Russell Keast

Phytochemistry: Ibuprofen-like activity in extra-virgin olive oil

Newly pressed extra-virgin olive oil contains oleocanthal — a compound whose pungency induces a strong stinging sensation in the throat, not unlike that caused by solutions of the non-steroidal anti-inflammatory drug ibuprofen. We show here that this similar perception seems to be an indicator of a shared pharmacological activity, with oleocanthal acting as a natural anti-inflammatory compound that has a potency and profile strikingly similar to that of ibuprofen. Although structurally dissimilar, both these molecules inhibit the same cyclooxygenase enzymes in the prostaglandin-biosynthesis pathway.

An overview of binary taste-taste interactions

The human gustatory system is capable of identifying five major taste qualities: sweet, sour, bitter, salty and savory (umami), and perhaps several sub-qualities. This is a relatively small number of qualities given the vast number and structural diversity of chemical compounds that elicit taste. When we consume a food, our taste receptor cells are activated by numerous stimuli via several transduction pathways. An important food-related taste question which remains largely unanswered is: How do taste perceptions change when multiple taste stimuli are presented together in a food or beverage rather than when presented alone? The interactions among taste compounds is a large research area that has interested electrophysiologists, psychophysicists, biochemists, and food scientists alike. On a practical level, taste interactions are important in the development and modification of foods, beverages or oral care products. Is there enhancement or suppression of intensity when adding stimuli of the same or different qualities together? Relevant psychophysical literature on taste–taste interactions along with selected psychophysical theory is reviewed. We suggest that the position of the individual taste stimuli on the concentration-intensity psychophysical curve (expansive, linear, or compressive phase of the curve) predicts important interactions when reporting enhancement or suppression of taste mixtures.

Oral sensitivity to fatty acids, food consumption and BMI in human subjects

Fatty acids are the chemical moieties that are thought to stimulate oral nutrient sensors, which detect the fat content of foods. In animals, oral hypersensitivity to fatty acids is associated with decreased fat intake and body weight. The aims of the present study were to investigate oral fatty acid sensitivity, food selection and BMI in human subjects. The study included two parts; study 1 established in thirty-one subjects (29 (sem 1.4) years, 22.8 (sem 0.5) kg/m2) taste thresholds using 3-AFC (3-Alternate Forced Choice Methodology) for oleic, linoleic and lauric acids, and quantified oral lipase activity. During study 2, fifty-four subjects (20 (sem 0.3) years, 21.5 (sem 0.4) kg/m2) were screened for oral fatty acid sensitivity using oleic acid (1.4 mm), and they were defined as hypo- or hypersensitive via triplicate triangle tests. Habitual energy and macronutrient intakes were quantified from 2 d diet records, and BMI was calculated from height and weight. Subjects also completed a fat ranking task using custard containing varying amounts (0, 2, 6 and 10 %) of fat. Study 1 reported median lipase activity as 2 mumol fatty acids/min per l, and detection thresholds for oleic, linoleic and lauric acids were 2.2 (sem 0.1), 1.5 (sem 0.1) and 2.6 (sem 0.3) mm. Study 2 identified twelve hypersensitive subjects, and hypersensitivity was associated with lower energy and fat intakes, lower BMI (P < 0.05) and an increased ability to rank custards based on fat content (P < 0.05). Sensitivity to oleic acid was correlated to performance in the fat ranking task (r 0.4, P < 0.05). These data suggest that oral fatty acid hypersensitivity is associated with lower energy and fat intakes and BMI, and it may serve as a factor that influences fat consumption in human subjects.

Biological Activities of Phenolic Compounds Present in Virgin Olive Oil

The Mediterranean diet is associated with a lower incidence of atherosclerosis, cardiovascular disease, neurodegenerative diseases and certain types of cancer. The apparent health benefits have been partially ascribed to the dietary consumption of virgin olive oil by Mediterranean populations. Much research has focused on the biologically active phenolic compounds naturally present in virgin olive oils to aid in explaining reduced mortality and morbidity experienced by people consuming a traditional Mediterranean diet. Studies (human, animal, in vivo and in vitro) have demonstrated that olive oil phenolic compounds have positive effects on certain physiological parameters, such as plasma lipoproteins, oxidative damage, inflammatory markers, platelet and cellular function, antimicrobial activity and bone health. This paper summarizes current knowledge on the bioavailability and biological activities of olive oil phenolic compounds.

Chemistry and Health of Olive Oil Phenolics

The Mediterranean diet is associated with a lower incidence of atherosclerosis, cardiovascular disease, and certain types of cancer. The apparent health benefits have been partially attributed to the dietary consumption of virgin olive oil by Mediterranean populations. Most recent interest has focused on the biologically active phenolic compounds naturally present in virgin olive oils. Studies (human, animal, in vivo and in vitro) have shown that olive oil phenolics have positive effects on certain physiological parameters, such as plasma lipoproteins, oxidative damage, inflammatory markers, platelet and cellular function, and antimicrobial activity. Presumably, regular dietary consumption of virgin olive oil containing phenolic compounds manifests in health benefits associated with a Mediterranean diet. This paper summarizes current knowledge on the physiological effects of olive oil phenolics. Moreover, a number of factors have the ability to affect phenolic concentrations in virgin olive oil, so it is of great importance to understand these factors in order to preserve the essential health promoting benefits of olive oil phenolic compounds.

Antimicrobial, antioxidant and anti-inflammatory phenolic activities in extra virgin olive oil

The Mediterranean diet is associated with a lower incidence of chronic degenerative diseases and higher life expectancy. These health benefits have been partially attributed to the dietary consumption of extra virgin olive oil (EVOO) by Mediterranean populations, and more specifically the phenolic compounds naturally present in EVOO. Studies involving humans and animals (in vivo and in vitro) have demonstrated that olive oil phenolic compounds have potentially beneficial biological effects resulting from their antimicrobial, antioxidant and anti-inflammatory activities. This paper summarizes current knowledge on the biological activities of specific olive oil phenolic compounds together with information on their concentration in EVOO, bioavailability and stability over time.

Reducing Sodium in Foods: The Effect on Flavor

Sodium is an essential micronutrient and, via salt taste, appetitive. High consumption of sodium is, however, related to negative health effects such as hypertension, cardiovascular diseases and stroke. In industrialized countries, about 75% of sodium in the diet comes from manufactured foods and foods eaten away from home. Reducing sodium in processed foods will be, however, challenging due to sodium’s specific functionality in terms of flavor and associated palatability of foods (i.e., increase of saltiness, reduction of bitterness, enhancement of sweetness and other congruent flavors). The current review discusses the sensory role of sodium in food, determinants of salt taste perception and a variety of strategies, such as sodium replacers (i.e., potassium salts) and gradual reduction of sodium, to decrease sodium in processed foods while maintaining palatability.

Marked differences in gustatory and gastrointestinal sensitivity to oleic acid between lean and obese men

BACKGROUND Both orosensory stimulation and feedback from the gastrointestinal tract contribute to energy intake regulation. OBJECTIVE We evaluated the hypothesis that overweight or obese subjects would be less sensitive to both oral and intraduodenal oleic acid exposure than would lean subjects. DESIGN Eleven overweight or obese and 8 lean men were studied on 2 occasions, during which antropyloroduodenal pressures, plasma cholecystokinin and peptide YY, and appetite were measured during 90-min intraduodenal infusions of saline or oleic acid (18:1 load: 0.78 kcal/min); energy intake (buffet lunch) was determined immediately afterward. Oral detection thresholds for 18:1 and recent dietary intake (2-d recall) were also quantified. RESULTS In lean subjects, the number of isolated pyloric pressure waves (IPPWs) was greater during 18:1 infusion than during saline infusion (P < 0.05); no significant differences were observed between the 18:1 and saline infusions in the overweight or obese subjects. In both groups, 18:1 stimulated plasma cholecystokinin and peptide YY and suppressed energy intake compared with saline (P < 0.05), with trends for reduced cholecystokinin and energy intake responses in the overweight or obese subjects. Detection thresholds for 18:1 were greater in overweight or obese (7.9 ± 0.1 mmol/L) than in lean (4.1 ± 0.4 mmol/L) subjects (P < 0.05). Overweight or obese subjects had greater recent energy (P < 0.05) and fat (P = 0.07) intakes than did lean subjects. There was a direct relation (r = 0.669) of body mass index with 18:1 detection thresholds and inverse relations (r < -0.51) of IPPWs with body mass index and 18:1 detection thresholds (P < 0.05). CONCLUSIONS The ability to detect oleic acid both orally and within the gastrointestinal tract is compromised in obese men, and oral and gastrointestinal responses to oleic acid are related. This trial was registered at www.actr.org.au (Australian New Zealand Clinical Trials Registry) as 12609000557235.

Recent fat intake modulates fat taste sensitivity in lean and overweight subjects

Objective:To evaluate the effects of a high-fat and low-fat diet on taste sensitivity to oleic acid (C18:1) in lean and overweight/obese (OW/OB) subjects.Design:Randomized cross-over dietary intervention involving the consumption of a high-fat (>45% fat) and low-fat (<20% fat) diet, both consumed over a 4-week period.Subjects:A total of 19 lean, mean age 33±13 years, mean body mass index (BMI) 23.2±2.2 kg m–2 and 12 OW/OB, mean age 39.5±3 years, mean BMI 28±2.6 kg m–2, subjects participated in the study, which measured taste thresholds for C18:1, fat perception and hedonic ratings for regular (RF) and lowered-fat (LF) foods before, and following consumption of a high- and low-fat diet.Results:Consumption of the low-fat diet increased taste sensitivity to C18:1 among lean and OW/OB subjects (P<0.05) and increased the subjects ability to perceive small differences in the fat content of custard (P=0.05). Consumption of the high-fat diet significantly decreased taste sensitivity to C18:1 among lean subjects (P<0.05), with no change in sensitivity among OW/OB persons (P=0.609). The hedonic ratings for several RF and LF foods differed following the diets.Conclusion:Alterations in the fat content of the diet modulated taste sensitivity to C18:1 among lean subjects, which was increased following a 4-week period of fat restriction and attenuated following the high-fat diet. The failure of the high-fat diet to alter fatty acid taste thresholds among OW/OB subjects suggests that these individuals were ‘adapted’ to high-fat exposure, perhaps because of differences in habitual fat consumption. Taken together, these data suggest that excessive dietary fat attenuates nutrient sensing epithelia response in the oral cavity, which could be associated with changes in diet and weight status.

Ibuprofen-like activity in estra-virgin olive oil

Newly pressed extra-virgin olive oil contains oleocanthal — a compound whose pungency induces a strong stinging sensation in the throat, not unlike that caused by solutions of the non-steroidal anti-inflammatory drug ibuprofen. We show here that this similar perception seems to be an indicator of a shared pharmacological activity, with oleocanthal acting as a natural anti-inflammatory compound that has a potency and profile strikingly similar to that of ibuprofen. Although structurally dissimilar, both these molecules inhibit the same cyclooxygenase enzymes in the prostaglandin-biosynthesis pathway.