For many kids, trips to their grandparents' house often means sugary treats or extrathat may not be allowed at home.
But new research suggests such indulgent behavior can have long-term consequences.
The study, published in the journal PLOS ONE, finds that the spoiling of grandchildren by their grandparents may inadvertently have a negative impact on children's health – even their risk of eventually developing cancer.
Researchers from the University of Glasgow reviewed 56 studies with data from 18 countries on the care provided by grandparents who are not the primary caregivers of their grandchildren.
The data showed that overall,in the areas of weight and diet – through "treating," overfeeding, and lack of physical activity.
Grandparents' tobacco habits also put kids at risk, the study found.
, diet, a , along with excess weight, have all been identified as risk factors for serious health problems, including heart disease, diabetes, and cancer.
"Children should never be exposed to second hand smoke," Professor Linda Bauld, Cancer Research UK's prevention expert, said in a statement about the findings. "With both smoking andbeing the two biggest preventable causes of cancer in the UK, it's important for the whole family to work together."
Many lifelong behaviors – both healthy and unhealthy – are learned from an early age from family members.
The study authors say that until now, research has largely focused on the role of parents and there has been only limited analysis of the potential impact of part-time caregivers such as grandparents.
They say the data suggests that the risks associated with grandparents' behavior are inadvertent.
"While the results of this review are clear that behavior such as exposure to smoking and regularly treating children increases cancer risks as children grow into adulthood, it is also clear from the evidence that these risks are unintentional," lead author Dr. Stephanie Chambers said in a statement.
"Currently grandparents are not the focus of public health messaging targeted at parents and in light of the evidence from this study, perhaps this is something that needs to change given the prominent role grandparents play in the lives of children," she continued.
The researchers pointed out that, of course, grandparents play a beneficial role in children's lives in many other ways. Spending time with grandma and grandpa can enhance kids'"social and emotional wellbeing," they write in the study, "and therefore, any recommendation to limit grandparent interaction with their grandchildren would be misplaced."
Societal changes, including having more women in the workforce, increased childcare costs, and a rise in single parenting have led families to lean more on grandparents for caregiving needs.
As a result, Chambers said that even when grandparents' less-than-optimal practices – including exposing kids to smoking and overfeeding them – were causing tension within the family, many parents often found it difficult to have conversations about them.
However, "given that many parents now rely on grandparents for care, the mixed messages about health that children might be getting is perhaps an important discussion that needs to be had," she said.