19-22 September 2007, Tanka Village Resort, Villasimius, Italy
Conjugated Linoleic Acid (CLA)
Conjugated Linoleic Acid is a general term used to describe a group of trans fatty acids identified by their very distinct structures. The different forms (or isomers) of CLA can be recognised by the positions of the double bonds they contain.
Some forms of Conjugated Linoleic Acid are naturally produced in the conversion of linoleic acid (an essential fatty acid) to other fatty acids in ruminant animals (such as cows and sheep), through the action of bacteria in the rumen.
Food products produced from ruminant animals such as meat and dairy foods naturally contain CLA with the predominant form being the cis-9 trans-11 isomer (c9, t11 CLA).
CLA can also be produced artificially and supplements usually contain an equal mixture of the cis-9 trans-11 isomer and the trans-10 cis-12 isomer (t10, c12 CLA).
Estimates of total CLA intake by humans in western countries are of the order of 50-500mg/day. More than 90% is consumed in the form of c9, t11 CLA from meat and dairy sources and it has been connected with numerous different health benefits.
Since the discovery of several potential health benefits of CLA, published research has grown steadily. Hundreds of papers are produced each year and it is becoming increasingly complex to keep track of new data and evaluate new findings.
The purpose of the conference was therefore to update attendees on current CLA research, to discuss the direction of future work and to stimulate ideas for new research by providing plenary lectures on key issues where CLA may play a role.
The first presentation of the conference was a plenary lecture given by Prof Paul Trayhurn from the Division of Metabolic and Cellular Medicine, University of Liverpool, UK on current findings in the study of obesity and the metabolic syndrome. Prof Trayhurn discussed the rising problem of obesity and its effects on health. He then described the various functions of white fat (which makes up a large percentage of body composition in obese individuals) including its role in fat storage. More recently discovered roles of white fat include controlling the release of factors such as hormones and substances which control inflammation within the body. As a result of the activities of fat tissue, obese individuals tend to experience long term, low levels of inflammation in the body and this inflammation is increasingly considered to be linked to the development of the metabolic syndrome and other disorders linked with obesity. Prof Trayhurn suggested that targeting the inflammation associated with obesity may be key to future treatment of obesity related disease. Some scientific research has linked CLA with potential anti inflammatory effects; therefore further researchinto links between CLA and inflammatory markers in obesity is required.
Dr Michael McIntosh from the University of North Carolina, Greensboro, USA gave the next presentation on the topic of CLA and adiposity. He began by discussing research which suggests that supplements containing an equal mixture of c9, t11 CLA and t10, c12 CLA or t10, c12 CLA alone may have the capacity to reduce levels of body fat both in animal and human studies. The mechanisms responsible for these effects are unclear, however recent studies suggest that the t10, c12 isomer may induce complex and specific changes which prevent the fat cells functioning correctly, resulting in reduced levels of body fat. Interestingly when the c9, t11 CLA isomer was compared separately it appeared to have completely opposite effects to the t10, c12 isomer. Further research is required to understand these mechanisms better.
Following this was a short communication given by Dr Paula Lopes from Faculdade de Medicina Veterinaria –CIISA, Portugal. She began by discussing how over the past 2 decades extensive research has indicated that mixtures of different CLA isomers could potentially provide numerous beneficial effects for human health including protection against cancer, atherosclerosis diabetes and obesity. The particular study she presented aimed to further investigate the possible role of CLA in protection against obesity. This was done by studying the number and size of fat cells in rats fed on a diet high in saturated fat (typical of western societies) and supplemented with c9, t11 and t10, c12 CLA isomers. The results of the study found that final levels of body fat were not significantly affected by either form of CLA. However, the c9, t11 CLA isomer was found to increase the size of fat cells whilst the CLA mixture did not affect the size or number of fat cells. Dr Lopes and her team concluded that the 2 forms of CLA used in this study have differing (possibly opposing) effects on fat tissue and that further research is needed to give insight into the potential roles that CLA may play in preventing obesity in the western world.
The CLA and obesity theme was continued by Dr Elizabeth Tarling from University of Nottingham, UK who followed on from this with a short communication on the effect of t10, c12 CLA on fat tissue. She began by discussing the considerable evidence available from studies in mice to suggest that t10; c12 CLA has a profound effect on reducing body fat. In fact, it now appears that the t10, c12 CLA isomer is specifically responsible for reducing body fat and possibly even increasing muscle growth. However, many of these studies use levels of CLA supplementation that would be unachievable in humans and evidence from studies in other species is much less convincing. In this study the effect of dietary t10, c12 CLA on fat tissue was studied in the Golden Syrian hamster –a model which appears to bear a closer resemblance to humans than the mouse model. The t10, c12 CLA isomer was found to significantly reduce fat tissue regardless of background diet however, when the c9, t11 isomer was used, no effect was seen. Interestingly, although levels of body fat were reduced this was accompanied by increased deposition of fat in the liver and increased levels of fats in the bloodstream which can increase the risk of developing cardiovascular disease.
Dr Frank Dunshea from the University of Melbourne Australia gave the next presentation on the biological effects of CLA on fat tissue. His recent research has focused on the grower-finisher pig model since newborn pigs are born with very little fat but undergo a huge amount of fat deposition, particularly around the belly, as they grow older providing a useful model to study. Dietary CLA, composed of a mixture of isomers but predominantly the c9, t11 isomer was found to significantly reduce deposition of fat under the skin. Levels of blood fats were also found to be increased in growing pigs after consumption of the CLA mixture. Interestingly deposition of fat within the muscle was found to be increased. These findings have important implications for the meat industry since increased intramuscular fat deposition is important for good quality meat.
The focus of the morning changed slightly with the next presentation given by Dr Gabriel Fernandes, University of Texas Health Centre at San Antonio, USA. Dr Fernandes talked about the potential role of CLA in protecting against loss of muscle and bone mineral during aging He began his presentation by discussing how aging, along with physical inactivity, is associated with increased risk of conditions such as obesity, cardiovascular diseases, osteoporosis and loss of muscle mass and strength (sarcopenia). CLA is suggested to have many positive effects on the body but some data suggest that certain isomers may have a positive influence on the deterioration of body composition and bone health experienced with aging. Humans begin to lose more bone than they replace after the age of 35 years and this bone loss increases dramatically following the onset of the menopause in women. In order to investigate possible effects of CLA on post menopausal bone losses, mice (reflecting post menopausal conditions) were given a CLA supplemented diet. The results found that the CLA supplemented mice experienced significantly less bone loss than mice who did not receive CLA. Dr Fernandes concluded by saying that these results suggest that incorporating CLA into the diet, specifically during aging, may help to protect against age related bone loss and loss of muscle mass and strength. However, further research is required to test this protective effect in an aging human population.
Dr Yeonhwa Park from the University of Massachusetts, USA was next to take the podium and discussed the effects of CLA on bone mass and obesity. She began by discussing how CLA has been shown to have a number of beneficial effects, particularly reducing body fat whilst enhancing bone mass. However, the results of studies have been inconsistent. Based upon previous research, Dr Park and her team suggested that CLA may enhance bone mass when supplemented with additional calcium. When t10, c12 CLA was supplemented with additional calcium a significant improvement in bone mass was recorded however when CLA was supplemented without additional calcium, no improvement was seen. The c9, t11 CLA isomer was found to have no effect. Dr Park then went on to discuss studies investigating the effects of CLA on body fat. Supplementation of the t10, c12 CLA isomer in animal models tends to give a fairly consistent and significant reduction in body fat, however studies in humans have reported farless dramatic results. For this reason, Dr Park and her team decided to investigate the effect of other conjugated fatty acids on body fat compared with CLA. CAN (conjugated nonadecadienoic acid C19:2) has previously been reported to reduce body fat more effectively than CLA and was therefore chosen to be compared directly against CLA in a study of mice. The results of the study found CAN to be five times more effective than CLA in reducing body fat. Dr Park therefore concluded that CAN may have different biological activities to CLA which require further investigation.
Dr P Degrace from Faculte des Sciences Gabriel, Dijon, France gave the final presentation of the first session. This was a short communication on the effect of t10, c12 CLA on transport of liver fats. He began by discussing how several studies have shown that mice fed a diet supplemented with t10, c12 CLA may experience reduced deposition of body fat but appear to develop an increased deposition of fat in the liver instead. Dr Degrace’s research has since focussed on understanding the molecular mechanisms responsible and he suggested that the effect may be due to increased production of proteins and enzymes in the liver, involved in uptake of fats, which are usually poorly expressed. Dr Degrace concluded that the data suggest that fats not stored in body fat may be able to modify gene expression in the liver to increase the capacity of this organ to take up blood fats.
The next session began with a presentation from Dr Josep Bassaganya Virginia Tech, Blacksburg, USA on CLA and inflammation. Scientific studies suggest that CLA may have the capacity to reduce inflammation; however the mechanisms responsible for this effect remain unclear. Dr Bassaganya and team investigated potential mechanisms involving a specialised receptor known as PPARγ since previous studies have suggested that CLA may naturally activate it. Dr Bassaganya and team specifically investigated the effect of CLA on PPARγ in colitis and inflammation-induced colorectal cancer in mice. This was done by breeding mice without the PPARγ gene in order to compare differences in mice with the gene. When CLA was supplemented in mice with the gene it was found to reduce production of inflammatory markers and improve colitis, however loss of the PPARγ receptor prevented the beneficial effects of CLA. The study provided molecular evidence to suggest that CLA can improve colitis and inflammation induced colorectal cancer through a mechanism involving PPARγ.
Dr Roger McLeod from Dalhousie University, Canada gave the next presentation on the relationship between CLA and atherosclerosis. He began by discussing how the potential for CLA to affect atherosclerosis in animals has been the focus of much research for over a decade. However to date, the results of studies investigating whether CLA can improve signs of atherosclerosis, such as abnormal blood fats and damage to blood vessels, remain inconsistent. The presentation examined evidence for and against a role for CLA in atherosclerosis, with focus on studies using Apo-E deficient mice (who develop atherosclerotic lesions on their blood vessels very quickly). Dr Mcleod concluded that dietary supplementation with CLA does not affect advanced atherosclerosis nor improve levels of blood fats. In addition, the t10, c12 CLA isomer was found to cause unwanted changes in fat cell function and breakdown of liver fats which were partially alleviated by combination with the c9, t11 CLA isomer.
The next presentation was a short communication by Dr Doris Bell from Global R & D, Cognis GmbH, Monheim, Germany on the effect of commercial CLA on blood-vessel-surface function and the metabolic syndrome. Dr Bell began by describing how CLA has been suggested to have several beneficial effects on health in animal studies but that results in human studies have been inconsistent. It has been suggested that this may be due to differences in the type of dietary fat used as a comparison against CLA. The aim of the study presented was to assess the effect of CLA supplementation in men on blood vessel surface function and risk factors for the metabolic syndrome, compared to 3 different control fats. These fats included native safflower oil, oxidised safflower oil and native olive oil. The results found that factors including body weight, blood pressure and fasting blood glucose were significantly improved in the group receiving CLA supplements compared with other groups. Dr Bell concluded that the results suggest that CLA induces beneficial metabolic effects in men receiving CLA supplements and may improve blood vessel surface function.
Following this was a presentation on the health effects of common trans fatty acids by Dr Andrew Salter from the University of Nottingham, UK. Dr Salter began by discussing how trans fatty acids have received much attention in recent years due to suggested negative effects on human health. Data from population studies show that trans fat intake in general can increase risk of cardiovascular disease, however recent evidence suggests that intake of ruminant trans fats (including CLA) are not associated with increased risk. This hypothesis was tested in male golden Syrian hamsters by feeding a diet similar in fat composition to the typical “western” diet. This was then supplemented with partially hydrogenated vegetable oil (suggested to be responsible for encouraging the development of raised cholesterol, which is a known risk factor for cardiovascular disease), elaidic acid or vaccenic acid (common trans fats found in cows milk and hydrogenated vegetable oils) for a period of 4 weeks. The results found that both vaccenic and elaidic acids reduced the concentration of potentially harmful lipoproteins compared with the partially hydrogenated vegetable oil. Dr Salter concluded by saying that the results suggest that components of partially hydrogenated vegetable oil other than vaccenic or elaidic acid must be responsible for it’s cholesterol raising properties. These findings contradict current recommendations which suggest avoidance of all dietary trans fats.
The subject of the next presentation, given by Dr Filippo Macaluso from the University of Palermo, Italy was the effect of CLA supplementation on the body during endurance training. He began by discussing how fat supplements especially CLA are becoming increasingly popular as ergogenic aids amongst endurance athletes. In order to investigate this further, Dr Macaluso and team investigated the effects of CLA supplementation on body weight, muscle growth, peripheral blood composition and bone marrow in young, healthy, endurance trained mice. CLA supplementation did not result in a reduction in body weight but did induce an increase in muscle size in trained mice. However CLA supplementation was also found to reduce numbers of white blood cells in the peripheral blood of trained mice. These results suggest that CLA may improve performance of endurance athletes by increasing muscle size but at the same time may reduce numbers of white blood cells needed for a strong immune system. Dr Macaluso concluded that despite positive increases in muscle size claimed by pharmaceutical companies, endurance athletes should avoid CLA supplementation as it seems to intensify stresses on the body caused by exhaustive exercise.
The second day of the conference began with a plenary lecture from Dr Dale Bauman from Cornell University, Ithaca, USA, on the production of CLA in ruminants. He began his presentation by discussing the history behind the discovery of CLA. Discovery of conjugated double bonds in summer milk fat in the 1930’s began the story. It is now known that ruminant fat contains many different forms of CLA produced as intermediates in the conversion of linoleic acid to other fatty acids by bacteria in the rumen. The c9, t11 isomer (also known as rumenic acid) is the major form of CLA in ruminant fat contributing 75-90% of total CLA. Consumption of rumenic acid has been suggested to reduce the risk of cancer and atherosclerosis (and hence cardiovascular disease) according to the results of animal studies. It is therefore the target of much interest as a functional food component for humans. The amount of rumenic acid in dairy foods can be significantly increased by altering the diet of cattle used to produce them and/or selecting cattle that naturally produce higher levels of rumenic acid and breeding from them. Following on from this Dr Bauman then discussed how studies have also found that certain forms of CLA have the capacity to alter the production of fat in milk. The t-10, c-12 CLA isomer has been most extensively studied and found to effectively reduce milk fat content. Other isomers including t-9, c-11, and c-10, t-12 CLA have also shown similar effects. The t-10 c-12 CLA isomer has also been connected to helping to reduce body fat in animal studies. However, interestingly, studies have shown that a diet containing approximately 0.5-2% CLA is needed to see a reduction in body fat in animal models but only 0.01-0.05% to inhibit production of milk fat. Overall, CLA isomers may have the potential for use in functional dairy foods to benefit human health and offer exciting opportunities for agricultural application.
The focus of the conference then moved onto the production of CLA, with a presentation by Dr John Wallace from the Rowett Research Institute, Aberdeen, Scotland. He began by describing how the rumen makes up a large proportion of the dairy cow and that digestion occurs through a complex process involving microbes. CLA’s are formed by ruminal bacteria as intermediates in the conversion of linoleic acid to other fatty acids in the rumen. Polyunsaturated fatty acids such as linoleic acid are toxic to bacteria in the rumen. The conversion (or biohydrogenation) process is therefore necessary in order for the ruminal bacteria to escape their effects, survive and multiply and the c9, t11 CLA isomer, also known as rumenic acid, is formed most actively by ruminal bacteria. More recent studies have aimed to find out which bacteria are involved in the production of the t10, c12 isomer of CLA however this remains unclear at present. Dr Wallace concluded that the results of studies imply that isomers of CLA are synthesised not only by different organisms in the rumen but also different mechanisms. He also noted that new research suggests that in the future it may be possible to manipulate conversion of fatty acids in the rumen through the use of plant extracts in feeds.
The next presentation was given by Dr Kevin Shingfield from MTT Agrifood Research, Finland, on the CLA content of meat and milk. Dr Shingfield began by re-iterating the fact that foods derived from ruminants are the principle source of CLA in the human diet. C9, t11 is the major isomer of CLA accounting for between 60-89% of total dietary CLA intake. Ruminant derived foods only contain trace amounts of the t10, c12 CLA isomer unless supplements (protected from the activities of the rumen) of CLA are fed. Dr Shingfield then went on to discuss how nutrition is the major factor influencing levels of CLA in milk and can be effectively enhanced by altering the diet of the animal. For example, feeding diets with additional plant and fish oils provides a source of vaccenic acid which can be converted to rumenic acid (c9, t11 CLA) by ruminal bacteria. However the results are very variable and depend upon the amount given, the form of oil added to the diet and the composition of the basic diet. In addition he mentioned the importance of preventing the conversion of vaccenic acid to other less useful products, such as other isomers of CLA or stearic acid when trying to increase levels of c9, t11 CLA. Sustainable production remains challenging but if successful it is possible to enhance the CLA concentration by as much as 10 fold. Dr Shingfield concluded that nutritional and management strategies can therefore be used to enhance the CLA content of ruminant milk and meat. This highlights the important role that ruminant derived foods play in increasing the intake of CLA in humans.
The bacterial production of CLA was further discussed in the next presentation given by Dr Alan Hennessy from TEAGASC, Biotechnology Centre, Cork, Ireland on CLA production by bifidobacteria. Dr Hennessy began by describing the importance of specific bacterial cultures such as dairy starter and probiotic cultures in the synthesis of CLA and their extreme importance to the dairy industry. Bifidobacteria, (a commonly used type of probiotic bacteria) commonly associated with benefits such as improved gastrointestinal health, have the ability to produce significant quantities of CLA. The aim of the presented study was to develop a fermented milk product enriched in CLA to be used as a functional food for the promotion of human health. A range of different supplements were studied which either acted by promoting bifidobacteria growth and hence CLA production, or directly stimulated the bacteria to produce CLA. Seven supplements were identified as being useful for the production of the c-9, t-11 CLA isomer however supplementation with a combination of sodium acetate, yeast extract and inulin was most successful.
The focus of the conference then moved on to the effect of CLA on the immune system with a presentation from Prof Philip Calder from The University of Southampton, UK. He began by explaining how the immune system is the host’s response to infection, injury, trauma etc and involves the movement of helpful cells to target areas. Significant variations in immune responses among healthy individuals exist as a result of differences in age, sex, hormones, diet and lifestyle factors etc. Studies investigating the influence of CLA on the immune system have found significant benefits in animal studies but evidence in human studies is much less convincing. Studies do show that human immune cells incorporate CLA when intake is high in the diet but most studies show little or no effect on immune function. Some studies have reported that CLA may have the ability to suppress the function of immune cells when given in high doses, however others have contradicted these by showing a modest increase in function. Prof Calder concluded by suggesting that there remains a need to conduct well designed studies of individual CLA isomers in order to determine the full role of CLA on immunity.
The host of the CLA conference Dr Sebastiano Banni from Universita degli Studi di Cagliari, Italy gave the next presentation on the effect of CLA on use of fat in the body. He began by discussing how at least 12 different forms of CLA have been found to be incorporated into animal and human tissues. As mentioned previously in other presentations he described how the main known biological activities of CLA involve two major isomers, c9, t11 and t10, c12 CLA with the former naturally present in milk and dairy products and the latter to have a stronger impact in fat deposition and metabolism. More recently, studies have shown that specific CLA isomers may influence other fat soluble molecules such as eicosanoids (signalling molecules) and lipid soluble vitamins such as vitamin A (retinol) through various mechanisms. Dr Banni then went on to describe how the particular structure of CLA strongly influences its distribution in body tissues i.e. CLA is more concentrated in peritoneal fat and mammary fat than other types of fat. He concluded that the biological activities of CLA depend upon the specific tissue in which it is found and that understanding how CLA isomers exert their effects on fat use in the body will help to clarify the conditions which promote the more positive biological effects of CLA and minimize the negative effects.
The interaction of CLA with other nutrients was then discussed by Dr Michihiro Sugano from Kyushu University; Fukuoka, Japan. He began by describing how specific isomers of CLA have been shown to significantly reduce body fat in animal studies and to some extent in human studies –but with less consistent and dramatic results. However in order to see an effect, large quantities of CLA must be consumed over a long period of time. Dr Sugano and team therefore aimed to identify other nutrients which might have the capacity to enhance the effect of CLA. Studies have found that CLA not only stimulates the breakdown of fat, but also fat synthesis (or formation), which limits its ability to reduce overall fat mass. Therefore finding substances that stimulate fat breakdown or inhibit fat synthesis may enhance its effect. Soy protein was tested as a potential candidate and was found to help to reduce body fat mass and improve levels of blood fats when supplemented with CLA in rat studies. Fish oil was also tested but found to have no additional effect on reducing body fat. Sesamin, a chemical compound (or lignan) abundant in sesame seeds, was tested as it is known to enhance fat breakdown and suppress fat synthesis. However no additional effect on top of CLA was seen on reducing body fat mass. Interestingly, when sesamin and soybean protein were combined together with CLA, a modest reduction in body fat was seen. Dr Sugano therefore concluded that the body fat reducing potential of CLA has the capacity to be readily increased by manipulation of the diet. He also suggested that multiple combinations of dietary factors may be more effective than one single factor.
The next presentation was a short communication by Dr Anke Jaudszuz from the Institute of Nutrition, Germany on prevention of asthma by c9, t11 CLA. She began by describing how milk consumption from early childhood has been found to reduce the risk of allergic sensitisation and onset of bronchial asthma. In addition c9, t11 CLA (the predominant form of CLA in milk) has been suggested to provide anti-inflammatory effects through a mechanism involving a receptor known as PPARγ, which has previously been shown to be closely involved in reducing airway inflammation. In her study, Dr Jaudszuz investigated whether the c9, t11 CLA isomer could inhibit airway inflammation in mice. The results found that mice fed the c9, t11 isomer developed significantly fewer signs of airway inflammation compared with controls through a pathway involving the PPARγ receptor. Dr Jaudszuz concluded that the c9, t11 CLA isomer was –at least in part –responsible for the protective effect of milk consumption of the development of allergic airway disease. She also suggested that in the future, oral intervention with c9, t11 CLA might be an attractive novel strategy for the prevention and treatment of asthma related conditions.
The final presentation of the day was a short communication by Dr Susana Martins from Faculdade de Medicina Veterinaria –CIISA, Portugal on the estimation of daily intake of CLA isomers in the Portuguese population. She began by discussing the potential protective effects of CLA and that despite favourable results in animal studies, beneficial effects in humans have yet to be fully established. As a result, studies to estimate the consumption of CLA in the human population are very important. The objective of Dr Martins study was the refore to estimate intakes of CLA isomers in the Portuguese population. The CLA content of the most regularly consumed Portuguese CLA-rich products was determined, and the average daily intake was estimated based upon consumption habits of these foods. The Portuguese intake was estimated as being fairly low compared to the intakes in other studies and the c9, t11 isomer was predominantly consumed, with the t10, c12 isomer coming mainly from supplements. Dr Martins concluded that estimation of CLA intake by the Portuguese population provides valuable information for understanding the specific effects of the different CLA isomers on human health.
The final day of the conference began with a plenary lecture on dietary long chain fatty acids and their activities given by Dr Robert Chapkin from University Health Science Center, Texas, USA. He began by discussing recent research on EPA and DHA (long chain Omega 3 fatty acids found in fish) and the conclusive evidence for health benefits in both animal and human studies. Omega 3 fatty acids have been suggested to protect against conditions such as cancer by inducing changes in cells which stop them from growing and multiplying. Other studies also show that Omega 3 fatty acids may help to reduce inflammation and suppress conditions such as irritable bowel disease. Studies investigating CLA suggest that specific isomers may also have the capacity to reduce the risk of cancer and evidence also exists to show that CLA may have the ability to both increase inflammation and decrease inflammation depending upon the cell type and the form of CLA used. However evidence for CLA’s health benefits is less available and consistent than omega 3 fatty acids. Dr Chapkin then went on to describe how as part of an ongoing commitment to provide consumers with innovative healthy products, food companies are now trying to incorporate these fatty acids into a wide range of novel foods in order to provide greater consumption of these bioactive compounds. However further research is needed to better understand the way in which these fatty acids impact human health and the mechanisms responsible for their effects.
The focus of the conference then moved onto the role of CLA in the development of cancer with a presentation by Dr Klaus Whale from The Robert Gordon University, Aberdeen, Scotland, UK on the effect of CLA on cancerous cells. He began by describing how CLA’s have been suggested to have anti-cancer effects since the 1980’s. Since then, numerous studies in animals have demonstrated the ability of CLA to help to prevent cancer and the proliferation of unwanted cells, and a number of different mechanisms have been proposed to explain these potential effects. The various different effects seen depend upon the CLA isomer, concentration and cell type, however many studies have found that a mixture of CLA isomers confer the best effect rather than any one specific isomer. Some studies have also found that certain CLA isomers may have the capacity to improve the effectiveness of standard cancer treatments which could have huge implications for future therapies. Dr Kent Erickson from University of California-Davis, USA gave the next presentation on the role of CLA in the development of tumours and spread of cancer. He began by describing how CLA has been suggested to have potential protective effects against the development of primary tumours. In fact studies have actually shown that CLA can alter tumour growth by reducing cell proliferation and inducing cell death in breast, colon, prostate and gastric cancers. Dr Erickson then went on to discuss how most failures in breast cancer treatment are due to metastasis (or spreading) of cancers from the initial site. Interestingly studies in mice have shown that mice fed diets containing CLA had reduced size and number of secondary cancers in the lungs. It is currently believed that stem cells in breast tumours may be responsible for the development of breast cancers, however current therapies do not target stem cells and therefore tumours have the ability to re-grow. Terminal end buds are major sites for stem cells and studies have shown that CLA can reduce terminal end buds. Therefore a potential target for CLA in the future may be the cancer stem cell. Dr Erickson concluded by saying that although results from animal and cell line studies indicate a beneficial effect of CLA in breast cancer, few studies in humans to date have clearly shown a link between dietary CLA and decreased breast cancer risk. However no investigations have used CLA supplementation in well controlled long term studies. These studies therefore need to be conducted in order to determine the full role of CLA in cancer prevention.
The topic of CLA and cancer was then continued with a short communication by Dr Isabel O’Reilly from Dublin City University, Ireland on CLA and breast cancer. She began by discussing how breast cancer is the most common cancer among women and the risk has increased from one in every ten women to one in every eight women since the 1970’s. The role of fat in cancer developmentis unclear but omega 3 fatty acids have been suggested to reduce risk in some animal models and fish oils have previously been shown to enhance the action of some current breast cancer drugs. The role of CLA also remains unclear, but studies in animal models of breast cancer suggest that specific isomers may have the ability to reduce cancer development through various mechanisms. Based on this information Dr O’Reilly and team decided to investigate the potential effect of CLA on drug resistant cancer cells. A mixture of CLA isomers and two single isomers c9, t11 CLA and t10, c12 CLA were investigated for their effects on the anti cancer drug Doxorubicin and CLA was found to enhance the effects of the anti cancer drug. The mixture of isomers was found to be most effective followed by the t10, c12 isomer and then the c9, t11 isomer. Dr O’Reilly concluded her presentation by saying that future work aims to determine whether CLA could be used as a potential therapeutic or co therapeutic agent for the treatment of cancer.
The final presentation of the conference was a short communication given by Dr Giuliana Muzio from Diapartimento di Medicina de Oncologia Sperimentale, Turin, Italy on anti cancer effects of CLA. He began by describing how CLA has been demonstrated to possess anticancer properties. In addition it has been shown to control apoptosis (programmed cell death) in several types of cancer cells. Dr Muzio and colleagues aimed to investigate the effect of CLA on human liver cancer cells. The results of the study found that CLA reduced growth and viability of liver cancer cells with the effects steadily increasing after 24hrs and even more after 48 hrs. The suggested mechanism behind this effect was increased apoptosis due to increased expression of several different genes.
The conference provided an extremely useful update on recent developments in the field of CLA research. At this stage it still seems that CLA may have the capacity to influence a broad range of different aspects of health and food production. However the precise roles of the different isomers remain unclear and at times appear to have conflicting effects. A great deal of further research is required to determine the true effects of CLA and its specific isomers.