What Happens When We Turn Our Fruits and Vegetables into Drinks? - Part 1 - Fibre

I can remember not so long ago, and they’re probably still floating around now, seeing ads on TV about the newest juicer or blender which would take your fruits and veggies and “extract vital nutrients from the plants cell wall and turn your produce into a super drink packed with nutrients”. Or something along similar lines. I had also heard as a kid that making smoothies would ruin the fibre from the ingredients and I was best to just eat my fruits and veggies whole. So, does blending destroy fibre? Is it better or worse for absorbing vitamins and minerals? This next series of articles will be unpacking what happens when we take our fruits and veggies and turn them into smoothies and juices. Here is a collection of some of the research and my interpretation.
 
Fibre
 
Fruits and vegetables can be a good source of fibre which is an important component of our diet. Fibre put simply is a type of carbohydrate that cannot be broken down in our gut. This allows it to pass through our small intestine which one, can help to keep us regular and two feeds our gut bacteria. Fibre also has other known benefits such as helping to reduce our cholesterol levels. Fibre is not just one compound/substance, think of it more of a group of different compounds that share the common theme of not being able to be broken down in the human gut. The difference between them is what happens as a result of them staying in our gut. For example, some act as a ‘bulking agent’, bulking up our stool (poop) whereas other types bind with water which can help us pass our stools more easily.
 
There is one train of thought that blending up our produce will destroy the fibre. Is this true? In the case of smoothie making we are not necessarily destroying the fibre but rather altering its composition. This is assuming we are adding whole fruit to our smoothies. When investigated it was found that when fruits where made into smoothies, they retained a significant amount of fibre (Saltaouras et al 2019) whereas juices generally have a much lower fibre content (potentially 10 times less) (Saltaouras et al 2019).   
 
Now the fibre that is still available in the smoothie does not necessarily have the same structure and function as whole fruit fibre. It has been shown in oat and wheat fibre, when blended their structure is altered leading to a change in function (Ann-Marie Cadden 1987). In a study looking at oat and wheat fibre the particles were both made smaller, but this resulted in different things for the two types. The wheat fibre had a decreased ability to hold onto water with the opposite occurring in the oat fibre after being blended.

Summary 

In short blending will not completely destroy the fibre per say, but rather alter its structure. Think of putting a log of wood through a wood chipper. You still have the wood but it’s now in a different form and so its function has been altered. We cannot make one generalised comment about what happens exactly to the function though. Blending will affect different fibres differently. There is still some fibre in-tact and so I would hypothesize we should still see some of its benefits like feeding our gut bacteria, but its effect on our bowel habits may be different depending on how it reacts with water. We do not however have conclusive evidence to say exactly what will happen to the fibre and how it will effect us.
 
Look out for the next post next week looking at what happens to the micronutrients followed by phytochemicals/antioxidants of fruits and vegetables when we turn them into drinks.
 
Thanks for reading.
 
Marco

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