[www.ncbi.nlm.nih.gov]

The leaves of onion are long, linear, hollow and cylindrical. When the plant reaches a certain stage of growth, the leaf bases become thick and form a bulb (5). Onion is categorized based on their color into yellow, red and white and based on their taste as sweet and non-sweet (6, 7).

Anti-cancer effects

Compelling evidence indicates that individuals who consume copious amounts of onion, their susceptibility to cancer at various organ sites is reduced (51-53). Polyphenolics such as flavonoids found in onion are partially responsible for this beneficial effect (42, 54). In addition, organosulfur compounds (e.g. cysteine, S-methyl cysteine, diallyl disulfide and diallyl trisulfide) content of onion play an important role in cancer chemoprevention as several studies are showing protective effects of these compounds against liver, stomach, colorectal and breast cancers (55-60). Moreover, onion, due to high-selenium content, can prevent some cancer occurrence without resulting in an excessive accumulation of tissue selenium, a concern associated with standard selenium compounds (61, 62).


Anti-diabetic effects

Consuming onion results in hypoglycemia in diabetic patients (1).

The results suggest that the anti-diabetic effect of onion could be due to the recovery or reproduction of pancreatic beta cells and improves the activity of enzymes in the pathways of glycolysis and gluconeogenesis (120).

In addition, allyl propyl disulfide and chromium content in onion have ability to decrease fasting blood levels of glucose and insulin and increase glucose tolerance (5). Quercetin by inhibiting ?-glucosidase is also able to prevent the release of D-glucose from oligosaccharides and disaccharides resulting in delayed absorption of glucose from intestine and controlling blood glucose levels (128, 129).

Anti-platelet effects

This plant also increases the coagulation time and fibrinolytic activity (132-136). Concerning the mechanism of the anti-platelet effect of onions, it can be noted that onion peel and bulbs extract through its constituents, quercetin, adenosine, allicin, and paraffinic polysulphides with upregulation of cyclic adenosine monophosphate (cAMP) levels and down regulation of thromboxane A2 (TXA2)

Bone effects

It has been suggested that one of the mechanisms of bone protection by onion is attributed to its base excess which is claimed to maintain calcium in bones (32, 150). In addition, quercetin present in onion has potential benefits for bone health by modulating inflammatory processes


Cardiovascular effects

A study indicates that aqueous onion extract reduces aortic nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and lipid peroxidation resulting in reducing systolic blood pressure (156). Along with this, Nausheen et al. demonstrated that the antioxidant activity of onion leaves extract resulted in protection against doxorubicin-induced cardiotoxicity in rats (157). In another experimental study, the antihypertensive effects of onion in NG-nitro-L-arginine methyl ester-induced hypertensive rats due to the antioxidant activity of onion were shown (158). The plant may also be considered as a heart tonic agent (159).


Gastrointestinal effects

Some studies have also shown that this plant stimulates the growth of useful microorganisms such as bifidobacteria and lactobacilli in the colon due to its high soluble fiber content, including inulin and fructooligosaccharides (40, 175). In addition, it has been reported that flavonoids (e.g. quercetin) content in onion has anti-spasmodic and anti-diarrheal activities (176). Moreover, quercetin appears to have a therapeutic potential in treating peptic ulcers by promoting mucus secretion and the inhibitory effect on Helicobacter pylori growth (177, 178).

Nervous system effects

It has been shown that onion administration causes improvements in behavioral deficits, motor incoordination and short-term memory induced by cerebral ischemia-reperfusion (IR) through decreasing LDL cholesterol and lipid peroxidation while increasing GSH and catalase (CAT) activities (5, 182).

Respiratory effects

The available data indicates that onion treatment can protect from bronchial asthma (189, 190). In an animal study, the aqueous extract of onion caused the reduction of lung inflammation and neutrophil, eosinophil and lymphocyte count (12). Another report showed that the methanolic onion extract decreased inflammatory cytokines (e.g. IL-5 and IL-13) and eosinophil peroxidase activity. The extract also relaxes tracheal smooth muscle (191).


Urogenital effects

Onion increases libido and strengthens reproductive organs against sexual impotence (5).

It was observed that treatment with fresh onion juice significantly increased sperm motility and sperm viability as well as decreased the percentage of sperm head abnormalities (44).

Suits me fine. I love raw onions. However, maybe, like tomatoes, their healthful benefits are improved by cooking? Anybody know? However, onions promote low blood sugar in diabetics; makes me wonder what onions would do to the blood sugar levels of persons who are not diabetic.

Raw onion has no noticeable effect on me. But I've never tries onion juice.

I don't like raw onions unfortunately, but scallions are okay.

Onions and onion skins are a Natural/Home Remedy for many ailments - especially the red onion. For example, for a toothache, put a small piece of red onion on or next to the tooth and it supposedly takes away the pain after a while. Putting a cut-up raw red onion by the bed at night is supposed to ward off and heal a cold. Allium Cepa - the homeopathic remedy - is indicated for colds. I once experimented with a raw onion poultice. I put sliced raw onion in my socks on the bottom of my feet at night - like with three layers of cotton socks - and wore it to bed for a couple of nights. I ended up with a runny nose and a cleaned out sinus situation, which was impressive.

The allium family includes garlic and leeks. I think some people - maybe some raw foodists - think they're not 'good for us.' Raw garlic three times a day is still part of my cold/flu protocol. I swear by it.

I had an experience with raw leeks years ago. For a workshop on Wild Edibles in my area, we were out in nature learning to identify and eating raw wild edibles. After eating wild leeks, I felt very strange. Like deep depression or anxiety. So weird.

I put sliced raw onion in my socks on the bottom of my feet at night - like with three layers of cotton socks - and wore it to bed for a couple of nights. I ended up with a runny nose and a cleaned out sinus situation, which was impressive.

I will keep this in mind.

lol - yeah, it sounds kind of gross. I forgot to say that each night I put a new slice of onion and different socks on and the first layer of socks was a tightish pair.

I also tried the onion by the bed thing to ward off a cold, but I ended up with bad dreams, so that was the end of that.