As we age, our bodies aren't as good at absorbing the nutrients we need for growth and healthy living, which may lead to physical or mental illness.
Consider vitamin D, which promotes calcium absorption, helps protect older adults from osteoporosis and has a role in cell growth and immune function. Vitamin D deficiency is related to depression, Alzheimer's disease and increased risk of certain cancers, including breast, colon and prostate cancer.
Those most at risk are "self-neglecting elders," said Jason Burnett, associate director of clinical and behavioral research for the Texas Elder Abuse and Mistreatment Center at the University of Texas Medical School at Houston. This category includes senior citizens who have difficulty taking care of themselves appropriately, live alone and have no support system, Burnett said.
Burnett is researching the correlation between vitamin D deficiency and self-neglecting elders' ability to function. His study, supported by a National Institutes of Health grant, shows that 16 of the 44 participants who are deficient in vitamin D also exhibited lower skills in physical performance tests.
According to the National Institutes of Health, the recommended dietary allowance of vitamin D for people between the ages of 51 and 70 is 600 IU (International Units). For those older than 70, it's 800 IU.
Burnett said the seniors' vitamin D levels were increased, but it's too soon to determine the effect. The study should wrap up this fall.
Vitamin D is stored in the body when skin is exposed to sunlight, but even seniors who are frequently outdoors may still be deficient. Vitamin D is available as a dietary supplement but also is found in some foods, including fortified milk.
Vitamin B12 deficiency also can be a problem for senior citizens, dietitian Sherry Marishak-Simon said. B12 is required for proper red-blood-cell growth and neurological function, but as with vitamin D, the elderly have trouble with absorption.
Senior citizens specifically require a crystalline form of B12, Marishak-Simon said, which is found in fortified cereals and is more easily absorbed than the B12 found in meat.
As the dietitian in charge of writing the menus for Meals on Wheels at Interfaith Ministries for Greater Houston, Marishak-Simon is up to date on the latest nutritional requirements for senior citizens.
Nutritional requirements are set by the state, she said, with eight target areas: two that have to be met daily and six that are met over a weekly average of five meals. This includes calorie intake, protein, sodium, potassium, fiber, calcium, vitamin A and vitamin C.
It's one thing to prepare and deliver meals to senior citizens, but whether they clean their plate is sometimes another story.
Dr. Nasiya Ahmed, a gerontology physician with UT Physicians in Bellaire and the Texas Medical Center, said lack of appetite can quickly lead to lack of nutrients and weight loss.
"As you get older, your sense of smell and taste sometimes diminishes," Ahmed said. "Things don't taste as good, so seniors tend to salt their food more, or they just stop eating altogether."
Some medications common to senior citizens also can affect appetite, Ahmed said, usually because of the side effect of dry mouth.
"Also remember that eating is very social," Ahmed said. "We eat with friends, we eat with family, we eat to celebrate. Seniors without social interaction tend to slow down eating because they don't want to eat alone."