Nicotine - when given independent of tobacco - could help protect the brain as it ages and even ward off neuro-degenerative diseases such as Parkinson's or Alzheimer's disease, US researchers have said.

The ability of nicotine - an important component of cigarettes - to be neuro-protective may be partly due to its well-known ability to suppress appetite, said Ursula Winzer-Serhan, Associate Professor at the Texas A&M University in the US, in a paper published in the Journal of Toxicology.

In the study, researchers added nicotine to drinking water of three different groups of mice and at three different concentrations (low, medium and high) corresponding to occasional, low and medium smokers, respectively, in comparison to a control group that did not receive any nicotine.

The two groups that received nicotine at low and medium doses did not show any levels of the drug in their blood and experienced no changes in food intake, body weight or number of receptors in the brain where nicotine acts.

Conversely, the group that received the highest concentration of nicotine ate less, gained less weight and had more receptors, indicating that at higher doses, the drug gets into the brain where it can impact behaviour.

But, even at high doses, it didn't seem to have worrying behavioural side effects like making the individuals more anxious, study said.

It did not produce a negative change in behaviour, in fact, the high levels of nicotine made the animal models less anxious, Winzer-Serhan added.

Previous studies had confirmed that tobacco products are bad for the health, and even the new e-cigarettes may have harmful toxins.

"Even if these weren't very preliminary results, smoking affects in so many health problems that any possible benefit of the nicotine would be more than cancelled out," Winzer-Serhan said.

However, it is also unclear if nicotine's effects are related only to its ability to suppress appetite, or if there are more mechanisms at work.

Still, researchers cautioned people not to purchase nicotine-containing products just yet.

"At the end of the day, we haven't proven that this addictive drug is safe. I want to make it very clear that we're not encouraging people to smoke," Winzer-Serhan noted, adding "smoking is only one possible route of administration of the drug, and our work shows that we shouldn't write-off nicotine completely."