Effects of Mixed Spices on Cardiometabolic Function - the PolySPice (PSP) Study

Spices have been used for centuries to enhance food flavouring and to maintain health. Use of spices as a culinary ingredient is common amongst people of all ethnicities within South and East Asia. Spices are also one of the main sources of polyphenols in the Asian diet. Several in vitro studies and some in vivo studies, mainly in animals have shown that individual spices, including turmeric (containing curcumin), cinnamon (cinnimic acid), ginger, garlic etc. have been shown to improve glucose and lipid metabolism.However, well-controlled randomised trials, within the normal dietary context in humans are limited.

This study will be conducted using a three-way randomised crossover design using the Latin square approach. In the two treatment sessions, each volunteer will consume a mixed spice dish at two doses (i.e., 'small portion' or 'large portion' curry sauce), and rice as the base ingredient. In the control session, the same base ingredient (rice) but without the mixed spices will be served. The total amount of mixed spices consumed, to be made from dried powders of turmeric, cumin, coriander, gooseberry (amla), cinnamon, clove and cayenne pepper, will be 6 g and 12 g for small and large portion curries respectively. In addition, as added vegetables, the curry meals will contain tomato, garlic, onion and ginger, whereas the control meal will just have tomato and peeled aubergine, although, the total amount of vegetables will remain the same across all dishes (treatment or control).

The primary objective of this study will be to measure postprandial and fasting changes in blood glucose, insulin, triglycerides (TG), free fatty acids (FFA), 24h ambulatory blood pressure (BP), endothelial function and inflammatory markers following consumption of increasing doses of mixed spices in a single meal, on separate occasions.

The secondary objective of the study will be to monitor changes in blood levels of gut hormones, plasma and urine metabolome including polyphenols such as benzoate and hippurate, gut microflora content and function, as a result of the mixed spice intake. A subset of the treatments (control and high spice dose only) will also have interstitial glucose monitored continuously for a period of up to 3 days using the continuous glucose monitoring system (CGMS).

Inclusion criteria

• Chinese Male
• Age between 21 to 40 years
• Body Mass Index between 18.5 to 27.5 kg/m2
• Waist circumference ≤ 90cm
• Fasting blood glucose < 6.0mmol/L
• Blood pressure <140mmHg systolic or < 90mmHg diastolic
• Do not partake in sports at the competitive and/or endurance levels and willing to stop any strenuous activity during or within 72 hours of test days

Exclusion criteria

• Smoking
• Allergic/intolerant to any of the test foods mentioned above, or any of the following common food and ingredients: eggs, fish, milk, peanuts, and tree nuts, shellfish, soya, wheat, gluten, cereal, fruits, dairy products, meat, vegetable, sugar and sweetener, natural food colourings or flavourings, etc.
• Have difficulty passing motion
• Have or had diarrhea in the past 1 month of study participation
• Have any metabolic or cardiovascular diseases (e.g., diabetes, heart condition) or any other diseases involving the small intestine or the colon (e.g., irritable bowel syndrome, inflammatory bowel disease, gastric reflux) Have any liver or kidney disorders or any family history of kidney stones
• Taking any prescribed medication or dietary supplements which may interfere with the study measurements, including consumption of probiotic drinks or supplements, taking antibiotics, laxatives or antidiarrheal medicines likely to interfere with study findings
• Excessive alcohol consumption: consuming alcohol on > 4 days per week with ≥ 6 alcoholic drinks per week
• Individuals who have donated blood within the previous 6 months