Benefits
Vitamin A from beta-carotene and alpha-carotene
In USDA data, 100 g of raw carrot supplies about 8.3 mg of beta-carotene and 3.5 mg of alpha-carotene, counted as 835 micrograms of vitamin A (RAE); NIH lists half a cup of raw carrots at 51% of the Daily Value. The body converts these carotenes to vitamin A. In 7 men given labeled carrots, about 15 mg of carrot beta-carotene yielded 1 mg of retinol.
Vitamin A status in lactating women and schoolchildren
In lactating women in Zimbabwe, 100 g of grated carrots daily for 60 days with a little oil raised serum retinol, while placebo did not; a second vitamin A marker improved with papaya and capsules but not carrots. In anemic Indonesian schoolchildren, meals with leafy vegetables and carrots raised serum retinol less than fruit or retinol-rich foods.
Satiety and later food intake with whole carrots in a meal
In a randomized crossover study in young women, a lunch with 200 g of whole or blended carrots gave higher fullness ratings than a lunch with the same carrot nutrients but no fiber or structure, and intake at a later meal and over the rest of the day was lowest with whole carrots. In 10 men, satiety rose with larger portions of boiled carrots.
Blood glucose and insulin response when carrots are added to a meal
In 10 healthy men, meals with 100, 200 or 300 g of boiled carrots were compared with a control meal matched for energy and digestible carbohydrate. Larger carrot portions gave lower glucose and insulin responses, with 200 g the smallest amount that made a significant difference. This was single-meal testing, not long-term blood sugar control.
Stool bulk and colon fermentation of carrot fiber
In 24 young women on a controlled low fiber diet, 3 weeks of raw or processed carrots adding 15 g of fiber a day increased stool weight by 2.4 to 3.7 g for each gram of carrot fiber compared with control periods, and 91 to 94% of the carrot fiber was fermented in the colon. Raw, blanched, frozen and canned carrots worked alike.
Blood lipids and blood pressure with carrots, carrot juice and purple carrot
Results do not agree. In one older study without a described control group, 200 g of raw carrot a day for 3 weeks lowered serum cholesterol by 11%, but a later controlled diet study found no change in total or HDL cholesterol. In an uncontrolled study, daily carrot juice for 3 months did not change lipids, and systolic pressure fell only as a trend. Dried purple carrot did not change LDL or blood pressure versus placebo.
Mechanism of action
Carotenes converted to vitamin A
Beta-carotene and alpha-carotene are provitamin A carotenoids that the body converts into retinol. NIH counts 12 micrograms of food beta-carotene or 24 micrograms of alpha-carotene as 1 microgram of vitamin A (RAE). Measured conversion from carrots varied widely between people, from about 8 to 25 parts of beta-carotene for each part of retinol.
Cooking and fat release carotenes from the carrot matrix
Carotenes are fat soluble and held inside carrot cells. NIH notes that people absorb about 10 to 30% of beta-carotene from foods and that cooking raises it. In a labeled carrot study, beta-carotene availability was about 11% from raw carrots and 75% from stir-fried carrots, and the vitamin A yield was 6.5 times higher after stir-frying.
Fiber and intact food structure
Carrot fiber is largely fermented in the colon and adds stool bulk. In meal studies, carrots with their fiber and cell structure intact gave more fullness and lower later intake than blended carrots or carrot nutrients without fiber, so the effects come from the whole food structure as well as its nutrients.
Anthocyanins in purple and black carrots (lab and animal work)
Purple and black carrots also contain anthocyanins and phenolic acids. Their anti-inflammatory and metabolic effects come from animal models; in a placebo-controlled human trial, dried purple carrot supplying 118.5 mg of anthocyanins a day for 4 weeks did not change weight, blood pressure, LDL or C-reactive protein.
Clinical trials
Randomized, repeated-measures crossover: a standardized lunch (3329 kJ) with 200 g of whole carrots, blended carrots or carrot nutrients without fiber or structure, matched for energy and nutrients, on three occasions 4 weeks apart. Fullness was rated on visual analogue scales and later intake was covertly weighed. Funding is not stated in the abstract (Moorhead et al. 2006, Br J Nutr)
Young women: 34 had the whole and blended carrot lunches and 32 the carrot nutrient lunch.
Whole and blended carrot lunches gave higher satiety than the carrot nutrient lunch (P < 0.05). Intake at the meal eaten 3 hours later and for the rest of the day differed between conditions (P < 0.05), falling in the order carrot nutrients, blended carrots, whole carrots.
Randomized-order meal tests: lunches with 100, 200 or 300 g of blanched, frozen and boiled carrots (2.9, 5.8 and 8.7 g fiber), carrots steeped in lactic acid, or a control meal without vegetables, balanced for energy (2000 kJ) and digestible carbohydrate (60 g). Funding is not stated in the abstract (Gustafsson et al. 1994, Eur J Clin Nutr)
10 healthy men around 40 years old, recruited from a district population list; none dropped out.
The larger the carrot portion, the lower the glucose and insulin/C-peptide responses and the higher the satiety scores; 200 g was the smallest amount with significant effects. Adding lactic acid to 200 g of carrots strengthened the effects on satiety and hormone response.
Two randomized crossover studies under strict dietary control: 405 to 688 g a day of raw frozen, blanched or canned carrots (first study) or raw or raw frozen carrots (second study), adding 15 g of fiber a day to a low fiber diet for 3 weeks, compared with control periods. Funding is not stated in the abstract (Wisker et al. 1994, Br J Nutr)
24 young women.
Each gram of carrot fiber added 2.4 to 3.7 g of stool, and stool dry matter, fiber and protein rose significantly during carrot periods. Carrot fiber was 91 to 94% fermented regardless of processing. No type of carrot changed serum total or HDL cholesterol or fecal bile acids.
Dietary intervention: 200 g of raw carrot at breakfast daily for 3 weeks, with follow-up 3 weeks after stopping. The abstract does not describe a control group, randomization or funding (Robertson et al. 1979, Am J Clin Nutr)
Volunteers; the number is not given in the abstract.
Serum cholesterol fell by 11%, fecal bile acid and fat excretion rose by 50%, and stool weight rose by 25%. The changes in cholesterol, bile acids and fat persisted 3 weeks after carrots were stopped. Without a described control group, the changes cannot be firmly attributed to carrots.
Before and after study with no control group: 16 fl oz of freshly squeezed carrot juice daily for 3 months without other diet changes. Funded by USDA-CSREES grants through the Vegetable and Fruit Improvement Center (Potter et al. 2011, Nutr J)
17 adults (8 men, 9 women) from university faculty and staff with elevated cholesterol and triglycerides.
Cholesterol, triglycerides, LDL, HDL, apolipoproteins, body fat, insulin, leptin, interleukin-1 alpha and C-reactive protein did not change (P > 0.1). Systolic pressure fell only as a trend (P = 0.06) and diastolic did not change. Plasma total antioxidant capacity rose and malondialdehyde fell from baseline (P < 0.05).
Randomized, double-blind, placebo-controlled trial: dried purple carrot supplying 118.5 mg of anthocyanins and 259.2 mg of phenolic acids a day for 4 weeks. PubMed lists non-US government research support (Wright et al. 2013, Can J Physiol Pharmacol)
16 overweight or obese men (mean age 53, mean BMI 32.8) with normal lipid and inflammatory markers.
There were no significant changes in body mass, body composition, appetite, food intake, LDL or total cholesterol, blood pressure or C-reactive protein. HDL cholesterol was lower in the purple carrot group (p < 0.05). Liver enzymes did not change.
Randomized, placebo-controlled trial: 6 mg beta-carotene capsules, 650 g of pureed papaya, 100 g of grated carrots or placebo daily for 60 days, with all groups given a meal containing 10 g of vegetable oil daily. PubMed lists non-US government research support (Ncube et al. 2001, J Nutr)
Lactating women with infants aged 2 to 12 months in Zimbabwe.
Serum retinol rose in the carrot group (P < 0.001), as in the capsule and papaya groups, but not with placebo; these are within-group changes. The relative dose response, a liver vitamin A marker, improved with capsules and papaya but not carrots. Hemoglobin rose more than placebo only with capsules and papaya.
Randomized feeding trial: 2 meals a day, 6 days a week, for 9 weeks supplying retinol-rich foods, orange fruit, dark-green leafy vegetables and carrots, or low-retinol, low-carotene food. PubMed lists non-US government research support (de Pee et al. 1998, Am J Clin Nutr)
238 anemic schoolchildren aged 7 to 11 in West Java, Indonesia (45 in the vegetable and carrot group, 46 in the low-carotene group).
Mean serum retinol changed by 0.07 micromol/L (95% CI 0.03 to 0.11) with vegetables and carrots versus 0.00 (-0.06 to 0.05) with low-carotene food, 0.12 with fruit and 0.23 with retinol-rich food. The authors estimated 26 micrograms of beta-carotene from leafy vegetables and carrots per retinol equivalent, 23% of the assumed value.