Durk Pearson & Sandy Shaw’s®
Life Extension NewsTM
Volume 16 No. 5 • May 2013

FennelChewing Fennel Seeds After a Meal as a Mouth 
Freshener Offers Surprising Health Benefits

A new paper1 reports that in the Indian sub-continent and around the world, chewing fennel seeds (Foneiculum vulgare) is a common way to freshen one’s mouth after eating a meal. But surprisingly, there appears to be a lot more to it than that. In the new paper, the researchers explain that they found that fennel seeds contain significantly higher amounts of nitrites and nitrates when compared to other commonly chewed post-meal seeds. Nitrites and nitrates are “known to play crucial roles in maintaining vascular and digestive function”1 by being chemically reduced in the body to nitric oxide, an important vasoactive compound. In this new study, the researchers show that nitrites derived from fennel seeds can modulate vascular functions. Quite a nice benefit for a little bit of post-prandial chewing. (And, incidentally, if you haven’t tried them, they are tasty, with a sort of licorice flavor.)

The authors1 cite recent animal studies exploring different potential applications of what they call “nitrite therapy” that included pulmonary hypertension, acute tissue ischemic injuries, cerebral vasospasm, myocardial infarction, and stroke. “Studies have demonstrated that a high intake of nitrite containing fruits and vegetables in one’s diet has protective effects on the cardiovascular system.”1 The authors even suggest that chewing fennel seeds could be a useful way to maintain nitric oxide levels at high altitudes to help prevent the onset of acute hypoxia.2 Sounds like a good method for mountain climbers to use to avoid altitude sickness.

Cautionary note on increasing dietary intake of nitrates: A recent paper3 reports on the risk of esophageal and gastric cancer subtypes in relation to dietary N-nitroso compounds in 120,852 men and women aged 55-69 when they were recruited in the Netherlands Cohort Study in 1986. N-nitroso compounds are naturally occurring compounds containing a nitroso group attached to a nitrogen atom that can be converted in animals to carcinogenic forms in the acidic environment of the stomach or in the lower gastrointestinal tract by contact with heme-iron derived from meat. The Netherlands Cohort Study3 found that high dietary intakes of N-nitroso compounds (NOC) increased the risk of esophageal squamous cell carcinoma in men, though there was no increased risk in women. Importantly, adequate amounts of vitamin C, an inhibitor of endogenous nitrosation, can prevent this increased risk.3


  1. Swaminathan et al. Nitrites derived from Foneiculum vulgare (Fennel) seeds promotes vascular functions. J Food Sci. 77(12):H273-9 (2012).
  2. Erzurum et al. Higher blood flow and circulating NO products offset high-altitude hypoxia among Tibetans. Proc Natl Acad Sci USA. 104(45):17593-8 (2007).
  3. Keszei et al. Dietary N-nitroso compounds, endogenous nitrosation, and the risk of esophageal and gastric cancer subtypes in the Netherlands Cohort Study. Am J Clin Nutr. 97:135-46 (2013).