Maryrose is a 47-year-old mother of two from California.

She’s fit and healthy — she gets regular checks at the doctor’s office every few months. And by all conventional measures — things like weight, blood sugar and cholesterol levels — she’s in top shape.

But Maryrose has an unusual habit.

For Australians, that’s half a litre — or about three times as much as the typical recommended serve of ice cream.

She’s a purist — vanilla only, thanks. And Maryrose says the nightly ritual is as much about winding down and relaxing as it is about the ice cream itself.

Her pint-a-night habit started when she was pregnant with her first child. After finding it didn’t seem to affect her health or energy levels, she never stopped.

Searching for answers online

I’m a food and nutrition scientist, and my instinctive reaction after speaking to Maryrose for our podcast series Cooked was that this habit definitely doesn’t fit our standard advice of balance and moderation.

How could it be that someone eating a pint a night bucks the conventional wisdom on what’s good for your health?

But what is healthy? And how can we make empowered decisions about what we eat? That comes down to two factors: understanding how evidence works, and what role food plays in our lives.

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Looking for advice, Maryrose asked an online forum of doctors whether ice cream could ever be healthy.

It might seem a silly question at first glance — but she got back more than she bargained for.

“They pretty much were uniformly saying that this was a bad idea, I can’t do this, maybe I’m fine now, but, you know, I’m gonna get diabetes, I’m gonna clog my arteries,” she says.

But among the responses was an article pointing to a complex and contested idea in nutrition science.

It discussed mixed evidence showing that in some cases, ice cream could have a protective effect against some negative health outcomes — such as diabetes and heart disease.

What does the evidence say?

Multiple scientific studies show a positive association between ice cream and health.

When diets are tracked and people are followed for a long time it appears that those who eat ice cream more often have a lower risk for type 2 diabetes and even cardiovascular disease.

“It is, I would say, what we would call a fairly classic and relatively strong epidemiological signal,”  epidemiologist Gideon Meyerowitz-Katz of the University of Wollongong says.

But there are scientific reasons the effect seen in these studies might not actually be “real” — a statistical anomaly rather than something that is happening in the real world.

The studies looked at this “ice cream paradox” are observational studies, where people are followed over time. That’s distinct from randomised controlled trials, experiments where you split people into groups and give them different treatments or interventions.

Observational trials can’t prove that ice cream has a protective effect on our health. They can only show that the two things are linked.

So the effect could be explained in other ways. It might be that richer people, who are typically healthier overall, also buy and eat more ice cream.

Or that less healthy people — say those with heart conditions or diabetes — have been told to avoid foods like ice cream by their doctor.

“People who know they’re at risk for diabetes don’t eat ice cream, and people who know, ‘Boy, I’m never going to get diabetes because I’m super healthy’ eat ice cream,” Dariush Mozaffarian says.

Weighing up the good with the bad

Dr Mozaffarian is director of the Food and Medicine Institute at Tufts University and has been involved in some of the studies finding health effects linked to ice cream.

“You get what’s called reverse causation, where … people who are less well and worried about their glucose tend to avoid ice cream, and so that could be why ice cream seems protective,” he says.

There are also published studies that show the opposite effect — a negative association of eating ice cream and health.

This mixed bag of findings isn’t unusual in nutrition research. There isn’t always one right answer. It can depend on the group of people studied and their context.

The studies that show benefits are typically from Western nations like the US. The ones showing no benefit or increased risk are from Asian cohorts such as South Korea.

It’s very likely that these places have different genetics in the population, different rates of the conditions being studied, different background diets, and maybe even different types and amounts of ice cream eaten.

Both sets of studies could be high quality; the results just might apply to different people.

So where does that leave us — and Maryrose?

Maryrose talks about her pint-a-night ice cream habit as an “incredibly relaxing” ritual.

This is a reminder that food is more than the nutrients it contains. It’s part of our life, culture and enjoyment.

Balancing all the reasons we eat and not focusing too much on single features or nutrients is part of making empowered eating decisions.

Ice cream is Maryrose’s only indulgence — the rest of her diet is made up mostly of veggies, fruits and lean meats — and she exercises regularly.

Healthy eating is often framed in terms of self-control. The idea is that we need to manage ourselves to resist temptations. 

This is why the idea of a pint of ice cream every night made me uncomfortable to start with. It grated against the deep-seated instinct that healthy eating requires the restriction of foods that we enjoy.

But research shows self-control isn’t necessarily all it’s cracked up to be.

Trying too hard to restrict ourselves can weaken our sense of self-control.

And it can be hard to have self-control in times of stress or a high burden of decision-making. Partaking in “indulgent foods” — the ones we tend to think of as less healthy — can actually help promote more controlled food choices overall.

As the research debate continues over ice cream and its health effects, the word from the experts we spoke to and from Maryrose was clear.

It’s all about context — what you eat the ice cream with, what you eat that isn’t ice cream, and how eating it makes you feel.

And don’t be afraid to talk to your doctor or a dietitian to help you figure out the evidence and the context for your specific joyful foods. They might end up being empowering and health-promoting too.

Emma Beckett is the presenter of the new Radio National series Cooked.

Dr Beckett is a food and nutrition scientist. She has received funding from the A2 Milk Company for two academic research projects, guest talks, hosting of events and the creation of fact sheets and infographics.

Hear about ice cream and the concept of healthy eating in the first episode of Cooked, and subscribe to the podcast for more.