Onions or shallots: which is healthier?

Most people comparing these two have a recipe that names one and a kitchen that holds the other. We found no study comparing them head to head, for flavor or health. Per 3.5 oz (100 g) shallots carry more than onions, 72 against 40 calories and 334 against 146 mg of potassium. But a tablespoon of chopped shallot weighs 0.35 oz (10 g) and holds about 7 calories and 33 mg of potassium, so the gap adds up to very little in a dish.

Pooled onion trials improved LDL cholesterol and blood pressure at onion supplement doses above 300 mg a day, not with onion eaten in food. The human trials on shallots enrolled 9 and 16 people. Observational data point two ways: no link with cancer overall in one meta-analysis, lower odds of stomach cancer at the highest intake in another, and neither looked at shallots alone.

One caution applies to both. If you have irritable bowel syndrome, a review lists onion and shallots together among the major high FODMAP foods (fermentable carbohydrates), without giving an amount, so swapping one for the other will not help.

Choose by taste. By USDA retention factors for fried vegetables in general, frying keeps the minerals and costs about 30% of the folate and 15% of the vitamin C in either.

Evidence behind this note

1. Level A Pooled onion trials show metabolic benefit, and the dose where it appears is a supplement dose. Clin Nutr ESPEN, 2023
2. Level A Pooling the studies, people who ate the most onions and garlic did not get less cancer. Front Nutr, 2021
3. Level B In a randomized crossover trial in 9 volunteers, quercetin from dry shallot skin gave about twice the blood exposure of quercetin from shallot flesh (AUC 47.23 vs 22.23 micromol x h/L). J Nutr, 2008
4. Level B In a randomized placebo-controlled trial in 16 people with allergic rhinitis, 3 g of shallot a day added to cetirizine for 4 weeks improved overall symptom scores in 62.5% vs 37.5% on cetirizine alone, with no excess of side effects. Asian Pac J Allergy Immunol, 2022
5. Level C Observational data link high intake of Allium vegetables, a group that includes shallots, with lower gastric cancer risk: a meta-analysis of 21 studies found an odds ratio of 0.54 for highest vs lowest intake. Gastroenterology, 2011
6. Level D For people with irritable bowel syndrome, shallots count among the major high FODMAP foods alongside onion and garlic, which is why low FODMAP diets restrict them. J Gastroenterol Hepatol, 2018
7. Level E By the USDA retention table for Vegetables and Vegetable Products when fried, about 30% of folate, 15% of vitamin C and thiamin and 10% of vitamin B6 are lost, while minerals stay. USDA Table of Nutrient Retention Factors, Release 6 (2007), Retn_Code 3780

Written from the studies and agency guidance we hold for both foods, reviewed by the Bioma editorial system. How we verify.

Read more about these foods

• Onions: the trials tested powder, extract and capsules
• Shallots: two tiny trials and a lot of borrowed onion data

Rankings and guides

• Fiber: what it does and how much you need
• Sodium: what it does and how much you need
• Which foods are highest in potassium?
• Onions: full nutrition facts

• Onions: USDA FoodData Central, Onions, raw, FDC ID 170000 · full profile · all forms of onions
• Shallots: USDA FoodData Central, Shallots, raw, FDC ID 170499 · all forms of shallots

Each food is one USDA entry, chosen as it is usually eaten. Other cuts, brands and preparations differ; the links show them. % DV uses FDA Daily Values for adults. How we verify.