Everyone, stop what you're doing and think about babies. Ah, tiny babies drinking milk. Does it fill you with a warm glow, thinking about those small, slow-blinking infants absorbing the nutrition they need from bottle or breast? Or do you find that the mental image alone drives you to inchoate rage and doubt? What if the babies are drinking the wrong sort of milk? How do we know what's right anyway? And what if you're a mum and – horror of horrors – suspected of doing a bad job of keeping your child healthy and well-fed?

This isn't just facetiousness: breast or bottle is one of the most intimate and essential decisions a new parent has to make. That's probably why the simple advice and support structures aimed at new mothers have an irrepressible tendency to mutate into inflexible dictates, head-shaking horror at other people's choices, and flinty self-criticism. It also probably explains why a new report published in the British Medical Journal on best practice for weaning has occasioned another round of this-milk-is-better-than-that-milk bickering. While the report itself makes the fairly limited claim that exclusively breastfeeding for six months (as recommended by the World Health Organisation) may not be advisable in all circumstances, it has been reported – and responded to – as though it was a full refutation of breast-is-best.

I entered the maternity ward with a very simple feeding plan: "No formula." Which meant that when an exhausting labour left me and baby too tired to get started properly and a midwife recommended supplementing breastfeeds with bottles, I was devastated. Here I was, a few days into parenthood and I'd already failed my baby. I'd made a hash of giving birth, and now couldn't manage something I'd convinced myself was the most natural thing in the world.

While "breast is best" is catchy, like most slogans it does a pretty poor job of conveying all the essential qualifiers. All things being equal, breast milk is the best choice for mother and child. But a few women can't. Some would like to, but don't have anyone to teach them how. (Yes, there really is a bit more to it than just socking a nipple in a baby's mouth and hoping for the best.) Some, from a combination of social pressure and personal qualms, just don't want to. And some, like me, need a bit of nutritional back-up: was I still doing what was "best"? Where was my neatly rhyming affirmation?

Absolutist positions are worse than flawed. We've come a long way since my aunt was dosed with drying-up pills at her post-labour breakfast, but a zeal for breastfeeding can be harmful too. There's the bruising of self-esteem that comes when physical or practical realities crush a heartfelt plan. And the breast-v-bottle war instils hostility where there should be none; for a while my nearest mother-and-baby group was a breastfeeding drop-in, which was absolutely lovely until I came to recommend places to a friend with an adopted newborn. Why, I suddenly wondered, was this a breastfeeding group and not just a baby group with breastfeeding support from a health visitor?

There's worse: I knew one mum with a degenerative eye disease who had come off her meds for the pregnancy and was now doggedly refusing to restart them until she'd given her son a full six months of breast milk – blinding herself in pursuit of maternal perfection. It's a fringe case, but a painful reminder that when one simple message starts to drown out all others, the important thing – the welfare of mother and child – begins to be lost. I hope sincerely that every woman gets all the support and help she needs in order to give her baby the best possible start, and usually that means breastfeeding. But turning milk into the frontline of a parenting war is the worst possible outcome.