What we eat doesn't just reflect in how we look but also on how we age, a new study says.

According to the study, seniors' health is closely linked with the kind of diet they have and also on the kind of organisms present in their guts. The study says dietary choices impact what kind of organisms grow in the body that in turn affect peoples' overall health.

"Our findings indicate that any two given older people, independent of [their] starting health status and genetic makeup, could experience very different rates of health loss upon aging due to dietary choices that impact on their gut bacterial ecosystem," Paul O'Toole, senior author of the study and a senior lecturer in genetics at University College Cork, Ireland, told HealthDay.

Researchers analyzed what kinds of organisms were present in the guts of more than 170 people over 78 years of age. They found that the gut microbiota varied according to where the people lived and also according to what they ate.

In general, people living in community were healthier and there was a great diversity in the kind of organisms that grew in their guts. People living long-term in care homes had lower diversity in their gut microbiota and were weaker than other participants.

"The diet of older people changes quickly when they move from community to long-term care (in a couple of weeks), but the microbiota changes more slowly -- up to a year for full change from community type to long-term residential type," One would not expect that the rate of heath decline in this time could be responsible for the change in microbiota composition. It's more plausible to be driven by diet," O'Toole said.

Earlier research said that, in the future, we might be given treatments based on our gut type (meaning what type of microorganisms are present in our guts) so that treatment can be made more effective. Old people have more microbes involved in digestion because as we age our digestive system becomes weak and so microbes have to take up the role of digestion.

"To combat frailty, it makes sense if our microbiota is helping our bodies to be as effective and efficient as possible," said O'Toole, to HealthDay. Gut organisms can also affect mood in old people.

"[Some studies] have shown that gut bacteria can 'talk' to the brain by synthesizing compounds that affect the brain-gut axis. An exciting theory is that altered gut bacteria in older subjects could impact on cognitive function or mood," said O'Toole.

According to previous research, when these microbes grow in the gut, they produce various by-products that are beneficial to the host. A good way to grow beneficial bacteria in the guts is to include fiber in the diet.

The study is published in the journal Nature.