What Is Arugula?
Arugula is an edible plant in the Brassicaceae family used as a leaf vegetable for its fresh peppery flavor. Its formal name is Eruca sativa, but it is also known as rocket (especially in British Commonwealth countries). Some additional names are “rocket salad”, “rucola”, “rucoli”, “rugula”, “colewort”, and “roquette”.
Other members of the Brassicaceae family include the cruciferous vegetables Brassica oleracea (e.g., broccoli, cabbage, cauliflower, kale, collards), Brassica rapa (turnip, Chinese cabbage, etc.), Brassica napus (rapeseed, rutabaga), Raphanus sativus (common radish), and Armoracia rusticana (horseradish).
According to Clifford Wright , arugula has a long history of cultivation in Europe and the Mediterranean as a salad vegetable and medicinal plant:
“The plant was cultivated by the Romans and thought by them to be an aphrodisiac. Both Galen and Dioscorides recommended eating arugula seeds to increase semen production.”
Wright also says that “the early Roman Catholic Church knew of arugula’s supposed erotic qualities and at one point banned its cultivation in monastic gardens.”
What is the nutritional value of arugula? According to the USDA food database ½ cup of raw arugula has:
- Calories: 5
- Carbohydrates 4 gm
- Protein 3 gm
- Fat 1 gm
- Fiber 2 gm
- Calcium 16 mg (2% DV)
- Vitamin K 9 µg (9% DV)
- Carotene, beta 142 µg
- Vitamin A 237 IU (26% DV)
- Lutein + zeaxanthin 306 µg
In addition, arugula has small amounts of the flavonols isorhamnetin, kaempferol and quercetin, as well as isothiocyanates such as sulforaphane and erucin. Flavonoids are a group of plant metabolites thought to provide health benefits through cell signaling pathways and antioxidant effects.
Isothiocyanates are derived from the hydrolysis of glucosinolates — sulfur-containing compounds found in cruciferous vegetables. Isothiocyanates may modulate the expression and activity of enzymes that are involved in the metabolism and elimination of xenobiotics (“foreign” chemicals) from the body.
Is There Any Research?
I did several searches of PubMed using different terms each time. Using “arugula” there are 78 papers, 1 review article and no clinical studies. The term “rocket salad” brought up 63 papers, no reviews and 1 clinical trial (pertaining to nitrate-rich vegetables and blood pressure).
The scientific term “eruca sativa” elicited 185 articles, with 2 reviews and no clinical trials. “Erucin” had 77 articles, 5 reviews and 1 clinical trial. On clinicaltrials.gov, there was 1 study that included arugula seeds.
In comparison, there are 16,695 articles, 601 reviews and 290 clinical trials on broccoli, another cruciferous vegetable. And the salad green kale had 18,034 articles, with 585 reviews and 329 clinical trials.
Does Arugula Aid in Weight Loss?
Arugula is a low-calorie, low-carbohydrate food, with only 5 calories in a cup. It also contains vitamins and other biologically active compounds (as mentioned above).
So, it’s healthy way to add bulk to a diet without adding many calories. However, there are no scientific studies that examine the role of arugula in weight loss.
Eat arugula because it tastes good in salads and is low in calories and carbohydrates, but there’s no scientific evidence to support any specific role in weight loss.
Does It Fight Cancer?
As it turns out, there have been studies that look at the role of bioactive components, especially glucosinolate hydrolysis products such as isothiocyanates, found in cruciferous vegetables as anticancer agents. Erucin is a an isothiocyanate derived from arugula (also found in kohlrabi and Chinese cabbage) which is structurally related to sulforaphane- a well-studied broccoli-derived isothiocyanate.
A review by Melchini and Traka looked at cell and animal model studies of erucin as a chemopreventive agent. Chemoprevention is the use of chemical agents to prevent or slow the development of cancer.
Zhang et al found that erucin and other sulforaphane derived products showed a protective effect on mouse cells through the stimulation of detoxification enzymes.
These findings were confirmed in rat, human, and human cancer cells in vitro . Other studies report that erucin has effects on growth inhibition, cell cycle regulation, and apoptosis induction (a system of programmed cell death) in in vitro prostate, lung, liver and colon cancer systems.
All of the above studies were done in animal models or with animal or human cells in a test tube. Having something happen in a test tube or in an animal species does not necessarily mean the same is true in a living, breathing human.
For example, it should be noted that in one of those studies , Hanlon found that erucin and sulforaphane did not upregulate detoxification enzymes in human tissue as it did with rats.
The only study done in humans looked at isothiocyanate concentrations and the conversion of sulforaphane to erucin when subjects ate fresh or frozen broccoli . Spoiler alert: Fresh was better than frozen!
Although there are some promising studies in animals and in vitro, it is way too early to claim that arugula can prevent cancer in humans. More studies are needed.
Does It Protect Heart Health?
A PubMed search any of the name options listed above found only one study which looked at the effect of Eruca sativa on blood pressure in rats . They found that E.sativa decreased blood pressure due to a dilating effect on blood vessels.
That being said, there are several studies (primarily epidemiological in nature) which look at the effect of leafy green vegetables (LGVs) or cruciferous vegetables (CV) on cardiovascular disease (CVD).
Note that these studies are not specifically looking at arugula (some don’t even mention it) but are talking about the broad range of vegetables in those categories.
A meta-analysis by Pollock , reviewed 8 studies that address the association between the consumption of green leafy vegetables (GLV) and risk of incidence of cardiovascular disease.
He concluded that there is a cardioprotective effect associated with high consumption of GLV (including CV). An increased intake of GLV significantly reduces the incidence of CVD by 15.8%.
A comprehensive review by Blekkenhorst et al did “an overview of the evidence for the relationships of specific types of vegetables, including leafy green, cruciferous, allium, yellow-orange-red and legumes, with subclinical and clinical CVD outcomes in observational epidemiological studies.”
These vegetables contain many nutrients and phytochemicals postulated to have cardiovascular benefits. Although some studies did not demonstrate an association between specific vegetables and CVD outcomes, inherit limitations of epidemiological studies may make these studies difficult to assess. The researchers conclude that:
“The evidence in this review suggests intake of leafy green and cruciferous vegetables may confer strong cardiovascular health benefits. Increasing vegetable intake, with a focus on consuming leafy green and cruciferous vegetables may provide the greatest cardiovascular health benefits.”
Although there is little specific evidence that arugula influences cardiovascular health, as a leafy green vegetable and cruciferous vegetable, it is a healthy option to include in your diet. Long term studies may clarify and support its role in the future.
Does It Protect Eye Health?
There are no specific scientific studies that look at arugula and eye health. However, arugula is a good source of Vitamin A, beta-carotene, lutein, and zeaxanthin- all of which are important for eye health.
Vitamin A is the name of a group of fat-soluble retinoids, including retinol, retinal, and retinyl esters. There are two different types of vitamin A. The first type, preformed vitamin A, is found in meat, poultry, fish, and dairy products.
The second type, provitamin A, is found in fruits, vegetables, and other plant-based products. The most common type of provitamin A in foods and dietary supplements is beta-carotene. Other carotenoids such as lycopene, lutein, and zeaxanthin, are found in food, but are not converted into vitamin A .
Vitamin A is critical for vision as an essential component of rhodopsin, a protein that absorbs light in the retina, and because it supports the normal functioning of the conjunctiva and cornea.
Age-related macular degeneration (AMD), or the loss of central vision as people age, is one of the most common causes of vision loss in older people. AMD’s etiology is usually unknown, but the cumulative effect of oxidative stress is postulated to play a role.
If so, supplements containing carotenoids with antioxidant functions, such as beta-carotene, lutein, and zeaxanthin, might be useful for preventing or treating this condition. Lutein and zeaxanthin, in particular, accumulate in the retina, the tissue in the eye that is damaged by AMD.
The Age-Related Eye Disease Study (AREDS), a large randomized clinical trial, found that participants at high risk of developing advanced AMD (i.e., those with intermediate AMD or those with advanced AMD in one eye) reduced their risk of developing advanced AMD by 25% by taking a daily supplement containing beta-carotene (15 mg), vitamin E (400 IU dl-alpha-tocopheryl acetate), vitamin C (500 mg), zinc (80 mg), and copper (2 mg) for 5 years compared to participants taking a placebo.
A follow-up AREDS2 study confirmed the value of this supplement in reducing the progression of AMD over a median follow-up period of 5 years. In this study, beta-carotene was replaced by lutein and zeaxanthin.
Although there are no specific studies linking arugula to eye health, arugula is a good source of Vitamin A, beta-carotene, lutein, and zeaxanthin, and as such should be considered as a part of a healthy diet.
Does It Help Maintain Healthy Bones?
As with eye health, there are no specific studies done on the effect on arugula on bone health. There is a relatively small amount of calcium in it, especially if compared to milk or sardines, or even collard greens.
Arugula, however, does have a reasonable amount of Vitamin K. Although known primarily for its important role in the body’s blood clotting system, Vitamin K’s effects include a role in bone metabolism and potential protection against osteoporosis (weakened bones).
Although there are no clinical studies that assess arugula’s effect on bone health, its possible that its vitamin K content confers some benefit.
Does It Improve Digestion?
I guess it depends on what you mean by digestion. By definition, digestion is the process of breaking down food by mechanical and enzymatic action in the alimentary canal into biochemicals that can be used by the body. Arugula doesn’t play a role in this process.
But about half of its carbohydrate is in the form of fiber (½ cup has about 6% of your daily recommendation), and fiber promotes intestinal motility and the prevention of constipation. Fiber also acts as a prebiotic – a food for the “good” bacteria that normally live in your gut.
I found one scientific paper by Fratianni et al that did an in vitro (test tube) study on the effect of Eruca sativa on the growth of 3 lactobacillus strains under simulated gastrointestinal conditions. Lactobacilli are some of the “friendly” bacteria that live in our digestive, urinary, and genital systems.
Lactobacillus is also found in some fermented foods like yogurt and in dietary supplements. Fratianni found that the presence of E. sativa in the lactobacteria’s growth medium increased the antioxidant and antimicrobial activity of two of the three bacterial species (L. acidophilus and L. plantarum).
The only scientific paper I found involving eruca sativa and the gastrointestinal tract was a paper by Alqasoumi et al who wanted to examine gastric anti-ulcer properties of Eruca sativa on experimentally-induced gastric secretion and ulceration in albino rats.
They used an ethanol extract of rocket salad and measured the baseline stomach acid secretion and the formation of stomach ulcers caused by a variety of agents. They concluded that rocket extract possesses anti-secretory, cytoprotective and anti-ulcer activities against experimentally-induced stomach ulcers.
There is not enough scientific evidence to make any conclusions about the role arugula can play in digestive health.
Does It Reduce Skin Inflammation and Infections?
Oil obtained from the arugula plant has been used for centuries in Middle Eastern medicine as a treatment for skin disorders such as psoriasis. A 2012 study by Yuhuda et al found that sulforaphane as well as an isothiocyanate from Eruca sativa (4-Methylthiobutylisothiocyanate-MTBI) had an anti-inflammatory effect in vitro in cultured human monocytes and macrophage cells.
Human skin samples (obtained from women undergoing plastic surgery) were grown in medium and subsequently exposed to a chemical called LPS to induce inflammation.
This skin was then incubated with MTBI. They found that the treated skin exhibited a significant decrease in secretion of pro-inflammatory mediators such as cytokines IL-1 and IL-6. Lastly, they tested a type of mouse which has a skin condition similar to psoriasis.
They found that MTBI or sulforaphane brought about partial or complete recovery of the skin rash in 2/8 or 3/8 mice (respectively) compared to 0/7 control mice. Similar results were found in a study by Cho, Lee, and Park .
They found that erucin exerted an anti-inflammatory effect on mouse skin (treated with LPS as in the Yuhuda study).
On the other hand, I found two cases, one by Foti of a woman who developed an allergic reaction with local swelling of her mouth, lips and tongue 5 minutes after eating arugula; the second, by Pigatto et al
who were able to document an Ig-E mediated contact and generalized urticaria reaction (hives) from Eruca sativa. Ig-E (Immunoglobulin-E) are antibodies produced by the immune system which plays a major role in allergic reactions.
Although oil produced from arugula leaves has been used in Middle Eastern medicine for many years, there is little scientific evidence to support these claims. People can develop an allergy to arugula which can become severe.
Does It Help Prevent Diabetes?
I could find only three articles that examined a possible role for arugula in the prevention or treatment of diabetes. The first, by Sultan et al , looked at a hydroalcoholic extract (HAE) from rocket salad. Rabbits made diabetic by giving them the chemical alloxan were treated with HAE.
They found that diabetic rabbits given HAE had a “hypoglycemic effect” that was less than that obtained when rabbits were treated with the known antidiabetic drug glibenclamide. I have two problems with this study.
First, HAE is never really characterized- we have no idea how it was prepared and what it contains. Secondly, there is only one graph related to the hypoglycemic effect and it is so small, you can’t read the values in it.
A second study, by El-Missiry and Gindy , used the oil of Eruca sativa seeds- EES (not the leaves we eat in salads). Daily administration of EES oil 2 weeks before or after induction of diabetes in rats with alloxan improved high blood glucose and other chemical abnormalities (glutathione levels, lipid profile, malondialdehyde) caused by the induction.
The last paper, by Hetta et al took E. sativa and processed it in several ways (aqueous, ethanol– 70 or 95% extraction, n-hexane soluble and defatted ethanol).
They took these extracts and did a variety of cell-based in vitro bioassays for antidiabetic activities in skeletal muscle cells, hepatocytes (liver cells) and adipocytes (fat cells)- three types of cells important in the regulation of blood glucose levels.
The extract they call ES3 is one that is rich in fatty acids (a list of these 24 compounds is present in the article). It was this fraction that seemed to show the most significant positive effects of glucose related metabolism in the different cell types.
The above-mentioned papers hint that some components of arugula may have positive effects on glucose metabolism. However, there are no human studies and much more evidence is needed to prove this.
Is Arugula Safe?
Overall, arugula is safe in usual portion quantities. However, eating anything to excess can cause problems. The sulforaphane in arugula, if taken in large quantities can cause gassiness and abdominal cramping.
As mentioned above, some people can develop an allergy to arugula. For those people, eating arugula can cause swelling of the lips, mouth and tongue and even their airways. Those with arugula allergy should carry an epi-pen with them.
As a leafy vegetable, arugula is subject to many of the possible bacterial contaminants that occur in other salad greens such as romaine lettuce. For example, a paper by Kinnula et al documented an outbreak of Shiga toxin-producing and enteropathogenic E.coli from rocket salad in Finland in 2016.
Lastly, patients taking blood thinners (especially warfarin- Coumadin ®) should be cautious about the amount of arugula they eat. Vitamin K can decrease the effect of warfarin, leading to increased blood clotting.
Arugula is a tasty, low calorie, green vegetable that contains significant amounts of dietary fiber, Vitamins A and K, as well as bioactive compounds such as flavonoids and isothiocyanates.
There is not enough clinical evidence that strongly supports specific health claims at the present time. But until the time comes when there might be, enjoy a big arugula salad (I like mine with lemon vinaigrette and grated parmesan cheese)!
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