Is Onion Acidic or Alkaline?
Onion (fresh) is alkaline: Negative PRAL: alkalizing after digestion.
Classification
Onions sit at −2.4 and are alkaline, since they supply potassium with little protein and consist mostly of water. Raw, fried or braised, the ratio stays similar; frying only adds fat. As an ingredient, an onion usually weighs 50 to 80 g and adds about −1 to −2. In onion tart, it pushes back against the bacon and dough but can't fully offset them.
In the Vegetables & Salad category, onion (fresh) ranks #80 of 110, sorted from alkaline to acid-forming. More alkaline options include Kohlrabi (−2.5), Cauliflower (−2.6), Savoy cabbage (−2.7). More acid-forming are Green bell pepper (−2.3), Pickled cucumbers (−2.0), Oyster mushroom (−1.7).
Acidic or alkaline: PRAL, not pH
On this site, acidic and alkaline refer to the PRAL (potential renal acid load). It estimates what a food leaves behind once it has been digested: a positive value is acid-forming, a negative value is alkalizing. That is different from the pH of the food itself: a lemon tastes sour, yet its PRAL is −4.0, so it is alkalizing. Your diet does not change your blood pH. It does change how much acid your kidneys have to deal with.
Goes well with
Frequently Asked Questions
Is onion acidic?
It depends on what you mean by acidic. The pH describes the food itself, for example how sour it tastes. The PRAL describes what it leaves behind after digestion: Onion (fresh) has a PRAL of −2.4 per 100 g, so it counts as alkaline in your daily acid-base balance.
How much onion do I need for a noticeable effect?
A serving (150 g) of onion adds −3.7 to your daily balance. For comparison: an egg is around +5.4, a slice of cheese around +6. So one serving of onion roughly offsets one of them.
Why is onion alkaline even though it is not a typical alkaline food?
The PRAL depends on the minerals left over after digestion, not on taste or pH. Onion provides more potassium, magnesium and calcium than phosphorus and protein, so the balance is negative (−2.4).
Onion logged, balance checked.
Basentracker adds up every meal automatically and shows whether your day is in the alkaline range. The same values as on this page, all 977 foods, photo scan, recipes.
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Compare all Vegetables & Salad: Vegetables & Salad table. Common questions are answered in Acidic or Alkaline?, and the PRAL calculator adds up a whole meal.
Source: Basentracker food database (PRAL according to Remer & Manz, calculated from protein, phosphorus, potassium, magnesium and calcium per 100 g). This information does not replace medical advice.