Scientific Background: In the overall population there is an increasing awareness that with a healthy lifestyle many chronic non-communicable diseases can be prevented or delayed in their progression. Among them diabetes type II, metabolic syndrome, hypertension and atherosclerosis are recognized as major public health issues also causing the highest proportion of deaths in the modern world. Food choices and eating habits in general play an important role in management of these diseases. There are, however, many popular diets for which there is yet no consensus on their actual possibility to exert health effects. Dietary protocols where whole food groups are excluded are especially known to have some beneficial but also some harmful effects, in particular when not planned properly and used for long periods. Two extremely different lifestyle choices are particularly common in recent years, namely low carbohydrate/high fat (LCHF) diet and vegetarian diet. In the first one, also called ketogenic diet, one eliminates all carbohydrate rich foods, such as fruit, legumes and cereals, but consumes a lot of fats, even up to 90 % of daily energy intake. Such diet is very efficient as a weight-loss program (Mohorko et al., 2019) and when used for shorter periods, was shown to have no adverse effects on total cholesterol or LDL levels. It was also efficient in decreasing the levels of serum glucose and triglycerides (Bueno et al., 2013), but in some cases was calcium deficient (Kenig et al., 2019). Long term effects have not been well investigated and a concern that high fat intake may cause more oxidative stress due to increased beta oxidation remains. Vegan diet, on the other hand, also eliminates a whole food group (meat and dairy products), which may cause depletion of some micronutrients, such as iron and vitamin B12. But, such diet is rich in antioxidants, decreases cholesterol levels and seems to increase longevity (Rizza et al., 2014). Again, studies investigating long-term effects are few.

Motivation for the proposal: In recent years, it has been shown that FTIR can identify many cellular characteristics that are related to the overall "health" of a cell. In the lymphocytes of rats under stress, increased lipid peroxidation was detected by FTIR (Vargas-Caraveo et al., 2014). In human oocytes spectral bands related to lipid saturation, membrane permeability, protein degradation and altered lipid synthesis were found to be changed with aging (Gioacchini et al., 2014). When investigating effects of diets, it is reasonable to expect that lipid content in the cells may change, there may also be differences in the extent of lipid peroxidation or other consequences of oxidative stress. DNA damage, for example, such as single and double strand breaks or DNA-protein cross links, could be induced or inhibited by different dietary ingredients and also identified with FTIR (Sofińska et al., 2020). All these parameters are very important, since increased lipid peroxidation is one of the factors contributing to the development of atherosclerosis, whereas lymphocyte membrane permeabilization and DNA damage are related to cell death and consequential impairment of the immune system. There are studies showing relevant contribution of different diets to these diseases, but underlying molecular mechanisms are not entirely clear. FTIR analysis could then provide interesting novel information, which is the objective of this proposal. In contrast to several biochemical parameters (i.e. cholesterol levels) that somewhat fluctuate depending on recently consumed foods, FTIR analysis of lymphocytes might give information on long-term consequences of a particular lifestyle.