What are the disadvantages of green smoothies?

Green smoothies have become increasingly popular in recent years as a healthy and nutritious beverage. Made primarily from leafy greens, fruits, and water, green smoothies provide a concentrated dose of vitamins, minerals, and antioxidants. However, there are some potential downsides to drinking green smoothies that are important to consider.

Nutrient Absorption

One possible disadvantage of green smoothies is that the nutrients may not be as readily absorbed compared to when greens are eaten whole or gently cooked. The high-speed blending breaks down the plant cell walls, releasing more nutrients but also making some nutrients more prone to oxidation. This means some of the heat-sensitive vitamins like vitamin C and B vitamins may degrade more rapidly in a green smoothie compared to eating the greens whole.

High Sugar Content

Green smoothies often contain fruit to improve the flavor. However, the fruits added can spike up the sugar content. For example, a 24 ounce green smoothie could easily contain 30-60 grams of sugar from added fruits like bananas, mangos, pineapples and dates. This is a lot of concentrated sugars in one drink. Consuming high amounts of fructose from fruit smoothies on a regular basis can potentially contribute to insulin resistance over time for some individuals.

Calorie Density

With the addition of fruits and other ingredients like nuts, seeds, nut butters or oils, green smoothies can quickly become high in calories. A 24-32 ounce smoothie could contain 500-800+ calories. While these ingredients add healthy fats, protein and carbs, it may be easy to mindlessly consume excess calories, especially when drinking them frequently or in large portions.

Fiber Removed

Blending greens removes most of the beneficial fiber, leaving only the extracted juice. This makes the nutrients easier to absorb, but without the fiber content, it also impacts gut health. The fiber in whole greens helps promote satiety, healthy gut bacteria, regular bowel movements and balanced blood sugar levels. Removing the greens’ natural fiber content can affect these mechanisms.

Phytic Acid

Some green smoothies include raw nuts and seeds or nut butters as thickeners or to boost the protein and healthy fat content. However, these ingredients contain phytic acid which impairs mineral absorption. The phytic acid in nuts, seeds and grains binds to minerals like iron, zinc, magnesium and calcium. Blending these ingredients into a smoothie retains the phytic acid, potentially inhibiting some mineral absorption.

Oxalate Content

Spinach and other leafy greens contain oxalates, which are antinutrients that can bind to calcium and other minerals, reducing their absorption. While cooking helps reduce oxalates, blending greens raw keeps the oxalate content high. For most people this isn’t a major concern, but those with kidney problems or recurrent kidney stones may want to avoid high oxalate greens.

Nutrient Loss From Oxidation

The process of blending greens at high speed introduces a lot of oxygen into the smoothie. This can accelerate oxidation and degradation of certain nutrients and plant compounds. Vitamin C, polyphenols, carotenoids and other antioxidants are especially prone to oxidation. For maximum nutrient retention, it’s best to consume green smoothies immediately after making them.

Potential For Contamination

Improperly washed leafy greens and other ingredients can potentially contaminate a smoothie with bacteria, parasites, pesticides or heavy metals. Greens should always be washed thoroughly before using in smoothies. Contamination is also possible from blenders that aren’t properly cleaned between uses.

Mouthfeel And Texture

Some people dislike the thick, green color and texture of green smoothies. The mouthfeel of blended leafy greens may take some getting used to, especially for kids or picky eaters. Starting with milder tasting greens like spinach and less green portions can help with adjusting to the texture.

Gas and Bloating

Green smoothies may cause gassiness or bloating, especially when consuming large amounts. The high fiber content from the greens, coupled with the sugars in the fruits, can lead to excess gas production from the rapid fermentation by gut bacteria. Introducing green smoothies slowly and in small amounts may help reduce digestive discomfort.

Potential Contaminants

There is a small risk of contamination from bacteria or mold if produce is not handled properly. To avoid this:

  • Wash all produce thoroughly before blending
  • Scrub firm produce like apples
  • Discard bruised or moldy produce
  • Refrigerate smoothies and consume shortly after making

Proper cleaning of the blender is also essential to avoid cross contamination.

High Fruit Content

Many smoothie recipes call for fruit to sweeten and thicken the smoothie. However, this can make the drink high in natural sugars. Some ingredients to watch out for:

Fruit Grams of sugar in 1 cup
Bananas 14 grams
Grapes 15 grams
Apples 19 grams
Mangoes 22 grams
Pineapple 16 grams

Going easy on high-sugar fruits and focusing more on greens creates a healthier sugar balance.

Nutrient Absorption Inhibitors

Some green smoothie ingredients can inhibit nutrient absorption. These include:

Ingredient Absorption interference
Spinach Calcium absorption inhibitor (oxalates)
Swiss Chard Iron and zinc absorption inhibitor (oxalates)
Nuts and seeds Mineral absorption inhibitor (phytic acid)

Balancing these with ingredients that promote absorption, like citrus and vitamin C, can help maximize nutrient intake.

High Calorie Density

With the addition of fruits, nut butters, seeds, oils or other mix-ins, smoothies can quickly get high in calories. For example:

Smoothie Ingredients Calories
1 banana 105
1 cup blueberries 84
2 tbsp peanut butter 188
1 cup spinach 7
1 cup almond milk 39
Total 423

Watching portion sizes and ingredients is key to avoiding excess calorie intake from smoothies.


Green smoothies can be a healthy addition to your diet when consumed in moderation. Focus on maximizing nutrient-dense ingredients like greens, healthy fats and proteins. Minimize high-sugar fruits and be mindful of calories and portion sizes to keep smoothies as a healthy beverage choice. Drink them fresh, rotate greens for variety, and adjust ingredients to find flavors you enjoy.

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