As we sat down to Sunday lunch with my brother and his family, I reached smugly for the organic apple juice to fill up the children's glasses. Being a particularly healthy family themselves, I thought they would be delighted with my choice of beverage. What I hadn't counted on was my sister-in-law playing her dentist card.
Having a dentist in the family often has its advantages -- but there are times you can get a lecture when you're least expecting it.
So I was aghast when she said that fruit juice was one of the many products that had led to widespread erosion problems in children as young as five.
"But it's healthy," I countered. "One of their five-a-day!"'
My sister-in-law, or to give her full title 'Dr Christine Sweeney', was having none of it.
She explained that fruit juices, and similarly acidic drinks, are one of the main culprits of the ever-growing problem of tooth erosion in children and young adults today.
Indeed, the British Dental Association states that more than half of children between the ages of four and 18 are now suffering some tooth erosion. Compare this to a generation ago and erosion was almost unheard of -- tooth decay was the main enemy to battle.
"The problem now is that fruit juices and fruit squashes are an everyday habit -- and often something our children have, not just once, but multiple times a day," Christine says.
"And each time they take a sip, the acid in the drink which causes the erosion gets another chance to soften the enamel on their teeth."
So what can we do about it?
Well the first thing to look at is the frequency of these drinks. Drinking a glass of juice at breakfast is far preferable to constant 'grazing' or sipping juice during the day. Also having these drinks with some sort of meal will cause less damage than having them alone.
Ali Gibbons, a 'fruiteteer' from Innocent Smoothies, has this to say: "In their schools pack (The Mighty Mouth), the Dental Health Foundation in Ireland acknowledges the nutritional benefit of unsweetened fruit juices by recommending them as a good choice for school lunchboxes.
"They suggest consumption is best at meal times to minimise any dental impact. All Innocent kids' drinks are sold with straws, to help minimise the contact of the smoothie or juice with the teeth."
So the clear message is that if you don't want to lose the health benefits of your child drinking these drinks, make sure they are given at mealtimes only rather than just as snacks.
The other thing to avoid, less obviously, is brushing your child's teeth straight after an acidic drink such as juice.
Christine explains: "The acidity in these drinks softens the enamel so if we immediately brush our teeth after drinking them the softened enamel is more easily brushed away.
"The best advice is to rinse with either water or an alcohol-free fluoride mouth wash straight after drinking them," says Christine.
But the threat doesn't end there. As parents we often think we are doing the best for our children with the choices we make -- but often there are hidden dangers we haven't been informed about.
Christine says: "I once had a lovely client who was very into a whole-food, vegetarian lifestyle.
"Every morning she would give her son hot water with some lemon juice in it to drink, as this is widely known to be good for cleansing your system.
"Unfortunately, however, the mother was unaware of the damage that the acidity of the lemon was doing to her son's teeth until the effect was noticeable."
So, I start to wonder, if fruit juices are as bad for teeth as they are good for your health, are there other hidden enemies out there that are being sold to us as wholesome?
Well, it turns out there are lots of them. The most surprising I found were both smoothies and yogurt drinks sold to boost our immune systems.
Over the past 10 years or so, both of these drinks have become more and more popular, particularly with middle-class parents hoping to sneakily bump up their children's resistance to infections.
Both drinks, however, are acidic and so carry the same danger of tooth erosion.
"Another huge problem we see are teenagers and young adults facing heavy erosion through continued use of sports drinks," warns Christine.
"For the type of activity they are doing, water is in fact the best thing for them to drink both pre- and post-exercise."'
Other 'danger foods' that are perceived by most of us as healthy are cereal/granola bars, which in fact are packed with honey and sugar; concentrated fruit bars that are processed to such a degree as to contain 'sticky' sugars; tomatoes (acidic); raisins that are pre-added to cereals; most dried fruits; and even fizzy water due to its carbon dioxide.
I start to get depressed.
How on earth, as busy parents, can we take heed of all this good advice?
"What I usually advise a client is firstly to get their children to eat and drink products in their most basic form," says Christine.
"For example, an orange is better than orange juice, but orange juice is better than fizzy orange.
"The other thing to do is to change from high frequency -- for example, sipping smoothies throughout the day, to low frequency -- having a smoothie at meal times only."
It seems that as parents we are doing our best with the information that we have available to us, but the choices we are making are not always right for the health of our child's teeth.
Christine's final advice is sobering: "Your child's taste buds will adapt to what you give them from an early age -- so if you feed them sugar they will crave sugary foods; if you give them salt they will want salty foods.
"Tooth erosion is far easier to prevent than to fix -- so it is worth taking stock of what your child eats and drinks, and how often."
Armed with all this new information, I feel that it's time to take action.
I'm off to break the news to my kids.