Can Onions Lower Cholesterol?
Does adding sautéed onions to marinara sauce or diced onions to salads help lower cholesterol? You may be right.
Onions are known for their culinary benefits, but they can also have health benefits. Studies have shown that onions can also help improve cholesterol levels.
Studies have shown that onions have a strong flavor and are rich in polyphenolic compounds, called flavonoids. Flavonoids include:
- Anti-inflammatory properties
- Anti-cancer properties
- Anti-proliferative properties
Some studies also suggest that onions may help improve cholesterol levels
In one study, flavonoids in onions lowered low-density lipoprotein (LDL) or “bad” cholesterol in obese people at risk for cardiovascular disease. Researchers attributed this to quercetin, a special type of flavonoid that is an antioxidant found in onions and other fruits and vegetables. Levels of high-density lipoprotein (HDL) or “good” cholesterol were not affected.
Another study looked at the effects of onion extract on cholesterol in rats. The researchers found no change in triglyceride levels, but a significant decrease in cholesterol levels. Some rats received onion extract and zinc sulfate and some rats received only onion extract or zinc sulfate. The rats that received the combination of onion extract and zinc sulfate had the best results.
Red onions have also been shown to help cholesterol levels; in a study published in Food and Function, male hamsters were fed a diet high in cholesterol. The rats’ diet was supplemented with a portion of red onion powder. The rats fed red onion powder had lower LDL cholesterol levels and maintained higher HDL cholesterol levels. This is the first study to use red onions.
Causes of unhealthy cholesterol levels in the body
There are two main forms of cholesterol, the first of which is LDL cholesterol, often referred to as “bad cholesterol”. High levels of LDL cholesterol in the body are considered unhealthy. The second, HDL cholesterol, is sometimes referred to as “good cholesterol.” High HDL cholesterol is a sign of good health.
If your doctor tells you that you have high cholesterol, he or she is usually referring to high LDL cholesterol or total cholesterol. Total cholesterol, sometimes called serum cholesterol, is the sum of LDL and HDL cholesterol and 20 percent of triglycerides; both LDL and total cholesterol can be used as indicators of your risk for cardiovascular disease and other complications.
Onions, Diabetes and Cholesterol
People with diabetes have an increased risk of cardiovascular disease and stroke. Diabetes often lowers HDL cholesterol and increases LDL cholesterol and triglycerides. It is important for people with diabetes to control their cholesterol.
One study examined the effects of the diabetes drug metformin (Glumetza, Glucophage, Fortamet and Riomet) in combination with onion extract. The combination was administered to diabetic rats. Researchers found that blood sugar levels and total cholesterol decreased. Despite these encouraging results, the researchers do not know exactly how the onion extract helped lower cholesterol levels or why it increased hunger and consumption in the non-diabetic rats. Also, many studies have only looked at the effects of onions on cholesterol in animals. Very few studies have been conducted on humans. More research needs to be done.
Raw and cooked
Most onion studies have used raw onions or concentrated onion extracts. It is not known what effect cooking onions at high temperatures has on the nutrients in onions.
When onions are cooked, the quercetin content is not changed. Instead, this antioxidant is transferred to the cooking water or other liquid. Therefore, onions are best eaten raw, cooked in liquid form, or sautéed over low heat.
Flavonoids are most abundant in the outer layer of the onion. In order to retain as many nutrients as possible, only the paper-thin layer of the onion is peeled off, leaving the fleshy layer intact.
When it comes to nutrition, not all onions are created equal. A study published in the Journal of Agricultural and Food Chemistry compared the nutritional value of 10 different types of onions. Of the varieties tested, shallots had the highest phenolic content and the highest antioxidant activity. Western yellow onions topped the list with the highest flavonoid content.
Most people can tolerate onions if they are consumed in small amounts. Although rare, some people may have an allergic reaction to onions. Also, some medications may interact with onions. Use caution if you are taking any of the following medications
- Anti-diabetic drugs
- Medications that affect the liver, such as acetaminophen, clozarone, ethanol, theophylline, and narcotics.
If you take these medications regularly, consult your doctor.
If you simply cannot tolerate the taste or pungency of onions, onion supplements may be an option for you. No standard dose of onion extract has been established. Consuming higher than normal amounts of onions in food is not recommended unless under the guidance of a physician. Also, purchase onion-based dietary supplements from a reputable source and follow label directions carefully.
Diagnosing High Cholesterol Levels
High cholesterol is usually asymptomatic. To check your cholesterol levels, you will need to have a blood test. Your doctor will do a blood test to check your blood lipid levels. This is called a lipid test and is a standard procedure for most primary care doctors. The results will usually look like this
- Total cholesterol
- High-density lipoprotein (HDL) cholesterol
- LDL cholesterol, which can include the number of particles in addition to the total amount
To get the most accurate results, you should avoid eating or drinking anything other than water for at least 10 hours before the test. In general, your doctor interprets the total cholesterol results as follows
Studies have shown that onions can help lower cholesterol. However, more research is needed to understand exactly how onions affect cholesterol metabolism. In the meantime, onions are an easy way to incorporate them into your diet. Try adding them to the following dishes
Next time you’re chopping onions, try smiling through your tears.
Looking for a healthy onion recipe? Use Grilled Onion Salad at your next garden barbecue, or try South Indian recipes for Oats and Onion Uttapam.