Christmas is a time for giving and this week we Brits will give more to charity than at any other time of the year.

All the fundraising carol singers, shopping-bag-packing Brownies, and charity tin-shakers make it hard for even the stingiest Scrooge to keep their wallets buckled shut.

But a couple of weeks ago, I witnessed thousands of acts of kindness that would make Santa proud.

Each year, Operation Christmas Child invites the public to fill shoeboxes with presents to send to countries in the developing world.

Individually wrapped and purposed for a boy or a girl, boxes are shipped to underprivileged youngsters in Africa, Eastern Europe and war-torn countries such as Iraq.

For many children, that solitary shoebox of gifts will be the only thing they receive this Christmas.

So it was in a ramshackle warehouse that magic was happening. Hidden in the corner of a Wiltshire trading estate, 20,000 gift-wrapped shoeboxes, donated by the people of the South West, were collected and waiting to depart.

Before they could be sent on their way, the contents of each had to be scrutinised: nothing sharp, nothing perishable, nothing offensive or religious, everything age-appropriate.

As I and other volunteers rummaged inside the boxes, it became profoundly obvious just how generous so many people are in 2014.

Sweets, toys, homemade cards and basic toiletries had been thoughtfully and deliberately bought and chosen for unknown children. Each box would soon bring a smile to the face of a child somewhere in the world.

But, bizarrely, that box would also be a source of health and wellbeing to the giver.

Science is increasingly showing us that being outward-focused and generous is linked to better health. In recent years, medics and psychologists have been discovering what good things happen inside the body when we do good things for others.

One important experiment showed that when volunteers were given cash to spend on someone else, they felt markedly less shame and more positive thoughts than when spending that amount on themselves.

Yes, feeling good after giving might seem obvious, but this experiment also showed one charitable act can change the body’s internal chemistry; significantly lowering levels of potentially harmful stress hormones.

For it is a life with high levels of stress hormones (particularly one called cortisol) that increases our risk of many health issues: digestive problems, heart disease, diabetes, chronic pain, weight gain and depression.

Lack of sleep, poor work-life balance and excessive alcohol all lead to high cortisol levels; whereas relaxation, massage and exercise can bring the levels back down again.

Now we know that big-heartedness also helps undo the ravages of modern life, it is one more reason to be pleased that it’s Christmas.

Be it a shoebox, a stocking filler, or a phone call to an auntie, acts of kindness can work wonders.

“Maybe Christmas, he thought, doesn’t come from a store. Maybe Christmas … perhaps … means a little bit more!” – From How the Grinch Stole Christmas, by Dr Seuss (Theodor Seuss Geisel, 1904-1991)