Oats vs. Weet-Bix: Which has more fibre?

by Jennifer Bowden / 19 May, 2016
Oats might be your idea of brekkie hell, but your body will thank you – and the bigger the flakes the better.
Photo/Getty Images/Listener Illustration
Photo/Getty Images/Listener Illustration


I’ve been making porridge with Harraways Wholegrain Oats, assuming they would contain more fibre than the usual flakes. But to my surprise they have the same 9.2g of fibre per 100g as Harraways Rolled Oats. How can this be when the wholegrain flakes are larger? Are larger flakes preferable as they make the intestines work harder? In the course of reading cereal-packet labels, I discovered Weet-Bix has 10.5g of fibre per 100g, whereas I thought it was more processed than oats.


It’s true that Harraways Wholegrain Oats have the same fibre content as flattened and sliced rolled oats and slightly less than Weet-Bix. But the good news is your instincts have taken you in the right direction, although partly for the wrong reason.

Dietary fibre is the fraction of the edible parts of plants that is resistant to digestion and absorption in the small intestine. So whether the oats are cut or not by the manufacturer will not appreciably alter the proportion of the food that is indigestible.

In the past, scientists thought dietary fibre provided no energy but acted as a brush through the gut. However, it’s now accepted that dietary fibre and whole grains promote the growth of beneficial gut bacteria. About 1-2kg of microbiota live in our gut, roughly the same weight as our brain, and like an organ of the body this microbial community plays a critical role in maintaining our health by contributing nutrients, energy and gut immunity.


Dietary fibre also aids the gut by promoting laxation and preventing constipation, haemorrhoids and diverticular disease. Increasing dietary fibre intake may also lower our risk of obesity, diabetes, certain cancers and cardiovascular disease. It’s thought dietary fibre reduces cardiovascular-disease risk through its ability to lower blood cholesterol levels, an effect that’s particularly strong in beta-glucan fibre found in oats and barley.

Where wholegrain oats may slightly outperform rolled oats is in the mouth. That’s because more chewing is typically required to swallow a mouthful of wholegrain oats than oats that have been rolled and cut by the manufacturer. And assuming that extra chewing takes place (rather than gulping the wholegrain oats straight down), this affects the production of hormones that alter our appetite and help maintain a healthy weight.

A clinical trial involving lean and obese men found that they reduced their total energy intake by 12% during a meal when they increased chews per bite from 15 to 40. ­Chewing seems to decrease the level of ghrelin, a hormone thought to stimulate appetite.

As for Weet-Bix, it has not only more fibre, but also added sugar and sodium. Compared with other processed breakfast cereals, however, Weet-Bix’s sugar and salt levels are relatively low.  But salt is not something we need more of in our diet; most New Zealanders consume far too much. So eating an oat-based porridge instead of a processed cereal limits our sugar and salt intake, unless you add them yourself. The benefit of choosing a natural whole grain for breakfast is that you control your sugar and salt intake.

Foods that are minimally processed are generally more nutritious and beneficial for our health than the ­processed variety. Your wholegrain oats are a good choice.

Some people might prefer the convenience of rolled oats as they cook more quickly than wholegrain oats, but if you’re happy with whole­grain’s cooking time, then relax and enjoy your porridge knowing you’ve chosen well.

Happy ­chewing. 

Email your nutrition question to: nutrition@listener.co.nz

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