"Indulgent grandparents may be having an adverse impact on their grandchildren's health, say researchers," BBC News reports.
The news was prompted by a review of previous research into whether grandparents providing informal childcare may have an impact on a range of health factors in children, including:
These factors were chosen as they're all known to affect cancer risk in later life.
The question of whether grandparents "spoil" their grandchildren by indulging them with unhealthy food has long been a cause of friction in families.
As more parents now work outside the home, childcare from grandparents is becoming more common – which means it's more important than ever to explore any adverse effects grandparents may be having on children's health.
Researchers from Scotland reviewed 56 studies from 18 countries, which represented very different cultures – ranging from the US and the UK to Latin America and China.
They found evidence that children cared for by grandparents were more likely to be overweight, and that parents often complained grandparents "undermined" their efforts to provide healthy meals and eating patterns.
Some grandparents smoked around the children, which increased the chances the children would later start smoking.
But the study didn't look at the "more general beneficial role" grandparents often play in children's lives in terms of social and emotional wellbeing.
The researchers concluded that grandparents should be included in advice and support currently offered to parents.
The study was carried out by researchers from the University of Glasgow, the University of Edinburgh, NHS Tayside and the University of Stirling, all in Scotland.
Unsurprisingly, the study was widely covered by the UK media. Most stories gave a reasonably balanced account of the findings, but didn't question the quality of the studies included in the review, which ranged from poor to good.
Most reports carried the same quote from a National Obesity Forum spokesman, which suggested that grandparents "bring out the biscuits at the slightest hint of a tantrum" and are unable to resist "manipulative and increasingly savvy grandchildren".
This is arguably an unproven generalisation many grandparents – and parents – will find unfair.
This systematic review of studies included information about the impact of grandparents on a range of health factors in children.
The review included all types of study, both quantitative (measuring numbers) and qualitative (recording people's views and experiences, through focus groups or structured interviews).
Systematic reviews are good ways to get an overview of the state of knowledge in a subject at any one time. But they're only as reliable as the studies included.
Researchers searched for all types of study that included information about the potential influence of grandparents on children's:
These factors were chosen because they're all known to affect cancer risk in later life.
The researchers reviewed all relevant studies, judged their quality (high, medium or low), and noted whether the studies suggested grandparents had beneficial, adverse, mixed or no impact on children's health.
The researchers said the studies measured differing outcomes, so they couldn't pool the results in a meta-analysis (where results of individual studies are combined).
They excluded any studies where the grandparent was the primary carer or the child had a serious health condition.
Diet and weight
The researchers found most evidence for grandparents' influence on children's weight and diet.
Most of the evidence suggested they had an adverse effect:
The evidence for adverse effects ranged from comments in qualitative studies that parents felt "undermined" by grandparents in their attempts to restrict unhealthy food, to a UK study showing that children were 15% more likely to be overweight if, between the ages of 9 months and 3 years, they were mainly cared for by grandparents rather than a parent (adjusted risk ratio ARR 1.15 (95% confidence interval [CI] 1.04– 1.27).
The 8 studies looking at physical activity were less conclusive, although 5 studies found grandparents had an adverse effect on physical activity or a mixture of adverse effects and no effect.
The researchers found 16 studies looking at tobacco, with 9 showing an adverse impact. Only 1 found children were less likely to smoke if they lived with a grandparent.
Other risk factors
Just 1 study looked at alcohol, but it was low quality and found no effect. The researchers found no studies looking at sun exposure.
Quality of studies
The studies varied in quality. The researchers said 18 were high quality, 23 were medium quality, and 11 were low quality.
Quality was assessed using well-validated checklists produced by the UK's National Institute for Health and Care Excellence.
The researchers said the results for diet, weight, physical activity and tobacco "strongly suggest that grandparents had an adverse impact on their grandchildren's health" in these areas.
But they acknowledged that "much of the evidence for these studies" came from parents, rather than grandparents themselves, although some objective studies of weight and tobacco exposure also support this conclusion.
They pointed out that "grandparents are likely to be one of many influences on health outcomes" and their study only looked at cancer risk factors, not at the many positive influences grandparents can have on children's lives.
They said any suggestion parents should restrict their children's time with grandparents is "misplaced", but healthy parenting advice should be extended to grandparents.
The actress Maureen Lipman is quoted in BBC News as saying that, "The grandparents' job is always definitely to indulge".
Many of us have fond memories of being spoiled with sweets or cakes by grandparents.
But what's acceptable as an occasional treat becomes a problem if the grandparent is caring for the child most of the time while the parents are at work.
Many grandparents play a big role in their grandchildren's care, and no doubt many of them ensure they eat healthily, get plenty of exercise and aren't exposed to tobacco smoke.
These grandparents probably don't take kindly to their characterisation as feckless child-spoilers who expose their grandchildren to an increased risk of cancer.
The study gives snapshots of grandparents' influence on certain aspects of children's lives in a variety of very different cultures around the world, from the UK and the US to Latin America, South Africa and China.
The studies vary in quality, and lumping them together as equally important may result in an overestimation of the potential adverse impact of grandparents.
The researchers' conclusions seem sensible, however – that healthy parenting advice on weight, food, exercise and other things that affect health should include grandparents, not just parents.
Those responsible for promoting healthy parenting advice need to remember that grandparents, as well as parents, may play a big role in a child's upbringing.