Onions are not only a familiar kitchen staple but also a scientifically proven kidney-protective vegetable. In a personal online post, Doctor Hung Yung-hsiang, a nephrologist with over 20 years of experience at Tri-Service General Hospital, stated that medical literature confirms onions contain high levels of antioxidant and anti-inflammatory compounds. These substances help stabilize blood pressure and blood sugar, thereby indirectly reducing the workload on the kidneys.

The kidney-protective abilities of onions stem from two main components: quercetin and sulfur compounds. Quercetin is a powerful natural antioxidant, most concentrated in the outer layers and root end of the onion. Research indicates that quercetin reduces oxidative stress, prevents glomerular fibrosis, and protects kidney cells from early damage. Furthermore, this compound inhibits uric acid synthesis and promotes its excretion, offering significant benefits for individuals with high uric acid levels or those managing kidney disease due to gout complications.

Meanwhile, sulfur compounds, which cause eye irritation when cutting onions, play an anti-inflammatory role and slow the progression of chronic kidney function decline. The combination of these active compounds means that incorporating onions into the diet can help reduce proteinuria and delay kidney function deterioration. This makes onions a valuable aid in the diet of patients with chronic kidney disease.

Illustrative photo: Getty Steward

Beyond kidney protection, Verywell Health highlights numerous other benefits of onions. These include cardiovascular protection by lowering bad cholesterol, stabilizing blood sugar for diabetic patients, and improving bone density with regular consumption. The sulfur compounds and quercetin found in allium vegetables can inhibit tumor formation and prevent the metastasis of malignant cells, particularly in gastric and colorectal cancers.

For diabetic patients, onions effectively help manage blood sugar by improving insulin resistance. Moreover, onions act as a "natural antibiotic," inhibiting the growth of harmful bacteria such as E. coli, Staphylococcus aureus, or H. pylori, which causes stomach ulcers. Another benefit of onions is their contribution to bone health. Studies show that onion consumption improves bone density and reduces age-related bone loss. For the digestive system, the inulin component in onions acts as a prebiotic, fostering an ideal environment for beneficial gut bacteria to thrive and supporting effective weight management.

Studies indicate that quercetin can aid in reducing body weight and excess fat. Half a cup of raw onion contains only about 30 calories but provides abundant essential nutrients, including: vitamin C, B6, potassium, folate, zinc, and selenium.

According to doctors, many people wonder whether to eat onions raw or cooked. Eating them raw offers the best kidney protection as it preserves more quercetin and sulfur compounds. However, due to their pungent taste, cooking is a milder alternative, though it results in some loss of nutritional value.

Regarding dosage, consuming one-quarter to one-half of a medium-sized onion daily is ideal for boosting the body. Onions can be flexibly prepared in salads, soups, or stir-fried with other powerful antioxidant foods like broccoli and olive oil. This combination not only enhances flavor but also creates a synergistic effect, comprehensively boosting kidney protection. Individuals with end-stage kidney failure, those on anticoagulant medication, or those with severe stomach conditions should consult a doctor and avoid excessive consumption.

The biggest concern when preparing onions is eye irritation. According to agricultural experts, the key is to minimize damage to onion cells to prevent the release of volatile sulfur compounds. When slicing onions, use a very sharp knife and make decisive cuts.

How onions are cut also determines the dish's flavor. Slicing along the grain of the onion preserves the fiber strands, creating a crunchy texture and characteristic pungent flavor, suitable for stir-fries. Conversely, slicing across the grain (cutting the fiber) makes the onion softer and sweeter, perfect for stews or soups.

To ensure food safety, consumers should choose whole onions that are intact, have dry outer skins, feel firm, and have not sprouted. Buying whole onions instead of pre-cut varieties not only helps maintain freshness longer but also minimizes the risk of bacterial contamination, allowing for maximum utilization of this "superfood's" nutritional value.

Binh Minh (According to United Daily News)