Pharm 100 - Lesson E.4
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Definition Food additives
Food additives are substances that are added to food to improve appearance, texture, and storage of food. This is the classical definition, but a broader definition would include additives to improve nutritive value, e.g. vitamins and minerals. There are two broad classes of food additives.
types of additives
The intentional additives would be consistent with the definition stated above. Unintentionaladditives are those that are added inadvertently as a result of the growing, manufacturing and storageprocesses. These unintentional additives are often termed contaminants and the amount that is presentin food is limited by regulations. On occasion compounds are added intentionally eg. Melamine tomilk.
Additives General Comments
Additives are convenience substances and are not necessarily required. Thus, the criteria usedfor safety evaluation must be very stringent as the entire population may be exposed. Most of the food additives could be eliminated, but his would result in a dramatic change in our lifestyles. Supermarkets would be reduced to one-fifth their current size. There would not be pancake mix, cak mix, or any products containing flour. The consumer would buy flour, baking powder, eggs and milkand use these ingredients to prepare a myriad of food products. Oh, for the good old days.
food additive limitations
- The efficacy of a food additive is easily determined, but there are a number of problems assessing toxicity. The risk/benefit ratio of additives must be carefully determined. The techniques used to determine risk/benefit is to study the toxicity in animals and then extrapolate the results tohumans. The limitations are:
- 1. Most food additives do not demonstrate toxicity at low concentrations. Toxicity is often difficult to detect at concentrations that are added to food. It may be difficult to detect, but this does not imply a lack of toxicity. It is prudent to consider that additives are administered to animals for one or two years, and that humans can be exposed for 80 years. Risk estimates must be made ona lifetime of exposure.
- 2. Additives are usually tested in animals and the highest no-effect dose is calculated and the acceptable human exposure limit or dose is then taken as 1/100 or 1/1000 of the maximum noeffect dose in animals. The assumption made is that studying high doses in animals will mimic low-dose, lifetime exposure in humans. Fortunately, the assumptions tend to over-estimate the actual risk.
- 3. While most toxicities can be serious, the key question asked with most food additives is what is the carcinogenic (cause cancer) and mutagenic (cause mutations which are inherited) potential ofthe compound. Food additives are usually carefully tested for carcinogenicity and mutagenicity,and if a positive response is observed in any test system, the compound is usually not allowed asa food additive. This concept may be excessively stringent, but not when we consider that the entire population is exposed to the additive
Some of the principles concerning food additives which have been adopted by the World HealthOrganization are:
- 1. Use of additives is justified if they enhance or maintain the quality or acceptability of food. While this statement has merit, it does not address the risk/benefit assessment of the additive. Ifthe risk is high, then no level of benefit would warrant use of the agent.
- 2. Additives should be used only in quantities sufficient to obtain stated ends.\
- 3. Additives should be pure. Additives often contain impurities, and in some cases the toxicity hasbeen associated with the impurity. Thus, toxicological evaluation of the impurity must beconducted.
- 4. Toxicological evaluation of additives should be undertaken. Society has used a number of additives for centuries. Should these compounds be exempt from toxicological assessment? Ifan agent has been used for 200 years, is it necessarily without risk? A reasonable position wouldbe to gather the available information on a specific compound and utilize that data to determine potential risk and the need for further study.
- 5. Special groups should be considered, i.e. those who may be expected to eat a large amount of aparticular substance. Risk assessments are determined on the concept that individuals exhibitsimilar behaviour or dietary habits. In other words, we do not eat ten bags of potato chips eachday. Unfortunately, some individuals do eat ten bags of potato chips each day and the riskassessments must be such as to include these individuals. A good example of this concept occurred in the early 1970's. There were a number of deaths due to cardiac causes in individualswith no apparent risk factors for heart disease. The causative factor was found to be cobaltchloride, a compound which inhibited the heart muscles from functioning. Cobalt chloride wasadded to beer to control the head (foam) on the glass of beer. Risk assessments determined thatindividuals would need to consume 24 beers every day for long periods of time to receive a toxicdose of cobalt chloride. Unfortunately, some individuals do and some of these succumbed to theeffects of cobalt chloride. The agent is no longer added to beer.
- This class of additives includes substances such as spices, flavouring agents, essence of smoke,synthetic flavours, etc.
- Flavouring agents pose the largest task, since it is difficult to evaluate such a large number ofsubstances. There are four to five thousand of these substances in use and most have not beenadequately tested, but are approved due to the experience obtained over years of use.
- Studies have shown that very few have demonstrated toxicities. In one or two instances,excessive use of some of these agents may lead to toxicities, e.g. hot pepper corns may beassociated with some forms of cancers of the mouth.
- This class of additives includes flavour enhancers, e.g. monosodium glutamate (MSG). MSGcauses a tightening of muscles in the face and neck, accompanied by headache, nausea andgiddiness. Some individuals are more sensitive to MSG than others and should avoid consumingthe additive.
- In the last decade, we have seen a large increase in simulated flavours used in confections, e.g.bacon-flavoured potato chips. These additives are mixtures of artificial flavours
- Colouring agents are organic dye stuffs. Most are well evaluated, but one is never sure of the carcinogenic potential. It is fortunate that colouring agents are used in small amounts as theymay have one of the greatest potentials for toxicity among the food additives.
- It has been claimed that since food colouring agents can be considered organic dye stuffs derived from coal tar, and since coal tar is a carcinogen, all artificial food colours are carcinogens andonly colouring agents from natural sources should be used. This statement has no scientificvalidity; the source of a compound does not predict its toxicity. Each compound must beassessed on its own merits.
- Colours are added to give food an appetizing appearance; studies have shown that food musthave an acceptable appearance for the average person to maintain an adequate diet.
- Allergic reactions have occurred to food colours. The most common reaction is to tartrazine, a yellow food colour. If an individual is allergic to aspirin, they will also be allergic to tartrazine.
- Canada allows only 10 food colours to be used, the U.S.A. – 11, and some countries allow muchmore, e.g. Denmark – 33. Canada has banned the use of Red Dye No. 2 as it produced cancers inexperimental animals when given in high doses. This dye is still used in the U.S.
3. Texture Agents
- This class of agents are added to improve or impart a specific texture to a product. Silicates areadded to flour and flour products to keep them free flowing. Emulsifying and thickening agents(gums, agar, alginates) are added to a number of frozen foods, e.g. ice cream and sherbet. Milkshakes contain a thickening agent.
- These substances are found in foods in relative high concentrations of up to 1-3% of the product. As a class, these agents possess little or no toxicity.
The use of agents to preserve the quality of food is one of the more rational uses of additives. It allows the delivery of food to distant destinations and ensures the appropriate quality of the food for the consumer. In most cases, the benefit outweighs the risk
Historically, sodium chloride was the first preservative used. It is still used today. It is effective as a preservative, especially when coupled with smoking or drying. Sodium chloride can be detrimental to individuals with cardiovascular and renal impairment. Excess sodium chloride isnot advisable for those on a low sodium diet.
Smoke is an age-old method of preserving food, mainly meat. It is also used to impart flavour tofood. The active ingredient is unknown and smoke is more effective if used with sodiumchloride (smoking and salting). The major concern of smoke is that some of the ingredients in charbroiled steak caused a higher incidence of tumours in rats than those fed a control diet. Itcan be concluded that natural smoke carries a small carcinogenic risk. Some of the currently used smoke flavouring products have had the carcinogens removed.
Sodium benzoate is added to food as it has antibacterial and fungistatic activity, thus preventing the spoilage of food. It is usually added in small amounts. There is no real known toxicity associated with sodium benzoate as it is rapidly metabolized and excreted in humans.
Parabens are derivatives of sodium benzoate and are used for the same purpose, and can beconsidered similar to sodium benzoate. These compounds can be found in a wide array of foodsas they are the major antibacterial and antifungal agents used as food additives.
Propionic acid and its salt
Propionic acid and its salts are used as preservatives. These compounds are more active antibacterials at lower pH values as they function as the free acid. Propionic acid and its derivatives are essentially non-toxic as propionic acid is part of normal metabolism.
Antibiotics would be the most effective antibacterial food additives. They are used in somecountries, but not in Canada. The most commonly used antibiotics are oxytetracycline and chlortetracycline. Canada does not permit the use of antibiotics as food additives as widespreaduse of antibiotics in foods would lead to the emergence of resistant strains of organisms and sensitization of individuals to the antibiotics.
Sugar is one of the earliest methods of food preservation. In syrups, the high sugar content will retard bacterial growth through osmotic effects. Very few organisms will survive in a syrup thatis 67% sugar. Sugar can be considered both a food and a food additive. Toxicity is usually not amajor problem
There is considerable controversy surrounding the use of nitrites in food. There has been attempts to reduce the use of nitrites. Sodium nitrite is added to meat for two reasons: (a) colour– NO2– + myoglobin ÷ nitrosomyoglobin (red in bacon and ham); and (b) it inhibits growth of Clostridium botulinum, thus is used as a preservative in prepared meats. Clostridium botulinum produces a toxin which leads to botulinum poisoning, a serious condition. Fortunately, only afew cases are reported each year. The adverse effects of sodium nitrite are: a decrease in bloodpressure, formation of methemoglobin (blood cannot carry oxygen) and nitrosamine formation. All nitrosoamines are known carcinogens. These nitrosamines are formed during cooking asdepicted in the equation below. A good case can be made for limiting the use of nitrites in food.
Sulphur dioxide (SO2) is used to prevent mould formation in wine. If wine consumption is high,then an individual may get SO2 toxicity; related to vitamin B1 deficiency. Good wine should nothave sulphur dioxide added.
- Antioxidants prevent the oxidation and thus rancidity and discolouration of foods. They improve storage and quality of the product. There are several types of antioxidants.
- Water soluble antioxidants are added to reduce the oxidation of carbohydrates, e.g. browning offruit, etc. The agents most commonly used are ascorbic and citric acids. A commonly used product is Fruit Fresh. Ascorbic acid has no toxicity at low concentrations. If in take is excessive, diarrhea can occur and there is an increase in the incidence of kidney stones.
- Lipid soluble antioxidants prevent fats from becoming rancid, i.e. oxidizing. They are used in alarge number of foods, e.g. potato chips, cookies, cakes, frozen foods, and indeed any foodcontaining fats. Two commonly used compounds are butylated hydroxyanisole and butylatedhydroxytoluene (BHT). BHT has no demonstrable toxic effect at the levels usually employed(0.01%), but at higher levels (> 0.2% of diet) it can cause fatty liver, impairment of growth, andother biochemical changes (impairment of phospholipid synthesis). Some of the antioxidantshave been shown to be hepatotoxins (cause liver damage). Tocopherols (vitamin E) are also usedan antioxidants. They are less effective than butylated hydroxytoluene, but possess a lowertoxicity risk.
The purpose of sequestrants is to bind metals. Metals, especially iron, can initiate the oxidationof fats, leading to rancidity. Ethylene diaminotetraacetic acid (EDTA) is used extensively, as arephosphates and citrates. These compounds also preserve colour. No known toxicity.
- Three agents have been used in addition to sugar – cyclamates, saccharin and aspartame.
- Rats, when given saccharin in large amounts (5-7.5% of diet), developed bladder tumours. While these studies were done at high dose, they demonstrated a potential for these agentsto cause cancer. Canada has restricted the use of saccharin. Prior to these studies, they werewidely used in confections and foods. The U.S.A. did not ban saccharin. In Canada, saccharin,as a single drug, is limited to pharmacies; intended for diabetics who cannot use sugar.
- Cyclamates and saccharin have been largely replaced by aspartame. Aspartame is a dipeptide(two amino acids) and the only toxicity of note associated with aspartame is that individuals witha condition known as phenylketouria cannot tolerate phenylalanine, one of the amino acids inaspartame. This is clearly stated on the label. Aspartame, weight for weight, has the same caloric value as sugar, but it is 200 times sweeter and is used in small amounts.
Conclusions on food additives
Food additives have become a part of our way of life. They are convenience substances, and forthe large part, could be eliminated if we were prepared to change our lifestyle. If we assume that the use of these agents will not be eliminated, it would be prudent to limit the intake of these substances. In most cases, the amount of additive in the food will not be harmful provided that the class of food isconsumed in moderation.
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