Stinky foods that offer health benefits

By John Murphy, MDLinx
Published March 5, 2019

Key Takeaways

Famously fragrant foods like onions, garlic, and leeks can really kick up your food a notch. What would Caesar salad or hummus be without garlic, for example? But besides creating flavor—and causing bad breath—these foods have some astounding health benefits. In a recent study in China, for instance, adults who ate high amounts of garlic, leeks, and onions (known as allium vegetables) had a 79% lower risk of developing colorectal cancer than adults who consumed low amounts.

Hold your nose because here’s a big stinking plateful of other benefits that these foods offer.


Besides adding zesty flavor to soups and salads, and as a tasty topping to burgers, onions are a great source of quercetin, a flavonoid with significant antioxidant properties. In studies, researchers have shown that quercetin inhibits low-density lipoprotein oxidation, a process involved in atherosclerosis and coronary heart disease. One medium-sized onion (100 g) contains an estimated 22.40 mg to 51.82 mg of quercetin, and daily consumption of onions appears to increase the amount of quercetin in the blood. (An onion a day keeps the doctor away?) Other foods, such as apples and tea, also contain quercetin; however, quercetin from onions is absorbed at twice the rate as that from tea and more than three times that from apples.

Onions also help to break up platelet aggregation, which is associated with atherosclerosis, cardiovascular disease, heart attack, and stroke. And the more pungent the onion, the greater the antiplatelet activity it has, researchers found.

According to the National Onion Association (yes, there is a National Onion Association!), investigators have shown that increased onion consumption is also associated with lower risk for certain cancer types, especially stomach, bladder, and colorectal cancers.

Onions also contain organosulfur compounds, which are believed to possess anti-inflammatory, anti-allergic, antimicrobial, and antithrombotic activity by inhibiting cyclooxygenase and lipoxygenase enzymes. Interestingly, these compounds don’t form until you cut the onion and disrupt its cell walls. Also, the outer layer of the onion (just beneath the paper skin) has the most benefits—so don’t over-peel your onions.

Lastly, do you cry when cutting onions? It’s because they release a gas with a lachrymatory factor (propanethial S-oxide), an eye irritant that causes tearing. To reduce the production of this chemical, put the onion in the fridge for an hour before cutting it.


Garlic has a multiplicity of uses. It adds a pungent zing to stir fry, roasted chicken, pizza, and pasta dishes—plus it wards off vampires. Garlic also has been shown to reduce blood pressure levels, lower cholesterol levels, and mitigate other risk factors for atherosclerosis-related diseases. More research indicates that garlic can benefit people with diabetes and certain cancer types.

In one comprehensive literature review, researchers reported that garlic supplementation reduced systolic blood pressure by 7 to 16 mmHg and diastolic blood pressure by 5 to 9 mmHg. Garlic also reduced total cholesterol by 7.4 to 29.8 mg/dL.

“That isn’t quite as good as cholesterol or blood pressure pills, but it’s certainly a nice effect,” said co-author Matthew Budoff, MD, professor of medicine, David Geffen School of Medicine, University of California Los Angeles, and endowed chair of preventive cardiology, Los Angeles Biomedical Research Institute, Torrance, CA, in a Consumer Reports article.

Garlic also appears to help people with diabetes control their disease. In a meta-analysis of randomized controlled clinical trials, researchers reported that people with type 2 diabetes who took a garlic supplement each day for 2 or 3 months had significant reductions in their fasting blood glucose levels.

Other research indicates that garlic may also help prevent colorectal cancer and cardiovascular mortality, although the effects have not been fully confirmed.

Many home remedies include garlic as a cure for the common cold. Indeed, in one small trial, people who took garlic every day for 3 months had fewer colds—24 colds in the garlic group compared with 65 in the placebo group. But researchers cautioned that this was only one small study that, in itself, doesn’t provide enough evidence that garlic can prevent or treat the common cold. Larger clinical trials are needed for that.


Leeks look like large scallions but have a sweeter, milder flavor. Not surprisingly, leeks are in the same family as scallions—allium vegetables—which also includes its odiferous cousins: onions, garlic, and shallots. Eaten regularly, leeks can provide similar cholesterol-lowering and cancer-protection benefits as onions and garlic.

Leeks are a great source of kaempferol, a flavonoid also found in broccoli, cabbage, kale, and tea. In many in vitro studies, kaempferol significantly inhibited cancer cell growth and triggered apoptosis in a variety of cancer cells, including leukemia, lung cancer, and glioblastoma. In the Nurses’ Health Study, for instance, investigators found that women whose diets contained the most kaempferol had 40% less incidence of ovarian cancer compared with women who ate the least kaempferol.

“Numerous preclinical studies have shown that kaempferol and some glycosides of kaempferol have a wide range of pharmacological activities, including antioxidant, anti-inflammatory, antimicrobial, anticancer, cardioprotective, neuroprotective, antidiabetic, anti-osteoporotic, estrogenic/antiestrogenic, anxiolytic, analgesic and antiallergic activities,” according to authors in Mini-Reviews in Medicinal Chemistry.

When using any of the allium vegetables as an ingredient, let them sit for 10 minutes after chopping and prior to cooking to preserve the maximum amount of healthful compounds.

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