David has been making these smoothies on a daily basis for a few years. He has the method down to a science, and though we sometimes tweak the ingredients, it’s been an easy, reliable recipe we both enjoy. We’ll make a large batch that makes two 16-ounce smoothies. We’ll either both have one in the morning for breakfast or cover the second smoothie with plastic wrap and keep it in the refrigerator overnight for the next morning. Maybe the top ¼ inch of the smoothie starts to turn a bit darker (like a banana going from yellow to brown), but the smoothies actually keep amazingly well overnight.
I’m sharing the recipe now because the health benefits stemming from the combination of tons of high-fiber fruit with a kefir and yogurt base is on my mind after attending the annual conference for dietitians in Massachusetts; one of the most interesting (and popular) presentations was on the role that gut bacteria play in our health (and the connection between gut bacteria, obesity, and diseases like diabetes). It’s fascinating to hear the emerging research on this topic.
Basically, it’s thought that the kinds of bacteria growing in our gut have an influence on our health, and the foods we eat can influence the types of bacteria we grow inside. Some of the research can be complicated, but there were several key takeaways that are applicable in the world of cooking. Some of the best lessons I gleaned from the presentation included:
- Research has found that the kind of bacteria inhabiting the guts of lean people is different from that of the bacteria in the guts of obese people
- Bacteria are involved in digestion and the extraction of energy (calories) from the food we eat
- Losing weight can shift what kind of bacteria inhabit your gut
- High-fat, high-calorie diets lead to changes in microbial composition (what kinds of bacteria are found in your gut) that can contribute to metabolic disease
- Low-fat, high-fiber diets contribute to staying lean or decreasing risk of obesity and contributes to the growth of lean-promoting microbes (researchers even explored this by transplanting bacterial colonies from lean to obese mice and vice versa)
So, what we eat has an influence on what kinds of bacteria grow in our intestines, which in turn can have an impact on our weight and risk for some diseases.
Probiotics and prebiotics are the words associated with this topic.
Probiotics are the actual living bugs that we consume in foods such as yogurt, kefir, or in pill form. Think of ads for yogurt (like Activia) that boast live cultures to help promote regularity and digestion. They’re talking about live cultures of bacteria that travel through our GI system with the food and then contribute to the colonization of our intestines. Probiotics help change these bacterial communities in our intestines.
Prebiotics are actual foods we eat. There are parts of foods (fiber) that we can’t digest, so this fiber travels through our GI tract and is then eaten by the bacteria living in our intestines. The kinds of foods we eat helps determine which kinds of bacteria will thrive in our gut; if we eat healthy high-fiber foods, we’re feeding and supporting lean-promoting bacteria cultures. If we don’t eat a lot of these foods, other kinds of bacteria that aren’t so helpful will thrive. In the studies discussed in the conference, researchers found that consumption of prebiotics led to improved glucose tolerance, decreased inflammation, and reduction of weight gain.
In the smoothie, ingredients like the kefir and yogurt are probiotics (delivering live bacteria cultures to our intestines), and the fruit and flaxseed provide fiber (prebiotics) to promote healthy growth of beneficial bacteria.
To make the smoothies, start by layering some of the softer ingredients at the bottom (bananas and yogurt), followed by the more solid fruits. This helps ensure that the blender processes everything without creating huge air pockets or tightly packed chunks of frozen fruit that get stuck.
Also check out my post on my professional site, Meg Salvia Nutrition.
Blueberry and Strawberry Fruit Smoothie
Ingredients
2 bananas
½ cup vanilla yogurt
¾ cup kefir (plain)
1 cup frozen strawberries
½ cup frozen pineapple chunks
½ cup frozen blueberries
2 Tablespoons flax seed
½ cup orange juice
Steps
1. Peel the bananas and break them in half. Place them vertically into the base of the blender. Add the vanilla yogurt, then add the frozen fruit and flax seed. Top with the liquid ingredients (the orange juice and kefir), allowing the liquid to run into the spaces between the frozen fruit. Cover the blender with the lid and puree until smooth. Pour out into two 16-ounce pint glasses.
Serve cold. Smoothies will keep for up to one day tightly covered with plastic wrap (we even use a rubber band to ensure a tight seal around the top of the pint glass). Quickly stir the smoothie the next day before drinking.
