How Much Oxalate Is in Kelp?
mg oxalate
per serving
Serving: 1 serving (100 g)
Verdict: 🟢 Safe
Per 100g: 200 mg
Data: Harvard T.H. Chan SPH (2024)
What this means: Kelp is rated Safe (🟢). At 6 mg oxalate per serving, it's well under the 25 mg safety threshold. You can include it regularly in a kidney stone diet. Pair it with calcium-rich foods (dairy, fortified plant milks) for additional protection, and drink plenty of water throughout the day.
Among vegetables, Kelp sits well below the category average of 27 mg. For context, 219 out of 271 vegetables (80%) are rated 🟢 Safe (under 25 mg oxalate/serving). The average vegetables in our database has 27 mg oxalate per serving — which means Kelp is 78% below the category norm. Within its specific category, Kelp ranks among the lower-oxalate options. This context matters because two 'Safe' foods can have very different oxalate levels — one might have 5 mg while another has 24 mg. Both are Safe, but the first gives you more dietary flexibility. Browse all vegetables rated Safe to compare within the same verdict level.
Why does oxalate per 100g matter?
Normalizing to 100 grams removes serving-size differences, so you can judge which food is genuinely denser in oxalate. It matters most when you eat a bigger or smaller portion than the listed serving. Kelp comes in at 6 mg oxalate per 1 serving (Safe) in the measured database.
How accurate is the oxalate measurement?
These values come from Harvard's 2024 ion-chromatography analysis — the gold-standard method for oxalate. Real measured data rather than estimates. Sample-to-sample variation exists, but no published source is more dependable for food oxalate. For Kelp, the measured oxalate value is 6 mg per 1 serving (Safe).
How does this compare to other foods?
The ratings split at 25 mg (Safe) and 100 mg (Avoid), with 25-99 mg in the Caution band. For context against similar foods, the category pages on OxalateWatch rank every item in that group by oxalate. Kelp comes in at 6 mg oxalate per 1 serving (Safe) in the measured database.