Effects of Varied Omega-3 Fatty Acid Supplementation on Postpartum Mental Health and the Association between Prenatal Erythrocyte Omega-3 Fatty Acid Levels and Postpartum Mental Health

We investigated the postpartum mental health of women who had consumed perilla oil or fish oil containing various omega-3 fatty acids for 12 weeks starting in mid-pregnancy. The association between fatty acids in maternal erythrocytes and mental health risk factors was also examined. Healthy Japanese primiparas in mid-pregnancy (gestational weeks 18-25) were randomly divided into two groups and consumed approximately 2.0 g/day of omega-3 fatty acids in either perilla oil (the ALA dose was 2.4 g/day) or fish oil (the EPA + DHA dose was 1.7 g/day) for 12 weeks. Maternal mental health was assessed using the Edinburgh Postnatal Depression Scale (EPDS) as the primary measure and the Mother-to-Infant Bonding Scale (MIBS) as the secondary measure. Data from an observational study were used as a historical control. Maternal blood, cord blood, and colostrum samples were collected for fatty acid composition analysis. In addition, completers of the observational studies were enrolled in a case-control study, wherein logistic regression analysis was performed to examine the association between maternal fatty acids and EPDS score. The proportion of participants with a high EPDS score (≥9) was significantly lower in the perilla oil group (12.0%, p = 0.044) but not in the fish oil group (22.3%, p = 0.882) compared with the historical control (21.6%), while the proportions between the former groups also tended to be lower (p = 0.059). No marked effect of omega-3 fatty acid intake was observed from the MIBS results. In the case-control study of the historical control, high levels of α-linolenic acid in maternal erythrocytes were associated with an EPDS score of <9 (odds ratio of 0.23, 95% confidence interval: 0.06, 0.84, p = 0.018 for trend). The results of this study suggest that consumption of α-linolenic acid during pregnancy may stabilize postpartum mental health.

Effects of different n-6/n-3 polyunsaturated fatty acids ratios on lipid metabolism in patients with hyperlipidemia: a randomized controlled clinical trial

Background and aims

Intake of n-3 polyunsaturated fatty acids (PUFA) is helpful for cardiometabolic health. It improves lipid metabolism, and increasing n-3 PUFA is often considered beneficial. However, the role of n-6/n-3 in the regulation of lipid metabolism has been much debated. Therefore, this study was performed on the effect of different proportions of n-6/n-3 diet on lipid metabolism, and quality of life in patients with hyperlipidemia, aiming to explore appropriate proportions of n-6/n-3 to provide the theoretical basis for the development and application of nutritional blended oil in the future.

Methods

These 75 participants were randomized and assigned into three groups, which received dietary oil with high n-6/n-3 PUFA ratios (HP group: n-6/n-3 = 7.5/1), dietary oil with middle n-6/n-3 PUFA ratios (MP group: n-6/n-3 = 2.5/1) or low n-6/n-3 PUFA ratios (LP group: n-6/n-3 = 1/2.5). All patients received dietary guidance and health education were monitored for hyperlipidemia. Anthropometric, lipid and blood glucose parameters and quality of life were assessed at baseline and 60 days after intervention.

Result

After 60 days, high-density lipoprotein cholesterol (HDL-c) level was increased (p = 0.029) and Total cholesterol (TC) level was decreased (p = 0.003) in the MP group. In the LP group, TC level was decreased (p = 0.001), TG level was decreased (p = 0.001), but HDL-c level was not significantly increased. At the end of intervention, quality of life' score was improved in both MP and LP groups (p = 0.037).

Conclusion

Decreasing the intake of edible oil n-6/n-3 ratio can improve blood lipids and quality of life. This is significant for the prevention of cardiovascular disease (CVD). It is also essential to note that an excessive reduction of the n-6/n-3 ratio does not further improve the blood lipid metabolism. In addition, the application of perilla oil in nutritional blended oil has particular significance.

Clinical trial registration

https://www.chictr.org.cn/indexEN.html, identifier ChiCTR-2300068198.

Perilla Pomace, a By-product of Oil Extraction, Is Rich in Nutrients and Can Favorably Modulate Lipid Metabolism in Sprague-Dawley Rats

Perilla pomace, a by-product of oil extraction, is rich in nutrients, such as proteins, but it has not been used for purposes other than livestock feeding. The aim of this study was to determine how perilla pomace modulates glucose and lipid metabolism in Sprague-Dawley rats. Dried perilla pomace was added to diet at a concentration of 16%. One experimental group was administered perilla oil equivalent to that in the perilla pomace. After four weeks, the animals were euthanized, and biochemical parameters were measured. Two experiments were conducted using a low-fat (7% by weight) and a high-fat (21% by weight) diet. Regardless of the level of fat in the diets, no differences in food intake were found among the groups. In the low-fat diet-fed rats (Experiment 1), epididymal adipose tissue weight was slightly, but not significantly, lower in perilla pomace-fed rats than in those fed the control diet. Hepatic triglyceride and cholesterol levels were significantly reduced by perilla pomace compared to those in the control group. Serum lipid profiles (triglycerides and cholesterol) were similar to those in the liver, without statistically significant differences. Perilla pomace significantly diminished hepatic fatty acid synthase (FAS) activity. In high-fat diet-fed rats (Experiment 2), pomace did not significantly lower epididymal adipose tissue weight. Hepatic cholesterol levels were lower in rats on the perilla oil than in control rats. The activity of hepatic enzymes involved in fat oxidation was significantly higher in rats fed the perilla pomace than in those fed the control diet. Collectively, these results show that perilla pomace favorably modulates fat metabolism, and the specific effects depend on the fat content in the diet.

Herbal Leaves Can Suppress Oxidation of Perilla Oil

Perilla oil is a valuable food source of α-linolenic acids. However, its high reactivity with oxygen shortens its shelf-life after opening. This study investigated the antioxidative profiles of 15 plant materials, including herbs, and examined methods to suppress the oxidation of perilla oil using these plant materials. These plant materials had wide ranges of phenolic, carotenoid, and chlorophyll contents. They exhibit radical scavenging activities and suppress lipid peroxidation, which show highly positive correlations with the phenolic contents. Dipping most of the plant materials examined in perilla oil suppressed its oxidation, and the peroxide values of the oil mixtures indicated a negative correlation with the carotenoid and chlorophyll contents of the plant materials. The leaves of Angelica, Astragalus, and Thyme herbs exhibited the same effect as that of ascorbyl palmitate, which was used as a positive control after 8 wk of incubation in the dark. The suppression of lipid peroxidation was found to be related to the herbal contents of carotenoids and chlorophylls, rather than phenols. Hence, herbal leaves can suppress the oxidation of perilla oil in the dark. The oxidation of n-3 polyunsaturated fatty acids could be suppressed effectively by utilizing plant materials with abundant carotenoids and chlorophylls.

Molecular Mechanism of Antioxidant and Anti-Inflammatory Effects of Omega-3 Fatty Acids in Perilla Seed Oil and Rosmarinic Acid Rich Fraction Extracted from Perilla Seed Meal on TNF-α Induced A549 Lung Adenocarcinoma Cells

Industrially, after the removal of oil from perilla seeds (PS) by screw-type compression, the large quantities of residual perilla seed meal (PSM) becomes non-valuable waste. Therefore, to increase the health value and price of PS and PSM, we focused on the biological effects of perilla seed oil (PSO) and rosmarinic acid-rich fraction (RA-RF) extracted from PSM for their role in preventing oxidative stress and inflammation caused by TNF-α exposure in an A549 lung adenocarcinoma culture model. The A549 cells were pretreated with PSO or RA-RF and followed by TNF-α treatment. We found that PSO and RA-RF were not toxic to TNF-α-induced A549 cells. Both extracts significantly decreased the generation of reactive oxygen species (ROS) in this cell line. The mRNA expression levels of IL-1β, IL-6, IL-8, TNF-α, and COX-2 were significantly decreased by the treatment of PSO and RA-RF. The Western blot indicated that the expression of MnSOD, FOXO1, and NF-κB and phosphorylation of JNK were also significantly diminished by PSO and RA-RF treatment. The results demonstrated that PSO and RA-RF act as antioxidants to scavenge TNF-α induced ROS levels, resulting in decreased the expression of MnSOD, FOXO1, NF-κB and JNK signaling pathway in a human lung cell culture exposed to TNF-α.

Partial Replacement of Dietary Fat with Polyunsaturated Fatty Acids Attenuates the Lipopolysaccharide-Induced Hepatic Inflammation in Sprague-Dawley Rats Fed a High-Fat Diet

In this study, we investigated whether the partial replacement of dietary fat with polyunsaturated fatty acids (PUFAs) ameliorated the lipopolysaccharide (LPS)-induced hepatic inflammation in rats fed a high-fat diet. Male Sprague-Dawley rats were divided into three groups and provided each of the following diets: (1) high-fat diet (HFD), (2) HFD with perilla oil (PO), and (3) HFD with corn oil (CO). After 12 weeks of dietary intervention, the rats were intraperitoneally injected with LPS (5 mg/kg) from Escherichia coli O55:B5 or phosphate-buffered saline (PBS). Following LPS stimulation, serum insulin levels were increased, while PO and CO lowered the serum levels of glucose and insulin. In the liver, LPS increased the triglyceride levels, while PO and CO alleviated the LPS-induced hepatic triglyceride accumulation. In the LPS injected rats, the mRNA expression of genes related to inflammation and endoplasmic reticulum (ER) stress was attenuated by PO and CO in the liver. Furthermore, hepatic levels of proteins involved in the nuclear factor kappa-light-chain-enhancer of activated B cells/mitogen-activated protein kinase pathways, antioxidant response, and ER stress were lowered by PO- and CO-replacement. Therefore, the partial replacement of dietary fat with PUFAs alleviates LPS-induced hepatic inflammation during HFD consumption, which may decrease metabolic abnormalities.

Effect of nanoemulsion particle size on the bioavailability and bioactivity of perilla oil in rats

The aim of this study was to investigate the bioavailability and bioactivity of perilla (Perilla frutescens) oil nanoemulsions prepared at different homogenization pressures by measuring the weight, fatty acid profile, and antioxidant and anti-inflammatory properties in rats. The high-pressure homogenization significantly reduced the particle size of perilla oil nanoemulsions and enhanced their stability, and the minimum particle size was 293.87 ± 6.55 nm at 120 MPa. There was an increase in the weight and fatty acid levels in the plasma and liver of test group rats. The highest glutathione (GSH) and the lowest malondialdehyde (MDA) levels of 18.76 ± 10.51 mg GSH/g prot and 20.27 ± 2.46 nmol/mg prot, respectively, were recorded in rats administrated perilla oil nanoemulsions prepared at 120 MPa. However, there was no significant difference in superoxide dismutase activity (SOD) between the groups. The interferon-gamma (IL-γ), interleukin-1 beta (IL-1β), IL-6 (interleukin-6), and IL-8 (interleukin-8) levels in the test groups were lower than those in the blank and control groups at 8 hr after lipopolysaccharide injection. The IL-1β, IL-6, and IL-8 levels were 49.52 ± 14.06, 90.13 ± 6.04, and 419.71 ± 32.03 ng/L, respectively, in rats treated with perilla oil nanoemulsions prepared at 120 MPa. Both perilla oil and its nanoemulsions decreased estradiol levels and damaged the ovaries. Overall, our findings show that the test nanoemulsions enhanced the bioavailability of perilla oil, which resulted in enhanced antioxidant and anti-inflammatory responses; thus, we provide a new approach to deliver perilla oil. PRACTICAL APPLICATION: Nanoemulsions can be used to deliver drugs and bioactive compounds, and perilla oil nanoemulsions can be used in healthcare products and beverage industries.

Lipase catalysis of α-linolenic acid-rich medium- and long-chain triacylglycerols from perilla oil and medium-chain triacylglycerols with reduced by-products

BACKGROUND

Medium- and long- chain triacylglycerols (MLCTs) are functional structural lipids that can provide the human body with essential fatty acids and a faster energy supply. This study aimed to prepare MLCTs rich in α-linolenic by enzymatic interesterification of perilla oil and medium-chain triacylglycerols (MCTs), catalyzed by Lipozyme RM IM, Lipozyme TL IM, Lipozyme 435, and Novozyme 435 respectively.

RESULTS

The effects of lipase loading, concentration of MCTs, reaction temperature, and reaction time on the yield of MLCTs were investigated. It was found that the reaction achieved more than a 70% yield of MLCTs in triacylglycerols under the conditions of 400 g kg^-1 MCTs and 60 g kg^-1 lipase loading after equilibrium. A novel two-stage deodorization was also applied to purify the interesterification products. The triacylglycerols reach over 97% purity in the products with significant removal (P < 0.05) of the free fatty acids, and the trans fatty acids were strictly controlled at below 1%. There was more than 40% α-linolenic in the purified products, with long-chain fatty acids mostly occupying the desired sn-2 position in acylglycerols, which are more active in hydrolysis.

CONCLUSION

A series of novel α-linolenic acid-rich medium- and long-chain triacylglycerols was prepared. Under appropriate reaction conditions, the yield of MLCTs in triacylglycerols was above 70%. A novel two-stage deodorization can be used to promote the elimination of free fatty acids and limit the generation of trans fatty acids. © 2020 Society of Chemical Industry.

Twelve-month Studies on Perilla Oil Intake in Japanese Adults-Possible Supplement for Mental Health

Perilla oil (PO), rich in α-linolenic acid (LNA, C18:3, ω-3), is increasingly alleged to have numerous health benefits in humans. However, the current reports detailing the effects of PO on human mental health are not adequate. Therefore, in the current investigation we compared the effects of PO or placebo treatment on the mental condition of healthy adult Japanese volunteers. At baseline and after 12 months of treatment, mental health condition was assessed using the Zung Self-Rating Depression Scale (SDS) and Apathy Scale, and serum biochemical parameters were determined. From baseline to 12 months of intervention, both SDS depression and apathy scores improved significantly in the PO-administered group. Compared to those of control group, serum norepinephrine and serotonin levels after 12 months decreased in the PO-administered group. The enhanced mental state observed in PO-subjects was accompanied by LNA level increases in erythrocyte plasma membranes. Our data demonstrate that PO intake enhances blood LNA levels and may maintain healthy mental conditions in adult subjects.

Fatty acid composition and quality properties of chicken sausage formulated with pre-emulsified perilla-canola oil as an animal fat replacer

The potential use of an oil in water (o/w) emulsion made from perilla and canola oil in chicken sausage as an animal fat replacer was assessed. The (o/w) emulsion was made from 50% (wt/wt) perilla-canola oil mixture in a 30:70 ratio, 3.20% (wt/wt) polyglycerol polyricinoleate, 4.48% (wt/wt) soy protein isolate, 14% (wt/wt) inulin, and 28.32% (wt/wt) water. The sausages were manufactured with 60% (wt/wt) ground chicken breast, 20% (wt/wt) fat (beef tallow as a control), and 20% (wt/wt) ice water. Full replacement of animal fat with a perilla-canola oil (o/w) emulsion reduced the fat content and estimated calories but increased the moisture, protein, ash, and carbohydrate content. The proportion of α-linolenic acid (C18:3n3) was increased when animal fat was replaced with either a perilla-canola oil mixture or pre-emulsified perilla-canola oil, resulting in a lower n6 to n3 polyunsaturated fatty acid ratio than the control. The perilla-canola oil (o/w) emulsion improved emulsion stability and minimized cooking loss during sausage manufacturing. Higher L* value (lightness) and whiteness were observed in the sausages formulated with the perilla-canola oil mixture, followed by the pre-emulsified perilla-canola oil and the control. The perilla-canola oil (o/w) emulsion also increased the hardness but maintained an acceptable appearance, flavor, and overall impression similar to the control. The shelf life could be extended by vacuum packing and storing the cooked sausages formulated with a perilla-canola oil (o/w) emulsion for 30 D at 2 ± 1°C. Pre-emulsified perilla-canola oil could be used to replace animal fat in reduced-fat chicken sausage manufacture.

A Second Derivative Fourier-Transform Infrared Spectroscopy Method to Discriminate Perilla Oil Authenticity

The aim of this study was to discriminate the authenticity of perilla oils distributed in Korea using their Fourier-Transform infrared spectroscopy (FT-IR) spectra with attenuated total reflectance accessory. By using orthogonal projections for latent structures discriminant analysis (OPLS-DA) technique, the =C-H cis-double bond, -C-H asymmetric and -C-H symmetric stretching are determined to be the best variables for discriminating the perilla oil authenticity. Comparing the integral and the second derivative methods between authentic and adulterated perilla oil samples, the most obvious and significant differences among the three variables is =C-H cis-double bond stretching. The procedure for applying the second derivative range of variables found in authentic perilla oil samples correctly discriminated between the adulterated samples of perilla oils with soybean oils and/or corn oils added at concentrations of ≥ 5 vol%. These results showed that the second derivative FT-IR analysis can be used as a simple and alternative method for discriminating the authenticity of perilla oil.

Perilla Oil Supplementation Improves Hypertriglyceridemia and Gut Dysbiosis in Diabetic KKAy Mice

SCOPE

The aim of this study is to examine whether perilla oil supplementation improves glucolipid metabolism and modulates gut microbiota in diabetic KKAy mice.

METHODS AND RESULTS

The successfully established diabetic KKAy mice are randomized into four groups: diabetic model (DM), low-dose perilla oil (LPO), middle-dose perilla oil (MPO), and high-dose perilla oil (HPO). C57BL/6J mice are fed a chow diet as normal control (NC). At the end of 12 weeks, mice are euthanized and glucolipid indications are analyzed. Gut microbiota analysis is carried out based on the sequencing results on V4 region of 16S rRNA. Although serum glucose, insulin, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, abundance-based coverage estimator, and shannon are unchanged, serum triglyceride significantly decreases in LPO compared with DM. The histopathological changes of hepatocellular macrovesicular steatosis and adipocyte hypertrophy are ameliorated by perilla oil supplementation. Blautia is significantly decreased in LPO, MPO, and HPO, compared with DM. Nonmetric multidimensional scaling analysis shows NC and LPO are relatively coherent.

CONCLUSION

These findings indicate that dietary supplementation with perilla oil can improve hypertriglyceridemia and gut dysbiosis in diabetic KKAy mice, which can be associated with potential benefits to human health.

Formula Optimization of a Perilla-canola Oil (O/W) Emulsion and Its Potential Application as an Animal Fat Replacer in Meat Emulsion

The formulation of an oil/water (o/w) emulsion made up of a mixture of perilla oil and canola oil (30/70 w/w) was optimized using a response surface methodology to find a replacement for animal fat in an emulsion-type meat product. A 12 run Plackett-Burman design (PBD) was applied to screen the effect of potential ingredients in the (o/w) emulsion, including polyglycerol polyricinoleate (PGPR), fish gelatin, soy protein isolate (SPI), sodium caseinate, carrageenan (CR), inulin (IN) and sodium tripolyphosphate. The PBD showed that SPI, CR and IN showed promise but required further optimization, and other ingredients did not affect the technological properties of the (o/w) emulsion. The PBD also showed that PGPR played a critical role in inhibiting an emulsion break. The level of PGPR was then fixed at 3.2% (w/w total emulsion) for an optimization study. A central composite design (CCD) was applied to optimize the addition levels of SPI, CR or IN in an (o/w) emulsion and to observe their effects on emulsion stability, cooking loss and the textural properties of a cooked meat emulsion. Significant interactions between SPI and CR increased the cooking loss in the meat emulsion. In contrast, IN showed interactions with SPI leading to a reduction in cooking loss. Thus, CR was also removed from the formulation. After optimization, the level of SPI (4.48% w/w) and IN (14% w/w) was validated, leading to a perilla-canola oil (o/w) emulsion with the ability to replace animal fat in an emulsion-type meat products.

Effect of 6-gingerol on physicochemical properties of grass carp (Ctenopharyngodon idellus) surimi fortified with perilla oil during refrigerated storage

BACKGROUND

Surimi is produced from deboned fish muscle through washing to remove blood, lipids, sarcoplasmic proteins and other impurities. There is an increasing interest in the fortification of surimi with ω-3 polyunsaturated fatty acids because of their health benefits. However, lipid oxidation should be considered as an important factor during storage. Hence, in this study, the quality properties and oxidative stability of surimi fortified with 30 g kg^-1 perilla oil (PO), or 5 g kg^-1 6-gingerol (GI) or their combination (PO+GI) was investigated.

RESULTS

Perilla oil significantly improved whiteness of surimi gel, but negatively influenced its gel strength, water holding capacity (WHC) and texture. However, there was no significant difference in texture properties among GI, PO+GI and control groups. During the whole storage period, GI and PO+GI groups had higher gel strength and WHC than control and PO groups. Moreover, lower thiobarbituric acid reactive substances (TBARS), total volatile basic nitrogen (TVB-N), carbonyl content and total plate count (TPC) were observed in GI group compared with other groups.

CONCLUSION

Perilla oil and 6-gingerol could be applied together to effectively fortify surimi qualities. Additionally, 6-gingerol could prevent lipid and protein oxidation and microbial growth of surimi during refrigerated storage. © 2017 Society of Chemical Industry.

Anti-atherosclerotic effects of perilla oil in rabbits fed a high-cholesterol diet

Anti-atherosclerosis effects of perilla oil were investigated, in comparison with lovastatin, in rabbits fed a high-cholesterol diet (HCD). Hypercholesterolemia was induced in rabbits by feeding the HCD containing 0.5% cholesterol and 1% corn oil, and perilla oil (0.1 or 0.3%) was added to the diet containing 0.5% cholesterol for 10 weeks. HCD greatly increased blood total cholesterol and low-density lipoproteins, and caused thick atheromatous plaques, covering 74% of the aortic wall. Hyper-cholesterolemia also induced lipid accumulation in the liver and kidneys, leading to lipid peroxidation. Perilla oil not only attenuated hypercholesterolemia and atheroma formation, but also reduced fat accumulation and lipid peroxidation in hepatic and renal tissues. The results indicate that perilla oil prevents atherosclerosis and fatty liver by controlling lipid metabolism, and that it could be the first choice oil to improve diet-induced metabolic syndrome.

Double emulsions to improve frankfurter lipid content: impact of perilla oil and pork backfat

BACKGROUND

The technology involving the use of water-in-oil-in-water double emulsions (DEs) offers an interesting approach to improve the fat content of foods. With this aim, the effect on frankfurter properties of replacing pork backfat with two different DEs prepared using perilla oil and pork backfat as lipid phases was assessed. This strategy was compared with straightforward addition of the lipid source and addition by means of an oil-in-water (O/W) emulsion.

RESULTS

As compared with all-pork-fat frankfurters, the ones with perilla oil had a higher proportion of n-3 polyunsaturated fatty acids. Reduced-fat frankfurters had similar water- and fat-binding properties irrespective of the lipid source or the technological strategy used to incorporate it. Moreover, the oil source but not its mode of incorporation determined the oxidation levels of frankfurters. In reduced-fat samples, except in the case of frankfurters formulated with a perilla oil-in-water emulsion, hardness was unaffected either by the type of fat or by its mode of incorporation. The replacement of pork backfat by perilla oil reduced the overall acceptability of products when perilla oil was added by means of the O/W emulsion and DE approaches.

CONCLUSION

This technology is suitable for labelling meat products with specific nutritional and health claims.

Perilla oil improves blood flow through inhibition of platelet aggregation and thrombus formation

The inhibitory effects of perilla oil on the platelet aggregation in vitro and thrombosis in vivo were investigated in comparison with aspirin, a well-known blood flow enhancer. Rabbit platelet-rich plasma was incubated with perilla oil and aggregation inducers collagen or thrombin, and the platelet aggregation rate was analyzed. Perilla oil significantly inhibited both the collagen- and thrombin-induced platelet aggregations, in which the thromboxane B₂ formation from collagen-activated platelets were reduced in a concentration-dependent manner. Rats were administered once daily by gavage with perilla oil for 1 week, carotid arterial thrombosis was induced by applying 35% FeCl₃-soaked filter paper for 10 min, and the blood flow was monitored with a laser Doppler probe. Perilla oil delayed the FeCl₃-induced arterial occlusion in a dose-dependent manner, doubling the occlusion time at 0.5 mL/kg. In addition, a high dose (2 mL/kg) of perilla oil greatly prevented the occlusion, comparable to the effect of aspirin (30 mg/kg). The results indicate that perilla oil inhibit platelet aggregation by blocking thromboxane formation, and thereby delay thrombosis following oxidative arterial wall injury. Therefore, it is proposed that perilla oil could be a good candidate without adverse effects for the improvement of blood flow.

Inhibitory effect of dietary perilla oil rich in the n-3 polyunsaturated fatty acid alpha-linolenic acid on colon carcinogenesis in rats

The inhibitory effect of dietary perilla oil rich in the n-3 polyunsaturated fatty acid alpha-linolenic acid against colon carcinogenesis was investigated in rats. Four groups of 26 F344 rats each received an intrarectal dose of 2 mg of N-methyl-N-nitrosourea 3 times a week for 2 weeks, and received a diet containing 12% perilla oil, 6% or 12% safflower oil (rich in the n-6 polyunsaturated fatty acid linoleic acid), or 12% palm oil (rich in saturated and monounsaturated fatty acids). At week 35, the incidence of colon cancer was significantly lower in perilla oil-fed rats than in other dietary groups; 19% vs. 46%, 56% and 58%. When examined at week 10, the concentration of fecal bile acids, known to be tumor promoters, was not significantly different among the dietary groups, and the intrarectal deoxycholic acid-induced colonic mucosal ornithine decarboxylase activity, a marker of tumor promotion, was significantly lower in perilla oil-fed group than in other groups. The serum and colonic mucosal fatty acid compositions and the blood plasma prostaglandin E2 level directly reflected the fatty acid composition of each dietary fat. The results suggest that the anti-tumor-promoting effect of dietary perilla oil was a result of a decreased sensitivity of colonic mucosa to tumor promoters arising from the altered fatty acid composition in membrane phospholipid of colonic epithelial cells, and was not a consequence of a decrease of promoters such as bile acids.