They may never top the Great British Baking Show, but our muffin recipe is a scientific winner

Our PREDICT 1 study – the largest nutritional response study of its kind in the world – involved a lot of muffins. More than 32,000 of them in fact, eaten by more than a thousand volunteers who wanted to find out more about how their bodies work.

Our second study, PREDICT 2, is now underway and hundreds of these little cakes are winging their way to participants across the US. Over the ten days of the study, everyone will have to eat a total of 20 muffins at specific times – sometimes washed down with a milkshake – gathering data about how their blood sugar and fat levels change as they digest them.

(It’s not all muffins, all the time. Participants are free to eat their own choice of foods the rest of the time, as long as it’s carefully logged – something we’ll be talking about more in a future post.)

So what’s in these muffins that makes them so special? And what can they tell us about individual responses to food?

Not your Grandma’s muffins

To start with, these aren’t the kind of towering treats you can pick up from a coffee stand or bakery. 

Every single one of our muffins is baked according to precise scientific specifications, containing a carefully controlled amount of calories, carbohydrate, fat and protein (macronutrients). 

Using these standardized muffins means that we remove the natural variability in foods, and minimise the impact of the ‘food matrix’ – that’s the way in which individual nutrients are physically and chemically bound together in foods, which affects how they’re broken down in the body.

Some of the PREDICT muffins are high-fat low-carb bakes with a heavy texture, while the high-carb low-fat ones are light and fluffy. Then there are ‘average snack’ muffins that fall somewhere in between.

By getting thousands of people to eat the same selection of muffins and measuring their nutritional responses, we can compare data between them.

This means that any differences must be down to their bodies, their microbiomes or the specific proportions of macronutrients in what they’ve eaten.

In case you were wondering, every single muffin is exactly the same plain vanilla flavor.

While it might be more fun to throw in some blueberries, choc chips or pumpkin spice, this would introduce more variation into the data and make it harder to figure out what’s going on.

Our family recipe

Like a long-held secret family recipe, the original recipe for our test muffins was handed down to us by Dr Sarah Berry, our lead nutrition scientist and collaborator at King’s College London. 

She’s one of the world’s leading experts in studying how we break down and use the food we eat (known as post-prandial metabolism), and is particularly interested in how different people digest and use fat. 

Although Sarah’s original muffin recipe has been fed to more than 1,000 volunteers over more than 15 years of studies at King’s College London, she and the team initially tried to develop standardized cream cheese sandwiches as a suitable food for testing personal nutritional responses in the PREDICT study.

But while a cheese sandwich may look simple, it actually has a remarkably complex food matrix. It also turned out to be too difficult to manipulate the levels of fat, protein and carbohydrate in the sandwiches to the extent required for the study without making them inedible.

It soon became clear that the best option was the tried-and-true muffins. 

They’re self-contained, easy to eat, and are simple to freeze, store and ship. They’re also made of basic ingredients with a simple food matrix that’s easily digested. 

And although it took some tweaking, the team were able to create muffins with the wide range of macronutrients that we needed for the study while still remaining palatable.

Sarah mainly studies responses to fat, so her original muffin recipe was quite oily. This meant that our test baker, Kate, still had to do a lot of experimentation to create the perfect range of muffins for PREDICT. 

Although the basic recipe for all our test muffins is the same – flour, sugar, baking powder, dried and liquid egg white and a blend of oils – the proportions vary depending on the levels of fat, carbohydrate and protein that we need, which took a lot of optimization to get right. 

And then there’s one muffin with a very special added ingredient. 

About those blue muffins…

While most of our muffins are golden brown, there’s one type that stands out from the crowd. 

On the third day of the PREDICT 2 study, every participant gets to eat a muffin containing dark blue food colouring. And a few days later, they get to see it come out the other end. 

Although producing bright blue ‘Smurf poop’ might come as a bit of a surprise, it provides a handy way of measuring how long it takes food to move all the way through the gut. Also known as transit time, this is an important readout of digestive health.

They may never win the Great British Bake Off (as our London team know it) but our muffins are an essential part of our PREDICT studies. We’re also planning to make gluten-free and vegan options in the future, so that we can open up our studies to even more participants. 

We’ll be writing a lot more about what goes on as part of our PREDICT studies in future posts, and you can read more and apply to take part on our website

Right now, we’re only recruiting for PREDICT 2 in the US, but you can join our mailing list to be the first to find out about opportunities elsewhere in the world. 

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