone health in children and adolescents.3

Other lifestyle factors:

Obesity, smoking, alcohol consumption, caffeine, soda consumption and poor food habits such as diet low in protein or high in sodium all contribute to poor bone as well as overall health in children, teens, and adults.2,3   Lifestyle changes such as sedentary behavior and growing indoor culture among children is also a big reason for development of vitamin D deficiency in children.6

Prevention of Vitamin D and Calcium Deficiency in Children and Adolescents

As both calcium and vitamin D are essential for good bone health, their deficiency will have negative impact on bone health.6

Vitamin D

About 90% of vitamin D is obtained through synthesis by skin on sunlight exposure.6  Sunlight is the ultimate source of vitamin D. Skin exposure to sunlight for up to 15 min twice or thrice a week synthesizes approximately 3000 IU of vitamin D. However people with darker skin tone require 3 to 5 times longer exposure to sunlight.3

Dietary sources of vitamin D are fewer namely cod liver oil, fortified foods and fishes such as sardines, tuna, salmon.3

Calcium

The primary source of calcium for neonates is mother milk. For children above 1-year dietary sources are also available such as milk and dairy products, legumes, green leafy vegetables, fruits, nuts and cereals (especially whole bran).3  Teenagers and older children have higher dietary calcium requirement in order to sustain bone growth.2

Calcium and vitamin D present in breast milk is not sufficient to meet the requirement of growing newborn. Hence calcium and vitamin D supplement is imperative to meet the need of growing body.6

Indian Academy of Pediatrics (IAP) Guidelines has recommendations for prevention and treatment of vitamin D and calcium deficiency presented below in the table6:

 

Age Vitamin D (IU/day) Calcium (mg/day
Prevention Treatment Prevention Treatment
Premature infants 400 1000 Intake of 150–200 mg/kg per day 175–200 mg/kg per day (maximum)
New born (<1 month) 400 2000 200 mg/day 500 mg/day
Infants (1–12 months) 400 2000 250–500 mg/day 500 mg/day
Children (1–18 years) 600 3000–6000 600–800  mg/day 600–800  mg/day
At risk children 400–1000 According to age group According to age group According to age group

 

Role of Healthcare Providers

Healthcare provider has prime role to play in promoting good bone health in children. He should counsel the children about the effect of malnutrition on health and encouraging them for the following3:

  • increased dietary consumption of calcium and vitamin D,
  • to take nutritional supplement,
  • perform require amount of physical exercise daily

Conclusion

Both calcium and vitamin D are essential for good bone health. Their deficiency will have negative impact on bone health.6  Proper nutrition along with exercise is important for good skeletal health during growing years as well as in later life.2

References

  1. Root AW. Disorders of calcium and phosphorus homeostasis in the newborn and infant. In: Sperling MA, editor. Pediatric endocrinology. 4th ed., Chapter 8. Philadelphia, PA: Saunders; 2014. p. 209-276.e1.
  2. McDevitt H, McGowan A, Ahmed SF. Establishing good bone health in children. Paediatr Child Health 2013;24(2):78-82.
  3. Golden NH, Abrams SA, Committee on Nutrition. Optimizing bone health in children and adolescents. Pediatrics 2014;134(4): e1229-43.
  4. Rang HP, Ritter JM, Flower RJ, Henderson G. Bone metabolism. In: Rang HP, Ritter JM, Flower RJ, Henderson G, editors. Rang & Dale’s pharmacology. 8th ed., London: Churchill Livingstone; 2016. p. 439-448.
  5. Ward L, Mughal MZ, Bachrach LK. Osteoporosis in childhood and adolescence. In: Marcus R, Feldman D, Dempster DW, Luckey M, Cauley JA, editors. Osteoporosis. 4th ed., Chapter 43. Waltham, MA: Academic Press; 2013. p. 1037-86.
  6. Khadilkar A, Khadilkar V, Chinnappa J, Rathi N, Khadgawat R, Balasubramanian S, et al. Prevention and treatment of vitamin d and calcium deficiency in children and adolescents: Indian Academy of Pediatrics (IAP) Guidelines. Indian Pediatrics 2017; 54:567-73.

 

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