Why A Smoothie is “Pre-Chewed” Food

In the interest of time, many people will throw a cup or more of fruit, some green veggies and maybe some protein powder into a blender to make a smoothie for breakfast without realizing the effect that blending has on their blood sugar, gut microbiome, and even the overall amount of food they eat.

Making a Smoothie 

Making a smoothie
For people with pre-diabetes or diabetes, a smoothie that has pureed fruit has a very different effect on blood sugar than eating the same ingredients as whole, intact foods. This is because the carbohydrate from the ingredients is now acellular, meaning “out of the cell”.

Cellular versus Acellular Carbohydrate

Cellular carbohydrates come from whole, intact food that remains in the cell wall. These take longer to be digested and absorbed into our bloodstream than carbohydrates that have been ground or pureed. As well, cellular carbohydrates have a lower “carbohydrate density” than processed carbohydrate, where the carbohydrate density are the grams of carbohydrate in a food, minus  the grams of fiber, based on the total gram weight of the food [1].

Acellular carbohydrates are no longer are contained within their cell wall, because they have been pureed (like fruit in a smoothie), or ground, such as flour, from grain. As a result, these foods have a much higher “carbohydrate density” because the fiber is no longer contained in the cell wall, along with the carbohydrate.

A Smoothie as “Pre-Chewed” Food

Most people think digestion begins in the stomach, but it doesn’t. It starts in the mouth when we chew food. As unpalatable as it sounds, smoothies are really “pre-chewed” food, and consuming carbs this way can disrupt our blood sugar, gut microbiota, and even affect the amount of food we consume.

  1. A 1977 study published in the journal Lancet demonstrated that when fruit is pureed fruit or juiced and then eaten, the glucose response 90 minutes later is significantly higher than if the fruit were eaten whole [2]. This is because the blender or juicer has made the carbohydrate acellular, by doing some of the work that chewing does. In this way, carbohydrate-containing smoothies are essentially “pre-chewed”. For those with pre-diabetes or diabetes, having a morning smoothie instead of eating the same foods intact has a very different effect on blood glucose. Keep in mind, that while 60g of a whole fruit, 60g of pureed fruit, and 60g of fruit that has been juiced have the same amount of carbohydrate and similar Glycemic Index (GI), the GI only indicates how quickly a food or drink will increase blood sugar, not how much higher blood sugar will go.  The two-part article, titled The Perils of Food Processing explains in scientific terms the effect of food processing on blood sugar.
  2. Carbohydrates that remain with their cell structure such as whole berries or fruit (i.e. cellular carbohydrates) have their carbohydrate density preserved until the digestive juices in the stomach begin to break down the cell wall of the fruit. Once free from the cell wall, the carbohydrate is absorbed in the large intestine, or colon. Acellular carbohydrates, on the other hand such as fruit-containing smoothies begin to be digested in the small intestine, instead of the colon (where cellular carbohydrates are digested). It is thought that this early fermentation may raise the risk of gut dysbiosis and leaky gut syndrome [1].
  3. Finally, the processing of acellular carbohydrates in a blender so we can drink our food, as opposed to eating it makes it too easy to have more than one would if eating the same amount of the intact food. Since acellular carbohydrates are higher in carbohydrate density than the diets made of intact, whole food, it is thought that this may raise the risk for obesity, and leptin resistance [1]. Leptin is the hormone that tells us when we are hungry, and it is thought that this negative feedback loop becomes dysregulated when we consume large amounts of acellular carbohydrates, including pureed fruit, flour-based baked goods, and refined grains.

Final Thoughts…

It is important to keep in mind that digestion begins in the mouth when we chew food and how we absorb the carbohydrate contained in those foods is very different when we eat whole, intact food, as opposed to pureeing them into a smoothie. Smoothies are really “pre-chewed” food that can disrupt our blood sugar, gut microbiota, and affect the overall amount of food we consume.

Instead of throwing some fruit, veggies and protein powder into a blender, why not eat a half cup of berries, with a cup of cottage cheese or plain Greek yogourt, and grab a handful of snap peas for the low carb veggies, instead? This is a quick, light meal that has all the protein and leucine required for adults to preserve their muscle mass — and there is no blender to clean, afterwards!

How I Can Help

I understand that not everyone who wants to eat healthy loves to cook. I often design Meal Plans for people based on easy-to-obtain foods that require minimum preparation and little to no cooking. Whether you love to cook or can’t be bothered, I can help.

For more information, please look under the Service tab or contact me through the Contact Me form above.

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  1. Spreadbury, I., Comparison with ancestral diets suggests dense acellular carbohydrates promote an inflammatory microbiota and may be the primary dietary cause of leptin resistance and obesity. Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy. 2012:5 175-189.
  2. Haber GB, Heaton KW, Murphy D, Burroughs LF. Depletion and disruption of dietary fibre. Effects on satiety, plasma-glucose, and serum-insulin. Lancet. 1977 Oct 1;2(8040):679-82. doi: 10.1016/s0140-6736(77)90494-9. PMID: 71495

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