Cilantro / Coriander
Written by Tiffany Tse & Subhas Ganguli, February 2018
Description
When describing coriander and cilantro, many people often get confused. Let’s start by defining some terms.
The leaves of the coriander plant are what make up cilantro, or Chinese parsley, the herb. However, the seeds of the plant are what make up coriander, one of the world’s oldest spices (1). All parts of this plant can be used as either a flavouring agent or as an herbal remedy for various illnesses, explaining why it has been used in different cultures for thousands of years.
We will now look at the usage of the coriander plant and its many health benefits.
Forms/selection/storage
Coriander exists in several forms, making it a useful plant for both culinary and medicinal purposes. Its fruit (otherwise known as its seeds) are aromatic and have a slightly bittersweet, spicy taste and are used as an important flavouring agent, (eg in curry powder). Coriander oil is used in cosmetics, body care products, and perfumes. The leaves, which have a distinctive smell, are used as herbs and are often found in many chutneys and sauces. Thus, each part of the plant serves a distinct purpose (2).
When purchasing and storing coriander, keep the following in mind to ensure you maximize its health benefits while cooking:
There are two main types of coriander seeds: European and Indian. Most of the coriander found in the American market are of European origins, as characterized by its more spherical shape and tan colouring. These should have a husk with two seeds inside, and appear uniform in colour with no signs of grit. While coriander can be sold in powdered form, it is most effective when used as a whole seed, as the oils dissipate quickly when the seeds are ground. Seeds can stay fresh for a year or more, but ground seeds only last for a few months (1). Both the seeds and powder should be stored in an opaque, tightly sealed container in a cool, dark, and dry place (3)
Dried parsley can be bought, but you cannot buy dried cilantro, as the leaves do not last in the drying process. Thus, when buying fresh cilantro, it is best to buy it with the roots intact, as that will keep the leaves fresh for the longest period of time. The leaves should be a vibrant green, without indicators of spoilage or colour discolouration and the stems should be firm (4). If you plan on using it soon, cilantro can be kept upright in water in the refrigerator without the roots, covered in a plastic bag, allowing it to last for several days (1).
Tips for preparing and cooking
Coriander is versatile and is used in many different types of cuisine. It mixes well with other spices, especially cumin.
If a more intense flavour is desired, you can roast the seeds before grinding them or even toast them in oil. They can be easily ground with a mortar and pestle and only ground coriander should be used in sweeter dishes. The seeds themselves are especially flavourful in casseroles, stews, long-cooking braises, and sauces, as their papery husks and grain-like consistency allow them to thicken the mixture (1). Before usage, you can also soak them in cold water for ten minutes first and drain them to revive their fragrant aroma (3)
The oil of the cilantro plant can also be drizzled over fries, salads, and dips – just be sure to check the label to ensure that it is safe for oral consumption (4)!
Fresh cilantro should be washed immediately before cooking because it is incredibly fragile. Simply place it in a bowl of cold water and swish it around with your hands, thus removing any dirt and sand. Remove the leaves from the water, refill it with clean water, and repeat this process until there is no dirt left.
For recipes using cilantro and/or coriander: see here, here and here.
Nutritional Profile
The seeds are the most widely used component of the coriander plant and the most important aspect of the seeds are their essential (<1%) and fatty (25%) oils. The oil contains a high amount of petroselinic and linoleic acid, both of which are fatty acids. The composition of coriander essential oils differs based on biological and geographical variability. In addition to environmental and genetic factors, the plant’s maturity and the method of extraction used can also affect the composition of the essential oil. Coriander is an important source of phytonutrients, dietary fiber, copper, manganese, iron, calcium, and vitamin K (3). The plant contains coumarins, terpenes, pirogalic, and flavones (11).
The leaves are less studied than the seeds, but contain essential oils, flavonoids, phenolic acids, and polyphenols. They are known to be a rich source of folates and ascorbic acid and contain a significant amount of caffeic, ferulic, gallic, and chlorogenic acids (5). Fresh leaves contain mostly moisture, but act as an important source of protein, calcium, phosphorus, iron, vitamin B2, vitamin C, and vitamin A. Interestingly, most studies can confirm that they are most known for their alcohol and aldehyde content (6).
Both the seeds and the leaves have been shown in several studies to be beneficial to health, especially due to their antimicrobial and antioxidative effects.
Overview of Possible Health Benefits
For the past few decades, different parts of the plant have been used to treat various symptoms. For example, the leaves have been used as antispasmodic, dyspeptic, and as an appetizer to treat abdominal discomfort. The leaves can also be ingested or applied externally to treat coughs, chest pains, and bladder complaints (7). The seeds, which have long been known as the “anti-diabetic” part of the plant (3), have been used to treat inflammation, indigestion, cough, bronchitis, vomiting, dysentery, diarrhea, rheumatism, and more (7).
With regards to the biologic effects that coriander has on the human body, it is known for its antimicrobial, antioxidative, antidiabetic, and mood enhancement activities with the antimicrobial potential of its leaves, seeds, extracts, and essential oils being the most widely reported activity (7).
In a randomized placebo-controlled study (16) of 68 subjects with migraines who were all given valproic acid, syrup made from the ethanol extract of coriander seeds resulted in a statistically significant decrease in the duration (37%), severity (62%), and frequency (38%) of migraine attacks.
Extracts of the essential oils have been shown to inhibit bacterial and yeast activity, especially amongst Gram-positive and Gram-negative bacteria. For example, in a study conducted by Thompson et al., aqueous extracts of coriander seeds were shown to significantly slow down the growth of E. coli, a Gram-negative bacteria (8). In terms of its anti-oxidative activity, the high phenolic content in cilantro leaves and shoots may contribute to its ability to deal with oxidative stress from free radical damage (9).
Interestingly, some studies have found higher anti-oxidative activity from coriander leaf extracts than when compared to coriander seed extracts (7). Many studies show that different parts of coriander have antioxidative effects in vitro, but models in vivo have contradicting information, indicating that more research should be done.
Additionally, coriander has been shown to have anti-diabetic effects – in fact, in some countries (e.g. Morocco and Saudi Arabia), coriander is still used to treat hyperglycemia (7).
A randomised controlled study (21) of 60 adults with type 2 diabetes (NIDDM) treated subjects with 5 grams/day of powdered coriander (C sativum) and aniseed (Pimpinella anisum) seeds for 60 days. As can be seen in the table below, coriander resulted in statistically significant decreases in blood levels of glucose (13%), cholesterol (15%), triglycerides (30%), LDL (9%),and rise in HDL (42%).
The above results were confirmed in an open-label study (19) of 50 patients with NIDDM who were given oral capsules with 1 gram of coriander seed powder daily for 6 weeks resulting in statistically significant decreases in glucose (4.8 mmol/L; 50%), total cholesterol (2.6 mmol/L;50%), triglycerides (1.3 mmol/L;55%), and LDL cholesterol (1.8 mmol/L;51%). A decrease in HDL was also seen (0.2 mmol/L) which was significant.
A study (10) in a diabetic mouse model of streptozotocin treated mice conducted by Gray et al. showed the following: 1) Administration of coriander seed extract was associated with significantly decreased glucose levels; 2) An aqueous extracts of coriander enhanced glucose uptake, glucose oxidation, and glycogenesis 3) Experiments using clonal pancreatic B-cells showed that coriander extract stimulated insulin secretion, consequently contributing to a lower blood sugar level. In another study of diabetic rats (17) an ethanol extraction of coriander leaves and stems had the following statistically significant effects which were similar in size to that of an anti-diabetic drug (glibenclamide) : 1) Lowering of blood sugar, 2) lowering of blood triglycerides, 3) Raising of HDL, 4) Lowering of LDL, 5) Lowering of total cholesterol. Another study (18) looked at the effect of coriander seed oil on blood lipids in rats fed a diet containing cholesterol and found that coriander reversed cholesterol-induced increase in total lipids, triglycerides, total cholesterol, and LDL cholesterol as well as raising HDL (‘good’) cholesterol.
A study of anesthetized rats (20) compared the effect of an intravenous infusion of an aqueous extract of coriander (at doses of 40 and 100 mg/kg) with furosemide (10 mg/kg), a commonly used diuretic. Both doses of coriander were more effective than saline but somewhat less effective than the furosemide. A similar trend was seen in the urinary excretion of sodium and potassium.
Lastly, coriander is known to have mood enhancement effects. In Iranian traditional medicine, it has been used as an anticonvulsant and antidepressant for its nerve soothing, sedative, and anxiolytic properties. One study found that linalool, a major constituent of coriander, relieved tension and anxiety in human subjects. This enhanced relaxation and increased parasympathetic nerve activity, as assessed by heart rate measurements (5).
Therefore, many parts of the coriander plant have health benefits, indicating that both the seeds and leaves can be added to various dishes to enhance the flavour and improve one’s health.
Possible Role in Detoxification
An in vitro study (12) used a sorbent prepared from coriander to remove inorganic and methyl mercury from water. Overall, the sorbent was found to remove more than 95% of the mercury in the pH range of 4 to 10 (our body pH is 7.35 to 7.45) with an optimum contact time of 45 minutes. The authors concluded, “Coriander appears an attractive material which could have the potential for use in decontaminating mercury”.
In another study (11), male Wistar rats were treated with 50 mg/kg of lead acetate intraperitoneally (injected into their abdominal cavity) and were then orally given various extracts of coriander leaves and stalks (methanol, hexane, chloroform, and insoluble fractions). Blood levels of lead were then measured at 3 weeks and found to be significantly (P<0.05) lower (less than half the level in the positive controls) in the rats given the insoluble fraction. Since the insoluble fraction was most decreased, it would appear that it is better to eat the stalks/leaves than an extract (eg essential oil, tincture) which would not include the insoluble fraction.
In another study (13), mice were fed lead nitrate for 40 days. After the first 7 days, some of them were also fed aqueous and ethanol coriander seed extract at various doses. While lead exposure had significant effects on antioxidant related variables (measured in testis tissue), this effect was significantly decreased by both aqueous and ethanolic coriander extract. Other results were as follows:
- Liver tests (AST, ALT, ALP) were significantly raised after lead nitrate; this effect was significantly attenuated by both aqueous and especially the ethanolic coriander extract.
- Lead nitrate was also associated with a rise in cholesterol levels which was significantly attenuated by the high dose of ethanolic coriander extract.
- Lead nitrate was also associated with a significant drop in testosterone levels which did not significantly change with ingestion of coriander extract.
- Sperm density also decreased significantly (going from 8.32 to 1.55 million/ml) with significant partial recovery (to 2.58 and 2.60 million/ml) with high dose aqueous and ethanolic coriander extract respectively.
- Tissue lead level went up significantly after exposure to lead nitrate (from 0.71 ppm to 2.25 ppm) which was partially attenuated to 1.90 with high dose ethanolic coriander extract (not significant).
In another study (14) mice were fed lead acetate in their drinking water and then ate the equivalent of 2.4 mg or 12 mg of the solid content of cilantro leaves and stalks. Lead is known to accumulate in bones so they looked at the levels of lead in bone. This was significantly lower in the mice fed the high dose cilantro than in the control mice (133.8 vs 170.7 Pb ppm; P<0.05).
In another study(15), rats were fed lead acetate for four week and lead levels in different regions of their brains were measured after one week of treatment with a alcohol based extraction of coriander seed at a low (250 mg/kg body weight/day) or high (500 mg/kg body weight/day) dose. Lead is also known to inhibit delta-aminolevulinic acid dehydratase activity(d-ALAD), and this is an indicator for lead toxicity. Toxic heavy metals are known to compete or interfere with essential micronutrients such as copper, zinc, and iron which are essential for myelin synthesis, structure and maintenance of oligodendrocytes. The researchers found that:
- Brain lead levels were significantly raised after lead acetate treatment; this effect was significantly reversed by coriander seed with a dose-response relationship.
- Brain copper, zinc, iron, and chromium levels were significantly lowered after lead acetate treatment; this effect was significantly reversed by coriander seed with a dose-response relationship.
These findings are summarised in the table below:
Warnings and Cautions
Coriander as a spice and seasoning is generally recognized as safe by the US Food and Drug Administration, but evaluations of the mutagenicity of the spice, coriander oil, and coriander extracts have yielded inconsistent results (5). Nonetheless, based on the history of the consumption of coriander oil without any reported side effects, the medicinal use of the essential oil at a usual dosage is overall safe for human consumption as a food ingredient and in cosmetics (7).
References
(1) Bharat B Aggarwal (2011). Healing Spices. New York, NY: Sterling
(2) Coriander (Coriandrum sativum L.): a potential source of high-value components for functional foods and nutraceuticals – a review. Sahib N. J., Anwar F., Gilani A., Hamid A. A., Saari N. & Alkharfy K. M. Phytotherapy Research 2013 27:1439-1456
(3) The World’s Healthiest Foods – Cilantro & coriander seeds. Mateljan, G. Accessed 29/12/2017
(4) Cilantro benefits, uses, and recipes. Dr. Mercola. Accessed 28/12/2017
(5) Coriander: overview of potential health benefits. Singletary K. Spices Series 2016 51(3): 151-161
(6) Nutritional and medicinal aspects of coriander (Coriandrum sativum L.) a review. Nadeem M, Anjum F. M., Issa Khan M., Tehseen S., El-Ghorab A. & Sultan J. I. British Food Journal 2013 115(5): 743-755
(7) Nutritional composition of selected green leafy vegetables, herbs, and carrots. Singh G., Kawatra A. & Sehgal S. Plant Foods for Human Nutrition 2001 56: 359-364
(8) Comparison of the antibacterial activity of essential oils and extracts of medicinal and culinary herbs to investigate potential new treatments for irritable bowel syndrome. Thompson A., Meah D., Ahmed N., Conniff-Jenkins R., Chileshe E., Philips C. O.,… Row P. E. Complementary and Alternative Medicine 2013 13: 338-357
(9) Variation in antioxidant activity and phenolic content of some common home remedies with storage time. Rahiman S., Tantry B. A. & Kumar A. African J Traditional Complementary & Alternative Medicine 2013 10(1): 124-127
(10) Insulin-releasing and insulin-like activity of the traditional anti-diabetic plant Coriandrum sativum (coriander). Gray A., M. & Flatt P. R. British Journal of Nutrition 1999 81: 203-209
(11) Evaluation of the chelating effect of methanolic extract of coriandrum sativum and its fractions on Wistar rats poisoned with lead acetate. MA Tellez-Lopez, G Mora-Tovar, IM Ceniceros-Mendez et al. Afr J Tradit Complement Altern Med 2017:14(2):92-102
(12) Removal and preconcentration of inorganic and methyl mercury from aqueous media using a sorbent prepared from the plant Coriandrum sativum.D Karunasagar MV Krishna J Arunachalam. J Hazard Mater 2005:118(1-3):133-9.
(13) Prophylactic efficacy of Coriandrum sativum(Coriander) on Testis of Lead-Exposed Mice. V Sharma, L Kansal,A Sharma. Biol Trace Elem Res 2010:136:337-354.
(14) Preventive effect of Coriandrum sativum (Chinese parsley) on localised lead deposition in ICR mice. M Aga, K Iwaki, M Kurimoto et al. J Ethnopharmacology 2001(77):203-208.
(15) Hydroalcoholic Seed Extract of Coriandrum sativum (Coriander) Alleviates Lead-induced oxidative stress in different regions of rat brain. MK Velaga, PR Yallapragada,R Bettaiya et al. Biol Trace Elem Res 2014:159:351-363.
(16) Effects of Coriandrum sativum Syrup on Migraine: A Randomized, Triple-Blind, Placebo-Controlled Trial. HD Kasmaei, Z Ghorbanifar, Z Mirzaei et al. Iran Red Crescent Med J 2016:18(1):e20759
(17) Antioxidant, Antihyperglycemic, and Antihyperlipidemic Effects of Coriandrum sativum Leaf and Stem in Alloxan-Induced Diabetic Rats. S Sreelatha, R Inbavalli. J Food Science 2012:77(7):T119-T123.
(18) Coriander (Coriandrum sativum L.) seed oil improves plasma lipid profile in rats fed a diet containing cholesterol. MF Ramadan, MMA Amer MES Awad. Eur Food Res Technol 2008(227):1173-1182.
(19) The Effect of Coriander Seed Powder Consumption on Atherosclerotic and Cardioprotective Indices of Type 2 Diabetes Patients. N Parsaeyan. Iran J Diabetes Obesity 2012:4(2):86-90.
(20) Acute diuretic effect of continuous intravenous infusion of an aqueous extract of Coriandrum sativum L. in anesthetized rats A Aissaoui, J El-Hilaly, B Lyoussi et al. J Ethnopharmacology 2008:115:89-95.
(21) Comparison of aniseeds and coriander seeds for antidiabetic, hypolipidemic, and antioxidant activities. U Rajeshwari, I Shobha, B Andallu. Spatula DD 2011:1(1):9-16.
