There is a saying that we aren’t what we eat, but rather we are what we absorb. Therefore following on from the last blog post, this article will investigate what happens to the vitamins, minerals and phytochemicals/nutrients when we turn our produce into drinks. If you haven’t read part one looking at fibre then click here.
Micronutrients sometimes referred to as micros include vitamins and minerals that are essential for our survival. They are needed in smaller amounts thus the name micro-nutrients and are important for helping our body produce everything it needs like hormones and enzymes. To read up on micros more click here.
Phytochemicals are another group of chemicals that are produced by plants. These chemicals are thought to provide beneficial effects to human health such as antioxidant, anti-inflammatory, and antifungal properties. It should also be noted that some micronutrients also exhibit anti-oxidant effects as well as having other roles in the body like vitamin c and selenium. Some examples of groups of phytochemicals include polyphenols and carotenoids (you don't need to remember that right now).
Some manufacturers of blenders, smoothie makers and juicers make claims that their machine will help unlock the trapped nutrients within fruits and vegetables making them more readily absorbed. Some will even claim these turn our ordinary foods into super-foods (sigh).
Are These Claims True?
We know that food does require breaking down to release certain nutrients. Plants hold different nutrients in different compartments, and so as part of the eating process we need to break these plants down to help our bodies absorb these nutrients. This is normally the job of our mouth (chewing) as well as the mechanical and chemical breakdown in our stomach and GI tract.
Looking at the effects of blending there is some research to suggest that putting our produce through this process will make the nutrients found inside more accessible. A study done in 2012 found that the smaller the particle size of the food (i.e the more it had been blended) the more accessible the nutrients investigated were (Katlijin et al 2012). This study, however, used much more extensive processing methods to breakdown their produce than found in the average kitchen. They vacuum packed the produce, then heated them in a water bath followed by soaking them in deionized water. Then some of the produce was taken through high-pressure homogenization. Nobody is doing that with their morning smoothies. What they were left with was a puree made up of different sized particles. Similar to Goldilocks and the three bears they were left with big pieces, medium-sized pieces and tiny little pieces of puree. It was the tiny pieces they were the most accessible but most of the particles were still big pieces and so not as “accessible”.
Looking at smoothies vs juices one study made drinks using with whole fruit or juices. It found that for some types of fruit, whole fruit smoothies lead to higher nutrient (vitamin c) content than those made with juice, but for other fruit, it was the opposite (Hee Pyo et al 2014).
Now just because the nutrients may now be more accessible, that does not necessarily mean greater absorption. Different nutrients have their own way of being absorbed within our intestine. Some nutrients will compete for absorption with others and so if we have more iron, for example, we may have less calcium absorption. There is also the possibility that once these nutrients are “released” and more accessible they may interact with other things in our blender and form new compounds (Parada et al 2007). This may lead to greater or reduced absorption. Think of it like being in a relationship, and your parents don’t like your partner. You might break up with them making you more “accessible”. You could end up with a new partner your parents like (increased absorption) or one that was worse than the original (decreased absorption).
What should also be noted is there are some phytochemicals thought to be bound to the fibre of our fruits and vegetables. Therefore with blending and juicing (which will remove/alter fibre content), there is also potentially the removal of the phytochemicals bound to the fibre (Bravo et al 1994)
What we need are well-conducted studies comparing the actual absorption of these nutrients in whole produce vs blended produce vs juiced produced. Unfortunately, we do not have this data. From what it looks like different nutrients and different plants will yield different results under different processing methods. There is no one rule, yet. So in short next time to read that blending your fruits and vegetables is going to help you absorb more of the nutrients found inside them, be skeptical. My interpretation and best advice would be the whole and less processed version should always be your first pick, because we know consumption of these is beneficial to our health and can significantly contribute to our nutrient intake .
Look out for the last part of this series talking about some of the other considerations when making these drinks and what their role is in a healthy balanced eating pattern.
Thanks for reading.