Featured Research

from universities, journals, and other organizations

Lack Of Sun Does Not Explain Low Vitamin D In Elderly Who Are Overweight

Date:
June 11, 2007
Source:
Tufts University, Health Sciences
Summary:
People who are overweight tend to have lower levels of vitamin D, which may increase their risk of osteoporosis and other chronic conditions. New research indicates that reduced sun exposure does not explain the low vitamin D levels of overweight Caucasians age 65 and older.

It's not yet clear why overweight elderly adults have low levels of vitamin D in their blood. However, researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University (USDA HNRCA) have found that lack of sun exposure may not account for low levels of vitamin D in elders who are overweight.

"People aged 65 and over with high percent body fat have lower levels of 25-hydroxyvitamin D, the storage form of vitamin D, compared to those who have lower percent body fat," says corresponding author Susan Harris, DSc, epidemiologist in the Bone Metabolism Laboratory at the USDA HNRCA.

Harris and co-author Bess Dawson-Hughes, MD, director of the Bone Metabolism Laboratory at the USDA HNRCA, interviewed 381 Caucasian men and women aged 65 and over about their sun exposure over a previous three-month period. Individuals reported how much time they spent outdoors, how much skin was exposed while outdoors, and whether or not they wore sunscreen. Seasonality, or when the individual entered the study, was also taken into account, because in Boston, where the study was conducted, sun rays are weak in winter compared with summer months.

The researchers measured participants' percent body fat using dual-energy x-ray absorptiometry (DXA), a precise method for determining body composition. Individuals were grouped into quartiles of percent body fat: less than 28 percent, 28 percent to 33 percent, 34 percent to 40 percent, and greater than 40 percent. Blood levels of 25-hydroxyvitamin D were measured and participants were asked to fill out a dietary questionnaire to measure the amount of vitamin D they obtained from food.

Harris and Dawson-Hughes found that when adjusted for sex, age, seasonality and dietary vitamin D intake, 25-hydroxyvitamin D significantly decreased as body fat increased, (P<0.024). When the researchers further adjusted for sunlight exposure variables, 25-hydroxyvitamin D values still significantly decreased as body fat increased. "Sunlight exposure could not account for low vitamin D stores in older people with high percent body fat," explains Harris.

Vitamin D is called the "sunshine vitamin" because it is produced by the body when the skin is exposed to ultraviolet (UV) rays from the sun. Vitamin D can also be obtained from foods such as fish and fortified milk and from supplements. When this fat-soluble vitamin enters the body it is converted in the liver to 25-hydroxyvitamin D. This is one of several important forms of vitamin D, and is the form that researchers and clinicians use as an indicator of vitamin D status in individuals. "Vitamin D is especially critical in maintaining bone health, and there is evidence that many older Americans have low blood levels of vitamin D, which can put them at risk for bone fractures and osteoporosis," says Dawson-Hughes, who is also a professor at Tufts University School of Medicine.

"These results cannot be carried over to other populations, such as young people, or elderly living in different climates. However, if low vitamin D stores are not attributed to low sunlight exposure in this population, it suggests that we should explore other possibilities," says Harris. "The most likely explanation seems to be that vitamin D is sequestered in fat tissue, reducing its entry into the blood."

This study was supported by the Agricultural Research Service of the U.S. Department of Agriculture and by a grant from the National Institutes of Health.

Article: Harris SS, Dawson-Hughes B. Journal of Clinical Endocrinology & Metabolism. Electronic version May 2007 doi:10.1210/jc.2007-0702. "Reduced Sun Exposure Does Not Explain the Inverse Association of 25-Hydroxyvitamin D with Percent Body Fat in Older Adults."


Story Source:

The above story is based on materials provided by Tufts University, Health Sciences. Note: Materials may be edited for content and length.


Cite This Page:

Tufts University, Health Sciences. "Lack Of Sun Does Not Explain Low Vitamin D In Elderly Who Are Overweight." ScienceDaily. ScienceDaily, 11 June 2007. <www.sciencedaily.com/releases/2007/06/070607112840.htm>.
Tufts University, Health Sciences. (2007, June 11). Lack Of Sun Does Not Explain Low Vitamin D In Elderly Who Are Overweight. ScienceDaily. Retrieved September 1, 2014 from www.sciencedaily.com/releases/2007/06/070607112840.htm
Tufts University, Health Sciences. "Lack Of Sun Does Not Explain Low Vitamin D In Elderly Who Are Overweight." ScienceDaily. www.sciencedaily.com/releases/2007/06/070607112840.htm (accessed September 1, 2014).

Share This




More Health & Medicine News

Monday, September 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Get on Your Bike! London Cycling Popularity Soars Despite Danger

Get on Your Bike! London Cycling Popularity Soars Despite Danger

AFP (Sep. 1, 2014) Wedged between buses, lorries and cars, cycling in London isn't for the faint hearted. Nevertheless the number of people choosing to bike in the British capital has doubled over the past 15 years. Duration: 02:27 Video provided by AFP
Powered by NewsLook.com
We've Got Mites Living In Our Faces And So Do You

We've Got Mites Living In Our Faces And So Do You

Newsy (Aug. 30, 2014) A new study suggests 100 percent of adult humans (those over 18 years of age) have Demodex mites living in their faces. Video provided by Newsy
Powered by NewsLook.com
Liberia Continues Fight Against Ebola

Liberia Continues Fight Against Ebola

AFP (Aug. 30, 2014) Authorities in Liberia try to stem the spread of the Ebola epidemic by raising awareness and setting up sanitation units for people to wash their hands. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com
California Passes 'yes-Means-Yes' Campus Sexual Assault Bill

California Passes 'yes-Means-Yes' Campus Sexual Assault Bill

Reuters - US Online Video (Aug. 30, 2014) California lawmakers pass a bill requiring universities to adopt "affirmative consent" language in their definitions of consensual sex, part of a nationwide drive to curb sexual assault on campuses. Linda So reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins