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Nitrates in Spinach: Risks and Benefits

Published: November 2, 2018

Many salad greens and leafy vegetables, such as spinach and arugula, contain high levels of nitrates. These controversial, but naturally-occurring compounds can be converted into nitrites and further into carcinogenic nitrosamines, but they may also provide some interesting health benefits. Here's the lowdown on what you need to know about nitrates in spinach.


Nitrate Content of Spinach

Spinach has been singled out as an exceptionally rich of nitrates, though on average, it contains nowhere near as much nitrate as arugula which is right there on top of the list of nitrate-rich foods. An analysis based on nearly 7000 samples of spinach found that on average, spinach contains 17 mmol of nitrate per kg. Arugula, by contrast, was found to contain 75 mmol of nitrate per kg. The nitrate content of spinach was also found to be slightly lower than that of beetroot, another vegetable that is known for its high nitrate content. (1)

It is worth noting, though, that the nitrate content of spinach can be affected by a variety of factors. For example, organically grown spinach has found to been contain lower levels of nitrates than its conventionally grown counterpart, and spinach harvested at earlier stages of plant growth has been shown to contain less nitrates than spinach harvested at the later stages (2).

Effect of Cooking on Nitrates in Spinach

Research shows that boiling spinach can reduce its nitrate content by more than 50 percent—if you discard the water in which it was cooked. Also blanching has been shown to reduce nitrates in spinach, though not to the same extent as boiling. If the spinach is washed prior to cooking, the loss of nitrates is even greater (3).

Spinach loses nitrates during washing, blanching and boiling because nitrates easily leach out of vegetables, but it is important to keep in mind that also water-soluble nutrients like vitamin C and B vitamins can easily escape from spinach during these procedures.

Spinach, Nitrates and Cancer Risk

Despite being one of the most concentrated whole food sources of nitrates, spinach as part of a healthy, balanced diet is unlikely to increase your risk of developing cancer. In fact, it might actually help reduce your risk of developing this dreadful disease. In 2015, a meta-analysis of existing research on nitrate/nitrite intake and gastric cancer risk concluded that while an increased intake of nitrates was associated with an increased risk of gastric cancer, a high intake of nitrates was not. In fact, a high intake of nitrates was associated with a slightly reduced the risk of gastric cancer. (4).

Now, for those who need a little refresher, nitrates are primarily found in plant-based foods, especially green leafy vegetables and some root vegetables, while cured meats and other processed meats are typically rich in nitrites. Fresh plant-based foods like spinach generally contain little or no nitrite, but certain bacteria can turn nitrates into nitrites. (5, 6)

So, why is it that green leafy vegetables do not seem to cause cancer, even if they are high in nitrates?

One reason is that spinach and other green leafy vegetables contain vitamin C, and research shows that vitamin C helps prevent nitrites from turning into carcinogenic nitrosamines in the stomach (7).

What's more, vegetables like spinach contain a wide range of cancer-fighting nutrients and phytochemicals which help outweigh the negative effects of nitrosamines. For example, the beta-carotene in spinach is thought to provide protection against breast cancer, and indeed, one study found that those who ate raw spinach at least once a week had a decreased risk of breast cancer. Also intake of cooked spinach was associated with a reduced risk of breast cancer, but the association was not as strong. (8)

Spinach also contains unique antioxidants which have been shown to exert chemopreventive effects against prostate cancer cell lines in laboratory experiments (9).

Cardiovascular Benefits

Not only does the claim that nitrate-rich vegetables can cause cancer seem unfounded, there is evidence that plant-based nitrates may even be beneficial because they can act as precursors to nitric oxide (10). Nitric oxide, or NO, is one of the most important molecules involved in the regulation of physiological processes. One of its most important roles is its ability to make blood vessels bigger, and studies suggest that it may play a key role in keeping the cardiovascular system healthy.

Indeed, a review published in Nutrition Research Reviews concluded that overall, dietary nitrate appears to acutely lower blood pressure in healthy humans, but pointed out that more research was warranted, especially studies involving people who have a high risk of developing cardiovascular disease (e.g. people with hypertension) (1). Since the publication of this review in 2013, the effects of dietary nitrates have also been tested in people with hypertension, with promising results. (11).

Benefits for Athletes

Nitrates from foods like spinach have also been found to increase the efficiency of mitochondria, the power generators of our cells, which means that nitrates can help the body do more work with the same amount of oxygen (12). This finding might explain some of the cardiovascular benefits of nitrates, but it is also the reason why athletes have been using beetroot juice to enhance their athletic performance (the nitrate content of beetroot is comparable to the nitrate levels of spinach).

In addition to having benefits for athletes and other sportsmen, this finding may also have implications for the management of lifestyle-related disorders that involve dysfunctional mitochondria (12).

Final Notes

Because of the apparent health benefits of nitrates from plant-based sources, some experts have called into question the rationale for recommendations to limit nitrate intake from plant-based whole foods like spinach in healthy individuals. In fact, even the famous DASH diet pattern, which is promoted by the U.S.-based National Heart, Lung, and Blood Institute, exceeds the World Health Organization's Acceptable Daily Intake (ADI) for nitrate by 550 percent for a 60-kg adult. (13)

Now, even though nitrates from fresh, frozen and cooked spinach seem to be remarkably safe for healthy adults, some caution is warranted. Dietary nitrates can cause infant methemoglobinemia, colloquially known as 'blue baby syndrome', which is why The American Academy of Pediatrics recommends that nitrate-rich vegetables are not given to young babies (14).


  1. D. Hobbs et al (2013). The effects of dietary nitrate on blood pressure and endothelial function: a review of human intervention studies. Nutrition Research Reviews, 26: 210-222.
  2. C. Colla et al (2018). Nitrate in fruits and vegetables. Scientia Horticulturae, 237, 221-238.
  3. K. Ekart et al (2013). Study on the influence of food processing on nitrate levels in vegetables. European Food Safety Authority.
  4. P. Song et al (2015). Dietary Nitrates, Nitrites, and Nitrosamines Intake and the Risk of Gastric Cancer: A Meta-Analysis. Nutrients, 7(12): 9872-9895.
  5. J. Hsu et al (2009). Nitrate and nitrite quantification from cured meat and vegetables and their estimated dietary intake in Australians. Food Chemistry, 115 (1): 334-339.
  6. A. Gorenjak (2013). Nitrate in vegetables and their impact on human health. A review. Acta Alimentaria, 42 (2)(2):158-172.
  7. Q. Zhan et al (2012). Esophageal Carcinoma. Recent Advances in Cancer Research and Therapy, p. 493-534
  8. M. Longnecker et al (1997). Intake of carrots, spinach, and supplements containing vitamin A in relation to risk of breast cancer. Cancer Epidemiology, Biomarkers and Prevention, 6(11), 887-92.
  9. S. Bakshi et al (2004). Unique natural antioxidants (NAOs) and derived purified components inhibit cell cycle progression by downregulation of ppRb and E2F in human PC3 prostate cancer cells. FEBS Letters, 573(1-3), 31-7.
  10. A. Torregrossa et al (2011). Nitric oxide and geriatrics: Implications in diagnostics and treatment of the elderly. Journal of Geriatric Cardiology, 8(4): 230-242.
  11. C. Kerley et al (2018). Dietary nitrate lowers ambulatory blood pressure in treated, uncontrolled hypertension: a 7-d, double-blind, randomised, placebo-controlled, cross-over trial. The British Journal of Nutrition, 119(6), 658-663.
  12. F. Larsen et al (2011). Dietary Inorganic Nitrate Improves Mitochondrial Efficiency in Humans. Cell Metabolism, 13(2), 149-159.
  13. N. Hord et al (2009). Food sources of nitrates and nitrites: the physiologic context for potential health benefits. The American Journal of Clinical Nutrition, 90(1):1-10.
  14. American Academy of Pediatrics (2005). Infant methemoglobinemia: the role of dietary nitrate in food and water. Pediatrics, 116(3):784-6.