If you are reading this, you probably already know about green smoothies and the many health benefits they provide.
But maybe you just read something on a blog that suggested that green smoothies weren’t the panacea of health they are made out to be. Maybe you’re worried that your daily green habit is going to bite you in the behind down the road.
Are there any side effects to drinking a daily green smoothie? Are there certain people who should not drink green smoothies? Do green smoothies have a dark side?
Let’s tackle the most common green smoothie controversies. (Skip to a section by clicking any of the links below.)
- Do Green Smoothies Contain Too Much Sugar?
- Will Green Smoothies Cause Weight Gain?
- Aren’t Green Smoothies Too High In Carbohydrates?
- Should I Make Green Smoothies With Less Fruit And More Greens?
- Do Green Smoothies Increase Diabetes Risk?
- Will The Fruit Sugars In Green Smoothies Rot Your Teeth?
- Will Raw Kale Destroy My Thyroid?
- Is The Oxalic Acid (Oxalate) Content Of Raw Spinach Bad For Me?
- Does Blending Destroy 90% Of The Nutrients In My Smoothies? What About The Fiber?
- Isn’t It Improper Food Combining To Mix Greens/Vegetables With Fruit?
- Blending vs. Chewing: Which Is The Better Way?
1) Do Green Smoothies Contain Too Much Sugar?
As a blend of sweet fruits and leafy greens, the majority of the calories in green smoothies come from carbohydrates – particularly sweet fruits. Since sweet fruit is high in sugars, is a daily green smoothie or two providing too much sugar in your diet?
I have looked into this issue extensively, and the bottom line is this:
1) Naturally-occurring sugars (like the ones found in fruit) do not cause the health problems associated with added sugars (like the ones found in soft drinks and baked goods).
2) Scientifically established sugar intake guidelines published by the World Health Organization (WHO), American Heart Association (AHA), and The National Institute of Medicine are for added sugars only, and specifically state that naturally-occurring sugars are not a health concern.
3) There is zero evidence that fruit, or the sugars in fruit, cause weight gain, or increase one’s risk for developing type 2 diabetes. In fact, the overwhelming body of medical studies suggest that diets higher in fruits and vegetables have lower risk for obesity and diabetes.
Read more about sugar, fructose, and green smoothies.
You don’t even have to avoid “high glycemic” fruits like bananas and watermelon, either. Read more about Glycemic Index vs. Glycemic Load.
2) Will Green Smoothies Cause Weight Gain?
I lost 40 pounds with green smoothies and a plant-based, whole foods diet. In the 8 years that I have had my blog, I have read thousands upon thousands of weight loss testimonials attributed to green smoothies.
It truly surprises me that there is even a controversy about using green smoothies for weight loss.
I will tackle some of the more specific weight loss-related controversies below. If you started drinking green smoothies and have either gained weight, or haven’t lost any weight, then read these tips for what went wrong.
Sugar Content Of Fruit And Weight Gain: Naturally-occurring sugars in whole foods (like fruit) do not cause weight gain.
Calorie Reduction Controversy: The most recent exposé about the “unhealthiness” of green smoothies cites this health study comparing the satiety of different forms of fruit (whole apple, apple sauce, apple juice and apple juice with fiber added) and how it affects total calorie intake.
The study found that eating a whole apple reduced calorie intake of the following meal by 15% while consuming apple sauce decreased calorie intake by 6% in the following meal. Drinking apple juice with fiber reduced calorie consumption of a meal by only 1% while straight up apple juice actually increased calorie intake by 3%.
Assumptions based on the data presented by this study suggests that eating whole fruits promotes a significant decrease in calorie consumption while pureed fruit is not as effective at reducing overall calorie intake. However, there is a big difference between a freshly blended green smoothie and cooked apple sauce. You can’t even compare the two as they contain different foods and are processed in completely different ways.
Furthermore, the conclusion of the study explicitly states that “more research is needed to test the effects of consuming different forms of fruit on energy intake over longer periods of time before conclusions about the role of fruit in different forms in weight management can be made.”
While it makes sense that consuming apple sauce may not be as satisfying, a green smoothie – especially when it is consumed as a meal – is filling and results in lower caloric intake overall.
A calorie-sufficient green smoothie MEAL will satisfy your hunger until your next meal and reduce overall calorie intake for the day – unless the rest of your diet isn’t healthy.
Excess Calories From Green Smoothies Because You Are Not Chewing Them: I recently read an argument stating that drinking green smoothies could add up to 100 excess calories per meal because chewing burns calories, where drinking does not. Therefore, eating your greens in a salad is better for weight loss than drinking your greens in a smoothie.
I’m not sure how they got the idea that chewing a meal consumes 100 calories. My calculations are closer to 27 calories consumed by chewing for a solid hour. In the grand scheme of things, burning 27 calories while chewing (for an hour, mind you) is not going to make or break your weight loss success.
If anything, you’ll burn more calories with green smoothies because they will be efficiently digested and provide more energy to exercise and live an active lifestyle. And you are more likely to stick with it. It’s much easier and way more convenient to drink a green smoothie every day than it is to eat a giant bowl of salad.
3) Aren’t Green Smoothies Too High In Carbohydrates?
A common question I get about green smoothies is regarding their carbohydrate content. A typical green smoothie meal may have excess of 50+ carbs.
Is that a bad thing? Will that make you fat? Will it increase your risk for diabetes?
No. Whole food carbohydrates behave differently in your body than carbs like pasta, white bread, white rice, cookies, and sweetened beverages.
There is not one single piece of medical evidence that suggests that consuming fruit or other whole food carbohydrates (quinoa, brown rice, whole grains), increase risk of obesity or disease. In fact, the evidence shows the opposite!
Good Carbs vs. Bad Carbs: You have probably heard about “good carbohydrates” and “bad carbohydrates”. Not all carbs are created equal. There’s no argument that donuts, pasta, white rice (and bread), soda and sweetened beverages, cookies, and cupcakes are all bad carbohydrates. These foods are at the forefront of the obesity epidemic.
However, fresh, whole, ripe fruits are in a completely different league than pastries. It’s a tragedy that so many people (including some doctors) lump them in with the “foods that must go” when you are trying to lose weight.
Fruits, even sweet fruits like bananas, mangoes and grapes aren’t just made up of sugar or carbohydrates. They provide excellent sources of vitamins, minerals and antioxidants. They contain lots of fiber, which slows down digestion so that you don’t get hit with a sugar rush, like you would drinking a bottle of soda.
While it is good practice to limit added sugars, sweet fruits don’t count as added dietary sugar because they are whole foods. (If you are diabetic, however, you may still need to limit your intake of carbohydrates from all sources – including fruit.)
Carbs Don’t Make You Fat, Excess Calories Do: Excess calories, rather than carbohydrates, are the cause of weight gain. Calories provide energy for your body, but excess calories are stored as fat. It doesn’t matter if these calories come from pizza (high-carb) or prime rib (low-carb). There is nothing special about a banana that makes fat cling to your hips. It’s not the sugar or carbohydrate, it’s excess calories from your overall, daily eating habits.
Fundamentally, weight loss is about reducing total calorie intake to create a deficit, which forces your body to burn accumulated fat as fuel.
So it really doesn’t matter if you go on a low-carb diet or a high-carb diet, you still need to cut calories to an appropriate level to facilitate weight loss.
Low carb diets are often promoted for weight loss because most high-carbohydrate foods are unhealthy. They are loaded with added sugars, refined wheat flour, trans-fats. They don’t fill you up or satisfy you. They make it very easy to go overboard on calories. It’s easy to tell people to avoid carbs.
Fresh fruits (and green smoothies), on the other hand, contain no added sugars, fats, or refined ingredients. While a blueberry muffin the size of your fist might contain 600+ calories, it would take 60 ounces or more of a blueberry green smoothie to match that amount of calories. I bet you’d certainly feel it if you tried to drink that much!
A 32-ounce green smoothie meal replacement will help you feel full and satisfied. The sweet fruit will help curb your cravings for sweets (without all of the negative effects of added sugars). And you’ve only consumed about 350-400 calories for your breakfast (a great start).
My Experience: I have done both low-carb and high-carb diets. I was able to lose weight with the Atkin’s diet, but I was often frustrated about what I couldn’t eat. Eating low-carb is difficult and cravings were a constant struggle. My mood was poor and I was ready to give up the diet once I got down to my weight goal (which, by the way was 20 pounds more than my current weight).
In short, I didn’t find the low-carb diet sustainable and I gained all the weight back once I stopped dieting.
4) Should I Make Green Smoothies With Less Fruit And More Greens?
There is no need to restrict or limit sweet fruit in your green smoothies unless you have a medical reason to do so.
Are you diabetic? Check out low-carb green smoothie recipes!
In general, my green smoothies contain 60% fruit and 40% greens by volume. My typical 32-ounce meal replacement green smoothie will contain about 300-400 calories (men will probably be more satisfied with a 500-calorie green smoothie – about 4 pieces of fruit – banana, mango, apple and orange) and an entire head of romaine lettuce (or four cups of other leafy green). Adding this much fruit provides the calories to make this smoothie a meal.
A vegetable-based smoothie will not provide sufficient calories to be a meal replacement smoothie. Even if you made a 32-ounce smoothie with just one apple, 1/2 cup blueberries, and a ton of vegetables and greens, you won’t come anywhere close to 400 calories. You’d be lucky to get 200 calories.
The problem with this is that you might still feel full from the fiber, but you risk under-consuming calories, especially if you follow a raw food or whole foods diet. Getting too few calories will sabotage weight loss and lead to nutrient deficiencies and health problems.
In short, fruit-based green smoothies can replace meals and are effective for weight loss. Plus, the 60:40 ratio (fruits to greens) is best for flavor, too.
Vegetable-based smoothies are too low in calories to be considered meals, so they are better used to supplement a calorie-sufficient whole foods diet between meals or consumed with meals – if you wish to do so.
Unless you are physically bothered by fruity green smoothies, I don’t think you need to worry about restricting fruit (or green smoothie intake). If you are concerned about sugar, look into other areas of your diet first. Cut out all refined sweeteners, soda/pop, fruit juice, white rice and white bread. Green smoothies should replace unhealthy foods.
5) Do Green Smoothies Increase Diabetes Risk?
There is no evidence for this. In fact, the overwhelming evidence from decades of published health studies show that people who consume more fruits and vegetables have a lower risk of developing diabetes. There is no evidence that the sugars in fruit will cause, or increase risk for diabetes.
The etiology of diabetes is much more complex than “eat sugar, get diabetes”. There are often genetic, lifestyle, environmental, and dietary (not just sugar and carbs, but also fat) that play a role rather than a simple dietary faux pas.
The health studies that have pointed to sugar as a potential risk factor for diabetes specifically state that added sugars are the culprit (specifically sugar-sweetened beverages), and NOT the naturally-occurring sugars found in fruits and other whole foods.
6) Will Drinking Green Smoothies Rot Your Teeth?
Sugars that are in the fruits that you blend in a green smoothie do come in contact with your teeth and feed the bacteria in your mouth that promote tooth decay. However, green smoothies are not the only source of sugars and even non- sugary foods like nuts can lead to dental problems.
It is important to good dental hygiene no matter what you eat. Fruit doesn’t rot your teeth, but poor dental hygiene or compromised health and lack of nutrients can lead to dental problems whether you eat “too much” fruit or not.
A major benefit from green smoothies is that you can increase your leafy green intake which will naturally boost the amount of calcium, magnesium and phosphorus in your diet – three minerals that help build and maintain strong bones.
7) Will Raw Kale Destroy My Thyroid
No, it will not. There isn’t any evidence that consuming a two handfuls of raw kale in a green smoothie every day will have any negative impact on thyroid function.
However, raw kale and other cruciferous vegetables like bok choy, broccoli, and cabbage, can exacerbate an existing thyroid condition. It may also interfere with thyroid medication.
If you have a thyroid disorder, it’s best to check in with your doctor or a dietitian to determine how much raw cruciferous vegetables are safe for you to consume.
If you have a healthy thyroid, then there is no need to worry about kale affecting it.
8) Is The Oxalic Acid (Oxalate) Content Of Spinach Bad For Me?
No, not unless you currently have, have had, or are at risk for developing calcium-oxalate kidney stones.
However, there is zero evidence that the oxalic acid content in spinach is harmful in any way, or that it increases risk of developing kidney stones.
9) Does Blending Destroy 90% Of The Nutrients In My Smoothies? What About The Fiber?
No, blending does not turn your nutritious fruit into junk food. There is absolutely no evidence that blending will reduce nutrient content by 90%.
Blending doesn’t destroy the fiber, either.
10) Isn’t It Improper Food Combining To Mix Greens/Vegetables With Fruit?
The food combining hypothesis was debunked more than 70 years ago, and is not consistent with what we now know about human digestion.
There is no scientific basis for abiding by food combining rules. There is nothing wrong with blending greens with fruit, or mixing acid fruits (citrus) with sweet fruits (bananas). Feel free to blend melons with anything you want in your green smoothies.
11) Blending vs. Chewing
I touched on this in the weight loss section earlier, but this is in regards to whether or not it is overall healthier to chew your food or drink it – specifically for digestion.
Chewing releases saliva and digestive enzymes. It’s the first step in the digestive process. However, that doesn’t mean that drinking a green smoothie will hinder proper digestion.
Saliva is still released as you drink a green smoothie. In fact, you’ll probably start salivating as you chop the ingredients and add them to your blender. I usually snack on bits of fruit and even greens as I make my smoothie. This helps rev up the digestive engine.
Each sip you take ads saliva. And your stomach and intestines are perfectly capable of digesting it.
Some people are concerned that drinking green smoothies can cause the jaw to atrophy and weaken. I find this fear to be totally unfounded. Your jaw is not going to atrophy by drinking one or two green smoothies per day.
As far as digestion is concerned, green smoothies are very easy to digest because they’ve been thoroughly blended (or mechanically chewed, you could say). If anything, a blended smoothie will digest more efficiently than chewed whole fruits. It’s still entering your mouth, mixing with saliva, and entering your stomach naturally.
For me, this is a non issue.
Sadly, there is a LOT of alarmism in the natural health movement – especially in the natural health blogosphere.
I frequently read alarmist, “click bait” headlines suggest that certain healthy foods are actually destroying our health. Low-carb proponents like to lump healthy carbs, like fruit, in with bad carbs.
There is a lot of confusion out there about what’s good for you and what’s not. But ultimately, every expert can agree on this: Eat more fruits and vegetables.
Green smoothies are a healthy way to increase fruit and vegetable consumption – especially leafy greens! Both my husband and I have had a green smoothie for breakfast every single day since January 2008! And as the author of a very popular green smoothie website, I’ve heard from thousands of people who have lost weight and dramatically improved their health with green smoothies.
So be skeptical of any claim that a healthy food is “destroying” your health. Articles like these sow confusion and do take a holistic approach to diet and lifestyle.
Enjoy your green smoothies!