The #1 nutrient to prevent kidney stones
Calcium for kidney stones, feta, my favorite recipe for Greek Salad, and the best way to store tomatoes!
👉This week, we’re talking about: calcium and kidney stones, feta cheese, the science behind storing tomatoes at room temperature, how what you eat on the holiday doesn’t define your diet, and I’m sharing my recipe for Greek Salad with Red Wine Vinaigrette.1
Key Takeaways
✅Getting enough calcium is one of the most important things you can do to prevent kidney stones.
✅Feta is among the more nutrient-dense cheeses with its Nutrivore Score of 189!
✅There’s science to explain why tomatoes are best stored on the counter rather than in the fridge!
✅For paid subscribers, your downloads this week are: Calcium Fun Factsheet and Greek Salad with Red Wine Vinaigrette
Calcium for Kidney Stones
🧬Kidney stones affect approximately 10.6% of males and 7.1% of females in the United States. Although there are different types of kidney stones, calcium oxalate kidney stones are the most common, accounting for about 80 percent of cases. These form when the concentration of oxalates and calcium in the urine becomes too high to dilute (a condition called hyperoxaluria), which causes calcium oxalate crystals to form in the kidneys and develop into stones. While high-oxalate foods often get the blame, the bigger culprits here are inadequate hydration and too little dietary calcium.
How much dietary calcium we eat has a direct effect on how much oxalate we absorb from food! Up to 20% of ingested oxalate is absorbed in the gastrointestinal tract of healthy humans with a daily 800 mg calcium intake, but at 1200 mg calcium per day, the mean absorption of oxalate is an insignificant 2.6%. And, intervention studies involving low-calcium diets (400 mg per day) for the treatment of high urinary calcium led to over a 50% increased risk of kidney stone recurrence compared to normal-calcium diets (1200 mg per day)! In fact, some small intervention studies have shown that as long as calcium intake is adequate (1000 mg per day), even relatively large intakes of oxalate don’t affect kidney stone risk.
Want to know the top 25 best food sources of calcium? Learn them here.
Get 16% DV Calcium with Feta Cheese
🧀Feta is a soft, white, crumbly, Greek pickled cheese, made from sheep’s milk or a combination of goat’s and sheep’s milk. During production, feta is first dry salted in metal vessels or wooden barrels for days, before aging in brine anywhere from weeks to several months, where it becomes sharper in taste and firmer in texture as it ages. Feta is often categorized into soft and firm varieties, the firm being more expensive as it is considered higher in quality.
Feta is so popular in Greece that it accounts for 70% of cheese consumption in that country—making it a key ingredient of many traditional Greek foods, and unfortunately leaving very little available for export. The designation ‘feta’ is protected by European Union law, meaning only cheeses manufactured in traditional ways, in select Greek regions, composed solely of sheep’s milk or up to 30% goat’s milk, can be called feta. Outside of the European Union, feta is used as a generic term to describe white, crumbly cheese, aged in brine, even when it is prepared from cow’s milk.
And, feta is among the most nutrient-dense cheeses, with a Nutrivore Score of 189! Per 1.5-ounce serving, feta delivers 16% DV calcium plus 30% DV vitamin B12, 27% DV vitamin B2, 11% DV each of selenium and zinc, and 10% DV vitamin B6.
Feta is the 430th most nutrient-dense food! Learn the Top 500 Nutrivore Foods here.
Greek Salad with Red Wine Vinaigrette Recipe
🥗 This recipe is is the ultimate example of simple ingredients combining into a deliciously complex yet balanced flavor—perfect for weeknights, meal prep, and parties. The salty feta, briny olives, cool cumbers, with the sharpness of the red onion make every bite of this salad bright and satisfying.
Add this recipe to your meal plan this week with Real Plans, the official Nutrivore meal planning app!
Nutrivore Mindset Corner
🧠Diet culture teaches us that certain foods are temptations to be avoided—and holidays like Christmas can make that message especially loud. So, let’s take a moment to zoom out.
A healthy diet is not built in a single meal, day, or even week. Instead, what matters is the overall pattern of how you eat on average. A holiday meal doesn’t define your diet any more than one salad does. From a Nutrivore perspective, looking at your diet through wider lens is essential. Some days include more vegetables, fiber, and micronutrients. Other days include more celebration foods, traditions, and desserts. Both belong. When you step back and look at the full picture, these variations don’t compete with health, they coexist with it.
On days like today, nourishment can include pleasure, connection, and satisfaction just as much as vitamins and minerals. Look for small ways to add more nutrients—a serving of salad, a veggie-rich side dish, a piece of fruit, or a handful of nuts—and enjoy the flavors of the holidays without guilt. Zooming out allows food to return to its rightful place: supportive, enjoyable, and part of a much bigger picture.
Learn everything you need to know about the Nutrivore philosophy in my book, Nutrivore: Eat Any Food, Get Every Nutrient, and Transform Your Health!
And if you’d like help building healthier overall eating patterns and a better relationship with food in 2026, then join my free Nutrivore90 Challenge starting January 5th!
Helpful Tip of the Week
💡Let’s talk about why tomatoes taste so much better when stored at room temperature. Tomatoes are a climacteric fruit, meaning they continue to ripen after harvest. At room temperature, enzymes involved in ripening remain active and continue producing volatile compounds that are key components of the characteristic aroma and flavor of a ripe tomato. Much of these volatile flavor compounds are lost when we chill tomatoes below about 54°F (12°C), resulting in loss of flavor. In addition, colder temperatures reduce the expression of some genes critical to volatile synthesis, not all of which recover to normal after the tomato is returned to room temperature, so volatile flavor compound levels are unable to ever be fully restored after a tomato has been chilled. So while storing tomatoes in the fridge can extend the shelf life of your tomatoes, it also causes an irreversible loss of tomato-y flavor.
For the best flavor and texture, store tomatoes at room temperature, out of direct sunlight, and with some airflow, such as on the counter or in a fruit basket. Depending on the cultivar, ripeness at purchase, and time of year, tomatoes may last anywhere from a few days to a few weeks.
Watch & Learn
🎥Check out my YouTube videos on leveraging habit stacking to build better eating habits and 12 ways to get enough dietary calcium! And don’t forget to subscribe and hit bell notifications, so you never miss a new video!
This Week’s Downloads
📥For paid subscribers, your downloads this week are:
Calcium Fun Factsheet - This 2-page PDF guide summarizes all the most important information about what calcium does, top food sources, and how much we need for each demographic group.
Greek Salad with Red Wine Vinaigrette Recipe - A beautifully-designed PDF version of this week’s recipe that you can save or print out, to build your own personalized Nutrivore Cookbook week by week.
You can find buttons to download at the bottom of this Substack. Thank you so much for supporting my work and Nutrivore!
Sincerely,
Dr. Sarah Ballantyne, PhD
Founder of Nutrivore
Medical Disclaimer: The information provided in this Substack is for educational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or another qualified healthcare provider with any questions you may have regarding a medical condition or dietary changes.
FTC Disclosure: Some links in this Substack may be affiliate links, meaning I may earn a small commission if you purchase through them at no additional cost to you. I only recommend products I genuinely believe in. Thank you for supporting my work!
