Green smoothies are perceived as the "healthy" version of fruit smoothies – but are they really so healthy? Detractors say green smoothies are:
• high in calories
• high in sugar
• low in nutrients including fibre, due to the blending process
• a source of toxic oxalates and goitrogens
I've been consuming two green smoothies every day since 2012 – so I suppose I'm a bit biased.
I have had a few health problems during that time, but I don't blame my green smoothie habit for them. I've managed to overcome these health problems, while continuing to drink two green smoothies every day.
What is a green smoothie?
Green smoothies are made from fruit and green vegetables blended with water. Simple as that. The recipes can be as varied as the recipe for a salad, as long as they contain fruit, greens and water and are not cooked.
Some people add yogurt or chia seeds, or even a pinch of cayenne! (I've tried adding cayenne to a green smoothie, and it's much nicer than you might think.)
I've fallen into a bit of a routine with my green smoothies – simply because this is a basic recipe that I love. It makes two green smoothies, or about 800-900ml:
• 2 medium-sized bananas, peeled
• 1/2 a mango OR 1/4 pineapple, peeled
• 1 medium-sized orange OR apple
• 1 handfuls of spinach OR kale
• 400-600ml water
Blend it all up in a powerful blender. I have an industrial-size Blendtec, but a Nutribullet will do. Basically, the more powerful your blender is, the smoother and less lumpy your green smoothie will be.
Green smoothies might not be everybody's cup of tea, but they are much more delicious than they look – depending on how they are made, of course.
Sometimes I vary the recipe a bit. Occasionally – if I run out of greens, for example – I add a handful of frozen berries instead.
In fact, scientific research indicates that drinking blended berries (ideally blackcurrants) actually improves blood sugar control, so if you're concerned about the possibility of green smoothies giving you a blood sugar spike, you could substitute mixed berries for the pineapple or mango in my green smoothie recipe.
Green smoothies tend to be quite high in natural sugar. My recipe contains 55g of sugar in total; 26.5g in each smoothie. However all of this sugar comes from fruit, and it is consumed along with fibre, which helps slow it down on its journey through the gut.
If you substitute berries for the mango/pineapple and orange, the total sugar content falls to about 35.5g for both smoothies, or 18g in each one.
I generally avoid eating any refined sugar unless it's my birthday, Christmas or after a big hillwalk, and a recent blood sample showed my blood sugar levels to be healthy.
So are green smoothies healthy or not?
Not particularly high in calories
The green smoothies I make total about 350 calories, so each one is about 175 calories, which I don't think is a large amount. I usually have my green smoothies for lunch, with some nuts, and that keeps me full until dinner time.
High in vitamins and minerals
Green smoothies are high in vitamins and minerals, supplying more than the US and UK recommended daily amounts (RDA) of vitamin A, vitamin C, vitamin K, and manganese. They are also high in many B vitamins, folate, magnesium and copper, AND they supply about 6g of protein.
This is the case even if nutrient loss from blending is taken into account, because the vitamin and mineral content of fruit and greens is so high compared to many other types of food.
Two green smoothies made with my recipe can also contain half the recommended daily amount of dietary fibre. I find that if I consume more than two green smoothies a day, my digestive system goes into overdrive, but two seem to provide the perfect amount of fibre to keep my bowels functioning well.
Does blending destroy the nutrients?
It's likely that some of the nutrient value of green smoothies is lost when they are blended, but probably nothing like as much as the 85-92% of nutrients that Dr Brian Clement of the Hippocrates Health Institute has claimed is lost when smoothies are blended for 90-120 seconds. Certainly, I know no one who blends their smoothies for this length of time. My Blendtec takes 30 seconds to blend my smoothies.
Korean scientists who compared the nutrient content of blended and juiced fruit blended apples, pears, persimmons and mandarin oranges for an astonishing three minutes at more than 20,000 rpm, still found that the blended juice contained significant amounts of polyphenols and flavonoids.
The research showed that although levels of ascorbic acid were lower in the blended apples, pears and oranges than in the juiced fruits, the blended persimmons had higher levels of ascorbic acid. All the blended fruits had significantly higher concentrations of citric and malic acids than the juiced fruit.
The research also found that total polyphenols and total flavonoids were significantly higher in blended persimmon and mandarin orange juices, but not in the other fruits.
Could green smoothies cause iodine deficiency?
Kale is a goitrogenic and if eaten raw in large amounts it can impair the absorption of iodine, which can lead to thyroid problems. Other goitrogenic foods include other cruciferous vegetables such as cauliflower and broccoli, as well as soy products, flaxseeds, millet, peanuts, peaches, pears, pine nuts, spinach, sweet potatoes, and strawberries.
As long as your iodine intake is sufficient, there is no need to avoid any of these foods.
What about the effects of oxalates?
Raw kale contains oxalic acid which, if consumed in large amounts, can bind with other minerals to cause inflammation, kidney stones and gout. The list of foods containing oxalic acid includes spinach, peppers, sweet potato, squash, pumpkin, chocolate, nuts, berries, tea and coffee.
Most of the oxalic acid in these foods is likely to be excreted by the body, with less than two percent being absorbed. Research suggests that the gut bacterium Oxalobacter formigenes helps to prevent conditions such as kidney stones by degrading oxalate activity. But this bacterium can be inhibited by the action of certain antibiotics, including clarithromycin and doxycycline.
So if you have a healthy gut, the small amount of oxalates consumed in green smoothies is unlikely to be problematic.
Hydration
Green smoothies are very hydrating, and as a regular hillwalker, I always take one with me when I climb a mountain.
Why not just eat the fruit?
Maybe it would be healthier to eat the ingredients of a green smoothie completely fresh and unblended, in a fruit salad perhaps.
But how many people would actually do that – eat that amount of raw fruit and greens every day? People who have a high raw or totally raw lifestyle probably do, but most people don't eat anything like that amount of fresh fruit or vegetables.
As a result, many people – especially those who eat a lot of processed food – are deficient in nutrients such as magnesium, vitamin A, vitamin C and fibre.
As long as I have my two green smoothies each day, I know that I'm getting at least most of my RDA of the above-mentioned vitamins and minerals.
How to make green smoothies even healthier
• Sip them slowly to avoid a blood sugar spike, rather than glugging them back all at once.
• Add healthy fats such as linseeds or avocado, to improve nutrient absorption.
• Drink your smoothies through a straw and/or rinse your mouth out with water after drinking, to mitigate the effects of acid in fruit which can lead to tooth enamel decay.
Convenience
Fruit salads are great, but if you want to eat them on the move, you need a salad box and a fork, while whole fruit, such as bananas or apples, can get squashed and dirty if you put them in your bag – unless you carry them in a bulky container.
Green smoothies can be carried around easily in a bottle. For me, they are the ultimate healthy convenience food.
Other sources
Plant-based diets: A Physician's Guide by Julieanna Hever, MS, RD, CPT
Green Smoothies: What Does the Science Say? by Michael Greger M.D. FACLM
Are There Toxins In Your Kale? – The Telegraph
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Great post!
I like the honest approach, looking at both pros and cons.
And I love green smoothies, so easy to make, quick way to get down a lot of plant foods, filled with nutrients and phytochemicals.
Thanks mariuse. Glad you enjoyed my post.
One thing i love about your post is that i get to learn new important things everyday , thanks fir the eye opener , don't stop giving us more of this , thanks alot
Thanks! Glad you enjoyed reading my post.
You are welcome
Great post! I try to control sugar as much as possible but vegetables and fruits are delicious and healthy!
Thanks felgue! I try to do the same. Refined sugar is so bad for you.
Very interesting, i wonder if they mean that its rich with fruitsugar, beacuse there aint no added sugar to the smoothies?
They look very tasty anyway, and i thing its so rcichwith vitamins and minerals that it adds up if there not so healthy.
Thanks mrpossible! I certainly don't add any sugar to my green smoothies, but if they contain fruit, then they contain fruit sugar. But then you also get the benefits of the nutrients in fruit too, and the fibre :)
Yes so its more healthy to drink it then not to drink it ;)
Exactly!
This was a great post! I don't think green smoothies are for me - I'm vegan so I do eat a lot of raw fruits and veggies every day. Having said that, I see how it's much easier (especially for younger people) to consume smoothies than raw vegetables. Quite informative, especially when it comes to iodine information... kind of makes me feel scared lol.
Glad you enjoyed my post Jeremy! Sorry it scared you - but iodine is one of my pet subjects, as I became iodine deficient a few years ago. I don't know if you're in the UK, but the UK is one of the few countries in the world that does not have a government policy of iodising salt. However iodine is added to livestock feed in the UK to improve their fertility - quite ironic really! So dairy products are among the few reliable sources of iodine in the UK. I have an intolerance to cow's milk, and I think that's how I became iodine deficient - I now take iodine supplements.
Certainly if you eat a lot of raw fruit and vegetables anyway you'll be getting enough vitamins and minerals that way - except possibly iodine, as it's distributed very erratically in the soil, so it all depends where the produce you eat comes from.
That's interesting. I'm from Malta (not UK). There are definitely a lot of minerals and vitamins in vegetables and fruit (and soil) - however, as you mentioned, it depends where the produce comes from. I will have to look up symptoms and signs of iodine deficiency - just to be extra cautious.
You might be OK in Malta. I live in Scotland, and a lot of our produce is subject to soil erosion due to excessive rainfall. I get a box of organic veg delivered every week – I think organic growing can improve the nutrient content, but I'm not sure about the iodine content.
Organic is always better overall, but yeah, doesn't mean it is sufficient in everything.
my green smoothie is red in color, lol.
i just prefer it in that color if i can, cucumber juice is my cleansing juice =)
Red smoothies are good too! Tomatoes are good in smoothies.
I am trying to drink a glass of juice every day. According to science, more than just a glass of juice is not metabolized (400ml), but I think it also depends on the body and on the quantity spread.
Do you know anything about this? Could I drink a glass of orange juice in the morning and in the evening drink a smoothie and get both nutrients processed?
Hmm... that's another post I think! The danger with orange juice is that juicing removes more of the fibre so the fruit sugar (fructose) can give you a blood sugar spike. That's why you shouldn't drink more than 400ml. It's not that it's not metabolized – it's metabolized too quickly. But you'll still be getting vitamins from the orange.
You could certainly drink a smoothie in the evening, or at lunchtime. The fibre in the smoothie should slow down the metabolism of the fruit sugar, especially if you add greens such as kale to it.
I will try starting tomorrow.
As for the metabolizing more than 400ml of juice per day, I am sure I read that somewhere.
If i find it, I will tell you!
I think the smoothies you've been having are high in antioxidants doing an excellent job repairing body and boosting immunity?
As long as berries of all kinds, spinach, ginger and lemon are added but no sugar syrup added, smoothies are good to consume.
Exactly - no sugar or yogurt with added sugar. Everything natural. Yes, raw ginger is a great ingredient too.
I make something myself similar and drink every now and then to detox myself :-)
good post
thank you
Glad you enjoyed it!
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It is just so hard to imagine something that looks and sounds so healthy being not so. I am going to assume these will not kill you, or me :). Thanks for this post. The pics are great as an added bonus.
Thanks cstrimel - glad you enjoyed it. Everything in moderation I suppose!
I am a diabetic, so drinks would contain more sugar, right? After being diagnosed as a diabetic, I am always unsure of what I should or should not eat. Thanks for the detailed post.
They do have a significant sugar content, but you can reduce this by substituting berries for the pineapple and orange in the recipe. You can check the sugar content of smoothies by using an online diet analyser like cronometer.com.
thanks for that information, really helpful