Drinking mixed fruits and vegetables can quench thirst after a hard workout.
But fitness fanatics may need to think twice about the liquid they use to make their smoothie if they hope to reap the most health benefits.
While oat, almond and soy milks are popular among vegans, they are no better than water with increasing levels of the antioxidant lutein when used to make a green smoothie, according to Swedish researchers.
Instead, cow’s milk and coconut milk, more often combined with breakfast cereal or used to make a curry, are best for boosting the compound, which is vital for eye health and reducing inflammation.
The researchers noted that while plant-based mixers are “increasingly common” in smoothies, some have a “negative effect” on the amount of lutein the body absorbs.
Starting in 2004, companies saw the popularity of green smoothies skyrocket as the country started a new trend of vegetarian drinks
The researchers made 14 other versions using dairy and plant-based mixers instead of water, including yogurt, cow’s milk and coconut milk (pictured)
Smoothies, which involve blending fruits and veggies into a drink with a blender, are popular among those trying to hit their five a day.
But those that contain vegetables, such as spinach and kale, can be a source of lutein.
The carotenoid, a type of antioxidant that the body cannot make itself, acts as an anti-inflammatory and promotes eye health, studies suggest.
To find out how to maximize the lutein content of spinach smoothies, researchers at Linköping University made the green drink by mixing spinach and water.
They then made 14 other versions using dairy and plant-based mixers instead of water, including yogurt, cow’s milk, and coconut milk.
They added digestive enzymes to the smoothies to simulate human digestion and measured the amount of lutein available for the body to absorb — called lutein liberation — for each smoothie.
While green vegetables can be packed with lutein, it needs gastric juice — which is made in the stomach to break down food — before it is released from the vegetable and absorbed by the body.
The results, published in the journal Nutrientsshow that only four of 14 smoothie blenders significantly increased lutein release compared to water.
These included high-fat and low-fat cow’s milk, which increased lutein release by 36 percent and 30 percent, respectively.
Meanwhile, pure coconut milk, with no additives, increased lutein release by 42 percent, while the same milk with additives caused a 25 percent increase.
This is because cow and coconut milk break down the compound the least, making more available for the body to absorb, the researchers said.
While other mixers, such as low-fat cow’s milk, Greek yogurt and almond milk, caused a small increase in lutein release compared to water, the scientists said these were not statistically significant.
And some mixers, such as pure soy milk and soy milk with additives, which are popular among vegans, reduced lutein release.
Other plant-based mixers, often made from nuts, legumes or oats, did not increase lutein release compared to water.
This means those who make smoothies are better off with water than plant-based milk, which has a “negative effect on lutein release,” the researchers said.
The team believes their findings could be explained by the different fat, carbohydrate, protein and fiber content of the mixers, which affected the amount of lutein available for the body to absorb.
And the fermentation process yogurt goes through could be the reason yogurt doesn’t release lutein properly, they suggested.
Study author Rosanna Chung, assistant professor of experimental cardiology and nutritional immunology at the university, said, “High-fat cow’s milk and coconut milk improved lutein release.
“But yogurt, which is considered similar to cow’s milk and commonly used in cafes and the like, didn’t show particularly good results.”
The researchers noted that the study tested the amount of lutein made available for the body to absorb rather than the amount actually absorbed.
So they now plan to conduct a separate human study to measure the amount of lutein absorbed from smoothies made with different blenders.