Heating garlic inhibits its ability to suppress 7, 12-dimethylbenz(a)anthracene-induced DNA adduct formation in rat mammary tissue

Antioxidant and Antiproliferative Activities of Several Garlic Forms

It is hypothesized that garlic, Allium sativum, might protect against oxidative stress that causes damage to cells and tissues leading to the development of various health conditions including cancer. However, it is not known whether garlic's potential anticancer benefits differ by form of garlic consumed. This study aimed to quantify and compare the in vitro antioxidant and antiproliferative activity of several garlic forms in water and alcohol extracts including fresh garlic, fresh garlic set aside, heated garlic, heated garlic set aside, garlic powder, black garlic, two commercially available garlic supplements. Antioxidant activity of different garlic forms were measured using three assays: DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) assay, superoxide assay, and hydroxyl assay. In vitro effects of garlic extracts were investigated against the most common lung cancer subtypes: H520, H1975, and A549 cell lines using the sulforhodamine B (SRB) assay. Among free radical scavenging assays, Garlicin®, a commercially available supplement, displayed high antioxidant activity in water and alcohol extracts (DPPH assay: 2.02 mg AAE (mg ascorbic acid equivalent)/g garlic and 3.53 mg AAE/g garlic, respectively; superoxide assay: 6.73 mg AAE/g garlic and 7.13 mg AAE/g garlic, respectively). In the hydroxyl assay, water extract of fresh garlic crushed and set aside for 10 min showed the highest antioxidant activity. Garlicin® alcohol extract and fresh garlic water extracts strongly inhibited the proliferation of H1975, A549 and H520 cells. Other forms of garlic including garlic powder and black garlic exhibited low antioxidant and antiproliferative activity. Our results demonstrate that the preparation and processing methods of garlic may lead to different antioxidant benefits.

Detoxification effects of phytonutrients against environmental toxicants and sharing of clinical experience on practical applications

According to the Food and Health Bureau and Trade and Industry Department of the Hong Kong Government, 90 % of the total food supply in Hong Kong was imported from the Mainland China. In addition, the hidden or illegal use of prohibited pesticides, food adulteration (e.g., using industrial salt in food processing, using gutter oil as cooking oil), and pollutions were periodically reported by the media. Excessive exposure to toxic heavy metals or persistent organic pollutants (POPs) from diet or environmental is inevitable amid industrialization and pollution. Understanding of the detoxification ability among nutrients in plant-based food (i.e., phytonutrients in green tea, onion, garlic, coriander, and turmeric) offers therapeutic and preventive effects against the poisoning effects due to these pollutants. Oxidative stress and pro-inflammatory actions are the common mechanisms for heavy metals or POPs toxicities, while phytonutrients counteracts these cellular insults by anti-oxidation, upregulation of anti-inflammatory pathways, and chelation.

Physiological Activities of Thiacremonone Produced in High Temperature and High Pressure Treated Garlic

To examine the possibility of using thiacremonone isolated from high-temperature-high-pressure treated garlic, this study investigated the physiological activities properties. The IC50 values of hydroxyl, superoxide, hydrogen peroxide, and nitric oxide radical scavenging activities of thiacremonone were 92.50, 65.05, 12.60, and 81.53 μg/mL, respectively. On the other hand, the activities of vitamin C were 104.93, 99.43, 42.42, and 122.64 μg/mL, and the activities of butylated hydroxyanisole were 37.22, 68.45, 22.47, and 40.54 μg/mL, respectively. The IC50 value of ACE inhibition activities of thiacremonone and captoprill were 0.265 and 0.036 μg/mL, respectively. The IC50 value of xanthine oxidase inhibition activities of thiacremonone and allopurinol were 39.430 and 9.346 μg/mL, respectively. The IC50 value of tyrosinase inhibition activities of thiacremonone and kojic acid were 101.931 and 65.648 μg/mL, respectively.

In vitro assessment of oxidative stress and apoptotic mechanisms of garlic extract in the treatment of acute promyelocytic leukemia

INTRODUCTION

Garlic supplementation in diet has been shown to be beneficial to cancer patients. Recently, its pharmacological role in the prevention and treatment of cancer has received increasing attention. However, the mechanisms by which garlic extract (GE) induces cytotoxicity, oxidative stress, and apoptosis in cancer cells remain largely unknown.

OBJECTIVE

The present study was designed to use HL-60 cells as a test model to evaluate whether or not GE-induced cytotoxicty and apoptosis in human leukemia (HL-60) cells is mediated through oxidative stress.

METHODS

Human leukemia (HL-60) cells were treated with different concentrations of GE for 12 hr. Cell survival was determined by MTT assay. The extent of oxidative cell/tissue damage was determined by measuring malondialdehyde (lipid peroxidation biomarker) concentrations by spectrophotometry. Cell apoptosis was measured by flow cytometry assessment (Annexin-V and caspase-3 assays) and agarose gel electrophoresis (DNA laddering assay).

RESULTS

Data obtained from the MTT assay indicated that GE significantly (p < 0.05) reduced the viability of HL-60 cells in a concentration-dependent manner. We detected a significant (p < 0.05) increase in malondialdehyde (MDA) concentrations in GE-treated HL-60 cells compared to the control. Flow cytometry data showed a strong concentration-response relationship between GE exposure and Annexin-V positive HL-60 cells. Similarly, a statistically significant and concentration-dependent increase (p <0.05) were recorded with regard to caspase-3 activity in HL-60 cells undergoing late apoptosis. These results were confirmed by data of DNA laddering assay showing a clear evidence of nucleosomal DNA fragmentation in GE-treated cells.

CONCLUSION

Our finding indicates that GE-induced cytotoxicity and apoptosis in HL-60 cells involve phosphatidylserine externalization, caspase-3 activation, and nucleosomal DNA fragmentation associated with the formation of MDA, a by-product of lipid peroxidation and biomarker of oxidative stress. At therapeutic concentrations, GE-induced cytotoxic and apoptotic effects in HL-60 cells is mediated by oxidative stress.

Diallyl sulfide inhibits murine WEHI-3 leukemia cells in BALB/c mice in vitro and in vivo

It is well documented that enhanced garlic (Allium sativum) consumption leads to decrease in the cancer incidences. Diallyl sulfide (DAS), one of the components of garlic, induces cytotoxicity and apoptosis in many cancer cell lines. The present studies are focused on the in vivo effects of DAS on leukemia WEHI-3 cells in the BALB/c mice. We examined the effects of DAS on the cytotoxicity of WEHI-3 cells and results indicated that DAS decreased the percentage of viable WEHI-3 cells and these effects are dose-dependent. We examined the effects of DAS on WEHI-3 in vivo and the results indicated that DAS decreased the percentage of Mac-3 and CD11b, indicating that the differentiation of the precursor of macrophage cells was inhibited. DAS stimulated the percentage of CD3 and CD19, indicating that the differentiation of the precursor of T and B cells promoted. The weights of liver and spleen indicated that DAS decreased the weight of these organs after being compared to the control groups. One of the major characteristic of WEHI-3 leukemia is the enlarged spleen in murine after intraperitoneal (i.p.) injection of WEHI-3 cells. In conclusion, DAS affects WEHI-3 cells both in vitro and in vivo.

Protective effects of garlic and silymarin on NDEA-induced rats hepatotoxicity

Background ­— The present study was conducted to investigate the chemopreventive effects of garlic extract and silymarin on N-nitrosodiethylamine (NDEA) and carbon tetrachloride (CCl₄)-induced hepatotoxicity in male albino rats. Methods and Results — Animals were pretreated with garlic, silymarin or both for one week prior to the injection of NDEA. Then animals received a single injection of NDEA followed by weekly subcutaneous injections of CCl₄ for 6 weeks. Oral administration was then continued along with the injection of CCl₄ for the duration of the experiment. Serum aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), hepatic lipid peroxidation (LPO), superoxide dismutase (SOD), reduced glutathione (GSH), glutathione-S-transferase (GST) and glutathione reductase (GSR) were measured. Injection of NDEA induced a significant elevation in serum AST, ALT and ALP. In the liver, NDEA increased oxidative stress through the increase in LPO and decrease in SOD, and GSH-dependent enzymes. Although administration of garlic or silymarin significantly reduced the liver toxicity, combined administration was more effective in preventing the development of hepatotoxicity. Conclusion — These novel findings suggest that silymarin and garlic have a synergistic effect, and could be used as hepatoprotective agents against hepatotoxicity.

Regulation of oxidative stress–mediated apoptosis by diallyl sulfide in DMBA-exposed Swiss mice

Diallyl sulfide, a sulfur-containing volatile compound present in garlic ( Allium sativum), exerts anticarcinogenic activity in various rodent tumor models. In the present study, apoptosis-inhibiting effects of diallyl sulfide against a carcinogenic polycyclic aromatic hydrocarbon, 7,12-dimethyl benz(a)anthracene (DMBA), in Swiss albino mice were observed. The animals were given either 250 μg/mouse or 500 μg/mouse of diallyl sulfide for 1 week after a single intragastric dose of 7,12-dimethyl benz(a)anthracene (50 mg/kg body weight). Results showed that diallyl sulfide supplementation effectively protects against 7,12-dimethyl benz(a)anthracene—induced oxidative stress, characterized by restored antioxidant enzyme levels (up to 64%) and lipid peroxidation (up to 25%). Flow cytometric analysis showed a reduction in apoptotic cell population in hypodiploid region in diallyl sulfide–supplemented animals. Inhibition of apoptosis was preceded by decrease in reactive oxygen species levels and restoration of mitochondrial transmembrane potential followed by decreased DNA fragmentation. In 7,12-dimethyl benz(a)anthracene–exposed animals, downregulation (~30%) of antiapoptotic Bcl-2 and upregulation (~60%) of pro-apoptotic Bax proteins were observed. These alterations were restored significantly by diallyl sulfide supplementation, indicating inhibition of apoptosis. Thus, these results show that diallyl sulfide provides protection against oxidative damage induced by 7,12-dimethyl benz(a)anthracene in mouse liver and may be an effective chemopreventive and therapeutic agent by modulating expression of cell-growth regulatory proteins.

Hypochlorous acid scavenging capacity of garlic

The ability of the following aqueous garlic extracts to scavenge hypochlorous acid (HOCl) was studied: (a) unheated extract of raw garlic (RG), (b) heated extract of raw garlic (HRG), (c) extract of boiled garlic cloves (BG) and (d) extract of microwave-treated garlic cloves (MG). The HOCl scavenging activity was evaluated following changes in the absorption spectrum of catalase (370-450 nm). RG, HRG and BG scavenged HOCl in a concentration-dependent way: the IC(50) (mg/mL) values for RG, HRG and BG were 0.339 +/- 0.028, 0.632 +/- 0.030 and 0.690 +/- 0.031, respectively. The HOCl scavenging ability of garlic was significantly decreased when garlic cloves or the extract of raw garlic were heated (BG and HRG, respectively); this scavenging ability was eliminated when garlic was subjected to microwave heating (MG). The IC(50) value for the reference compound, ascorbic acid, was 0.500 +/- 0.049 mg/mL. In summary, raw garlic concentration-dependently scavenged HOCl; this ability was eliminated in extracts of microwave-treated garlic cloves but not in heated extracts of raw garlic or extracts of boiled garlic cloves.

Anti-cancer activity of highly purified sulfur in immortalized and malignant human oral keratinocytes

Sulfur is commonly used in Asia as an herbal medicine to treat inflammation and cancer, and potent chemopreventive effects have been demonstrated in various in vivo and in vitro models for sulfur-containing compounds found in naturally occurring products. Here, we report the growth inhibitory and apoptosis-related effects of a newly developed highly purified sulfur (HPS) on immortalized human oral keratinocytes (IHOKs) and on oral cancer cells representing two stages of oral cancer (HN4, HN12) based on a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, Western blotting, cell cycle analysis, and nuclear staining. The purity of the sulfur preparation was verified by high-performance liquid chromatography. HPS inhibited the proliferation of immortalized and malignant oral keratinocytes in a dose- and time-dependent manner. FITC-annexin V staining, DNA fragmentation testing, and Hoechst 33258 staining revealed that HPS inhibited cell growth via apoptosis. HPS increased the sub-G1 cell cycle fraction, with decreased expression of cyclins D1, D2, and E and their activating partners cdk2, cdk4, and cdk6, and a concomitant induction of p53 and p21/WAF1. Furthermore, HPS treatment increased the cytosolic level of cytochrome c and resulted in caspase-3 activation; this effect was correlated with Bax up-regulation and Bcl-2 down-regulation. Thus, these data suggest that HPS is a potential candidate for anti-cancer therapy in oral cancer.

Biomarkers for diet and cancer prevention research: potentials and challenges

As cancer incidence is projected to increase for decades there is a need for effective preventive strategies. Fortunately, evidence continues to mount that altering dietary habits is an effective and cost-efficient approach for reducing cancer risk and for modifying the biological behavior of tumors. Predictive, validated and sensitive biomarkers, including those that reliably evaluate "intake" or exposure to a specific food or bioactive component, that assess one or more specific biological "effects" that are linked to cancer, and that effectively predict individual "susceptibility" as a function of nutrient-nutrient interactions and genetics, are fundamental to evaluating who will benefit most from dietary interventions. These biomarkers must be readily accessible, easily and reliably assayed, and predictive of a key process(es) involved in cancer. The response to a food is determined not only by the effective concentration of the bioactive food component(s) reaching the target tissue, but also by the amount of the target requiring modification. Thus, this threshold response to foods and their components will vary from individual to individual. The key to understanding a personalized response is a greater knowledge of nutrigenomics, proteomics and metabolomics.

Effect of heating on peroxynitrite scavenging capacity of garlic

The ability to scavenge peroxynitrite (ONOO(-)) was studied in the following aqueous garlic extracts: (a) unheated extract of garlic powder (GP), (b) heated extract of garlic powder (HGP), (c) unheated extract of raw garlic (RG), (d) heated extract of raw garlic (HRG), (e) extract of boiled garlic cloves (BG), (f) extract of microwave-treated garlic cloves (MG), and (g) extract of pickled garlic (PG). All the extracts scavenged ONOO(-) in a concentration-dependent way. IC(50) (mg/mL) values for each extract were 0.30+/-0.02 and 0.35+/-0.04 for GP and HGP, respectively; and 0.84+/-0.08, 0.59+/-0.04, 0.76+/-0.09, 1.71+/-0.19, and 1.45+/-0.07 for RG, HRG, BG, MG, and PG, respectively. The ONOO(-) scavenging capacity (IC(50) values) was not decreased in HGP (vs. GP, p>0.05) and in HRG and BG (p>0.05 vs. RG). In contrast, the ONOO(-) scavenging capacity decreased in MG and PG (vs. RG, p<0.001). The IC(50) values for the reference compounds nordihydroguiaretic acid and penicillamine were 1.1 and 4.5mug/mL. The heating before or after garlic cutting was unable to eliminate the capacity of the extracts to scavenge ONOO(-); this capacity was significantly decreased in PG and MG.

Effect of cooking on garlic (Allium sativum L.) antiplatelet activity and thiosulfinates content

The raw form of garlic and some of its preparations are widely recognized as antiplatelet agents that may contribute to the prevention of cardiovascular disease. Herein, we examined the in-vitro antiaggregatory activity (IVAA) of human blood platelets induced by extracts of garlic samples that were previously heated (in the form of crushed versus uncrushed cloves) using different cooking methods and intensities. The concentrations of allicin and pyruvate, two predictors of antiplatelet strength, were also monitored. Oven-heating at 200 degrees C or immersing in boiling water for 3 min or less did not affect the ability of garlic to inhibit platelet aggregation (as compared to raw garlic), whereas heating for 6 min completely suppressed IVAA in uncrushed, but not in previously crushed, samples. The latter samples had reduced, yet significant, antiplatelet activity. Prolonged incubation (more than 10 min) at these temperatures completely suppressed IVAA. Microwaved garlic had no effect on platelet aggregation. However, increasing the concentration of garlic juice in the aggregation reaction had a positive IVAA dose response in crushed, but not in uncrushed, microwaved samples. The addition of raw garlic juice to microwaved uncrushed garlic restored a full complement of antiplatelet activity that was completely lost without the garlic addition. Garlic-induced IVAA was always associated with allicin and pyruvate levels. Our results suggest that (1) allicin and thiosulfinates are responsible for the IVAA response, (2) crushing garlic before moderate cooking can reduce the loss of activity, and (3) the partial loss of antithrombotic effect in crushed-cooked garlic may be compensated by increasing the amount consumed.

Inhibition of carcinogen-induced DNA damage in rat liver and colon by garlic powders with varying alliin content

The present study was designed to investigate the protective efficiency of three garlic powders, obtained from bulbs grown in soils with different levels of sulfur fertilization, against DNA damage. Increasing fertilization of soil resulted in an increased alliin content of the powders. Garlic powders were administered to rats for 2 weeks (5% of the diet) and their antigenotoxic effects were examined in the liver and the colon using the comet assay. Consumption of the different garlic powders induced a 35-60% reduction in DNA damage induced by N-nitrosodimethylamine (NDMA) in rat liver. Increased alliin content of the garlic powder was associated strongly with a proportional decrease in NDMA induced DNA alteration. DNA damage induced by aflatoxin B1 in the liver or by 1,2-dimethylhydrazine in the colon were also decreased strongly by the three garlic powders but these decreases were not correlated to the alliin content of the garlic powders. Feeding garlic powders did not modify the genotoxic activity of the direct-acting carcinogen methylnitrosourea in the colon. Part of our results supports evidence that fertilization can have an impact on the protective capacity of garlic bulbs.

Reactive oxygen species scavenging capacity of different cooked garlic preparations

It was studied if the ability of aqueous garlic extracts to scavenge superoxide anion (O(2)(*-)), hydrogen peroxide (H(2)O(2)), and hydroxyl radical (OH(*)) is altered in the following aqueous preparations: (a) extracts of boiled garlic cloves (BG), (b) extracts of microwave-treated garlic cloves (MG), and (c) extracts of pickled garlic (PG), and heated extracts of (a) garlic powder (HGP) and (b) raw garlic (HRG). The data were compared with the unheated raw garlic (RG) or with the unheated garlic powder (GP). Extracts of GP and RG scavenged O(2)(*-), H(2)O(2), and OH(*) in a concentration-dependent way. The reactive oxygen species scavenging capacity was not decreased in the aqueous garlic extracts except in MG and HRG (for O(2)(*-)) and in HGP and PG (for H(2)O(2)). The heating before or after garlic cutting was unable to eliminate the capacity of the extracts to scavenge H(2)O(2), O(2)(*-), and OH(*).

The role of reactive oxygen species (ROS) production on diallyl disulfide (DADS) induced apoptosis and cell cycle arrest in human A549 lung carcinoma cells

Diallyl disulfide (DADS), an oil soluble constituent of garlic (Allium sativum), has been reported to cause antimutagentic and anticarcinogenic effects in vitro and in vivo by modulating phases I and II enzyme activities. In recent years, several studies suggested that the chemopreventive effects of DADS can also be attributed to induction of cell cycle arrest and apoptosis in cancer cells. In the present study, we reported that DADS-induced cell cycle arrest at G2/M and apoptosis in human A549 lung cancer cells in a time- and dose-dependent manner. Additionally, a significant increase of intracellular reactive oxygen species (ROS) was induced in A549 cells less than 0.5h after DADS treatment, indicating that ROS may be an early event in DADS-modulated apoptosis. Treatment of A549 cells with N-acetyl cysteine (NAC) completely abrogated DADS-induced cell cycle arrest and apoptosis. The result indicated that oxidative stress modulates cell proliferation and cell death induced by DADS.

Anticarcinogenic properties of garlic: a review

Garlic is a popular spice added to several edible preparations and is a remedy for a variety of ailments. Epidemeological as well as laboratory studies have shown that garlic consumption reduces certain cancer incidences in the stomach, colon, mammary, cervical, etc. This article focuses on the general chemistry, metabolism, anticarcinogenic properties, mechanism of action behind the anticarcinogenic effects, functional foods based on garlic; and future areas of research. Garlic has been shown to metabolized into N-aceryl-S-allyl cysteine, allyl mercaptan, diallyl disulfide, diallyl sulfide, diallyl sulfoxide, diallyl sulfone, and allyl methyl sulfide. Garlic has been thought to bring about its anticarcinogenic effect through a number of mechanisms, such as the scavenging of radicals, increasing gluathione levels, increasing the activities of enzymes such as glutathione S-transferase, catalase, inhibition of cytochrome p4502E1, DNA repair mechanisms, prevention of chromosomal damage etc. Future research should standardize the dosage of garlic and type, ie., whether it should be taken fresh, cooked, or aged. The formulation of odorless functional foods with the retention of anticarcinogenic activity should be further studied.

Garlic's ability to prevent in vitro Cu2+-induced lipoprotein oxidation in human serum is preserved in heated garlic: effect unrelated to Cu2+-chelation

Background

It has been shown that several extracts and compounds derived from garlic are able to inhibit Cu²⁺-induced low density lipoprotein oxidation. In this work we explored if the ability of aqueous garlic extract to prevent in vitro Cu²⁺-induced lipoprotein oxidation in human serum is affected by heating (a) aqueous garlic extracts or (b) garlic cloves. In the first case, aqueous extract of raw garlic and garlic powder were studied. In the second case, aqueous extract of boiled garlic cloves, microwave-treated garlic cloves, and pickled garlic were studied. It was also studied if the above mentioned preparations were able to chelate Cu²⁺.

Methods

Cu²⁺-induced lipoprotein oxidation in human serum was followed by the formation of conjugated dienes at 234 nm and 37°C by 240 min in a phosphate buffer 20 mM, pH 7.4. Blood serum and CuSO₄ were added to a final concentration of 0.67% and 0.0125 mM, respectively. The lag time and the area under the curve from the oxidation curves were obtained. The Cu²⁺-chelating properties of garlic extracts were assessed using an approach based upon restoring the activity of xanthine oxidase inhibited in the presence of 0.050 mM Cu²⁺. The activity of xanthine oxidase was assessed by monitoring the production of superoxide anion at 560 nm and the formation of uric acid at 295 nm. Data were compared by parametric or non-parametric analysis of variance followed by a post hoc test.

Results

Extracts from garlic powder and raw garlic inhibited in a dose-dependent way Cu²⁺-induced lipoprotein oxidation. The heating of garlic extracts or garlic cloves was unable to alter significantly the increase in lag time and the decrease in the area under the curve observed with the unheated garlic extracts or raw garlic. In addition, it was found that the garlic extracts were unable to chelate Cu²⁺.

Conclusions

(a) the heating of aqueous extracts of raw garlic or garlic powder or the heating of garlic cloves by boiling, microwave or pickling do not affect garlic's ability to inhibit Cu²⁺-induced lipoprotein oxidation in human serum, and (b) this ability is not secondary to Cu²⁺-chelation.

Mechanisms by which garlic and allyl sulfur compounds suppress carcinogen bioactivation. Garlic and carcinogenesis

Overall, a host of studies provides compelling evidence that garlic and its organic allyl sulfur components are effective inhibitors of the cancer process. These studies reveal that the benefits of garlic are not limited to a specific species, to a particular tissue, or to a specific carcinogen. Several mechanisms are likely to account for this protection. Notable among these is a depression in nitrosamine formation and a reduction in carcinogen bioactivation. The benefits provided by garlic must be viewed as part of the entire diet, since several dietary constituents can influence the degree of protection. More than one compound is responsible for the anticancer properties associated with garlic. Future research should focus on how genetic variability and daily environmental factors influence the anticancer benefits attributed to garlic and its allyl sulfur components.

Organosulfur compounds from Allium and the chemoprevention of cancer

Allium vegetables and their associated organosulfur constituents are extensively studied for their chemopreventive potential against cancer. This article overviews their anticarcinogenic and antigenotoxic properties. Epidemiological studies (mostly case-control studies) provide strong evidence that Allium vegetable consumption reduces the incidence of gastric and colon cancer while the association between Allium vegetable consumption and other cancers is less convincing. Furthermore, many experimental studies have demonstrated that organosulfur compounds and Allium extracts have inhibitory effects on carcinogenesis in animals. These inhibitory effects are supported by many diverse mechanisms, including inhibition of carcinogen formation, modulation of carcinogen metabolism, inhibition of mutagenesis and genotoxicity, inhibition of cell proliferation and increase of apoptosis, inhibition of angiogenesis, and immune system enhancement. Before such constituents or extracts can be used in chemopreventive trials, it is important to verify their lack of toxicity and to investigate further their precise mechanisms of action throughout the whole process of carcinogenesis.

A historical perspective on garlic and cancer

Epidemiological and laboratory studies provide insight into the anticarcinogenic potential of garlic and its constituent compounds. Both water- and lipid-soluble allyl sulfur compounds are effective in blocking a myriad of chemically induced tumors. Part of the protection from these compounds probably relates to a block in nitrosamine formation and metabolism. However, blockage in the initiation and promotion phases of the carcinogenicity of various compounds, including polycyclic hydrocarbons, provide evidence that garlic and its constituents can alter several phase I and II enzymes. Their ability to block experimentally induced tumors in a variety of sites including skin, mammary and colon, suggests a general mechanism of action. Changes in DNA repair and in immunocompetence may also account for some of this protection. Some, but not all, allyl sulfur compounds can also effectively retard tumor proliferation and induce apoptosis. Changes in cellular thiol and phosphorylation stains may account for some of these antitumorigenic properties. The anticarcinogenic potential of garlic can be influenced by several dietary components including specific fatty acids, selenium, and vitamin A. Since garlic and its constituents can suppress carcinogen formation, carcinogen bioactivation, and tumor proliferation it is imperative that biomarkers be established to identify which individuals might benefit most and what intakes can occur with ill consequences.

Functional foods: the US perspective

Widespread interest in the possibility that selected foods might promote health has resulted in the coining of the term functional food, although agreement about what is and what is not a functional food is lacking. Public interest in functional foods is increasing because of higher health care costs; the passage of federal legislation affecting many food categories, including the expanded category of dietary supplements; and recent scientific discoveries linking dietary habits with the development of many diseases, including coronary heart disease and some cancers. A variety of foods have been proposed as providing health benefits by altering one or more physiologic processes. Biomarkers are needed to assess the ability of functional foods or their bioactive components to modify disease and to evaluate the ability of these foods to promote health, growth, and well-being. Evidence suggests that several biomarkers may be useful for distinguishing between diseased and nondiseased states and even for predicting future susceptibility to disease. A variety of biomarkers will probably be needed to develop a profile for an individual that reflects the impact of diet on performance and health. Another area of interest is the interaction of nutrients and their association with genetics. These interactions may account for the inconsistent interrelations observed between specific dietary constituents and the incidence of disease. Greater understanding of how diet influences a person's genetic potential, overall performance, and susceptibility to disease can have enormous implications for society. As new discoveries are made in this area, consumers will need access to this information so that they can make informed decisions.

Garlic and onions: their effect on eicosanoid metabolism and its clinical relevance

Garlic (Allium sativum) and onion (Allium cepa) are among the oldest of all cultivated plants. Additionally, both plants have been used as medicinal agents for thousands of years. Both garlic and onion have been shown to have applications as antimicrobial, antithrombotic, antitumor, hypolipidaemic, antiarthritic and hypoglycemic agents. In recent years, extensive research has focussed on the beneficial and medicinal properties of garlic and onions. In particular, the use of these agents in the treatment and prevention of cardiovascular disease and cancer is an area of considerable investigation and interest.

Nutritional and Health Benefits of Inulin and Oligofructose. Proceedings of a conference. Bethesda, Maryland, USA. May 18-19, 1998

Statements about the ability of selected foods to reduce the risk of diseases and to enhance the quality of life continue to captivate, and at times polarize, opinions. Interests in these "functional" foods and their active components are being propelled by increasing health care cost, recent legislative events and mounting scientific evidence. Increasingly, scientists are being asked to clarify the precise role that foods have in maintaining and promoting health. Accepting this movement as an opportunity to "optimize nutrition" rather than as a way in which to endorse good or bad foods or as a marketing gimmick will surely make it more acceptable to many scientists. However, the response to functional foods depends on several factors, including genetics, physiologic state and the composition of the entire diet. Although evaluation of the benefits or risks of foods normally does not entail the same extensive examination as that required of drugs, this does not negate the need for sound scientific information for making recommendations to the consumer. Identification of sensitive and reliable biomarkers will be key to adequate assessment of the true effect of foods and their components. Inulin and oligofructose are components of the diet that deserve added attention for their potential health benefits. Evidence that oligofructose and inulin alter several biomarkers, including gastrointestinal transit time, experimentally induced neoplasia and colonic microflora, suggests that these nondigestible carbohydrates are naturally occurring dietary constituents that may improve the quality of life and increase disease resistance in both humans and animals.