Carrageenans: uses in food and other industries
Fatma G. Huffman
Carrageenans, also known as Irish Moss, are derived from the seaweed Chondrus crispus. Until recently, they have been used in small amounts, in a limited number of foods, to alter taste, texture, or appearances. Evidence from animal studies indicates that they may be associated with both potentially adverse and beneficial physiological responses in segments of the population who may be ingesting higher amounts considerably in excess of the previous estimates of 2.5 grams.
Globally, Chondrus crispus, a marine species of Rhodophyta (red algae), is one of the most widely used edible seaweeds (Matsuhiro and Urzua, 1991), yet there are few consumers familiar with the natural appearance of the weed. In its chopped, dried, or composted form, the seaweed, a good supplemental source of protein, fiber, vitamins, and minerals (Holland et al., 1991), has been utilized by the agricultural industry in animal fodder and in fertilizers that improve the nutrient content as well as the mechanical properties of the soil (Lobban and Wynne, 1981). This in turn impacts on the nutrient content and quality of the resulting animal and plant products (Lobban and Wynne, 1981). The amount consumed directly by humans has little impact on nutritive intake.
Although human diets rarely include C. crispus in its natural form, in countries such as Ireland, this fresh seaweed is still collected from wild populations along the coastline and home-processed for use as a thickener in porridges, desserts, and other dishes (Lobban and Wynne, 1981). Caribbean consumers can purchase dried, packaged C. crispus that is used to prepare “Sea Moss,” a thick milkshake-type drink (Nestle, 1990). In most industrialized countries, carrageenans extracted from C. crispus are incorporated into food products (Matsuhiro and Urzua, 1991, Pintauro and Gilbert, 1990), so the consumer never comes into contact with the natural seaweed. Carrageenans, a term used interchangeably with C. crispus and Irish moss, encompass a group of sulfated polysaccharides that form gels and viscous liquids (Tong and Hicks, 1991). They have been popularized in the food industry because their performance is superior to the previously used alginates or the gelatins from animal sources (Guiry and Blunden, 1991). As emulsifiers, sta bilizers, binders, and fat substitutes, carrageenans are used in food products such as ice cream, baby foods, processed and low-fat meat products, salad dressings, cheeses, and candies (Lobban and Wynne, 1981). Several other industries, such as the pharmaceutical/biomedical and cosmetic industries, also make use of the carrageenans extracted from C. crispus (Isaacs, 1990).
The pharmaceutical uses of carrageenans range from stabilizers, emulsifiers or colloids for suspensions, and gel coatings for pills, to bases for antacids, cough syrups, and ointments (Guiry and Blunden, 1991). Other areas of the biomedical industry use carrageenans as growth media in the production of antibiotics, or to hold bacteriostatic agents for ease of application (Mussenden et al., 1991).
The cosmetic industry, like the food and biomedical industries, depends heavily on carrageenans. Commonly used products such as soaps, shaving foams, and body lotions all contain carrageenans. These products capitalize on the dual ability of carrageenans to emulsify oil and water preparations yet allow them to be easily removed with water. Other products such as medicated creams, toothpastes and deodorants rely on the ability of carrageenans to hold bacteriostatic agents (Guiry and Blunden, 1991).
Some research has been done on the physiological effects of carrageenans in experimental animals. Researchers agree that many of the potential adverse effects, such as gastrointestinal tract ulceration (Nicklin and Miller, 1989) and depressed immunity (Baker et al., 1986) are dose-dependent. The beneficial effects of carrageenans, however, are not dose-dependent. Schlemmer (1989) discovered that under the simulated buffered conditions of the intestines, carrageenans did not bind minerals such as Ca, Zn, or Cu to the same extent as other dietary fibers.
In the study of heart disease, the effects of carrageenans on serum cholffterol and on intestinal mucinase activity have been studied. It was found that rats fed carrageenans at 5%, 10%, and 15% of the diet experienced approximately the same lowering effect on serum cholesterol. However, although the 5% carrageenan level decreased intfftinal mucinase activity, the higher levels of carrageenans increased the activity of this enzyme (Shiau and Huang, 1987).
Most evidence suggests that only high levels of carrageenan intake can lead to nutritional risk. However, little research has been done to accurately estimate the average intake of Americans; nor has any attempt been made to investigate populations, such as dieters, the elderly, or infants who are likely to consume more than average amounts of carrageenan-containing products. The number of commonly used foods that contain carrageenans has grown almost exponentially. since the late 1980s, when tke average daily adult intake was estimated at 0 to 2.5 grams (Pintauro and Gilbert, 1990); however, this estimate neglected to take into account consumption of carrageenan-containing pharmaceutical products.
Carrageenan research carried out in the past generally involved blends of kappa, iota,-and lambda carrageenans. Because these different types of carrageenans have slight variances in chemical structures and physical properties, it may be advantageous to observe the effects of the various typff of carrageenan on gastrointestinal lining tissues, as well as to compare their impacts on serum cholesterol and mineral bioavailability. It may also be useful to compare carrageenans with pectins, which are widely accepted as a beneficial soluble fiber for the same parameters.
Carrageenan, because of its soluble fiber properties, is incorporated widely into food and pharmaceutical products cornmonly ingested by humans. Yet little research has been done to compare carrageenans with other soluble fibers in terms of their physiological or other effects in animals.
Research in this area is particularly significant for populations such as infants who do not have fully developed gastrointestinal barriers in terms of permeability to pathogens and biological}y active molecules. Because of the use of carrageenans to replace fats in foods dieters may consume sufflciently high proportions of this extract, to be susceptible to colitis or other damage to the gastrointestinal tract. The information gathered may be meaningful in planning the diets or establishing carrageenan intake limits for populations who are at risk of heart disease, gastrointestinal tract darnage, and related immunosuppression. These populations include the elderly, infants, and individuals with HIV infection or diseases of the gastrointestinal tract and the immune system.
Carrageenans, increasingly are being incorporated into foods and pharmaceutical products in amounts ranging from 0% to 1.5% (Nicklin and Miller, 1989), and these carrageenan-containing products are gaining in popularity among both corlsumers and manufacturers be cause of their stability and convenience. However, not enough research has been done to truly guarantee the safety of these seaweed galactans, especially in view of research that has chronicled detrimental effects in experimental animals, even with small intalces of high quality (high molecular weight and viscosity) carrageenans.
Irish moss (C. crispus) is a red marine algae species (Fig. 1). In the wild, this temperature-sensitive seaweed is limited geographically to the cold regions of the North Atlantic Ocean, off the coast of Newfoundland, northern Norway, and New Jersey in the northern hernisphere, and Mauritania in the region of the African continent (Luning, 1990). In these areas, the water currents maintain the temperature around 17 [degrees] C (Luning, 1990). C. crispus appears to require a temperature of 15 [degrees] C to enter its sporophytic stage; photosynthesis ceases at 18 [degrees] C, and above 20 [degrees] C there is massive cell damage resulting in death (Guiry and Blunden, 1991).
C. crispus, like most red algae, has cell walls that appear to be layered and fibrillar under the electron microscope. The thickness and orientation of the layers vary from area to area within the same plant, largely dependent on the period for which the plant has been fixed in one location. The inner microfibrils (layers of the cell wall) are composed of cellulose, whereas the outer microfibrils and wall matrix are made of sulfated polysaccharides such as phycocolloids, mucilages, and the galactans known collectively as carrageenans. The term carrageenan is used interchangeably with Irish moss and C. crispus; however, technically, carrageenans are galactans that are primarily chains of beta-l,3 and alpha-1,4-linked galactose residues extracted from C. crispus (Chapman, 1979). Most of the approximately 300,000 tons, fresh weight, of C. crispus harvested globally per year is used for the extraction of carrageenan (Isaacs, 1992, Lunning, 1990). The technology and uses pertaining to carrageenan have proliferated to such an extent that an industry devoted solely to the extraction of carrageenan has been created. Extracted algal polysaccharides is the form in which most people in industrialized nations, with the exception of Japan, utilize seaweed products. Therefore, the demand for carrageenan from industry has far exceeded the rate of harvesting and extraction of these galactans from cultivated and wild populations (Lobban and Wynne, 1981).
THE CARRAGEENANS: BIOCHEMICAL COMPOSITION
The carrageenan content of C. crispus varies depending upon which of the two phases in its life history the seaweed is harvested (Matsuhiro and Urzua, 1991). During the gametophytic (plant exhibiting alternation of generations that bears sex organs) stage of the life cycle, C. crispus carrageenan is mainly (73%) composed of the kappa family of carrageenans. These form helices in the presence of ions such as calcium and sodium, and gel in aqueous solutions above pH 3.3 at temperatures below their melting points (Tong and Hicks, 1991). During the sporophytic stage (plant exhibiting alternation of generations that bears asexual spores), mainly the lambda family is found (Matsuhiro and Urzua, 1991). As with the kappa carrageenans, these differ only in the a-Dgalactose residues (Bodeau-Bellion, 1983) and sulfation levels. The lambda carrageenans are viscous liquids which do not gel because they cannot form the helices that are characteristic of the kappa carrageenans (Tong and Hicks, 1991). The primary differences that influence the properties of kappa, iota, and lambda carrageenans are the number and position of the ester sulfate groups on the repeating galactose units (Fig. 2).
COMMERCIAL UTILIZATION OF C. CRISPUS
There is evidence that dates back to 600 to 800 B.C., that the Chinese, Greeks, and Romans utilized various seaweeds in ways that gave rise to modem usage (Lobban and Wynne, 1981). C. cnspus in recent years has been increasingly utilized in a myriad of ways by the agricultural and other industries (Lobban and Wynne, 1981).
The desirable structural and gelling properties of the carrageenans in C. cnspus result in approximately 80% of the 15,500 metric tons of carrageenan produced globally per year being utilized in the food industry, and the remaining 20% is divided equally between the cosmetic and pharmaceutical industries (Guiry and Blunden, 1991). The specific, generally kappa, iota, and lambda carrageenans, that are commercially desirable exist within the immediate cell wall and the wall matrix (Chapman, 1979).
ROLES IN THE AGRICULTURAL INDUSTRY
The agricultural industry uses C. crispus as animal fodder and as fertilizer. Its fiber, vitamin, and mineral content make it an excellent supplement to the regular animal diet. In coastal areas, after observing wild animals eating seaweed, farmers often allowed their animals to forage along the shoreline, especially when terrestrial fodder crops failed or were in short supply. This led to the commercial harvesting and processing of seaweed as a fodder supplement; later the by-products of seaweed processing were also utilized by other industries (Lobban and Wynne, 1981).
C. crispus, because of its nutritional composition, is chopped, liquified, composted, dried, or ashed for use as fertilizer by agronomists. It has a nitrogen content similar to that of regular,barnyard manure and 3 times the level of potassium, but only one third the phosphorus content. In addition, the high organic matter content of the seaweed improves the mechanical and water retention properties of the soil. Fertilizers based on C. crispus contain small amounts of naturally occurring substances: auxin, cytokinin, and gibberellin that promote growth and ripening, as well as pathogen-inhibiting phenolic compounds. As an added bonus, these fertilizers are devoid of the fungi and weeds that often impair terrestrial plant growth. C. crispus, in its fertilizer and fodder roles, contributes greatly to the quantity, quality, and nutritional value of the animal and plant products of the agricultural industry (Lobban and Wynne, 1981).
CARRAGEENANS IN THE FOOD INDUSTRY
Unlike most edible seaweeds (eg wakame, kombu, kelp, and nori), which are eaten as vegetables in conjunction with other types of food, C. crispus is processed to extract its carrageenans, which in turn are used to alter the appearance, taste, texture, or flavor of other foods (Tong and Hicks, l991). The nutrition composition of carrageenan is outlined in Table 1.
Nutrient Content of C. crispus
Per 100g C. cirspus
Proximated composition (components)
Edible portion (g) 1.00
Water (g) 81.3
Nitrogen (g) 0.24
Protein (g) 7.1
Fat (g) 1.6
Carbohydrate (g) tr
Energy (kcal) 8
Carbohydrate fractions (nutrients, in g)
Total sugars tr
Total dietary fiber 12.3
Soluble noncellulosic fiber 12.3
Insoluble noncellulosic fiber 0
Vitamin and mineral content
Vitamin C (mg) n/a
Retinol ([micro]g) 0.0
Carotene ([micro]g) n/a
Vitamin D ([micro]g) 0.0
Vitamin E ([micro]g) n/a
Thiamin (mg) 0.01
Riboflavin (mg) 0.47
Niacin (mg) 0.6
Vitamin [B.sub.6] (mg) n/a
Vitamin [B.sub.12] ([micro]g) tr
Folate ([micro]g) n/a
Pantothenate (mg) 0.18
Biotin ([micro]g) n/a
Sodium (mg) 67
Potassium (mg) 63
Calcium (mg) 72
Magnesium (mg) n/a
Phosphorus (mg) 160
Iron (mg) 8.9
Copper (mg) 0.15
Zinc (mg) 1.0
Sulfur (mg) n/a
Chlorine (mg) n/a
Manganese (mg) 0.4
Selenium ([micro]g) n/a
Iodine ([micro]g) n/a
From Holland et al., 1990
The dairy industry has extensively used kappa carrageenans to enhance a variety of products, from cheeses (Kailasapathy et al., 1992) to desserts (Descamps et al., 1986), and even infant formulas (Pintauro and Gilbert, 1990). The carrageenans with the ability to gel have been used to improve the texture of cottage cheese. Further, carrageenans were found to bind casein micelles; thus, more of the miLk proteins previously lost in the whey during cheese production were captured by the carrageenan. The yield and protein-content of the cheeses were greatly increased. At 1000 ppm, kappa and iota carrageenan increased cottage cheese curd yield by approximately 15% to 20%, respectively. The bitterness that results from calcium fortification of cottage cheese by the addition of calcium salts such as lactates and citrates, appears to be masked when 10% to 30% of the cheese is replaced with a 1.5% carrageenan solution. Other carrageenans in the lambda family, because of their ability to provide firmness without gelling, are used in low-fat cheeses to mimic the textural aspects of high-fat cheeses (Brummel and Lee, 1990). In dairy desserts and puddings, carrageenans are used in conjunction with low levels of starch to control the viscosity and texture of the final products after they have been subjected to the ultra-high temperatures required during processing. The carrageenans diminish syneresis, which frequently occurs in manufactured products containing starches, making them undesirable. In addition, when carrageenans are used in conjunction with starches, lower proportions of the starches are required to produce the desired texture, and thus the final product has fewer calories (Descamps et al., 1986). In the manufacture of flavored milk drinks (eg chocolate, strawberry), carrageenans are used as a stabilizer which prevents the separation and settling of the flavoring agents (Lobban and Wynne, 1981).
Use of carrageenans as binders and stabilizers has also escalated in the meat-processing industry, for fish, poultry, and meat products such as patties and sausages (Lobban and Wynne,1981). The increasing consumer demand for low-fat meat products has prompted the development of low-fat hamburgers such as the McLean Deluxe marketed by the McDonald’s Corporation. Iota carrageenan freezes and thaws well, which makes it even more valuable to the low-fat meat products industry (Egbert et al., 1991).
Lambda carrageenans have been used as an alternative to the previously used sulfites, which are potentially harmful to asthmatics, to prevent enzymatic browning through oxidation of polyphenols in cut, uncooked, or unblanched fruits and vegetables or juices (Tong and Hicks, 19913. Neither lambda carrageenan nor citric acid alone prevents browning; however when used together they inhibit browning for up to 7 days. The viscous lambda carrageenans are also thought to form a thin coating over the fruit and vegetables, thereby preventing nonenzymatic browning, the Maillard reaction between sugars, amines, amino acids, peptides, or proteins (Tong and Hicks, 1991).
In general, carrageenans have been used for a myriad of reasons, in a multitude of food products. A selective listing is provided in Table 2.
Food Products Containing C.
Crispus or carrageenans
Ice Creams/Ice milks
Low fat cheeses
Cake and pie fillings/glazes
Low-calorie jams and jellies
Instant breakfast drinks
Low-fat processed meats–sausages,
Browning inhibiters (fresh
Carrageenan leaves (for home use as a
CARRAGEENANS IN THE COSMETICS INDUSTRY
The ability of carrageenans to absorb and relinquish high proportions of water is perhaps one of the most significant reasons for their use in the cosmetic industry. In sunscreens, carrageenans provide a stable gel base for screening agents, and as the water in the gel evaporates, there is the bonus of a pleasant, cooling sensation, and only a thin film of screening agents is left on the skin. Carrageenans, ability to emulsify and stabilize oil and water mixtures promotes their use in products such as creams, lotions, soaps, facial masks, and shaving foams that can be easily removed by rinsing with water. Easy removal with water also makes carrageenans ideal for use in hair-styling products.
In antiseptic products such as antigingivitis toothpastes and medicated antiacne creams, carrageenan gels have replaced the formerly used alginates because of their superior stability and ability to hold bacteriostatic agents. In deodorants, these bacteriostatic agents inhibit the growth of the bacteria causing an offensive odor (Guiry and Blunden, 1991).
CARRAGEENAN IN THE PHARMACEUTICAL INDUSTRY
The list of uses of C. crispus in the pharmaceutical industry is truly extensive, with the seaweed having long been used in cough syrups, lozenges, and in soothing treatments for chest and stomach ailments (Lobban and Wynne, 1981). However, the carrageenans and other extracts of C. Crispus are used in the pharmaceutical industry, which focuses on the thickening, emulsifying, and stabilizing abilities of carrageenans in relation to oil-in-water preparations. Nevertheless, other uses are found for the non-helix-forming carrageenans in soluble aspirin or for coatings that encase pills and capsules for ease in swallowing (Gordon-Mills, 1990).
More recent experimental uses of C. crispus center on the antipathogenic extracts of the seaweed. In the late 1970s, researchers speculated on the possible antibacterial/antiviral functions of the newly discovered seaweed extracts, Kainic and Domoic acids (Lobban and Wynne, 19813. Later research showed that the youngest tissues in new C. crispus growth produced these phenolic acids as a defense against bacterial and fungal attack (Lobban et al., 1985).
In addition to the ;previous pharmaceutical uses, kappa carrageenan beads have been used as a growth medium for the aerobic microorganism Penicillium chrysogenum, a major source of penicillin (Mussenden et al., 1991). The P. chrysogenum requires a medium that can provide a large enough surface area, moisture, and adequate access to oxygen to support rapid growth (Mussenden et al., 1991).
REGULATIONS AND PROCEDURES REGARDING EXTRACTION
Because C. crispus and its carrageenan and other extracts are ingredients in so many of-a variety of commonly used products throughout the world, it is of great concern to manufacturers and consumers that the raw seaweed be relatively free of harmful contaminants and toxins. Although wild populations of the seaweed are likely to be adulterated, especially where they are exposed to hospital or sewer effluents or industrial pollution, globally regulated and accepted processing generally removes impurities (Gordon-Mills, 1990; Nicklin and Miller, 1989).
Standardization and monitoring of processing are perhaps the only means of ensuring the safety and quality of seaweed derivatives that are incorporated into manufactured products (Anderson, 1992). The poorest quality of carrageenans are those referred to as “degraded”, and these are the lowmolecular-weight (approximately 20,000), low-viscosity products of acid hydrolysis of native (a mixture of kappa, lambda, and iota) carrageenans (Baker et al., 1986). In several experimental animals, degraded carrageenans have produced ulceration of the gastrointestinal tract (Baker et al., 1986). In general, carrageenans are marketed as blends of the kappa, lambda, and iota forms (approximate}y 500,000 molecular weight) that conform to specified minimum viscosity levels (Anderson, 1992). These regulations, however, have proved inadequate, in that some unscrupulous manufacturers blend enough high-quality, high-viscosity carrageenans with the poorquality, low-viscosity, degraded form, to meet specifications. Most of the global producers of carrageenans belong to an alliance that funds toxicological studies and testing, and they follow strict specifications regarding extraction procedures. Recently, however, regardless of protests by other world nations, the government of the Phillipines successfully lobbied to have their seaweed derivatives approved by the U.S. Food and Drug Administration, despite their neglect o f the alcoholic precipitation step for removal of soluble contaminant residues in their extraction procedures. The Filipino extraction process is cheaper and faster be cause there are fewer steps, meaning that their products can be sold cheaper and faster. No toxicological analyses were performed on the Filipino products before FDA approval, and outwardly there are na distinguishable differences between the products of the Phillipines and other world seaweed processors. Members of the global alliance of seaweed processors fear that any adverse reactions that occur cur from the use of the Filipino products may be associated with their products (Anderson, 1992).
THE EFFECTS OF DIETARY CARRAGEENANS
The wide usage of carrageenans in the food industry generates some concern over its potential negative effects on the nutritional and physiological health in man (Nicklin and Miller, 1989). The dairy and diet industries have capitalized on the characteristics of the carrageenans that allow them to alter texture, flavor, fat and caloric content of foods (Descamps, 1986), and to suspend proteins (Nicklin and Miller, 1989).
As carrageenans gain in popularity as food and pharmaceutical additives, they are incorporated into more products, and normal daily intakes especially for infants and dieters may increase far in excess of the-levels currently estimated at up to 2.5 grams. Immunological disorders (Nicklin and Miller, 1989), as well as gastrointestinal ulceration (Baker et al., 1986), colon cancer (Pintauro and Gilbert, 1990), and negative consequences on mineral balance (Schlemmer, 1989) are some of the potential adverse effects of extended consumption of sizable amounts of native and degraded carrageenans. Although there are recognized hazards of dietary carrageenans, there are also benefits such as decreased gastrointestinal tract transit time and decreased lumenal pressure due to bulking (de Saint Blanquat and Klein, 1984), and lower serum cholesterol (Shiau and Huang, 1987).
Immunocompetence has been shown to be compromised in experimental animals after extended dietary consumption of both native and degraded carrageenans. In earlier studies, only the smaller molecular weight (approximately 20,000) degraded carrageenans were thought to cross the intestinal barrier; however, it was later discovered that there is limited penetration by high-molecular-weight native carrageenans. Although the relatively small amounts of carrageenans crossing the intestinal mucosa may not cause acute toxicity, there may be some chronic repercussions. Carrageenans are biologically active molecules that may cause dose-dependent suppression of lymphocyte responsiveness, thus depressing humoral immunity against heterologous T-cell-dependent antigens. It has also been proposed that macrophages may suffer altered ability to produce immunostimulatory and inhibitory factors. The immunosimulatory factor has been identified as interleukin-1 (IL-1), and the inhibitory factor, although not yet identified, is thought to be a prostaglandin because of its mode of action in depressing humoral antibody production. Tn young animals that have relatively-permeable intestinal testinal epithelial barriers and not yet fully developed gut-associated lymyhoid tissue, there may be heightened risks to dietary exposure to carrageenans (Nicklin and Miller, 1989). Because a new market for carrageenans has been found in infant formulas (Pintauro and Gilbert, 1940), the threat to the immunity of infants through the extended use of these formulas should be monitored.
Carrageenans are also thought to affect immunity through their interactions with the complement system in a series of enzyrmatic proteins that are found in normal serum and that interact with each other and subsequently join the antigen-antibody complex. It is thought that the carrageenans precipitate the C1 component of the complement system and activate the elements of the complement system involved in antibody-mediated immune lysis, phagocytosis, opsonization, and anaphylaxis (Baker et al., 1986).
The immune responses to dietary carrageenans may be related to the gastrointestinal problems that are also associated with consumption of those seaweed extracts (Nicklin and Miller, 1989).
The key to gastrointestinal ulceration in response to dietary carrageenans appears to be their effect on intestinal macrophages. After carrageenan consumption, lysosomal enzyme release and macrophage necrosis were noted, succeeded by intestinal lining tissue damage and ulceration (Nicklin and Miller, 1989). Gastrointestinal ulceration may also be preceded by degradation of the mucins that protect the intestinal lining from ulceration and act as a barrier to pathogens and toxins (Shiau and Huang, 1987). Mucinase, an enzyme produced by colonic bacteria, is responsible for the degradation of mucins (Shiau and Huang, 1987). Deficiency of a nutrient such as vitamin C, which maintains connective tissue strength and prevents hemorrhagic tendencies in the gut, has also been found to exacerbate the ulceration that ensues from long-term carrageenan use in guinea pigs (Langman et al., 1985).
CANCER OF THE COLON
The relationship between carrageenans and colon cancer is one that involves the drug-metabolizing enzyme system (DMES) and the promotion of chemically initiated carcinogenesis, as well as intestinal mucosal cell proliferation. The DMES consists of enzymes in two phases: phase I consists of cytochrome P-450, and phase II includes glucuronosyl transferase and glutathione transferase. In the presence of carrageenans, the enzymes in phase I drug metabolism convert precarcinogens such as azoxymethane to their carcinogenic forms, but the phase II enzymes do not further transform the carcinogenic substances to less toxic conjugates.
A 5% ungraded carrageenan diet fed to rats also caused a significant increase in colonic thymidine kinase activity. Escalation in the activity of this enzyme is identified with the rapid colonic cell proliferation characteristic of colon cancer (Pintauro and Gilbert, 1990).
C. crispus is a relatively concentrated but insignificant dietary source of minerals such as Ca, Fe, P, K, Cu, and Zn (Table 2), since daily consumption is low. In addition, because seaweed is also high in dietary fiber, there was concern regarding its effect on endogenous mineral bioavailability. However, in vitro experiments conducted to investigate the binding of kappa carrageenan to Ca, Cu, and Zn showed that under the buffered conditions of the intestine, kappa carrageenan does not bind Ca, Cu, or Zn to any nutritionally significant level.
CARRAGEENANS IN A DIETARY FIBER ROLE
Dietary fiber has long been recognized for its ability to decrease gastrointestinal transit time and reduce the risk of diverticular disease (de Saint Blanquat and Klein, 1984), reduce the risk of colon cancer, and reduce serum cholesterol (Shiau and Huang, 1987). C. crispus, which contains 12.3% by weight dietary fiber which is entirely composed of noncellulosic polysaccharide (Holland et al., 1991), does not, however, perform all the beneficial functions of dietary fiber (Pintauro and Gilbert, 1990).
In research conducted in Taiwan, carrageenans were fed to rats at levels of 5%, 10%, and 15% of a basal diet, and the results were compared with the effects of a 5% cellulose and a fiber-free diet (Shiau and Huang, 1987). The serum cholesterol levels of the carrageenan-fed rats, at all three levels of carrageenan, were significantly lower than those of the fiber-free diet rats, but similar to those of the cellulose-fed rats. The 10% and 15% carrageenan diets produced no significantly greater effect on serum cholesterol than the 5% carrageenan diet, but higher levels of carrageenan did increase colonic mucinase activity, indicative of the degradation of the protective mucosal secretions.
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Dr. Fatma G. Huffman is professor and director of graduate prograrns in the Deparhnent of Dietetics and Nutrition, College of Health, Florida International University. She has served on the faculty at Turkegee University and Howard University. Her research interests include mineral bioavailability from plant products. Correspondence can be addressed to Florida International University Deparhnent of Dietetics and Nutrition, University Park, FL 33199
Zara C. Shah received her M.S. degree from Howard University in Washington D.C. She has been accepted to the Ph.D. program at Florida International University. She has worked with Dr. Huffman to study the effects of carrageenan on rat lipid profile.
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