HerbalEGram: Volume 14, Issue 1, January 2017
Editor’s Note: Each month, HerbalEGram highlights a conventional food and briefly explores its history, traditional uses, nutritional profile, and modern medicinal research. We also feature a nutritious recipe for an easy-to-prepare dish with each article to encourage readers to experience the extensive benefits of these whole foods. With this series, we hope our readers will gain a new appreciation for the foods they see at the supermarket and frequently include in their diets.
The basic materials for this series were compiled by dietetic interns from Texas State University in San Marcos and the University of Texas at Austin through the American Botanical Council’s (ABC’s) Dietetic Internship Program, led by ABC Education Coordinator Jenny Perez. We would like to acknowledge Jenny Perez, ABC Special Projects Director Gayle Engels, and ABC Chief Science Officer Stefan Gafner, PhD, for their contributions to this project.
By Hannah Baumana and Lisa Carriggb
a HerbalGram Associate Editor
b ABC Dietetics Intern (TSU, 2016)
Sesamum indicum (Pedaliaceae) is an annual flowering plant with fuzzy, slender, oblong leaves that are arranged opposite to one another on the stem.1,2 The plant reaches an average of two to four feet (0.6-1.2 meters) in height and produces small, bell-shaped pink, violet, or white flowers arranged closely to the stem. The plant produces oblong seed capsules that contain many small oval-shaped seeds.1 There are three color varieties of seeds: black, white, and red/brown. Sesamum indicum grows in well-drained soil in warm or hot climates and does not tolerate frost or poorly draining soil. It is, however, a robust plant that will grow in poor soil, drought, and high heat conditions where most other crops will not.3
While the leaves of the plant are also edible, the sesame plant is grown primarily for its seeds, and the oil pressed from the seeds is an important commercial and medicinal product. Sesame seeds are possibly one of the oldest seed crops known to humankind. The exact origins of domestication are uncertain, but it is believed that sesame originated in Africa, and its cultivation and use spread to Egypt, India, the Middle East, and China.3 Currently, S. indicum is cultivated in dry tropical and subtropical regions of Asia, Africa, and South America.1,4,5
Phytochemicals and Constituents
Although small in size, the sesame seed is densely packed with nutrients. Sesame seeds are rich in protein (approximately 20-25% by weight) and oil (approximately 50% by weight). Sesame additionally contains fiber, vitamin E, thiamine, riboflavin, niacin, and minerals, such as copper, zinc, magnesium, phosphorus, iron, and calcium.6 Sesame oil contains approximately 38% monounsaturated fat (MUFA) and approximately 44% polyunsaturated fat (PUFA).7 The unsaturated fatty acids oleic acid and linoleic acid account for the majority of the oil weight of the seed (more than 800 g/kg). Sesame seeds are low in saturated fat.8 PUFAs have anti-inflammatory, antithrombotic, anti-arrhythmic, lipid-lowering, and vasodilatory properties.9,10
Sesame seed may be of particular interest to those who follow vegetarian or vegan diets due to its amino acid and calcium contents. Unusual for a plant-based protein source, sesame has a mostly complete amino acid profile, missing only lysine. Sesame is rich in the amino acid methionine, which is often the missing amino acid in legume-based diets.11 Calcium is one of the predominant minerals found in sesame, along with manganese, phosphorus, and iron. One ounce (28 grams) of whole toasted sesame seeds contains approximately 28% of the daily value of calcium based on a 2,000-calorie diet. In comparison, one cup of nonfat dairy milk contains approximately 31% of the daily value of calcium. However, the bioavailability of the calcium content in plant foods is very different than that of animal-based products. Although the whole sesame seed contains a high amount of calcium, the degree to which the body is able to absorb this calcium is not well-studied.
Other constituents present in sesame include oxalic and phytic acids.7 These compounds may interfere with the absorption of certain nutrients. In addition, consuming high amounts of oxalates, which are derivatives of oxalic acid, may be problematic for individuals with a history of oxalate kidney stones.
While sesame has robust macronutrient and micronutrient profiles, other bioactive compounds present in the plant that have caught the attention of researchers. These compounds include phytosterols and a group of antioxidants known as lignans.9 Antioxidants are substances that can prevent or slow down the damage that reactive oxygen species (ROSs) can inflict on cells. Phytosterols possess similar chemical structures to cholesterol, which is not found in plants. When present in sufficient amounts in the diet, phytosterols have been shown to reduce cholesterol levels in the blood. The fat-soluble lignans (e.g., sesamin, sesaminol, sesamolinol, and sesamolin) are the most-studied compounds in the sesame plant. Lignan glycosides, in which a sugar molecule is attached to a lignan, are also present in sesame, but are found only in the whole seed, and not in sesame oil. Although the lignan glycosides have no direct antioxidant role, these compounds within sesame seeds can be converted in the body to form sesaminol and thereby function as antioxidants.12
Historical and Commercial Uses
The use of sesame as a food, medicine, and component of spiritual or ritual practices dates back more than 4,000 years in Egypt and the Middle East, spreading from these regions to India and Europe.1 In the Hindu tradition, the sesame seed represents immortality. In the Babylonian Empire (located in present-day Iraq; 18th century to 6th century BCE), sesame oil was used to make perfumes and medicine. Records reveal that ancient Egyptians also used sesame as a medicine, and the oil was used for ceremonial purification in 1500 BCE. Europeans first encountered sesame seeds when they were imported from India during the first century CE, and sesame seeds were brought to the United States from Africa in the 17th century.
Various preparations of the plant have been used for medicinal purposes. In Ayurveda, a traditional medicine system of India that has been practiced for millennia, powdered seeds were given orally in combination with a warm sitz bath containing a handful of bruised seeds for treatment of amenorrhea and dysmenorrhea.2 Topically, a poultice of seeds was applied to ulcers, burns, and scalds, and sesame seed paste was combined with ghee (clarified butter) to treat bleeding hemorrhoids. Sesame oil was commonly used as a base for perfumed oils for anointing the body and hair, and traditionally used as a hair wash to promote hair growth.
In traditional Chinese medicine, sesame is known as a yin tonic, which moistens dry tissues and increases body fluids. Due to these properties, the seeds were used to promote lactation in breastfeeding mothers.13 In Europe, the oil was rubbed onto eyelids or dropped into eyes for eye complaints and also used internally for treating gonorrhea. The leaves of the sesame plant were decocted and consumed to resolve bowel afflictions, such as dysentery and cholera.2
In addition to its traditional medicinal uses, S. indicum continues to be an important food and lends itself to being prepared and used in a wide variety of ways. Grown predominately for sesame oil, the seeds themselves can be eaten raw or roasted.14 When the seeds are hulled, they can be easily crushed into a flour or ground further into a paste. Hulled seeds are widely used in their ground form as a paste in Eastern Mediterranean and Middle Eastern cuisines. In Europe and North America, the seeds are mainly used for bakery products, such as sesame seed buns.
In most cultures, the seeds have traditionally been roasted or baked before consumption or prior to oil extraction, a practice that enhances the sweet, nutty flavor and aroma of the seed and produces darker-colored oil. Traditionally, the sesame seeds are cold-pressed for oil. In European and North American cultures, a hot-pressed and refined oil is more highly desired, since this creates a colorless and neutral oil, which is better suited for cooking and use in salad dressing.14 The young leaves of the plant can be eaten in stews, a practice seen in Africa today.5 In Korea, the leaves are used to make a kind of wrap eaten with meats and other vegetables. The sesame cake (leftover plant material after the oil has been removed from the seeds) is used for livestock feed and can serve as a subsistence food in times of scarcity.2 In African and Asian cuisines, the seeds are used in both sweet and savory dishes. With globalization, many cultural foods have traveled from their continents of origin to become commonly consumed in the United States and elsewhere. For example, tahini, or ground sesame seed paste, has emerged from the Middle Eastern culinary tradition as a familiar grocery store item in the United States.13
Current research investigating the potential efficacy of S. indicum and its constituents covers a wide range of applications. Research on sesame’s lignan content and inherent antioxidant potential is most prolific, specifically on the synergy of action of the lignans in combination with vitamin E.8 Additionally, there were a number of studies on S. indicum published in 2016, adding to the body of evidence on the efficacy of therapeutic use and effective dosage.
Cardiovascular Disease Risk Factors and Serum Lipid Profile
Oxidative stress and inflammation play a large role in the development and progression of atherosclerosis. A cardioprotective diet and exercise are an important part of prevention and treatment. Two types of fats, polyunsaturated and monounsaturated fatty acids, are present in the sesame plant and have been reported to lower cholesterol. Other potential mechanisms for the cardioprotective effects of sesame have been described, and sesame oil may have multiple constituents that affect the atherogenic process in various ways.15
The fat-soluble lignans in sesame may affect fat in the bloodstream and the ability of the liver to process fat, particularly triglycerides. A group of researchers cultivated a sesame variety that contained two times more sesamin and sesamolin than conventional sesame to observe the effect of these two compounds on health parameters.16 The results showed that consumption of these seeds compared to seeds of a conventional sesame variety effectively increased activity of enzymes located in the liver and involved in fatty acid oxidation. This increase was correlated with a decrease in serum triglyceride levels. The researchers noted that it is unclear if these effects are solely a result of the difference in concentration in the fat-soluble lignans or if other compounds may be involved in the observed physiological activity of the seeds.
A 2016 systematic review examined scientific literature to discern the effect of dietary intake of sesame seed and its derivatives on the lipid profile and blood pressure of hypertensive and dyslipidemic individuals.6 Of the seven studies that fit the review criteria, most were not randomized, and those that were did not describe the blinding of participants or personnel. Five clinical trials on patients diagnosed with hypertension found significant results for the reduction in both systolic blood pressure (SBP) and/or diastolic blood pressure (DBP). Of the three studies that included a lipid profile, two found significant reductions in total cholesterol (TC) and low density lipoprotein cholesterol (LDL-c) levels and one found a significant increase in high density lipoprotein cholesterol (HDL-c) concentrations in the sesame treatment groups.
The dosage and administration of sesame to medicated hypertensive patients varied across studies. Positive outcomes for SBP (reduction by approximately 3%) and DBP (reduction by approximately 2%) were noted with as little as 7.6 grams per day of encapsulated black sesame flour, the use of sesame oil for 45-60 days, or 60 grams of encapsulated sesamin taken for four weeks.
Two studies examining the use of sesame flour in individuals with dyslipidemia found that it positively impacted lipid profiles. The exact mechanisms are still being studied. The reviewers noted, however, that further research with low risk of bias is necessary to obtain more conclusive results, since the seven clinical trials reviewed contained a high risk of bias.6
Both sesame seed and sesame oil have been studied for their cardioprotective benefits. Daily supplementation with sesame oil was shown to increase flow-mediated dilation levels, suggestive of an improvement in the vascular function, after meals when compared to supplementation with corn (Zea mays, Poaceae) or olive (Olea europaea, Oleaceae) oils in hypertensive men receiving medication.17 Furthermore, a randomized, double-blind, placebo-controlled trial showed supplementation with sesame paste ground from unhulled seeds improved lipid profiles and atherogenic lipid parameters in patients receiving treatment for type 2 diabetes.18 The researchers concluded that in addition to drug treatment, dietary modification using functional foods, such as sesame seeds, may have beneficial effects for the prevention of cardiovascular and diabetes complications. Additionally, a study using a substitution of 35 grams per day of sesame oil as the only edible oil for 45 days in hypertensive women resulted in significant decrease in serum TC, and SBP and DBP. However, this study was uncontrolled.19
While the underlying mechanisms remain unclear, sesame’s strong antioxidant capacity may be protective against neurodegenerative disorders. Antioxidant nutrients from food may play an important role in lessening the consequences of oxidative stress in cerebral ischemia (a type of stroke) and recirculation brain injury. Sesamin and sesamol have demonstrated the ability to elevate levels of alpha-tocopherol (a form of vitamin E) in the plasma, liver, and brain of rats, displaying an inhibitory effect on endogenous lipid peroxidation as well as oxidative DNA damage in rat plasma and liver and protective effects on hypoxia in neurons.12 Based on the strong antioxidant activities of sesame, it could be considered neuroprotective against cerebral ischemia and stroke, though further studies need to be conducted in support of this.
Although not common, there is the potential for an allergic reaction upon consumption of sesame seeds or sesame oil.20,21 Since allergic reactions are mainly due to protein found in the seed, there may be no reaction or less of a reaction to the oil, with the exception of cold-pressed oil. Cold-pressed oil may still contain varying amounts of protein.
Individuals who are predisposed to kidney stones or are chronically undernourished in calcium, vitamin D and phosphorus may exercise caution and consider total dietary intake of foods high in oxalic acid. Sesame seeds contain 1-2% oxalic acid, which may interfere with calcium, magnesium, and protein absorption in the body.21,22 Additionally, certain types of kidney stones are composed of oxalic acid. It is important to note that the hull of the seed contains the highest amount of oxalic acid.23 The presence of oxalic acid can be reduced significantly through processing of the seeds and in particular through sprouting the seeds prior to consumption.11 Cooking and toasting the seeds before consumption or pressing the seed for oil also can reduce levels of oxalic acid and maximize the bioavailability of sesame’s beneficial constituents.24 Additionally, some bioactive constituents of sesame are found in highest amounts in sesame oil produced from toasted or otherwise heated sesame seeds.
Macronutrient Profile: (Per 1 tablespoon [approx. 9 grams] sesame seeds)
1.6 g protein
2.11 g carbohydrate
4.47 g fat
Secondary Metabolites: (Per 1 tablespoon [approx. 9 grams] sesame seeds)
Very good source of:
Manganese: 0.22 mg (11% DV)
Good source of:
Calcium: 88 mg (8.8% DV)
Magnesium: 32 mg (8% DV)
Iron: 1.31 mg (7.2% DV)
Phosphorus: 57 mg (5.7% DV)
Thiamin: 0.07 mg (4.7% DV)
Dietary Fiber: 1.1 g (4.4% DV)
Molybdenum: 2.66 mcg (3.6% DV)
Vitamin B6: 0.07 mg (3.5% DV)
Niacin: 0.41 mg (2.1% DV)
Folate: 9 mcg (2.3% DV)
Potassium: 42 mg (1.2% DV)
Riboflavin: 0.02 mg (1.2% DV)
Vitamin E: 0.02 mg (0.1% DV)
Vitamin A: 1 IU (0.02% DV)
DV = Daily Value as established by the US Food and Drug Administration, based on a 2,000-calorie diet.
Recipe: Sticky Sesame Bars
Courtesy of Camilla V. Saulsbury26