Mediterranean diet: 'sentinel' test explains benefits in case of obesity and overweight

That the Mediterranean diet is the ideal nutritional model is now well established. Thanks to the balance of macro- and micronutrients, as well as a good fibre intake due to the presence of the classic five portions of vegetables as well as sufficient whole grains, it is considered the best in terms of health and prevention. All this, considering also the positive impact that social aspects such as conviviality and the 'timing' of food preparation, according to our traditional recipes and the healthiest ingredients, can have. Our food model, in short, is good for everyone. And at all ages. But there are people for whom deviating from these general guidelines may be even more wrong. Because the benefits are even greater. How to recognise those who really cannot do without the habits of our grandparents? The answer may come from Chinese research, published in Life Metabolism. Thanks to a simple blood sample, one could in fact know the value of a post-prandial 'marker', called SPARC: if detected one hour after the end of the meal, it indicates who will benefit most from adopting a Mediterranean diet. And above all, it is a kind of 'vanguard' towards precision nutrition.

The study was coordinated by Jiqiu Wang and Guang Ning of the Ruijin Hospital of Shanghai Jiao Tong University and involved 235 Chinese adults with overweight or obesity and prediabetes for six months. The participants were assigned to three different calorie-restricted dietary patterns: in the first group the focus was on the classic Mediterranean diet, in the second on the Jiangnan diet (traditional healthy eating pattern of the Yangtze river delta, characterised by high consumption of seasonal vegetables, freshwater fish, pulses and brown rice, with moderate use of rapeseed oil and red meat, with mainly steaming and boiling) or a 'modern' control diet from the Shanghai area. For all, a decrease of a quarter of total calories through controlled meals five days a week was proposed.

Blood values of SPARC, a secreted protein associated with adipose inflammation, were measured on an empty stomach, 1 hour and 2 hours after glucose intake. Result: Measurements at 1 hour after glucose intake at baseline, not fasting or 2 hours, predicted the extent of metabolic improvement in the group on the Mediterranean diet. Individuals with lower basal one-hour SPARC levels also showed a more efficient improvement trend in insulin resistance, fasting insulin and fasting blood glucose after six months of adherence to the calorie-restricted diet. These traces of possible metabolic interference were not observed in those following the Jiangnan diet or the control diet, suggesting a metabolic interaction specific to the Mediterranean diet. In short: the measurement of SPARC one hour after the meal acted as a valid predictor of who could benefit even more from the Mediterranean diet. Thus, a single postprandial biomarker could help identify those individuals most likely to gain significant cardiometabolic benefits from this dietary pattern.

'The study is certainly of great interest, also in the light of our knowledge of SPARC, a protein that can have different functions, also depending on the cells that favour its production,' comments Michelangelo Giampietro, specialist in Food Science, Director of the Institute of Sports Medicine - Sport and Health. For example, the one produced during muscular activity (endocrine-immune organ) would seem to have a beneficial effect over time and in the adaptation phase, explaining its positive potential for the organism. In this specific case, speaking of production linked to adipose tissue, a drop in the SPARC protein in the first hour would have an anti-inflammatory action and thus may help those on the Mediterranean diet. So we need to understand the dual value of SPARC, which was even proposed in the Covid era as a detector to record the benefits of physical activity. What can be said, in conclusion, is that we have one more piece to explain the value of the Mediterranean diet and its benefits also and especially in cases of overweight and dysmetabolism'.