3 Potential Side Effects of Spinach
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Spinach Is Healthy, but Not Without Its Side Effects

Spinach Is Healthy, but Not Without Its Side Effects
Natasha Breen/Adobe Stock
By
Andra Picincu, CN, CPT
Updated on July 31, 2025
by

Spinach is one of the healthiest foods to eat. It's loaded with vitamins and minerals but low in calories. It fills you up quickly and can be prepared in a multitude of ways.

However, as with everything else, moderation is key. Eating too much spinach may cause issues, such as creating digestive distress and promoting the formation of kidney stones due to its high oxalate content.

Here's what to know about the possible side effects of spinach.

Spinach and Kidney Stones

Along with kale, beets, and most nuts, spinach is a kidney stone–forming food. This veggie boasts high levels of oxalates. Too many oxalates in your kidneys increase your risk of kidney stones, especially if you are dehydrated.

Eating high-oxalate foods, such as spinach and nuts, promotes stone formation in people susceptible to them. A high intake of oxalates may lead to calcium oxalate stones, the most common type of kidney stone. This type forms when oxalate concentration is above normal.

If oxalates are a concern for you, you can reduce the oxalate content of spinach by 40 percent by boiling it and then dropping it into ice water. Cooking spinach breaks down oxalates and helps you absorb more calcium, which also lowers your risk of developing stones.

Eating calcium-rich foods, like dairy, with your spinach can also reduce your risk of forming kidney stones.

Effects of Spinach on Digestion

One serving of raw spinach, about two-thirds of a cup, provides almost 2 grams of fiber. A serving of cooked spinach contains even more fiber.

Fiber promotes digestive health, prevents constipation, and slows sugar absorption into your bloodstream. Too much fiber, on the other hand, can have the opposite effect. Bloating, gas, diarrhea, constipation, stomach cramps, and other gastrointestinal symptoms may occur when adding too much fiber to your diet too quickly.

Some studies suggest that fiber may interfere with mineral absorption. However, the research is mixed. Since fiber is considered safe, no upper level of intake has been set for it.

The fiber in spinach can help you maintain a healthy weight, suppressing your appetite and keeping your digestive system running smoothly. Some individuals may experience gastrointestinal symptoms. Increasing your fiber intake suddenly, for example, is more likely to cause digestive distress than gradually adding more fiber to your diet.

Spinach and Salicylates

Salicylates are natural compounds found in many plants, including spinach. When you have a sensitivity to salicylates, or if you have an aspirin intolerance, you may need to avoid eating certain fruits and veggies. Spinach, broccoli, chile peppers, cucumbers, and squash have a higher amount of salicylates.

For those with a sensitivity to salicylates, the most common reactions include fatigue, a stuffy or runny nose, sneezing, headaches, skin rash and itching, and stomach upset.

Research suggests that limiting the amount of spinach you eat can lessen these side effects, though more studies are needed.

The Takeaway

  • Eating spinach can increase your risk of forming kidney stones if you're susceptible to them. Cooking your spinach or eating it with calcium-rich foods, like dairy, can help lower this risk.
  • When consumed in moderation, spinach is a healthy addition to most diets. Adding too much spinach to your diet too quickly can upset your digestive system. If you experience bloating, indigestion, or other gastrointestinal discomfort, downsize your portions, and then slowly increase your serving size.
  • People with a salicylate sensitivity or aspirin intolerance may experience fatigue, allergy-like symptoms such as a stuffy nose and sneezing, headaches, and stomach upset after eating spinach.
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
  1. Howland J. Mayo Clinic Minute: What can you eat to avoid kidney stones? Mayo Clinic. March 30, 2023.
  2. LeWine HE. How to prevent kidney stones. Harvard Health Publishing. June 13, 2023.
  3. Calcium Oxalate Stones. National Kidney Foundation.
  4. Branch J. 8 Vegetables That Are Healthier Cooked. Consumer Reports. September 27, 2019.
  5. 7 Reasons You Should Eat More Spinach. Cleveland Clinic. February 16, 2024.
  6. Dietary fiber: Essential for a healthy diet. Mayo Clinic. December 11, 2024.
  7. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Institute of Medicine. 2006.
  8. Understanding Salicylate Sensitivity. Academy of Nutrition and Dietetics.
  9. Salicylate Sensitivity: Symptoms and Management. Cleveland Clinic. June 25, 2025.
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Kayli Anderson, RDN

Medical Reviewer
Member of American College of Lifestyle Medicine

Kayli Anderson has over a decade of experience in nutrition, culinary education, and lifestyle medicine. She believes that eating well should be simple, pleasurable, and sustainable. Anderson has worked with clients from all walks of life, but she currently specializes in nutrition therapy and lifestyle medicine for women. She’s the founder of PlantBasedMavens.com, a hub for women to get evidence-based, practical, and woman-centered guidance on nutrition and cooking, hormone health, fertility, pregnancy, movement, mental well-being, nontoxic living, and more.

Anderson is board-certified in lifestyle medicine and serves as lead faculty of the American College of Lifestyle Medicine’s (ACLM) "Food as Medicine" course. She is past chair of the ACLM's registered dietitian member interest group, secretary of the women's health member interest group, and nutrition faculty for many of ACLM's other course offerings. She is the coauthor of the Plant-Based Nutrition Quick Start Guide and works with many of the leading organizations in nutrition and lifestyle medicine to develop nutrition content, recipes, and educational programs.

Anderson frequently speaks on the topics of women’s health and plant-based nutrition and has coauthored two lifestyle medicine textbooks, including the first one on women’s health, Improving Women's Health Across the Lifespan.

She received a master's degree in nutrition and physical performance and is certified as an exercise physiologist and intuitive eating counselor. She's a student of herbal medicine and women's integrative and functional medicine. She lives with her husband in the Colorado Rocky Mountains, where you’ll find her out on a trail or in her garden.

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Andra Picincu, CN, CPT

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