Watercress or lettuce with a high-fat meal in healthy men
What it found
In 16 healthy young men, adding watercress to a moderately high-fat meal did not change blood sugar, insulin, blood fats or inflammatory markers over the next 4 hours.
Lettuce, by contrast, lowered the blood sugar and insulin response.
What they found
Studies in people
Blood sugar response
The 0 to 4 hour blood sugar response was lower after the lettuce meal than after the control meal and the watercress meal. Watercress was not different from the control.
Insulin response
The insulin response was lower after the lettuce meal than after the control meal. There was no difference between the lettuce and watercress meals.
Blood fats
Triglycerides, total cholesterol, HDL cholesterol and LDL cholesterol rose after all three meals, but there were no significant differences between the meals. HDL cholesterol tended to be higher after lettuce or watercress than after the control.
Inflammatory markers
Levels of IL-6 and TNF-alpha did not differ among the three meals.
Other findings
Fiber and texture
Lettuce contains more fiber than watercress (2.4 g versus 0.5 g per 100 g), and the authors suggest this, along with lettuce's harder texture, may partly explain the lower blood sugar response with lettuce.
What the authors conclude
“This study showed that in healthy adults, the addition of lettuce in meals could delay postprandial glycemic response, while watercress results in no change in the overall glycemic response.”
Also in their conclusions
- They say that in healthy adults, adding lettuce to a meal delayed the blood sugar response, while watercress produced no change in the overall blood sugar response.
- They note that the effects of these vegetables on responses after a meal in people with heart or metabolic risk factors still need to be studied.
How it was done
Vegetables may help blunt the rise in blood sugar, blood fats and inflammation that happens after a meal, and the authors wanted to test whether lettuce or watercress could do this.
Sixteen healthy young men ate the same moderately high-fat fast food style meal three times, each time with either 100 g of lettuce, 100 g of watercress, or a control powder. Blood was sampled at 0, 1, 2, 3 and 4 hours after each meal.
What it can’t tell you
- The study was small and only included healthy young men with normal body weight, so the results may not apply to women, older people, or people with obesity or other health conditions.
- Blood was first sampled one hour after the meal, so any earlier peaks in blood sugar or insulin would have been missed.
- The study looked at a single meal, so it cannot show what happens with longer-term eating patterns.
Who paid
- Conflicts
- The authors declare no conflicts of interest.
- Authors work at
- Shahid Beheshti University of Medical Sciences, Iran
The paper
- Title
- The acute effect of incorporating lettuce or watercress into a moderately high-fat meal on postprandial lipid, glycemic response, and plasma inflammatory cytokines in healthy young men: a randomized crossover trial
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Shokraei S, Khandouzi N, Sina Z, Nasrollahzadeh J (2021). The acute effect of incorporating lettuce or watercress into a moderately high-fat meal on postprandial lipid, glycemic response, and plasma inflammatory cytokines in healthy young men: a randomized crossover trial. Lipids in health and disease. doi:10.1186/s12944-021-01487-9Free full textPubMed 34261489DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error