21st September 2026

Newsletter Monday

Hello Reader,

For as long as I have been a GP, pregnant women have asked me about peanuts.

“Should I avoid eating nuts while I’m pregnant?”

Usually because they’ve heard that eating peanuts during pregnancy might make their baby more likely to develop a peanut allergy.

And, actually, this didn’t originate with TikTok, Instagram or somebody selling a pregnancy nutrition course.

We did say it.

Until 2009, UK government advice suggested that women might want to avoid peanuts during pregnancy and breastfeeding if there was a family history of allergic disease.

It sounded plausible.

Peanuts cause peanut allergy. Perhaps exposing a developing baby to peanut proteins increases their chances of becoming allergic to them.

Except the evidence didn’t support the advice, so it was eventually withdrawn.

Today, the NHS advice is quite straightforward: unless you are allergic to them yourself, you don’t need to avoid peanuts during pregnancy or breastfeeding.

But health warnings have a remarkably long half-life.

Once we have told people that something might be harmful, removing the warning doesn’t necessarily remove the fear.

Eggs know all about this.🥚

We spent years warning people about eggs because they contain cholesterol. The advice moved on a very long time ago, yet I still regularly encounter people carefully rationing their eggs because somewhere in the back of their mind is a health message they absorbed in the 1980s.

Once an idea gets lodged in our collective health consciousness, good luck getting the wretched thing out again.

And I think this matters particularly during pregnancy.

Because pregnancy comes with an extraordinary weight of responsibility.

Suddenly what you eat, drink and do isn’t just about you. Every decision has the potential to be framed in terms of what it might do to another human being for the rest of their life.

And if something subsequently does happen to your child, it is remarkably easy to look backwards and wonder whether you caused it.

That is an enormous burden to place on women.

Which is why I think we should be very careful before adding anything else to the pregnancy to-do list.

And this week, a fascinating study published in the New England Journal of Medicine did exactly what good science should do: it tested another entirely plausible idea.

We now have good evidence that introducing foods such as peanut appropriately during infancy, rather than deliberately delaying them, can reduce the risk of allergy.

So researchers asked an obvious question.

Could we go even earlier?

What if mothers ate lots of peanuts and eggs during pregnancy and breastfeeding? Could exposure through pregnancy and breast milk help the developing immune system become tolerant and reduce the baby’s chance of developing an allergy?

You can already imagine the Instagram reel.

“Pregnant? Here are TWO foods you should be eating to protect your baby from allergies…”

Add some pictures of peanut butter and scrambled eggs, mention “supporting your baby’s developing immune system”, put some uplifting music underneath it and we’re away.

Except somebody actually tested it.

More than 2,100 pregnant women whose babies were considered at increased familial risk of allergy were randomly allocated to one of two groups before 23 weeks of pregnancy.

One group was asked to consume at least six eggs and 60 peanuts every week.

Sixty peanuts.

Every week.

They continued doing this through pregnancy and for four months after birth while breastfeeding.

The comparison group ate substantially less.

Then the researchers looked at how many babies had developed an IgE-mediated egg or peanut allergy by the age of one.

In the high egg-and-peanut group: 7.8%.

In the comparison group: 8.4%.

In other words, no convincing difference.

Eating industrial quantities of omelettes and peanuts during pregnancy did not prevent food allergy.

And I love this study precisely because nothing exciting happened.

Because negative trials matter.

They stop plausible ideas becoming instructions.

There was absolutely nothing ridiculous about the hypothesis. In fact, it made enough biological sense for researchers to conduct a large randomised controlled trial to find out whether it was true.

But “this makes biological sense” and “therefore you should do it” are two very different things.

And this is where modern health advice can get itself into such a mess.

A plausible mechanism gets discussed.

Somebody turns it into a recommendation.

The recommendation becomes a reel.

The reel becomes “five things EVERY pregnant woman should be doing”.

And several million views later, an interesting scientific hypothesis has somehow become another thing for women to worry about.

The person giving the advice doesn’t necessarily have to come back five or ten years later and say:

“Remember that thing I confidently told you to do? Turns out it made no difference.”

They’ve moved on.

Science, frustratingly slowly, has to stick around and find out.

Of course, science has been responsible for some of this mess too. The old advice to avoid peanuts is a perfect example.

That’s why I think we need to be more comfortable saying:

“We don’t know.”

Or:

“That is plausible, but it hasn’t been demonstrated.”

Neither makes a particularly exciting Instagram reel. But both are considerably more honest.

For now, the advice for pregnant women regarding peanuts is wonderfully boring.

• If you’re not allergic to them and you like them, you can eat them.
• If you don’t like them, you don’t need to force down 60 a week on behalf of your unborn child’s immune system.

And if anyone tells you that something “makes biological sense”, remember:

That’s an excellent reason to study it.

It’s a considerably less good reason to tell millions of people to start doing it.