Green smoothies have become increasingly popular in recent years as a way to boost your intake of fruits and vegetables. Blending leafy greens with fruit creates a beverage that’s nutritious and easy to drink. However, some people find that green smoothies upset their stomachs. This article explores why green smoothies may cause digestive distress and how you can avoid it.
What’s in a green smoothie?
A green smoothie typically contains some combination of leafy greens, fruit, liquid, and optionally other ingredients like protein powder or nut butter. Here are some of the most common ingredients:
- Leafy greens – spinach, kale, chard, lettuce, etc.
- Fruit – banana, mango, berries, apple, etc.
- Liquid – water, almond milk, cow’s milk, coconut water, juice
- Extras – protein powder, nut butter, seeds, coconut flakes
The leafy greens provide vitamins, minerals, and plant compounds like carotenoids and polyphenols. The fruit contributes natural sweetness plus vitamins and antioxidants. The liquid blends everything together into a drinkable smoothie.
Why green smoothies may cause stomach upset
There are a few reasons why green smoothies could potentially irritate your digestive system or cause stomach discomfort:
Leafy greens and fruit skins contain quite a bit of fiber. While fiber is healthy, ramping up your fiber intake too quickly can definitely cause gas, bloating, diarrhea, and abdominal pain.
For example, 1 cup of raw spinach contains almost 1 gram of fiber. Blending several cups of spinach into a smoothie can provide a mega dose of fiber your body isn’t accustomed to.
Some greens contain compounds like oxalates and lectins that can be more difficult to digest when the greens are raw. Light cooking can help deactivate these compounds.
Spinach and chard are higher in oxalates, while kale contains more lectins. Blending them raw could irritate the digestive tract.
Green smoothies made with a lot of fruit can deliver quite a bit of fructose. Some people don’t absorb fructose well, especially in large amounts. This is called fructose malabsorption.
When fructose isn’t properly absorbed in the small intestine, it passes into the large intestine. There, it draws in water and gets rapidly fermented by gut bacteria, causing gas, bloating, and diarrhea.
Chewing starts the digestion process in your mouth. Saliva contains enzymes that help break down carbohydrates and fats. Thorough chewing also makes food easier for your body to digest.
Since smoothies require no chewing, your stomach has to work extra hard to digest everything. This can lead to indigestion in some people.
Finally, probiotics from fermented greens like kimchi or sauerkraut can cause temporary digestive distress when introduced to your gut. Side effects may include gas, bloating, cramping, and diarrhea.
Your body should adjust as the good bacteria proliferate, but it can take a week or two.
Tips to prevent stomach upset from green smoothies
Here are some tips to make green smoothies gentler on your stomach:
1. Start with sweeter, lower-fiber fruits and veggies
If you’re new to green smoothies, start with produce lower in fiber, like cucumber, zucchini, romaine lettuce, spinach, ripe banana, pineapple, or papaya. This gives your body time to adapt to the extra fiber.
2. Remove peels and seeds
Fruit and vegetable peels and seeds are extra high in fiber. Remove them if smoothies give you digestive trouble.
3. Cook hearty greens
Lightly cooking veggies like kale, collards, chard, and broccoli can make them easier to break down. Try steaming them first before adding to your smoothie.
4. Go easy on high-fructose fruits
If you suspect you have fructose malabsorption, stick to lower-fructose fruits like blueberries, strawberries, and oranges. Avoid large quantities of apples, pears, mangoes, cherries, and dried fruits.
5. Add probiotic foods gradually
Start with small amounts of fermented foods like yogurt or kefir and gradually work up to more over a few weeks to allow your gut to adjust.
6. Chew each sip
Chewing starts digestion, so “chew” each sip of your smoothie by swishing it around your mouth before swallowing. This mixes it with saliva so your body can digest it more easily.
7. Stay hydrated
Drink plenty of water throughout the day to help move fiber through your digestive tract. Proper hydration reduces constipation and bloating.
8. Limit other high-fiber foods
Avoid overdoing it on other gas-producing high-fiber foods like beans, cruciferous vegetables, and whole grains when adding green smoothies to your diet.
9. Take a probiotic supplement
A daily probiotic can help get your gut microbiome ready for the mix of fibers, probiotics, and other compounds in green smoothies.
10. Go slowly
Gradually increase the amount of leafy greens and fiber sources in your smoothies over time. This gives your body a chance to get used to the higher fiber intake.
What to do if green smoothies upset your stomach
Making a few simple diet and lifestyle changes can help if green smoothies are causing indigestion or other stomach troubles:
- Drink smoothies slower or opt for smaller portion sizes.
- Add ginger, fennel, mint, or chamomile to smoothies for their digestive benefits.
- Temporarily avoid fermented add-ins like yogurt, kefir, kimchi, etc.
- Try an over-the-counter digestive enzyme supplement like papain or bromelain.
- Reduce high-fiber foods in the rest of your diet.
- Exercise regularly to keep bowels moving.
In most cases, your body just needs time to adjust to the extra fruits, veggies, and fiber in green smoothies. Slowly increasing your intake should help minimize stomach issues.
However, see your doctor if you have persistent digestive problems after trying green smoothies. You may need testing to identify any underlying conditions.
When to avoid green smoothies
While green smoothies agree with most people, you may need to avoid them if you have:
Irritable bowel syndrome (IBS)
IBS triggers vary by individual but often include high-fiber foods. The raw greens and produce in smoothies may worsen IBS symptoms like abdominal pain, cramping, bloating, gas, diarrhea, and constipation.
Inflammatory bowel disease (IBD)
IBD involves chronic inflammation of the digestive tract. The compounds in raw, leafy greens may aggravate the intestinal lining. Cooked vegetables are often better tolerated.
Diverticula are small pouches in the colon that can become inflamed or infected (diverticulitis). The seeds, skins, and fibers in smoothies may get trapped and further irritate these pouches.
With gastroparesis, the stomach’s muscles contract slowly, delaying food emptying into the small intestine. Smoothies provide less chewing action, so large food particles may worsen symptoms.
People with colostomies have part of their colon removed and digestive waste emptied into a bag on the abdomen. The greens and fiber in smoothies can be difficult to digest and quickly fill the bag.
Some people simply tolerate smoothies poorly. The raw greens and fruits disagree with their digestion despite efforts to prevent stomach upset.
The bottom line
When prepared properly, green smoothies can be refreshing and good for you. Start slowly, use gentle ingredients, and give your body time to adjust to the extra fiber and nutrients. This minimizes the risk of stomach upset.
However, skip green smoothies or proceed cautiously if you have IBS, IBD, diverticulitis, gastroparesis, a colostomy, or simply don’t tolerate them well. Pay attention to your body’s signals and adjust your intake accordingly.
With a little trial and error, most people can find the right green smoothie recipe, preparation, and amount to comfortably boost their fruit and vegetable consumption.