Why You Should Add Eggshells To Your Smoothies

Smoothies are endlessly customizable. You've got the classic add-ins like fruits, vegetables, and a liquid base, but nothing is stopping you from incorporating underrated ingredients like beans for a protein boost or frozen cauliflower for a silkier texture. Another creative add-in that veers towards the more unconventional side of things is eggshells ... yeah, you read that right. But hear us out; leftover shells are your secret weapon for turning your smoothies into nutritional powerhouses. To learn more about the science behind this, Food Republic spoke with Dr. Zoe Lees, medical writer at ZipHealth with a PhD in Metabolic Medicine.

Eggshells are primarily composed of calcium carbonate, Lees explained. Calcium carbonate is what makes eggshells a great fertilizer for your garden. Beyond the greenhouse, calcium has a wide range of benefits for the human body — most famously for building and maintaining strong bones and teeth. According to Lees, "Grind the eggshell into an ultra-fine powder using a clean grinder, since the coarse texture poses a primary risk for irritating the digestive system." If you don't have a blender, you can use a food processor or even a mortar and pestle.

Although eggshells are a creative potential source of calcium, Lees stressed that they are by no means a substitute to other sources. The most obvious sources of calcium are dairy products, like milk, Greek yogurt, and cheeses, as well as lesser-known sources like fish with edible bones or green vegetables like kale or okra. According to Lees, research on the viability of eggshells as a calcium source is limited, so you shouldn't rely on them alone and continue to make use of a diverse array of sources, like combining eggshells, milk, and kale for a super calcium-rich smoothie.

There are plenty of reasons not to toss your eggshells straight in the bin, but if you're planning to give them a second life in the kitchen, a little caution goes a long way. Taking the right steps to prepare them properly is key, not just for getting the most out of them, but for keeping yourself safe. According to Dr. Zoe Lees, eggshells can carry Salmonella, which can cause a whole host of unpleasant side effects if consumed without proper sterilization.

"Begin by thoroughly rinsing [the eggshells] under warm water for about 10 minutes[,] followed by drying completely, preferably in an oven for 10 to 20 minutes," Lees recommended. For peace of mind, boiling the shells is also a reliable way to kill off any lingering Salmonella.

There's no one smoothie that works best with eggshells since they're essentially tasteless. The key is grinding them extremely finely, as no one wants to sip a smoothie and hit stray shell fragments. You don't need to use too much, either. "Half a teaspoon of the ground eggshell may deliver calcium levels comparable to a glass of milk," Less told us. On top of that, calcium absorption depends on your having vitamin D in your system. While sunlight is the most common source, you can also boost your intake by adding vitamin D-fortified ingredients to your smoothies, such as fortified plant milks, orange juice, or yogurts.