Jessie Inchauspé says we should avoid smoothies. What does the science say?
In a recent social media post, Jessie Inchauspé, aka the Glucose Goddess, claims that fruit smoothies are unhealthy due to their impact on dietary fibre and glucose levels. The post suggests that blending fruit destroys its fiber, causing glucose spikes and increasing cravings. This claim has garnered significant attention, raising questions about whether smoothies are a poor dietary choice.
Research suggests that glucose responses following the consumption of smoothies can vary depending on what type of fruit was blended. However, moderation and balance are key. Nutritional guidelines indicate that smoothie consumption should be limited to one serving of 150ml per day.
Misleading nutrition advice can cause unnecessary fear and confusion. Smoothies are a practical way for many to increase fruit and vegetable intake, particularly in populations that struggle to meet daily fibre requirements. Understanding the nuance behind such claims helps consumers make informed, balanced dietary choices. Keep reading to separate fact from fiction!
Spot Absolutes: Claims using “always” or “never” are red flags. Health and nutrition are nuanced, not black-and-white.
Let's break down the claim about smoothies and their impact on fibre, sugar, and glucose spikes.
1. Does blending destroy fibre?
Jessie mentions that the blending process “pulverizes the fiber in them”, leading her to the conclusion that “the fiber can no longer help reduce the spike from the sugar in the fruit.” This conclusion seems to imply that blending fruits in a smoothie destroys fibre, which is not accurate. In a paper published in Nutrients, researchers studied the health benefits associated with different fibres. They write about the effects of processing foods on dietary fibre:
Blending fruits or vegetables will not decrease fiber content, as dietary fiber does not decrease with mechanical forces.
2. Should you avoid smoothies because of glucose spikes?
The suggestion that smoothies always cause bigger glucose spikes oversimplifies how our bodies process food, and is not supported by scientific evidence. Dr Nicola Guess addresses this question (in response to the same post by Jessie Inchauspé) on her Instagram account:
Blending fruit rather than eating it whole doesn’t necessarily raise your blood sugars more. In fact some studies show that if you blend the fruit, you’ll actually get a lower glycemic response. And we think this might be because when you blend the seed, you can release soluble fiber, which increases the viscosity, the stickiness of the contents of your gut lumen, so it slows down the absorption of glucose. But many health professionals will recommend eating a fruit rather than drinking it. And it’s for 2 reasons: Firstly it’s just super easy to drink a ton of calories without realizing it, especially given the serving size you find in some stores. The second reason has to do with fructose. Fructose is a great sugar because it’s low glycemic. But in excess there is concern that it can cause elevated blood lipids. Absolutely none of this means fruit or fruit juice is bad. As always, the dose is what matters, so if you enjoy fruit juice, just limit yourself to one serving a day of about 150 ml.
3. Should you only eat whole fruits?
Registered Dietitian Katia Mashni from Top Nutrition Coaching shared her thoughts and advice on consuming fruits through smoothies or whole fruits:
Blending fruit can make it easier to digest and absorb. In some cases, blended fruit can be a good way to add fiber to people's diets and aid in digestion.
One might argue that smoothies can raise blood sugar levels faster than eating fruit; the reason for that is not necessarily the fiber content but the content of sugars in the fruit and the ability of the body to absorb the sugars more quickly in a blended form vs. a solid form. To avoid spikes in blood sugar levels from sugar in the fruit, dieticians always recommend having the fruit with a source of protein or fat to slow down the absorption of sugar into the bloodstream. For example, blend some nut butter, avocado or flax seeds with your fruit smoothie or add protein powder to it, and if you have the fruit, enjoy a handful of raw nuts or nut butter with it.
Whole fruits are fantastic, but smoothies can be a convenient way to consume fruit, especially if you're short on time. This is particularly important in our Western context, where a large majority of the population does not consume enough fibre. Plus, smoothies allow you to incorporate other nutritious ingredients like spinach, nuts, seeds, or yoghurt.
Yes, enjoy whole fruits too—but don't fear your blender! Balance is key.
Why Words Like "Always" and "Never" Matter
The post uses words like "always" and "never," which are often red flags in nutrition advice. Sound dietary guidance recognises that individual needs vary. What works for one person might not work for another, and blanket statements can oversimplify complex topics. Nutrition is about balance and personalisation—not rigid rules.
Sources
Dr Nicola Guess on Instagram: https://www.instagram.com/p/DBHG2uiIMdi/
Bates, D., & Price, J. (2015). Impact of Fruit Smoothies on Adolescent Fruit Consumption at School. https://pubmed.ncbi.nlm.nih.gov/25588935/
Crummett, L. T., & Grosso, R. J. (2022). Postprandial Glycemic Response to Whole Fruit versus Blended Fruit in Healthy, Young Adults. https://pubmed.ncbi.nlm.nih.gov/36364827/
Timm, M., et al. (2023). Beyond Insoluble Dietary Fiber: Bioactive Compounds in Plant Foods. https://pubmed.ncbi.nlm.nih.gov/37836422/
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