Boost Immunity and Fight Disease with Spinach

From salads to smoothies and stir-fries, spinach is a culinary chameleon that adds a nutritional boost to countless dishes. But beyond its versatility, spinach is a nutritional powerhouse that’s earned its reputation as a functional food. 

What Is Spinach? 

Spinach (Spinacia oleracea) is a dark leafy green that belongs to the amaranth family, along with beets, quinoa, and Swiss chard. [1] It has a rich history dating back nearly 2,000 years to ancient Persia, where it traveled along trade routes to China, India, and Europe. [2]  

Spinach’s popularity surged in the U.S. during the early 1800s, but a cartoon sailor named Popeye truly cemented its place in popular culture. When Popeye debuted in 1929, his legendary strength—fueled by a can of spinach—is said to have boosted spinach sales by a whopping 33%. 

Type of Spinach 

There are a few main types of spinach: smooth or flat leaf, savoy, and red. You’ll also find hybrids like semi-savoy, and even baby spinach. 

In the U.S., flat-leaf spinach is the most popular. It has smooth, tender leaves that are great for eating fresh, canning, or freezing. Savoy spinach, also called curly leaf, is more bitter, and the crinkly leaves can be a bit tough to clean. 

Semi-savoy spinach is a middle ground. It’s less crinkly and easier to clean than savoy, making it a good choice for fresh eating, processing, or cooking. Red spinach has a unique look with green leaves and a red center. The leaves are round, tender, and have a slightly sweeter flavor. 

And then there’s the popular baby spinach, which is just flat-leaf spinach harvested earlier for extra tenderness. Finally, there’s baby spoon spinach, a type of savoy with tiny, crispy leaves and a sweeter taste. 

The Nutritional Power of Spinach 

Packed with vitamins, minerals, and antioxidants, spinach offers a range of benefits, from protecting against disease to supporting brain, heart, and eye health. [3]  

Spinach contains an impressive array of vitamins and minerals. Thanks to its high carotenoid content, It’s a great source of vitamin A. You’ll also find a healthy dose of vitamin C, a powerful antioxidant that supports skin health and immune function. 

Spinach is an excellent source of vitamin K1, crucial for blood clotting, with just one leaf providing over half of your daily needs. You’ll also find a healthy dose of folate (vitamin B9), which is vital for cell growth and function, especially during pregnancy. [4] 

Iron is another key nutrient found in spinach. It’s essential for producing hemoglobin, the protein responsible for carrying oxygen throughout your body. And don’t forget about calcium, a mineral vital for strong bones and proper nerve, heart, and muscle function. 

Beyond these, spinach also boasts other valuable nutrients like potassium, magnesium, and vitamins B₆ and E, making it a true superfood for overall health and well-being. [4,5]  

May Protect Against Oxidative Stress 

Spinach contains compounds that can help protect our bodies from oxidative stress. Oxidative stress occurs when we have too many free radicals (unstable molecules that can damage our cells) and not enough antioxidants to neutralize them. Over time, oxidative stress can increase the risk of chronic diseases like cancer, diabetes, and heart disease. [6,7] 

Supports the Immune System 

Spinach is an excellent source of vitamin C and antioxidants, which can help protect your body against illnesses, including respiratory infections such as colds, COVID-19, and the flu. [8] It also provides a dose of vitamin A, which is essential for healthy vision, reproduction, and overall well-being.  

May Reduce Cancer Risk 

Spinach is a rich source of carotenoids, plant compounds that may help protect against cancer. These carotenoids work by neutralizing harmful free radicals that can damage our DNA and lead to the formation of cancerous tumors. [9,10] 

Studies have linked higher levels of carotenoids in the blood to a reduced risk of certain cancers, such as breast and lung cancer. Cooked spinach is also a good source of fiber, which has been associated with a lower risk of colorectal cancer. [11] 

May Lower Blood Pressure 

Spinach is a good source of nitrates, compounds that help lower blood pressure by increasing nitric oxide production in the body. This, in turn, relaxes and widens blood vessels, promoting better blood flow. Studies have even shown that the nitrates in spinach can contribute to improved heart health. [12] 

Cooked spinach also provides a healthy dose of potassium, another nutrient that plays a key role in blood pressure regulation. Potassium helps your body get rid of excess sodium, which can raise blood pressure. It also helps relax blood vessel walls, further promoting healthy blood pressure levels. [13] 

Potential Risks of Too Much Spinach 

Spinach contains oxalates, naturally occurring compounds that can sometimes contribute to kidney stones and other health issues. If you have a history of kidney stones or are at risk, it’s best to enjoy spinach in moderation. Consider pairing it with calcium-rich foods or eating it cooked, as those help reduce that risk. [14] 

Also, spinach is high in vitamin K, which can interact with certain medications, especially blood thinners. If you’re taking any medications, it’s always a good idea to talk to your doctor about potential interactions with spinach or any other foods. [15] 

How to Select and Store Spinach 

Although available year-round, spinach thrives as a cool-season crop, reaching its peak flavor and quality in the spring and fall. You’ll find it in most grocery stores in various forms, including bunches, pre-washed bags, frozen, and canned varieties. 

When selecting fresh spinach, look for vibrant green leaves that are crisp and free of blemishes. To ensure optimal freshness, wash and thoroughly dry spinach before storing it. A salad spinner or paper towels can effectively remove excess moisture. Then, place the leaves in a container lined with paper towels or a plastic bag, and store them in your refrigerator’s crisper drawer.  

Fresh spinach typically lasts about a week when stored properly. For pre-washed spinach, check the sell-by date and anticipate a similar shelf life. Frozen spinach can be stored for up to six months, while canned spinach offers an even longer shelf life. 

RELATED: Fresh, Frozen, or Canned Vegetables and Fruits—Which Are More Nutritious? 

How to Cook Spinach 

While spinach sometimes receives criticism for its slightly bitter or metallic taste (a result of its high iron content), this can be easily balanced by pairing it with creamy ingredients. 

Generally, spinach boasts a milder and sweeter flavor profile compared to many other leafy greens. However, its taste can vary depending on the variety and maturity of the leaves. Fresh baby spinach offers a delicate sweetness, while larger, mature leaves tend to have a more robust flavor.  

Delicious both raw and cooked, spinach complements a wide range of flavors. Raw spinach is a popular base for salads, especially when paired with bold dressings and toppings like nuts and dried fruit. It’s also a nutritious and convenient addition to smoothies. 

It’s worth noting that different cooking methods can influence spinach’s nutrient content. We already know that cooking spinach reduces its oxalate content. [16] However, some studies suggest that consuming spinach raw helps preserve lutein, a nutrient crucial for eye health, while high-heat methods like frying can significantly reduce it. [17] 

If you’re aiming to maximize vitamin K intake, microwaving appears to be the most effective cooking method. While blanching can diminish vitamin C content, steaming offers a gentler approach that helps preserve this essential nutrient. Interestingly, while cooking can reduce vitamin E, it can actually enhance the availability of vitamin A. [18] 

Keep in mind that spinach wilts significantly when cooked, so be generous with your portions. Enjoy it as a simple side dish, or incorporate it into soups, stews, and curries for a nutritious boost. 

Resources 

1. Know Your Produce Commodity | Spinach Market & Industry Summary [Internet]. Produce Blue Book. 2024. Available from: https://www.producebluebook.com/know-your-produce-commodity/spinach/  
2. Spinach History – Different Types of Spinach [Internet]. Vegetablefacts.net. 2023. Available from: https://www.vegetablefacts.net/vegetable-history/spinach-history/  
3. Roberts JL, Moreau R. Functional properties of spinach (Spinacia oleracea L.) phytochemicals and bioactives. Food & function [Internet]. 2016;7(8):3337–53. Available from: https://www.ncbi.nlm.nih.gov/pubmed/27353735  
4. https://fdc.nal.usda.gov/food-details/168462/nutrients  
5. Tang G. Spinach and Carrots. Bioactive Foods in Promoting Health. 2010;381–92. Available from: https://www.sciencedirect.com/science/article/abs/pii/B9780123746283000256 
6. Roberts JL, Moreau R. Functional properties of spinach (Spinacia oleracea L.) phytochemicals and bioactives. Food & function [Internet]. 2016;7(8):3337–53. Available from: https://www.ncbi.nlm.nih.gov/pubmed/27353735  
7. National Cancer Institute. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/oxidative-stress [Internet]. www.cancer.gov. 2011. Available from: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/oxidative-stress  
8. Pisoschi AM, Pop A, Iordache F, Stanca L, Geicu OI, Bilteanu L, et al. Antioxidant, anti-inflammatory and immunomodulatory roles of vitamins in COVID-19 therapy. European Journal of Medicinal Chemistry [Internet]. 2022 Mar;232:114175. Available from: https://www.sciencedirect.com/science/article/pii/S0223523422000770 
9. Total and individual carotenoids and phenolic acids content in fresh, refrigerated and processed spinach (Spinacia oleracea L.). Food Chemistry [Internet]. 2008 May 15;108(2):649–56. Available from: https://www.sciencedirect.com/science/article/pii/S0308814607011910 
10. Sui J, Guo J, Pan D, Wang Y, Xu Y, Sun G, et al. The Efficacy of Dietary Intake, Supplementation, and Blood Concentrations of Carotenoids in Cancer Prevention: Insights from an Umbrella Meta-Analysis. Foods [Internet]. 2024 Jan 1 [cited 2024 May 19];13(9):1321. Available from: https://www.mdpi.com/2304-8158/13/9/1321 
11. Spinach: Nutritional Powerhouse [Internet]. American Institute for Cancer Research. Available from: https://www.aicr.org/cancer-prevention/food-facts/spinach-and-cancer/ https://www.aicr.org/cancer-prevention/food-facts/spinach-and-cancer/ 
12. Jovanovski E, Bosco L, Khan K, Au-Yeung F, Ho H, Zurbau A, et al. Effect of Spinach, a High Dietary Nitrate Source, on Arterial Stiffness and Related Hemodynamic Measures: A Randomized, Controlled Trial in Healthy Adults. Clinical Nutrition Research [Internet]. 2015 Jul 1;4(3):160–7. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4525132/  
13. American Heart Association. How Potassium Can Help Control High Blood Pressure [Internet]. Heart.org. 2015. Available from: https://www.heart.org/en/health-topics/high-blood-pressure/changes-you-can-make-to-manage-high-blood-pressure/how-potassium-can-help-control-high-blood-pressure  
14. Salgado NC, Mafalda Alexandra Silva, Maria Eduardo Figueira, Costa HS, Albuquerque TG. Oxalate in Foods: Extraction Conditions, Analytical Methods, Occurrence, and Health Implications. Foods. 2023 Aug 25;12(17):3201–1. Available from: https://www.mdpi.com/2304-8158/12/17/3201
15. National Institutes of Health. Vitamin K [Internet]. Nih.gov. 2021. Available from: https://ods.od.nih.gov/factsheets/vitaminK-HealthProfessional/  
16. Chai W, Liebman M. Effect of Different Cooking Methods on Vegetable Oxalate Content. Journal of Agricultural and Food Chemistry. 2005 Apr;53(8):3027–30. Available from: https://pubmed.ncbi.nlm.nih.gov/15826055/ 
17. Chung RWS, Leanderson P, Gustafsson N, Jonasson L. Liberation of lutein from spinach: Effects of heating time, microwave-reheating and liquefaction. Food Chemistry. 2019 Mar;277:573–8. Available from: https://www.sciencedirect.com/science/article/abs/pii/S0308814618319617 
18. Lee S, Choi Y, Jeong HS, Lee J, Sung J. Effect of different cooking methods on the content of vitamins and true retention in selected vegetables. Food Science and Biotechnology [Internet]. 2017 Dec 12;27(2):333–42. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6049644/