Today is World Kindness Day, a reminder that it is important to celebrate the trait that makes us human (and makes the world a better place).

While being kind to others should be done because it is the right thing to do rather than because of what you can gain from it, here are some beneficial side effects that come with it:

1. It makes you happy

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Random acts of kindness may not make you feel euphoric, but studies have shown that being good to others does make you happier.

A meta-analysis by Oxford University, which involved combing through 400 published papers, found overall effect of kindness on happiness to be relatively modest, but study leader Dr Oliver Scott Curry pointed out: “Humans are social animals. We are happy to help family, friends, colleagues, community members and even strangers under some conditions.

“This research suggests that people do indeed derive satisfaction from helping others. This is probably because we genuinely care about others’ welfare, and because random acts of kindness are a good way of making new friends, and kick-starting supportive social relationships.”

2. And in turn, you’ll be less stressed

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A small study published in Clinical Psychological Science showed that people who performed small acts of kindness – such as holding the door open for others or giving directions – felt decreased levels of stress.

Results from a survey of 77 people showed that on the days when participants were feeling stressed about their own lives, helping others decreased negative feelings.

While it is unclear how helping others minimised the detrimental effects of stress, the theory is that performing acts of kindness stimulates certain biological systems that somehow lower or inhibit emotional stress response.

3. It’s good for the heart

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You may wonder why being kind to others creates that warm and fuzzy feeling inside.

Research has shown that kindness leads to emotional warmth which causes the brain to release a feel-good hormone called oxytocin. Another great side effect of this chemical is that it is known to improve the cardiovascular system.

As Dr David Hamilton, a scientist and author of Why Kindness is Good For You, puts it: “Oxytocin causes the release of a chemical called nitric oxide in blood vessels, which dilates (expands) the blood vessels.

“This reduces blood pressure, and therefore oxytocin is known as a ‘cardio-protective’ hormone because it protects the heart (by lowering blood pressure).”

4. It can keep you young

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A study by the University of California at Berkeley found that kindness activates the vagus nerve – the longest bundle of nerves in the human nervous system.

As well as regulating heart rate, the vagus nerve also controls inflammation levels in the body. Chronic internal inflammation is believed to be one of the key components of physical ageing.

A study also found that loving kindness meditation (LKM) – a form of meditation practised by Buddhist monks in Tibet – reduces inflammation in the body.

Dr Hamilton believes LKM’s beneficial effect on the vagus nerve may have something to do with it.

5. It helps you feel better if you are socially anxious

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Research suggests doing good deeds can make socially-anxious people feel better.

Scientists from the University of British Columbia found that when people with social anxiety performed small tasks such as holding the door open for someone, doing chores for other people, donating to charity or buying lunch for a friend, it boosted their positive moods.

Study leader Dr Lynn Alden said: “Acts of kindness may help to counter the socially anxious person’s fear of negative evaluation by promoting more positive perceptions and expectations of how other people will respond.”

6. It is contagious

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When we’re kind, we inspire others to be kind. A 2010 study by researchers from the University of California, San Diego and Harvard found that kindness creates a ripple effect.

Their observational research found that when one person gives money to help others in a “public-goods game” – where people have the opportunity to co-operate with each other – the recipients are more likely to give their own money away to other people in future games.

This, the researchers said, creates a domino effect in which one person’s generosity spreads three-fold.

Lead scientist Dr James Fowler said: “Personally it’s very exciting to learn that kindness spreads to people I don’t know or have never met.

“We have direct experience of giving and seeing people’s immediate reactions, but we don’t typically see how our generosity cascades through the social network to affect the lives of dozens or maybe hundreds of other people.”