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The prevalence of overweight and obesity in adolescents is increasing worldwide.  Studies have shown that obese children and adolescents have an increased prevalence of metabolic risk factors for cardiovascular disease, type 2 diabetes, and, more recently, fatty liver disease.

In parallel with increasing prevalence of obesity in adolescents, it is expected that long-term morbidity in this population will increase.  A recent Australian research investigated the association between measures of adiposity (body mass index and waist circumference) and risk factors for heart disease, type 2 diabetes, fatty liver disease, and the clustering of risk factors in middle adolescence.

496 year 10 students (mean age – 15.4 years) in the Sydney metropolitan area were included in this study.  Blood samples were collected for biomarker studies including lipids (HDL and LDL cholesterol, triglycerides), insulin and glucose, liver health (ALT and GGT), high-sensitivity CRP (a marker for inflammation and risk predictor for cardiovascular disease), and blood pressure.

The study found that:

  • The prevalence of overweight and obesity in adolescent boys was 27.6%, based on BMI (body mass index calculated as weight in kilograms divided by height in meters squared), and 20.0% based on waist circumference cut points. The prevalence of overweight and obesity in adolescent girls was 19.4% based on BMI and 18.0% based on waist circumference.
  • Adolescent boys are more likely to have multiple risk factors than adolescent girls, particularly if they are overweight or obese.
  • 95% of obese and 80% of overweight adolescent boys had at least 1 risk factor.
  • Obese adolescent boys and girls were significantly more likely to have 2 or more risk factors than non-overweight adolescents.
  • The cardiovascular risk factors were relatively common, with high blood pressure being the most prevalent risk factor in adolescent boys (22.1%) and girls (10.8%).
  • Low HDL cholesterol levels and elevated high sensitivity-CRP levels were also relatively common, with 10.7% of adolescent boys and 3.9% of adolescent girls having low HDL cholesterol levels and 7.5% of adolescent boys and 8.6% of adolescent girls having high hs-CRP levels.
  • 4.5% of adolescent boys and 6.3% of adolescent girls have abnormal LDL cholesterol level.

Analysis on the clustering of risk factors indicates that Insulin, ALT, GGT, HDL cholesterol, high-sensitivity CRP, and blood pressure were significantly associated with overweight and obesity in adolescent boys. In adolescent girls, insulin, high-density lipoprotein cholesterol, and high-sensitivity C-reactive protein were significantly associated with overweight and obesity.

Previous studies suggested that the presence of more than 1 risk factor in childhood presents an increased risk of cardiovascular disease in adulthood.  Identifying adolescents at risk for long-term morbidity and offering early intervention may improve long-term outcomes.

Elizabeth Denney-Wilson et al (2008); Arch Pediatr Adolesc Med. 162(6):566-573

A high prevalence of vitamin D deficiency has been reported in healthy growing children and adolescents in a number of countries.  Vitamin D deficiency is associated with an elevation of PTH concentration in blood and an increase in the blood concentration of markers for bone turnover.  Such changes in growing children and adolescents suggest that there may be suboptimal bone mass growth.

Vitamin D deficiency rickets has been reemerging as a public health problem in some developed and developing countries. Persistent severe vitamin D deficiency causes rickets in children and osteomalacia in adults, whereas mild vitamin D deficiency may also be associated with hyperparathyroidism and increased bone turnover.

A cross-sectional study by researchers in Australia, China, and Malaysia investigated the influence of low-vitamin D status on bone mass, bone turnover, and muscle strength in 301 healthy Chinese adolescent girls in Beijing, China.  The researchers measured the Blood plasma 25-hydroxyvitamin D [25(OH)D], the plasma and urine biomarkers of bone turnover; and the bone mineral content (BMC) and density and bone area for the whole body and the distal and proximal forearm

Vitamin D deficiency was defined as a serum 25(OH)D concentration of <=50 nmol/L.  Severe
Deficiency was defined as <25 nmol/L.  58% of the adolescent girls were vitamin D deficient and 31% were severely deficient.

The study results showed that girls with adequate vitamin D status had higher size-adjusted BMC for the whole body, distal forearm, and proximal forearm than those with poorer vitamin D status.  Similar results were also found for handgrip muscle strength.

Girls with adequate vitamin D status had significantly lower concentrations of biomarkers for bone resorption compared with those of the vitamin D-deficient girls, suggesting that low vitamin D status is associated with greater rates of bone remodeling.

Adolescent girls with adequate vitamin D status had significantly higher bone mass and muscle strength compared with those with poor vitamin D status. This may be attributed in part to a lower rate of bone remodeling with adequate vitamin D status.

These findings suggest that adequate vitamin D status during adolescence is important for optimizing bone mass, which may lead to higher peak bone mass at maturity. Poor vitamin D status also compromises forearm muscle strength.

In conclusion, adequate vitamin D status is important in enhancing muscle strength and in attaining higher peak bone mass. This effect on bone may in part be attributed to lower rates of bone remodeling when vitamin D status is adequate.

Leng Huat Foo et al. (2009) J. Nutr. 139: 1002–1007

With festive and the holiday seasons, teenagers often party hard and are more likely to ignore their nutritional requirements. A recent Australian study emphasized the importance of ensuring diet quality in adolescence and its potential role in modifying mental health over the life course.

Studies have demonstrated inverse relationships between diet quality and the common mental disorders in adults. However, little is known about such association in adolescents. Given that three quarters of lifetime psychiatric disorders will emerge in adolescence or early adulthood, a recent prospective study investigated the temporal relationships between diet quality and mental health and the associations between change in diet quality and change in psychological symptoms.

Researchers collected diet and mental health information from 3040 Australian adolescents aged 11–18 years at baseline in 2005–6 and followed up in 2007–8.  The study found that boys had significantly higher scores on the Unhealthy diet scale than girls and were also more active; and that improvements in diet quality were mirrored by improvements in mental health over the follow-up period, while deteriorating diet quality was associated with poorer psychological functioning.

The researchers hypothesized that diet quality influences the genesis and/or progression of depressive illnesses by modulating inflammatory, oxidative and/or neurotrophic factors.

Given that adequate nutrition is essential during periods of rapid physical development, and that the majority of mental health problems first manifest in adolescence and early adulthood, further intervention studies are now urgently required to test the effectiveness of preventing the common mental disorders through dietary modification.  For the parents, the foods available and provided to adolescents need to be receiving much greater attention.  Particular attention should be paid to creating environments that promote healthy eating in supporting adolescents to maintain good nutrition during a difficult life stage.

Jacka FN et al. (2011) A Prospective Study of Diet Quality and Mental Health in Adolescents; PLoS ONE 6(9): e24805. doi:10.1371/journal.pone.0024805

Pre-eclampsia is a major cause of death in pregnant women and newborn babies worldwide. Preterm birth is often caused by high blood pressure and is the leading cause of newborn deaths.

Pre-eclampsia and eclampsia are common causes of serious morbidity and death. Calcium supplementation may reduce the risk of pre-eclampsia through a number of mechanisms, and may help to prevent preterm birth.

To assess the effects of calcium supplementation during pregnancy on hypertensive disorders of pregnancy and related maternal and child outcomes, a recent Cochrane meta-analysis reviewed 13 randomised controlled trials involving 15,730 women.  All trials compared at least 1 gram of daily calcium supplementation during pregnancy with placebo.

The study found that the average risk of high blood pressure and preterm birth was reduced in the calcium group. There was also a reduction in the average risk of pre-eclampsia associated with calcium group.  Calcium supplementation appears to approximately halve the risk of pre-eclampsia, to reduce the risk of preterm birth and to reduce the occurrence of the composite outcome ‘death or serious morbidity’. The effect was greatest for women with low dietary calcium intake at baseline and those selected as being at high risk.

The study authors found that calcium supplementation during pregnancy is a safe and relatively cheap means of reducing the risk of pre-eclampsia in women at increased risk, and women from communities with low dietary calcium. No adverse effects have been found but further research is needed into the ideal dosage for supplementation.

Hofmeyr GJ, Lawrie TA, Atallah ÁN, Duley L. Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems. Cochrane Database of Systematic Reviews 2010, Issue 8. Art. No.: CD001059. DOI: 10.1002/14651858.CD001059.pub3

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