The Effect of Body Weight on Vitamin D Metabolism

NCT ID: NCT02629198

Last Updated: 2015-12-14

Basic Information

• Recruitment Status: COMPLETED
• Total Enrollment: 112 participants
• Study Classification: OBSERVATIONAL
• Study Start Date: 2012-10-31
• Study Completion Date: 2013-04-30

Brief Summary

There is current interest in the role of vitamin D in the prevention and treatment of many chronic diseases, including osteoporosis, cancer and neurological disease. The majority of vitamin D in the UK comes from the action of sunlight on skin, and very little from dietary sources. Half of the adult United Kingdom (UK) population have vitamin D insufficiency (according to the Institute of Medicine definition). There are still several important unknowns, including what the optimum levels of vitamin D are, and whether the same intake of vitamin D is appropriate for all sections of the population.

Low 25(OH)D and high parathyroid hormone (PTH) have been observed in people with high adiposity (obesity), and the summer rise in vitamin D is blunted in obesity. The potential causes of low 25(OH)D levels include an inadequate supply of vitamin D (by reduced sunlight exposure or poor nutrition), the large pool size of adipose tissue or increased metabolic clearance rate.

The investigators will measure metabolites of vitamin D and the kinetics of 25(OH)D using stable isotope techniques in lean, overweight and obese men, women and children to establish whether age, gender and obesity affect vitamin D metabolism and clearance rate.

If low 25(OH)D in obesity is related to poorer skeletal health and is due to increased clearance of 25(OH)D or large pool size, then total requirements, and hence supplementation requirements, would be larger for obese people than for lean people.

Detailed Description

Part 1: Measurement of vitamin D and metabolites (adults and children) Circulating levels of vitamin D metabolites are influenced by calcium intake, so participants will be asked to complete a seven day diet diary before the first vitamin D measurement. Measured vitamin D is influenced by vitamin D binding protein, lipids and inflammatory cytokines, so the investigators will include and correct for these measurements.

Visit 1 Consent Height and weight Diet diary instructions Urine collection instructions

Visit 2 Return of 24h urine collection for calcium and creatinine Return of diet diary Fasting blood sample for vitamin D, binding protein and metabolites C reactive protein (CRP), lipids and creatine kinase (CK), PTH, insulin-like growth factor -1 (IGF-1), creatinine, calcium, albumin, phosphate

Part 2: Measurement of vitamin D clearance rate (adults only) Kinetic studies will be perturbed by acute changes in vitamin D (most likely to be caused by sunlight exposure on a sunny day), and so the studies will all be conducted in the autumn, winter, and early spring when sunlight in Sheffield will not be strong enough to deliver large doses of vitamin D.

The administration and sampling protocol for the kinetics study has been developed by statisticians at the Sheffield School of Health and Related Research (ScHaRR) in collaboration with the Medical Research Council Human Nutrition Unit, based on modelling from their previous use of the stable isotope tracer method.

Visit 2 Oral administration of stable vitamin D isotope

Visit 3 (5-7 days after visit 2) Blood sample for tracer and vitamin D metabolites

Visit 4 (9 days ± 2 after visit 2) Blood sample for tracer and vitamin D metabolites

Visit 5 (27 days ± 2 after visit 2) Blood sample for tracer and vitamin D metabolites

Visit 6 (30 days ± 2 after visit 2) Blood sample for tracer and vitamin D metabolites Height and weight

The effect of obesity on vitamin D metabolites will be determined by regression models of BMI and vitamin D measurements corrected for age and gender.

The effects of obesity on vitamin D kinetics will be determined by modelling metabolic clearance rate on age, gender and BMI.

Subjects' previous data from the 'Effects of obesity on bone structure and strength'study (STH 15688) and the 'Body weight and bone' study (STH16199) will be used to evaluate relationships between vitamin D metabolism and body fat distribution, bone density and structure, and bone biochemistry.

Conditions

Osteoporosis; Obesity

Keywords

Vitamin D

Study Design

• Observational Model Type: ECOLOGIC_OR_COMMUNITY
• Study Time Perspective: CROSS_SECTIONAL

Study Groups

normal weight

Healthy men and women ages 25-40 and 55-75. BMI 18.5 to 25.0

No interventions assigned to this group

overweight

Healthy men and women ages 25-40 and 55-75. BMI 25.0 to 30.0

No interventions assigned to this group

obese

Healthy men and women ages 25-40 and 55-75. BMI over 30

No interventions assigned to this group

Eligibility Criteria

Inclusion Criteria

Caucasian

BMI of 18.5 kg/m2 or above for adults, 2nd-91st centile or above 98th centile for children

Ages 8 to 15 (children), 16 to 42 years (and premenopausal if female) or 55 to 77 years (and postmenopausal (at least 5 years since last menstrual period (LMP) if female)

Able and willing to participate in the study and provide written informed consent Completed either STH15688 or STH16199 and gave consent to be approached about future studies

Exclusion Criteria

History of any long term immobilization (duration greater than three months)

Current confirmed or possible pregnancy (urinary pregnancy test if LMP >28 days)

Previously-diagnosed diabetes mellitus

History of or current conditions known to affect bone metabolism, including

• Diagnosed skeletal disease
• Chronic renal disease
• Malabsorption syndromes
• Diagnosed endocrine disorders
• Hypocalcemia or hypercalcemia
• Diagnosed restrictive eating disorder Use of medications or treatment known to affect bone metabolism, including
• Depot medroxyprogesterone or the combined oral contraceptive pill

Alcohol intake of greater than 21 units per week

Competitive athlete, defined as participating in competitive sport at amateur or professional level

Holiday with significant sunlight exposure in the last six weeks

• Minimum Eligible Age: 8 Years
• Maximum Eligible Age: 77 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

Department of Health, United Kingdom

OTHER_GOV

Sponsor Role: collaborator

University of Sheffield

OTHER

Sponsor Role: collaborator

MRC Human Nutrition Research

OTHER_GOV

Sponsor Role: collaborator

Sheffield Teaching Hospitals NHS Foundation Trust

OTHER

Sponsor Role: lead

Responsible Party

Responsibility Role: SPONSOR

Principal Investigators

Jennifer S Walsh, MBChB PhD

Role: PRINCIPAL_INVESTIGATOR

University of Sheffield

Other Identifiers

STH16353

Identifier Type: -

Identifier Source: org_study_id