To maximize the heart-healthy antioxidant lutein, in a green spinach smoothie, try adding coconut milk or cow’s milk, a new study suggests. Kseniya Ovchinnikova/Getty Images
To get the most antioxidants from spinach in a green smoothie, use coconut milk or medium- or high-fat milk in the drink, a new study suggests.
One particularly beneficial antioxidant is lutein, a carotenoid associated with improved eye and heart health, which must be released from spinach to be absorbed by the digestive system.
According to the study results, soy milk, whipped cream and Greek yogurt fail to release lutein. Spinach is one of the most popular sources of “green” in a green smoothie.
Along with a wide range of nutrients, spinach contains important plant compounds such as the antioxidant lutein. Lutein contributes to eye and heart health through its anti-inflammatory properties. A new study compared 14 liquids commonly used in smoothies to see which best release lutein from spinach for absorption by the human gut. She revealed that not all spinach-based green smoothies are created equal.
The results show that spinach smoothies containing coconut milk with or without additives, as well as high-fat and medium-fat cow’s milk, release lutein the best. Coconut milk without additives increased lutein release by 42%, and milk with additives by 25%. High-fat cow’s milk increased lutein availability by 36%, while mid-fat cow’s milk increased it by 30%.
Soy milk surprisingly had the opposite effect, reducing lutein release by 61%. For smoothies based on soy milk and additives, the result was better (40%).
Almond milk and oat milk had no significant effect on lutein release. The study was recently published in the journal MDPI.
Why spinach is so healthy
Spinach is rich in dietary nitrates which help dilate the arteries, allowing for better blood circulation and lowering blood pressure. Spinach contains vitamins C and K, as well as carotenoids from which our body produces vitamin A. This dark green vegetable also contains iron, folic acid and calcium, as well as many plant compounds in addition lutein. These include kaempferol, nitrates, quercetin and zeaxanthin. Cooking spinach can reduce its nutritional value, as can freezing. This is why raw, uncooked spinach in a smoothie has the most health benefits.
The health benefits of lutein
A study has shown that sufficient amounts of lutein can prevent or improve age-related macular degeneration. It is the main cause of age-related blindness and other vision problems. Indeed, numerous studies have shown that lutein can suppress the key process of inflammation, so an increased daily intake of lutein could potentially benefit people with chronic inflammation, such as coronary heart disease.
To be effectively absorbed by our digestive system, lutein needs a minimum amount of fat. However, we generally don’t eat enough lutein-rich foods to get enough lutein into our systems to derive any noticeable health benefit. Determining the optimal amounts of lutein for eye and heart health is a topic for future research.
What about fruit juices?
The researchers did not test fruit juices, often used in smoothies, as part of the study. Lutein is not water soluble, whereas our diet and intestinal environment are filled with water. Since the release of lutein requires emulsification with fats, the components of fruit juices and fruits are unlikely to affect the release of lutein.
However, the very high-fat liquids tested in the study were found not to increase lutein release. These include whipped cream and Greek yogurt.
Whipped cream and Greek yogurt are made very differently, with significantly different compositions than cow’s milk. The reason whipped cream and Greek yogurt are less effective at releasing lutein is that the milk fat in these two products tends to clump together, affecting their ability to dissolve lutein. Milk fat tends to aggregate in high concentrations (whipping cream) and after fermentation (yogurt).
Certain types of nuts, such as walnuts and almonds, contain certain types of soluble fiber that may reduce fat absorption. In theory, lutein could therefore also be affected by the co-consumption of these nuts. This hypothesis still needs to be confirmed by further research.
Should plant-based milk be avoided in smoothies?
Although the presence of a high-fat liquid in a smoothie may seem counterintuitive, fats are needed to facilitate subsequent absorption. Although this study showed that plant-based milks reduced lutein, it is important to note that lutein is a fat-soluble antioxidant. This means that it needs fat to be absorbed. You can therefore consume these plant milks as long as you add heart-healthy fats to facilitate the absorption of lutein.
In addition, and beyond the release of lutein, fruit also provides useful nutrients in a smoothie. Whole fruits rich in vitamin C, such as kiwi fruit, mangoes and strawberries, may increase the absorption of plant-based iron found in spinach. It is best to use whole foods rather than fruit juice to avoid excess sugar which can increase inflammation in the body.
Make a better smoothie
The key to getting more antioxidants from the foods you eat is also in the method of consumption. Researchers have already found that consumption methods can make a significant difference in the lutein levels of spinach. This study may help people pay more attention to these two important factors: consumption methods and food companions when making a good smoothie.