Vitamin D deficiency is a public health concern here in the UK, with an estimated 30% to 40% of the UK population said to be vitamin D deficient from October to March. This is because the main source of vitamin D, the sun, is not strong enough during the winter months for our bodies to make a sufficient supply.

Although the food we eat provides us with some vitamin D, this tends to be a small amount and is usually not enough to meet our requirements alone. However, recent research indicates that exercise might ‘unlock’ the vitamin D stored in our bodies, helping to keep our levels topped up during winter.

Vitamin D has several vital roles in maintaining our health, including keeping our bones strong, helping cells to grow, and keeping our immune systems healthy. This study will aim to investigate whether, and to what extent, just a single bout of treadmill exercise may mobilise stored vitamin D and increase vitamin D levels in the blood.

What's involved in the study

After an initial screening meeting, we will ask you to attend the laboratory at the University of Bath on five separate occasions. These visits will be undertaken within a period of 2 to 3 weeks, lasting between 10 minutes and 2 hours. During these visits, you will be asked to:

• wear a small wrist-worn device which monitors physical activity levels for 7 days
• undertake a treadmill-based fitness test
• allow us to measure the energy you expend at rest
• allow us to take blood samples during 4 of the laboratory visits
• consume personalised meals which will be provided and tailored to your specific energy requirements for two separate days

Please note: Due to the current COVID-19 pandemic, participants will not be required to attend the university for the study until the social distancing guidance permits safe reopening of the laboratories to research volunteers.

Eligibility

We are looking for men and women who:

• are aged between 25 and 60 years
• do not smoke
• do not take vitamin D supplements (and have not taken any within the last 3 months)
• have not experienced a change in body weight of more than 5% (of total body weight) in the last 6 months

What you'll get for taking part

You will receive invaluable, detailed physiological health data for participating in this study. This data will include a detailed report of your resting metabolic rate, energy expenditure and fitness. When the whole study is completed, you will also receive data on your blood vitamin D metabolites.

Furthermore, you will be making a potentially invaluable contribution to scientific knowledge that will pioneer new findings in this area of research.

You will also be reimbursed for any travel to and from the University.

Confidentiality

All identifiable data will be stored in a locked cabinet or in a password protected spreadsheet on the University’s servers. For this reason, only the lead investigator and principal supervisor will be able to identify participants. As a participant, you will be able to access your own data upon request. This study has received ethical approval.¹