Kale

Also known as: Brassica oleracea var. acephala, curly kale, leaf cabbage, borecole

Evidence under review. — Not yet rated

Nutrient-dense leafy green with early evidence for blood sugar and inflammation benefits.

What it does

Kale is a leafy cruciferous vegetable packed with carotenoids, anthocyanins, and other plant compounds. Early clinical trials suggest that high daily intake may help reduce HbA1c and insulin...
Evidence quality

Evidence base hasn't been formally rated yet. See research below.
Clinical dose

No established dose from provided studies; study doses ranged from 78.75g to ~341g fresh kale equivalent daily
Found in

310 Greens - Mixed Berry, Smartvita Men's Total Synergy Multivitamins, WonderGreens Veggie Gummies and 16 more

What the Science Says

Kale is a leafy cruciferous vegetable packed with carotenoids, anthocyanins, and other plant compounds. Early clinical trials suggest that high daily intake may help reduce HbA1c and insulin resistance in people with type 2 diabetes, and a kale extract showed anti-inflammatory effects comparable to ibuprofen after dental surgery. A small skin study also found that daily carotenoid-rich kale extract improved collagen levels in the dermis over 5-10 months.

What It Doesn't Do

Not a proven diabetes medication — the T2D study was tiny (30 people) and needs replication. Won't replace anti-inflammatory drugs for most people. No solid evidence it detoxifies the body or prevents cancer. No proof it meaningfully changes estrogen metabolism. Eating kale occasionally won't produce the effects seen in studies using very high daily doses.

Evidence-Based Benefits

High daily kale intake reduced HbA1c and insulin resistance in type 2 diabetes patients over 12 weeks.

Weak Evidence

Effective at: ~341g fresh kale equivalent daily (as freeze-dried bars)

Supporting studies (click to view on PubMed):

PMID 39519473

Kale extract (500mg anthocyanin equivalent) reduced post-surgical inflammation markers comparably to ibuprofen.

Weak Evidence

Effective at: 500mg anthocyanin equivalent daily for 7 days

Supporting studies (click to view on PubMed):

PMID 39599607

Daily carotenoid-rich kale extract improved skin collagen levels in middle-aged women over 5-10 months.

Weak Evidence

Effective at: 1650µg carotenoids daily

Supporting studies (click to view on PubMed):

PMID 28753935

Absorption & Bioavailability

Unknown for most compounds in supplement form; carotenoids from kale extract appear to accumulate in skin tissue over months, suggesting reasonable absorption with consistent use

Red Flags to Watch For

Very high kale intake (as used in studies) can interfere with thyroid function due to glucosinolates, especially in people with thyroid conditions
Kale is high in vitamin K, which can interfere with blood-thinning medications like warfarin
Most clinical trials are very small (20-30 participants) — results may not hold in larger populations
Supplement doses vary wildly across products; the 1000+ registered products have no standardized dosing
Some microgreen and kale products may contain cyanogenic glycosides — a potential toxicity concern flagged in recent analytical research

Supplement

Overhyped

Sunfood Supergreens & Protein

Supplement

Overhyped

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Frequently Asked Questions

What does Kale do?

Nutrient-dense leafy green with early evidence for blood sugar and inflammation benefits.

What is the effective dose of Kale?

No established dose from provided studies; study doses ranged from 78.75g to ~341g fresh kale equivalent daily

Is Kale safe?

Very high kale intake (as used in studies) can interfere with thyroid function due to glucosinolates, especially in people with thyroid conditions

What doesn't Kale do?

Not a proven diabetes medication — the T2D study was tiny (30 people) and needs replication.

Research Sources

PubMed
NIH DSLD

This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-05-25