Onion benefits for health facts and nutrients


Onion is a vegetble for life time to used and the basic way to proceed the new flavour to food in any dish in asia. Onion benefits for health has a big way of grow in every case of health and the fundamental nutrients.

Health Benefits

Onions Are Rich in Conventional Nutrients As Well As Unique Phytonutrients

While onions rank in our WHFoods rating system as a very good source of biotin and a good source of manganese, vitamin B6, copper, vitamin C, fiber, phosphorus, potassium, folate, and vitamin B1, this richness in conventional nutrients is accompanied by their unique phytonutrient content. While a good number of the unique phytonutrients found in onions are sulfur-containing, many are not. The chart below shows onion phytonutrients that are receiving special attention in today’s health research:

Flavonoids Organic Acids Sulfur-Containing Compounds
fisetin ferulic acid dimethyltrisulfide (DMTS)
quercetin protocatechuic acid S-1-propenyl-1-cysteine sulfoxide (PRENCSO)
kaempferol myristic acid DMS (diallyl monosulfide)
isorhamnetin DDS (diallyl disulfide)
S-methyl-L-cysteine sulfoxide (MCSO)
onionin A

Even within this limited chart showing a dozen or so phytonutrients, there are health benefits that stretch across most of our body’s organ systems, including our cardiovascular system, endocrine system, digestive system, immune and inflammatory systems, and musculoskeletal system. Of special interest in the health research has been the risk-reducing impact of onion intake on the cardiovascular system.

The health benefits of onion phytonutrients are not yet as well researched as the health benefits of its fellow allium vegetable, garlic. But we suspect that contributions of onion will become better recognized as health research on this beloved allium vegetable moves forward.

Cardiovascular Benefits of Onions

Unlike the research on garlic and its cardiovascular benefits, research specifically focused on onion has mostly been conducted on animals rather than humans. In these animal studies, there is some form of onion extract used to test potential health benefits. Interestingly, however, researchers have tried to look specifically at different types of onion extracts (for example, extracts from red versus yellow versus white onions) as well as extracts from cooked versus raw onions. In these animal studies, there is evidence that onion’s sulfur compounds may work in an anti-clotting capacity and help prevent the unwanted clumping together of blood platelet cells. There is also evidence showing that sulfur compounds in onion can lower blood levels of cholesterol and triglycerides, and also improve cell membrane function in red blood cells.

Perhaps the most fascinating recent studies in this area involve a group of messaging molecules called oxylipins. Oxylipins are routinely made in the body from polyunsaturated fatty acids. Their very name comes from their origin: “oxy + lipid” can roughly be translated as “fats that have undergone oxidation.” Normally, you might jump to the conclusion that oxidized forms of fat are a bad thing. Sometimes this conclusion would be true—for example, when an excessive amount of fat-related tissue along our blood vessel walls becomes oxidized. But in other circumstances, oxidized forms of fat can play a helpful role in our metabolism, and oxylipins can be a great example here.

Some oxylipins fall into the category of what are called the “omega-3 oxylipins.” These oxylipins are made from omega-3 fatty acids like alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Consumption of onions has been shown to increase the levels of omega-3 oxylipins in the liver, and this increase in omega-3 oxylipins may help explain the ability of onions to help regulate proper blood fat levels as well as blood levels of cholesterol. We expect to see much more work in this area of onion intake and oxylipin changes. There is a good likelihood that these oxylipin changes may not only be related to our cardiovascular health but also to our ability to maintain good blood sugar regulation and to lower certain obesity-related risks as well.

In human studies, most of the cardiovascular benefits related to onions have not been connected with onions themselves, but with onion-containing diets. This difference is an important one, because in general, it has been difficult for researchers to estimate exactly how much onion study participants have consumed. Onions (like garlic, leeks, chives, and scallion) are often included in relatively small amounts and scattered through a meal plan in the form of sauces, soups, and other combination foods. This “scattered presence” of onions in onion-containing diets has made it difficult for researchers to pinpoint what degree of cardiovascular risk reduction is associated with what level of onion intake.

Before leaving the topic of onion intake and cardio support, it is important to point out the outstanding antioxidant and anti-inflammatory richness of onions. We’ve seen recent studies attesting to antioxidant benefits in all types of onions including red, yellow, and white. Since chronic oxidative stress and chronic inflammation inside of our blood vessels (especially our arteries) is linked to increased risk of several cardiovascular diseases (for example, atherosclerosis), the proven health benefits of onions for this body system make good sense to us. We have also given this category of onion health benefits (antioxidant and anti-inflammatory) its own special section below.

Antioxidant and Anti-Inflammatory Benefits of Onions

At the very outset, it is worth remembering that onions are a good source of vitamin C and the mineral manganese, two “conventional” nutrients that play a key role in our body’s antioxidant support. With respect to vitamin C, we are talking not only about better protection of genetic materials like RNA and DNA but also protection of many cell structures. Additionally, vitamin C helps Phase 1 (“mixed function oxidase”) enzymes in our body’s detoxification system function properly because it helps keep metal cofactors for those enzymes in place. With respect to manganese, we are talking about another set of important antioxidant benefits. Heading up this set of benefits would be proper functioning of the enzyme superoxide dismutase (SOD) in a form that requires manganese (abbreviated MnSOD). MnSOD is one of the key enzymes in our mitochondria, cell components that are critical for oxygen-based energy production. Good antioxidant protection in our mitochondria is quite critical since these cell components are so vigorously engaged in oxygen metabolism and can trigger problems unless functioning safely.

However, it’s equally important—and perhaps even more important—to recognize the unique antioxidant and anti-inflammatory phytonutrients provided by onions. Perhaps most famous here are the quercetin flavonoids (and quercetin glycosides) that are so plentiful in onions (and especially red onions). Also well studied here are the anthocyanin flavonoids that give red onions their wonderful color. Yet studies also show that yellow and white onions can also be concentrated sources of antioxidant and anti-inflammatory phytonutrients. At the beginning of this Health Benefits section, you will find a chart showing key flavonoids, organic acids, and sulfur-containing compounds in onions. Virtually all of these nutrients have been shown to have antioxidant and anti-inflammatory properties and to be contained in most varieties of onions, including yellow and white varieties. (With the anthocyanin flavonoids, it is a different story, since these flavonoids are only concentrated in red or purple onion varieties.)

While still mostly researched in the lab or in animal studies, some of the unique anti-inflammatory phytonutrients found in onion are especially worth noting. For example, onionin A, a sulfur-containing compound so clearly named after the onion, is a unique anti-inflammatory moledule that is found in the bulb portion (or root) of the onion plant. Onionin A has been shown to inhibit the activity of macrophages, specialized white blood cells that play a key role in our body’s immune defense system. Since one of the defense strategies employed by these white blood cells can involve the triggering of large-scale inflammatory responses, overactivity on their part can sometimes be a harmful event if these large-scale responses are not needed. In other words, it is sometimes very helpful to prevent this overactivity. In lab and animal studies, onionin A from the root portion of the onion appears to provide exactly this kind of help.

Most researchers would point to quercetin as the hallmark flavonoid antioxidant and anti-inflammatory substance in onions. The quercetin content of onions is especially well-studied in the case of red onions, which appear to be richer in this compound that either white or yellow varieties. In animal studies, the potential value of quercetin from onions has been especially thought provoking, and you can find more details about this potential value in the final topic (“Other Potential Health Benefits from Onion’) addressed in this Health Benefits section.

Potential Cancer Protection From Onions

Several servings of onion each week may be sufficient to statistically lower your risk of some types of cancer. For colorectal, laryngeal, and ovarian cancer, between 1–7 servings of onion per weekmay provide you with risk reduction. But for decreased risk of oral and esophageal cancer, you are likely to need multiple servings of onions per day. In general, it has been quite difficult for cancer researchers to arrive at strong, indisputable links between cancer risk and levels of allium vegetable intake because it isn’t easy for study participants to estimate exactly how many servings of allium vegetables they consumed. Onions, garlic, leeks, chives, scallion, and other allium vegetables are often included in relatively small amounts in sauces, soups, and other combination foods, and in this sense they can become “hidden” in a meal and more difficult to quantify. Overall, we would describe this area of onion health benefits as one in which there are still some significant “research gaps.”

An overall take-away from the research at this point in its progression: we believe it makes sense to err on the high side if you want to obtain the full potential cancer-related benefits of onion. For example, while a few slivers of sliced onion on a tossed salad can definitely be a good thing—and tasty as well—they are probably not enough to provide you with the cancer-related onion benefits you are seeking. At WHFoods, we consider 1 cup of cooked, chopped onion to be equivalent to one serving. Our outstanding recommended level of allium vegetable intake is two-thirds of a cup per day. If you were going to obtain this entire outstanding recommended level from onions alone, you would need to consume two-thirds of a cup of onion per day. (Of course, there are other outstanding allium vegetables that can help you meet this recommended intake level for allium vegetables, including garlic and leeks.) Still, whenever you believe that onion might make a tasty addition to a soup, sauce, salad, or entrée, consider adding the equivalent of one whole medium-sized onion, rather than some far smaller portion. And for a great example of a well-balanced diet that includes onions every day of the week in a serving equivalent of two-thirds of a cup, take a look at our 7-Day Menu. You will also find both red and yellow onions included in our 7-Day Menu in a way that perfects the flavors and textures in the recipes, as well as the appearance of the recipes when served.

Other Potential Health Benefits From Onions

In animal studies, onions have shown potential for improvement of blood sugar balance, even though it is not yet clear about the carry over of these benefits for humans who are seeking better blood sugar balance from their diet. Most of the animal studies have been conducted on laboratory rats, and most have used onion juice or onion extract as the form of onion tested. Future research is needed to clarify onion’s potential for helping lower blood sugar and improving blood sugar control, especially in persons with blood sugar problems. However, one exciting new line of evidence in this area involves the impact of quercetin from onion on skeletal muscle, mitochondrial metabolism, and insulin sensitivity. The configuration of events hypothesized by researchers is as follows: first, it is possible that the impact of quercetin initially takes place at a genetic level, or more specifically, on the way in which gene activities are regulated. Here the focus has been on a molecule called peroxisome proliferation activated-receptor gamma coactivator 1 alpha (or Pcg-1α). Through their impact on Pcg-1α, components in onion may be able to improve mitochondrial function in skeletal muscle, thereby improving events related to healthy mitochondrial function, including insulin sensitivity and glucose tolerance. There is also a very likely connection here to risk of obesity, since skeletal muscle metabolism, mitochondrial metabolism, insulin sensitivity, glucose tolerance, and risk of obesity are closely related in health research.

While not as well researched as garlic in terms of antibacterial benefits, onion has nevertheless been shown to help prevent bacterial infection. Along with its sulfur-containing compounds, the flavonoid quercetin contained in onion helps provide these antibacterial benefits. We’ve seen studies showing antibacterial activity of onion in relationship to the bacteria Streptococcus mutansand Streptococcus sobrinus. (These bacteria are commonly involved in the production of tooth cavities). Antibacterial benefits have also been shown in the area of gum (periodontal) disease bacteria, including Porphyromonas gingivalis and Prevotella intermedia. Interestingly, in one study, fresh, chopped, uncooked onion had antibacterial effects on these potentially unwanted gum bacteria, but non-fresh, uncooked onion (raw onion that was chopped and then left to sit for 2 days at room temperature) did not demonstrate these same antibacterial properties nor did fresh onion that was grated and then steamed for 10 minutes. While it is not possible to draw broad conclusions from a single lab study, these findings suggest that length of storage (for onion that has been chopped but not cooked) and duration of heat exposure (in this case involving exposure to steam for 10 full minutes) can affect some of onion’s health benefits. For these reasons, special care may be needed in the storage, handling, and cooking of this allium vegetable.


While we may not usually think about them in this way, onions are a food of astonishing diversity. They are enjoyed in virtually all parts of the world—and so much so that you will find countries in Asia (including China and India), Southeast Asia (including Indonesia and Myanmar), the Middle East (like Turkey and Iran), South America (Brazil), and Russia all being included among the major onion-producing countries of the world. But even this level of diversity fails to tell the full story, since the top onion-consuming countries in the world are also found in North America (the United States), Northern Africa (Libya and Algeria), and Europe (the United Kingdom and France).

Nutrients in Onion
















Calories 40
% Daily Value*
Total Fat 0.1 g 0%
Saturated fat 0 g 0%
Polyunsaturated fat 0 g
Monounsaturated fat 0 g
Cholesterol 0 mg 0%
Sodium 4 mg 0%
Potassium 146 mg 4%
Total Carbohydrate 9 g 3%
Dietary fiber 1.7 g 6%
Sugar 4.2 g
Protein 1.1 g 2%

Vitamin A 0% Vitamin C 12%
Calcium 2% Iron 1%
Vitamin D 0% Vitamin B-6 5%
Vitamin B-12 0% Magnesium 2%


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