Benefits
Lower post-meal blood sugar when lentils replace rice or potato
In two crossover groups of 24 healthy adults, replacing half the carbohydrate of white rice or instant potato with cooked lentils lowered the post-meal blood glucose rise by about 20% for rice and 35% for potato. Large green lentils with rice fell just short of significance. Insulin fell with potato but not with rice.
Post-meal glucose and insulin with lentil muffins, chili and soup
When cooked green or red lentils replaced 25 g of carbohydrate in muffins, chili or soup, glucose and insulin responses were mostly lower than with wheat, rice or potato versions; green lentil muffins did not lower glucose significantly. In adults with blood sugar problems, whole lentils and lentil flour both blunted the rise versus a glucose drink, with no overall difference between them.
Insulin resistance marker over 8 weeks of lentil lunches
In 30 adults with a large waist, HOMA-IR, a fasting insulin resistance estimate, rose 1.2 units over 8 weeks of meat-based lunches and was 0.9 and 1.5 units lower relative to that with lunches holding 300 or 600 g of cooked green lentils a week. A later 12-week trial by the same group found no HOMA-IR difference.
Blood cholesterol when lentil lunches replace meat lunches
In 38 adults with a large waist, total and LDL cholesterol differed between groups after 12 weeks of daily lentil versus meat-based lunches, mainly because both rose in the meat group; LDL fell only 0.03 mmol/L with lentils, so the result reflects replacing meat. HDL fell slightly with lentils, and triglycerides did not improve.
Appetite, fullness and later-meal food intake after lentil meals
In 25 young men, a lentil meal lowered appetite and food eaten at a pizza meal over 4 hours later, compared with macaroni and cheese. Green lentil chili raised fullness versus rice chili but did not reduce food eaten later, red lentil chili and lentil muffins had no effect, and 12 weeks of lentil lunches did not change body weight.
Plant protein, fiber, folate and iron in a cup of lentils
USDA data give one cup of boiled lentils about 18 g protein, 16 g fiber, 358 mcg DFE folate and 6.6 mg iron. The iron is non-heme, which the body absorbs less well than iron from meat; phytate in beans reduces it further. In 19 women, only about 2% of the iron in a lentil dal was absorbed, versus 24% from ferrous sulfate.
Mechanism of action
Fewer fast carbohydrates in the meal
In the replacement trials, lentils took the place of part of the rice, potato or wheat, so the meal delivered less rapidly digested starch. Eight lentil varieties tested in 10 people all had low glycemic index values (10 to 23), but no single starch fraction, including resistant starch, predicted the response on its own.
Intact seed structure matters
Processing changes the response. Blending lentils raised appetite ratings by about 6% versus whole lentils without changing blood sugar, and in adults with type 2 diabetes lentil flour gave higher blood sugar than whole lentils at 30 minutes, though total responses did not differ. Lentil foods and flours should not be assumed to act like whole cooked lentils.
Cooking inactivates lectins and trypsin inhibitors
Raw pulses contain lectins, which bind to proteins on cell surfaces and, when active, can cause nausea, vomiting and diarrhea, and trypsin inhibitors, which reduce protein use. A review concluded that proper soaking and cooking inactivates both, while noting that validated cooking times for each pulse type are lacking.
Fermentable sugars and gut gas
Pulses contain galacto-oligosaccharides that gut bacteria ferment, which is linked to flatulence and discomfort. A review described this effect as transient for most people. In two lentil feeding trials, most participants reported no or mild symptoms.
Clinical trials
Randomized crossover trial: 50 g available carbohydrate from white rice or instant potato alone, or half replaced by large green, small green or split red lentils; registered NCT02426606. Co-authors from Agriculture and Agri-Food Canada; funding not stated in the abstract. (Moravek et al. 2018, J Nutr)
Two groups of 24 healthy adults (rice arm and potato arm), mean age about 27.
Versus rice alone, glucose iAUC was lower with small green (P = 0.002) and split red lentils (P = 0.006), with large green lentils just short of significance (P = 0.057). With potato, all 3 lentils lowered glucose and insulin; with rice, insulin did not change. Relative glycemic response fell about 20% (rice) and 35% (potato). Single meals in healthy adults only.
Randomized crossover studies replacing 25 g available carbohydrate with cooked green or red lentils versus wheat muffin, rice chili or potato soup controls; funded by the Agriculture and Agri-Food Canada and Pulse Canada Agri-Innovation Program. (Chamoun et al. 2024, Nutrients)
Healthy adults: 24 (muffin), 24 (chili) and 20 (soup).
Green lentils lowered glucose iAUC in chili and soup (p < 0.0001) but not muffins (p = 0.07), and lowered insulin iAUC in all three foods. Red lentils lowered glucose in all three foods and insulin in chili and soup but not muffins (p = 0.09). Relative glycemic response was 84 to 88% for lentil muffins and 48 to 61% for lentil chili and soup.
Two randomized crossover studies replacing rice (chili) or wheat (muffins) with green or red lentils, with appetite ratings over 180 minutes, an unlimited test meal and 24-hour food records; registered NCT03128684 and supported by Agriculture and Agri-Food Canada. (Clark et al. 2019, J Nutr)
Healthy adults: 24 in the muffin study and 24 in the chili study.
Green lentil chili raised fullness (17.5%) and lowered desire to eat versus rice chili; red lentil chili did not. Neither lentil chili changed test-meal food intake or 24-hour energy intake, and the lentil muffins did not differ from wheat muffins on any outcome.
Randomized crossover of 4 isocaloric meals: canned lentils, chickpeas or yellow split peas (250 kcal) with macaroni and tomato sauce, or macaroni and cheese as control; food intake measured at a pizza meal 260 minutes later. Funding not stated in the abstract. (Mollard et al. 2011, Appl Physiol Nutr Metab)
25 healthy young men, mean age about 21.
Lentil and yellow pea meals lowered appetite before the pizza meal and food intake at it, versus macaroni and cheese. Blood glucose was lower 20 minutes after all pulse meals, but the pre-pizza glucose area did not differ (p = 0.07). After the pizza, glucose was lower following the lentil and chickpea meals. One meal per arm only.
Randomized trial of 5 isocaloric prepared lunches a week with 0, 300 or 600 g of cooked green lentils per week for 8 weeks, with weekly gut symptom surveys; Europe PMC lists the USA Dry Pea and Lentil Council as funder. (Wilson et al. 2022, Nutr Res)
30 nondiabetic adults with a large waist (mean age 42, BMI 35) completed.
HOMA-IR rose 1.2 units with meat-based lunches and fell 0.9 (P = .03) and 1.5 units (P < .01) relative to control with the 300 g and 600 g lentil lunches. Most participants (87%) reported no to mild gut symptoms. The abstract does not report results for the glucose tolerance test areas or satiety.
Randomized trial of 7 prepared lunches a week with 980 g cooked green lentils per week or meat-based lunches for 12 weeks, with a high-fat meal challenge; funded by the USDA-ARS Pulse Crop Health Initiative. (Chamberlin et al. 2024, Nutrients)
47 adults with a large waist and high post-meal triglycerides randomized; 38 completed (mean age 47, BMI 34).
Total and LDL cholesterol differed between groups, mainly because they rose with meat lunches (LDL +0.29 mmol/L) while LDL fell 0.03 mmol/L with lentils; HDL also differed, falling 0.07 mmol/L with lentils and rising 0.11 mmol/L with meat. Glucose after a high-fat test meal was lower with lentils, but fasting glucose, insulin and HOMA-IR did not differ. At baseline the groups differed in total cholesterol and HDL, and 61% of the meat group versus 20% of the lentil group had metabolic syndrome. Triglycerides, the main focus, did not improve, and body weight, waist and fat mass did not differ. Gut symptoms did not differ by group.
Crossover stable-isotope study comparing iron absorption from 330 g of dal made with intrinsically labeled lentils and a ferrous sulfate reference dose; Europe PMC lists the USDA Agricultural Research Service and Saskatchewan Pulse Growers as funders. (DellaValle et al. 2015, J Nutr)
19 nonpregnant women, 6 of them anemic.
Mean iron absorption was 2.2% from the lentil dal versus 23.6% from ferrous sulfate (P < 0.001). Absorption from both sources was higher in women with lower ferritin and hepcidin, meaning the body takes up more when iron stores are low.