Vitamin D status and its relationship to body fat, final height, and peak bone mass in young women

Vitamin D and adolescent health

Vitamin D is a hormone sequentially produced at different body sites, and which plays a significant role in human health, particularly bone health. However, other roles are emerging. When the serum concentration of vitamin D is very low, the risk of rickets, osteomalacia and osteoporosis is increased. In children and adolescents there is a high prevalence of low vitamin D status, especially in females and during the winter–the prevalence being lower than during the summer. Although there is no unanimous agreement over the minimum values necessary for good health, serum 25-hydroxyvitamin D [25(OH)D] levels below 20 ng/mL may be regarded as a vitamin D-deficient condition, and levels between 20–30 ng/mL may be the range of vitamin D insufficiency. Mild low levels have been associated with bone mass accrual alterations in children and adolescents, diminished muscle strength, negative cardiovascular outcomes, insulin resistance and obesity, and neurological disorders. Effective preventive strategies are needed to guarantee adequate vitamin D levels throughout childhood and adolescence, taking into account the geographical setting, season of the year, the level of environmental pollution, skin characteristics, eating habits and body weight, with a view to securing optimum health during these phases, and the prevention of complications in adulthood. There needs to be a renewed appreciation of the beneficial effect of moderate sunlight for providing all humans with the vitamin D needed for ensuring good health. Prolonged sun exposure is not advised, however, due to the risk of skin cancer. In addition, a balanced diet is indicated, since vitamin D-rich foods are better assimilated than supplements. When such conditions cannot be met, then the supplementation of 400 IU/day of vitamin D is advised in children and adolescents–though correcting vitamin D insufficiency or deficiency may require 1000 IU/day or more. High-dose calcifediol depots are an alternative for guaranteeing treatment adherence and in patients with liver disease.

Serum 25-hydroxyvitamin D is related to indicators of overall physical fitness in healthy postmenopausal women

OBJECTIVE

Inadequate vitamin D status is related to increased adiposity, risk of falls, and muscle weakness, particularly in older people. We hypothesized that serum 25-hydroxyvitamin D [25(OH)D] is related to physical fitness indices (androidal fat, whole body lean mass, balance, strength) in healthy postmenopausal women.

METHODS

Covariates for fitness indices included age or years since menopause, weight, 25(OH)D, energy expenditure, and calcium intake. Overall and regional (androidal fat mass = waist + hip fat) body composition was assessed (N = 242) via dual-energy x-ray absorptiometry.

RESULTS

Regression analyses revealed that 71% of variability (P <or= 0.0001) in androidal fat mass was accounted for by weight (53.0%, P <or= 0.0001), white blood cell (WBC) count (2.0%, P <or= 0.0001), supplemental calcium (1.7%, P = 0.0004), years since menopause (1.1%, P = 0.0034), 25(OH)D (1.0%, P = 0.0051), and vegetable servings (0.6%, P = 0.027); 64% of variability (P <or= 0.0001) in lean mass was accounted for by weight (63.1.%, P <or= 0.0001), WBC count (1.4%, P = 0.0038), and 25(OH)D (1.0%, P = 0.013); 12% of variability (P <or= 0.0001) in balance (right + left leg) was accounted for by age (3.8%, P = 0.0019), 25(OH)D (2.0%, P = 0.025), and WBC count (1.8%, P = 0.032); 14% of variability (P <or= 0.0001) in handgrip strength (right + left) was accounted for by weight (9.3%, P <or= 0.0001), 25(OH)D (2.4%, P = 0.013), WBC count (2.1%, P = 0.019), and age (1.6%, P = 0.044); and 22% of variability (P <or= 0.0001) in torso strength was accounted for by site (15.0%, P <or= 0.0001) and weight (4.6%, P = 0.0003).

CONCLUSIONS

Serum 25(OH)D was the common contributor to physical fitness indices (androidal fat mass, lean mass, balance, handgrip strength) in healthy postmenopausal women.

Possible Health Implications and Low Vitamin D Status during Childhood and Adolescence: An Updated Mini Review

Vitamin D deficiency is common in the developing countries and exists in both childhood and adult life. The great importance of Vitamin D is the moderation of calcium (Ca) and phosphorus (P) homeostasis as well as the absorption of Ca. While insufficiency of vitamin D is a significant contributing factor to risk of rickets in childhood, it is possible that a more marginal deficiency of vitamin D during life span contribute to osteoporosis as well as potentially to the development and various other chronic diseases such as cardiovascular disease, cancer and diabetes. This paper reviews the metabolism, epidemiology, and treatment of vitamin D and calcium insufficiency as well as its relation to various diseases during childhood and adolescence.

Breastfeeding does not protect against urinary tract infection in the first 3 months of life, but vitamin D supplementation increases the risk by 76%

Our goal was to determine if breastfeeding provides any protection against urinary tract infection (UTI) and if vitamin D supplementation imposes any additional risks for UTI in infants < 3 months of age. In this study, 40% of the children who had urine cultures were breastfed, and 18.7% of the children were exclusively breastfed. Twenty percent of all of the urine cultures tested positive, and this number was greater in females (22.5%) than in males (18.1%, P < .05). There was no significant difference between the rates of positive urine cultures in exclusively breastfed (22% vs 21%, nonsignificant [NS]) formula-fed infants. The relative risk of UTI with breastfeeding versus formula feeding was 1.03 (0.58-1.82), and any breastfeeding versus no breastfeeding was 0.92 (0.58-1.45). Vitamin D supplementation increased the UTI risk, with a relative risk of 1.76 (1.07-2.91, P < .05). However, only formula-fed infants showed an increased risk of UTI after vitamin D supplementation.

Association of plasma vitamin D levels with adiposity in Hispanic and African Americans

CONTEXT

Previous studies have suggested vitamin D insufficiency is associated with increased obesity; however, the relationship between 25-hydroxyvitamin D (25[OH]D) and 1,25-dihydroxyvitamin D (1,25[OH](2)D) and measures of adiposity has not been well characterized in minority populations.

OBJECTIVE

The objective of the study was to examine the relationship between levels of 25[OH]D and 1,25[OH](2)D and measures of adiposity in Hispanic and African-Americans at baseline and on change in these measures over time.

DESIGN AND SETTING

The Insulin Resistance Atherosclerosis (IRAS) Family Study examined 917 Hispanics and 439 African-Americans at baseline and again 5.3 yr later (n = 1081 at follow-up).

MAIN OUTCOME MEASURE

25[OH]D (nanograms per milliliter) and 1,25[OH](2)D (picograms per milliliter) were measured at baseline. Abdominal sc adipose tissue (SAT), visceral adipose tissue (VAT; both determined by computed tomography scan), and body mass index (BMI) were measured at baseline and follow-up.

RESULTS

25[OH]D was inversely associated with BMI, VAT, and SAT in both populations at baseline (P < 0.001). 25[OH]D was marginally inversely associated with baseline visceral fat to sc fat ratio in African-Americans (P = 0.049) but not Hispanics. 1,25[OH](2)D was inversely associated with BMI (P < 0.0001, P = 0.002) and VAT (P = 0.0005, P = 0.012) in Hispanics and African-Americans, respectively, whereas 1,25[OH](2)D was inversely associated with SAT in Hispanics (P < 0.0001) and with visceral fat to sc fat ratio in African-Americans (P = 0.02). Adjusting for 25[OH]D attenuated these associations; 1,25[OH](2)D remained associated with BMI in both populations (P < 0.05) and with SAT (P = 0.004) in Hispanics. No significant associations between 5-yr change in adiposity and 25[OH]D or 1,25[OH](2)D were seen.

CONCLUSIONS

Vitamin D levels were inversely associated with baseline BMI, SAT, and VAT in Hispanic and African-Americans but were not associated with 5-yr change in adiposity.

Vitamin D and adolescents: what do we know?

PURPOSE OF REVIEW

Vitamin D has become the focus of many studies in recent years. Vitamin D deficiency has been linked to many chronic illnesses other then the well known musculoskeletal complications. In this review, we summarize new data regarding causes, prevalence, and complications of vitamin deficiency in adolescents and discuss them in the context of what is known in adults. In addition, we emphasize adolescence as a unique period for growth and development, and distinguish the consequences of vitamin D deficiency in young teenage patients from those in adults with regard to the presentation and potential health implications.

RECENT FINDINGS

Vitamin D deficiency is common among both healthy and ill adolescents worldwide, even in sunny countries. Although much of the data relating vitamin D status to biological markers and complications has been obtained in adults, the information emerging from studies of adolescents supports the premise that maintaining sufficient levels of vitamin D during the teenage years can improve long-term health outcomes. There are currently knowledge gaps regarding the most well tolerated and appropriate supplementation regimen to prevent vitamin D deficiency among adolescents.

SUMMARY

Further studies are needed to examine the implications of vitamin D deficiency among adolescents and the most appropriate treatment regimens to prevent this problem. There are sufficient data to support the importance of educating, preventing, and treating vitamin D deficiency in adolescents to improve their long-term health.