Onion and blood sugar in lactose-tolerant and intolerant adults
What it found
In a small trial in people, an onion meal reduced peak blood sugar more in lactose-intolerant adults than in lactose-tolerant adults.
The onion meal reduced blood sugar in both groups.
What they found
Studies in people
Peak blood sugar
The onion meal lowered peak blood sugar by 44.2% in lactose-intolerant people and by 19.3% in lactose-tolerant people. This difference was statistically significant.
Overall blood sugar
The onion meal lowered the overall blood sugar response more in lactose-intolerant people (54.5%) than in lactose-tolerant people (42.1%), but this difference was not statistically significant.
Timing of effect
In lactose-tolerant people, the onion meal inhibited glucose uptake from 30 to 120 minutes. In lactose-intolerant people, it only lasted until 60 minutes.
Other findings
Onion composition
The onion meal contained 2.0 µg/ml quercetin, 39.5 µg/ml quercetin-4'-O-glucoside, 3.5 µg/ml quercetin-3-O-glucoside and 26.5 µg/ml quercetin-3,4'-O-diglucoside.
What the authors conclude
“A diet containing quercetin glucosides may be of greater benefit for glycaemic control in lactose-intolerant people than in lactose-tolerant people.”
Also in their conclusions
- They conclude that the onion meal inhibited glucose uptake in both groups, but the effect was greater in lactose-intolerant people.
- They suggest that a diet containing quercetin glucosides may be of greater benefit for blood sugar control in lactose-intolerant people than in lactose-tolerant people.
- They note that lactose tolerance could be a confounding factor in studies comparing blood sugar responses to diets between regions.
How it was done
The authors wanted to test whether lactose-intolerant people, who do not make the enzyme lactase, keep quercetin glucosides from onion intact so they can block glucose uptake, while lactose-tolerant people break them down.
They gave 12 lactose-tolerant and 12 lactose-intolerant adults a glucose drink on one day and a glucose drink with a filtered onion meal on another day. Blood sugar was measured over 2 hours after each drink.
What it can’t tell you
- This was a small pilot study with 24 people, so the results may not apply to everyone.
- The study cannot rule out that other components in the onion meal caused the reduced glucose uptake.
Who paid
- Authors work at
- University of Hertfordshire, UK
The paper
- Title
- Inhibition of the glycaemic response by onion: a comparison between lactose-tolerant and lactose-intolerant adults
- Type
- Clinical trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Hoffman R, Ranjbar G, Madden AM (2016). Inhibition of the glycaemic response by onion: a comparison between lactose-tolerant and lactose-intolerant adults. European journal of clinical nutrition. doi:10.1038/ejcn.2016.44Free full textPubMed 27026422DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error