Onions contain antioxidants and compounds that fight inflammation, decrease triglycerides, and reduce cholesterol levels — all of which may lower heart disease risk. Their potent anti-inflammatory properties may also help reduce high blood pressure and protect against blood clots. Garlic is widely recognized for its ability to fight bacteria, viruses, fungi, and even parasites. One study found that allicin, an active component of freshly crushed garlic, had antiviral properties and was also effective against a broad range of bacteria, including multidrug-resistant strains of E. coli.