Besides enhancing romance between couples, candlelit dinners also help maintain a healthy heart.

Lund University researchers said that inhaling candle smoke enhances heart rate variability. The researchers claim that the tiny salt particles of sodium and potassium released when a candle burns, regulates the heart rhythm positively.

For the study, the scientists observed hearts of participants while they were exposed to candle smoke in a small room under the supervision of medical experts. The researchers found that when the participants breathed candle smoke, their variability in heart frequency increased even at relatively low indoor concentrations, indicating that the heart and nervous system were all functioning well.

Researcher Christina Isaxon theorized that the salts of sodium and potassium in the smoke increase heart rate. The salt particles are generated when the candle flame does not flicker. However, soot is generated instead of salt particles when the flame starts flickering.

Previous studies have linked the airborne particles with cardiovascular problems.

"We haven't found anything to indicate that calmly burning pure stearin candles is unhealthy. On the contrary", Isaxon, the doctoral student in Ergonomics and Aerosol Technology, said in a statement.

Inger Hagerman, consultant cardiologist at Karolinska Institute, said that a good balance of sodium and potassium salts is required to maintain proper heart rhythm regulation.

"What is particularly interesting is that we have seen a positive effect on the part of the autonomous nervous system that is connected to better heart health", says Inger Hagerman.

Indoor particle concentrations increase significantly while cooking, using a toaster or microwave and while burning candles. As a result, higher concentrations of particles are generated indoors than outdoors.

Researchers said that since humans spend 85 percent of time indoors, of which 65 percent is spent at home, studies of indoor air and its impact on human health are very significant.

"So far, it is not totally clear how these particles affect our bodies," Isaxon said.

Isaxon said that she hopes to closely examine the properties of the candle particles to explain the positive cardiovascular effects. She is also planning to examine effects of other indoor particle sources on health.