Onions have a dense collection of phytonutrients that give many health benefits. These include powerful sulfur-containing molecules like allyl propyl disulfide and a multitude of flavonoids including quercetin. Eating onions can help increase efficient processing of free-floating glucose in the body. Allyl propyl raises free-floating insulin in the blood by preventing it from becoming inactivated in the liver. Chromium also decreases blood sugar by making cells more responsive to insulin, resulting in cellular glucose uptake. Onions are also heart healthy by reducing the amount of cholesterol and homocysteine in the blood, both linked to heart problems. Quercetin is an antioxidant that benefits the colon by protecting against carcinogens. Another onion compound blocks osteoclasts (cells that break down bone), which is beneficial for elders whose bone production has slowed. Vitamin C, quercetin and isothiocyanates reduce joint swelling.
Vitamin and Mineral Content
Vitamins: C, B6 (Pyridoxine) and B9 (Folate)
Minerals – Chromium, Manganese, Molybdenum, Potassium, Phosphorus and Copper
Allyl propyl and chromium act to reduce demand for insulin, which can stave off or help manage diabetes. By lowering cholesterol, homocysteine levels and blood pressure, the vitamins (especially folate) and minerals reduce the risk of atherosclerosis, heart disease, stroke and heart attack. Eating onions regularly has also been linked with lower risk for a number of cancers: esophageal, oral cavity, pharynx, colorectal, laryngeal, breast, prostate, ovarian and kidney. The anti-inflammatory properties help deal with rheumatoid arthritis, osteoarthritis and asthma.
How to Grow
Onions are great to have in the kitchen. They are versatile, store well, come in many different flavors and cook easily. Choose a site full of sunshine. Work in plenty of organic matter in the form of aged compost, manure or planting mix. Best pH is roughly 6.5; add lime to raise if needed. To save space and a few dollars, sow multiple onion seeds together. They grow next to each other and push each other over slightly to make room as they enlarge. Sow 6-7 seeds together. If you want to start early, they germinate well indoors in trays on the windowsill or under a fluorescent light. Indoors, you need to gradually accustom them to being outside before transplanting. Otherwise, sow them similarly in shallow drills roughly 1 foot apart just after spring begins. Thin seedlings to a couple inches apart. Sow the Japanese varieties toward the end of summer in the same way. Fertilize this variety in the spring to encourage the rest of growth. With onions, you must keep beds weed free to minimize nutrient and sunlight competition. Water during dry weather but not overmuch. When tops turn brown, pull or dig up bulbs and let them dry in the sun for a couple days. If weather is unpredictable, put them in shelter to dry out. Once they are dry, remove their tops, and store them in a perforated sack or net in a well-ventilated, warm, shaded place to cure and avoid rot.
Pests are not generally a problem with onions, especially the Allium species. Common pests include onion maggots, onion eelworm and onion flies. Attacking from early to mid-summer, the onion fly can be controlled by hoeing around each plant to expose the maggots to birds. Or put sand around the base of each plant to deter female egg laying. Alternatively, multiple sowing avoids the need to thin out the plants, which prevents releasing the attractive smell to female onion flies. Onion eelworms get inside the bulbs. The only way to get rid of them is to dig up the affected plants and replace for a couple years with something that is not a host (broccoli, lettuce, cabbage or another crucifer). If the risk of infestation is high in your location, interplant onions among other plants to give pests a smaller target to attack. A number of the Allium species ward off pests like aphids, beetles and carrot flies from other garden plants like carrots, lettuce and parsnips.
For a continual harvest, grow a main crop variety and a Japanese crop that harvests first. To avoid sun burning while waiting for onions to dry on a hot day, cover one plant’s bulb with another’s shoots.