Are breakfast cereals really good for us?

Fortified breakfast cereals can be a useful source of fibre, vitamins and minerals – but some are considered ultra-processed food.

We're often told that breakfast is the most important meal of the day. Get this decision right and your nutritious morning meal can help keep you energised and focused for whatever challenges come your way. Yet the choice of what to eat for breakfast – or what to give your children if you have them – can feel overwhelming at times.

If, like 53% of the US population you decide to go the breakfast cereal route every week, then you can take your pick. There's porridge oats, granola, muesli, bran flakes, corn flakes, and puffed rice – the options are endless, with each colourful box promising to deliver a healthy, nutritious meal. Yet, although breakfast cereals have traditionally been seen this way, some scientists warn that these are ultra-processed snacks – and they are not actually good for us at all.

So, what is the truth, and what kind of cereals – if any – should we be eating?

First off, some facts. Cereals are grasses from the Poaceae family, cultivated for their edible seeds, or grains. Cereal crops include wheat, rice, oats, barley and corn. Each cereal grain has three main edible components. There's the outer layer of bran, which is rich in fibre, B vitamins and trace minerals. Then there's the endosperm, which is packed with starch and proteins to support the developing plant embryo. Finally, the germ contains the embryo, and is rich in oils, vitamins and minerals.

One of the first people to come up with the idea of turning grains into breakfast cereals was John Harvey Kellogg, an American physician. At the time he was a superintendent of the Battle Creek Sanatarium – a kind of hybrid between a hospital and a health resort. To improve the patients' diet, Kellogg developed, patented and introduced a variety of new foods, including Granola and Corn Flakes. However, these have now become so ubiquitous that there are dozens of generic versions on the market.

Today the production of breakfast cereals is an industrial affair. After the grains are harvested, breakfast cereals will undergo various processing steps before being packaged and sent to supermarket aisles. Some cereals – such as bran flakes – are made from the entire, or whole grain, while in others, such as some corn flakes, the grain is crushed between large metal rollers to remove the outer layer of bran. Some cereals then undergo further processing where the grain is milled into flour.

The resulting product is then mixed with flavourings, salt, sweeteners and other ingredients such as vitamins and minerals. They are then cooked and shaped into flakes, loops or other forms. Finally, the cereal is baked or toasted to give it a crisp texture.  

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Because cereals are fortified with minerals and vitamins, they have long been seen as an effective way of ensuring that people get the nutrients they need. This is especially true for individuals with restricted diets who may struggle to get the vitamins they require from food. Vegetarian and vegan diets, for example, tend to be low in vitamin B12, while a person with lactose intolerance may avoid milk and therefore not get enough calcium and vitamin D. As we get older, we absorb certain nutrients less efficiently, which can increase the risk of malnourishment. Pregnant women and children are also at greater risk of nutrient deficiencies.

Research confirms that there may be some benefits from eating fortified breakfast cereals. For example, studies have shown that many populations around the world are deficient in key nutrients. A study in the US, meanwhile, found that without fortification, a high percentage of children and adolescents wouldn't get enough micronutrients, risking long term health problems. Many breakfast cereals are also high in fibre, a nutrient that fuels the "good" bacteria in our guts – which 90% of us don't get enough of.

"Generally speaking, fortified cereals can make a useful contribution to some of the vitamins and minerals that, in the UK, some of us are deficient in," says Sarah Berry, professor of nutrition at King's College London.

For example, Berry points to the fact that in the UK, almost 50% of girls aged 11 to 18 have low iron intakes. Meanwhile, 14% of adults in the US have inadequate intakes of this nutrient. (Read more from the BBC about the global challenge of iron deficiency, and the debate over when to take iron supplements.)  

"However, you have to balance this out against the fact that there are many cereals that are high in sugar, low in fibre, and have a high glycaemic index, which means they aren't going to keep you full for long," says Berry. There are also ways of getting these vitamins and minerals that might be better for you, such as fruits, nuts, and vegetables, she says.

While some breakfast cereals are high in fibre, vitamins and minerals, many are also high in added sugar, salt and unhealthy fats.

According to the British Heart Foundation, a charity that funds cardiovascular research based in the UK, a 30g serving of sugar-frosted corn flakes, for example, contains around 11g of sugar. This is 12% of the maximum total recommended intake (RI) for sugars in the UK. (In the US, there isn't a recommended limit for total sugars, but the daily reference intake for added sugars is 50g per day (based on a 2,000 calorie diet). Meanwhile, a 45g serving of granola with dried fruit, nuts, and seeds, meanwhile, has 9.6g of sugar (10.7% of your total RI).

Eating so much sugar in one go is likely to lead to large blood sugar spikes, which over time may leave you at greater risk of developing diabetes, heart disease and other conditions. People who experience blood sugar spikes and dips are also inclined to feel hungrier sooner, leading to unhealthy snacking.

"We know from our own research that if you eat a breakfast high in sugar or refined carbohydrates, then two to four hours afterwards you tend to feel less energetic, more hungry, and less alert as well," says Berry. "What we've also shown is that people who have that dip after their breakfast tend to consume their next meal 30 minutes before someone who has a breakfast that doesn't cause them to have a dip, and they tend to consume, on average, 100 calories more at their next meal."

There is also concern that some breakfast cereals are an ultra-processed food, which means that they have undergone significant industrial processing. They frequently contain added sugars, preservatives, artificial colours and other additives.

"As a mum and a scientist, I am cautious about allowing my children to eat cereals that contain a lot of colourants," says Berry.

"Whilst in the UK there are stringent regulations in place to show the safety of these additives and colourants, I think there's a lot that we still don't know about how they may impact our health in the long term," adds Berry. "We are starting to understand that they may negatively impact factors such as our gut microbiome, but we just don't know enough yet."

However, not everyone agrees. Some experts and health charities argue that lumping all ultra processed foods (UPF) together is too simplistic – and not all processed foods are bad for you. For example, a 2024 study by researchers at the Harvard T H Chan School of Public Health, Massachusetts, found that while sugary drinks and processed meats raised the risk of cardiovascular disease, the opposite was true for ultra processed breads, breakfast cereals, yogurts and dairy desserts.

And not all breakfast cereals are created equal. Berry counts granola and muesli as healthy options, as long as they don't contain too much added sugar. "It's about building a breakfast that has the fats, the protein, and the carbohydrate that's going to cause that more sustained release of energy and keep you feeling fuller for longer," she says. "Granolas and muesli have lots of nuts, seeds and berries in them, so they have got loads of fibre, but also protein and fat from the nuts. That will keep you full for longer and will therefore balance your energy levels better."

Another popular breakfast choice is porridge, or oatmeal as it is known in the US. One large review study included data from more than 470,000 individuals, and followed their health outcomes over years or decades. The researchers found that those with the highest oat intake had a 22% lower likelihood of developing type 2 diabetes compared to those with the lowest consumption. Those who consumed at least 19g per day also had a 24% lower risk of death from all causes compared to those who ate the least.  

The key ingredient thought to be responsible for the health benefits of oats is a dietary fibre known as beta glucan. Beta glucan has been shown in many clinical trials to reduce circulating cholesterol levels, particularly low-density lipoprotein (LDL), the 'bad' cholesterol linked to heart disease. Some studies also suggest that beta glucan may reduce a person's risk of developing type 2 diabetes, and help them develop better insulin control.

However, many oat-based breakfast cereals are made from finely ground oat flours that do not have the same health benefits as whole, rolled oats. Compared to the latter, the large surface area of breakfast cereals made with oat flour means they are more quickly digested, causing sugar to rapidly enter the bloodstream. The same is true of pre-cooked porridges made from "instant oats".

In one clinical trial, volunteers were asked to eat rolled oats on one day, and instant finely-ground oats on another day. The researchers found that despite the oats containing the same amount of fibre, protein, fat, and carbohydrates, the more finely ground oats produced a much larger spike in the participants' blood sugar levels.

Meanwhile, breakfast cereals made from refined grains, where the nutrient and fibre-rich bran and germ layers have been stripped away, may also have fewer benefits. While studies have shown that the consumption of whole grains is linked to a reduced risk of cancer, cardiovascular diseases and type 2 diabetes and other chronic diseases, research suggests that some of these health effects don't seem to apply when grains are consumed in their refined forms.

"Whole grain cereals are healthy because they are packed with fibre," says Riccardo Caccialanza, a clinical nutritionist at the University of Pavia in Italy. He explains that one important function of this nutrient is to slow down the digestion of food, so you get fewer glucose peaks and better glucose control. "However, if you take the fibre away, which happens when you refine the grain, then the glucose increases more quickly," he says.

So, are breakfast cereals good or bad for us? It depends entirely on the cereal.

One study in Australia looked at over 140,000 people aged 45 years and older. It found that eating muesli for breakfast lowered the risk of heart disease, stroke, and diabetes. Another large study asked over 186,000 participants aged 40 to 69 years in the UK about their dietary habits – including breakfast cereal consumption – and then followed the participants for an average of 13 years. It found that people who ate at least one bowl muesli, bran-based cereals, and porridge a day were 15%, 12%, and 11% less likely to die during the follow up period than people who did not eat breakfast cereals. On the other hand, individuals who ate sweetened cereals for breakfast were more likely to die of cancer during the study period.

The key, then, is to look at the back of the pack carefully, say experts. "If you're selecting cereals that have about less than five grams of sugar a portion, and more than three grams of fibre per portion, then you're on track to making a healthier choice for your cereal," says Berry.

But to make it extra healthy, both Berry and Caccialanza suggest 'hacking' or customising your cereal so that it doesn't just contain carbohydrates, but also has a good mix of healthy fats and protein that will keep you feeling full for longer.

"I love a granola, but I add extra nuts and kefir yoghurt to it," says Berry. "I make a supermarket standard granola healthy by what I overlay on top. And I think that's something that people should be thinking about a little bit – what can they do to add some balance to [breakfast cereals]?"

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