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Vitamin B₁₂, folate, and vitamin B₆ are the main determinants of homocysteinemia. The vegan diet provides no vitamin B₁₂, but also less strict forms of alternative nutrition may suffer from a deficit of this vitamin. The plasma homocysteine level was measured in alternative nutrition groups of adults (lacto- and lactoovovegetarians, n = 62; vegans, n = 32) and compared with the levels in a group consuming traditional diet (n = 59), omnivores). In the group of vegetarians the average homocysteine level is 13.18 vs. 10.19 μmol/l in omnivores; the frequency of hyperhomocysteinemia is 29 vs. 5% in omnivores. In the group of vegans the average homocysteine value is 15.79 μmol/l (53% of the individual values exceeded 15 μmol/l). Omnivores consume the recommended amount of methionine; however, in individuals consuming an alternative diet, the intake of methionine is deficient (assessed by food frequency questionnaire; lower content of methionine in plant proteins). Under conditions of lower methionine availability the remethylation pathway prevails; therefore, vitamin B₁₂ and folate were evaluated in relation to the homocysteine level. The serum vitamin B₁₂ levels are significantly lower in the alternative nutrition groups (214.8 pmol/l in vegetarians, 140.1 pmol/l in vegans vs. 344.7 pmol/l in omnivores); a deficit (<179.0 pmol/l) was found in 26% of the vegetarians and in 78% of the vegans vs. 0% in omnivores. The serum folate levels were within the range of reference values in all groups; however, they were significantly lower in omnivores. The results show that the mild hyperhomocysteinemia in alternative nutrition is a consequence of vitamin B₁₂ deficiency.

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Conditions predisposing to metabolic syndrome (MetS) are associated with increased oxidative stress and inflammation. We studied, in vegetarians (n = 90) and omnivores (n = 46), the impact of the dietary regimen on the occurrence of MetS risk factors (RFs: BMI, blood pressure, glucose metabolism and lipid profile) in relation to oxidative status (advanced glycation end products (AGEs), advanced oxidation protein products (AOPPs), malondialdehyde, ferric reducing ability of plasma, vitamins A, E, C, beta-carotene and superoxide dismutase activity) and microinflammation (C-reactive protein, leukocytes and neopterin). The proportion of subjects without/positive for one or two MetS RFs was comparable between the groups. From the components of MetS only immunoreactive insulin levels differed significantly (95% CI: omnivores: 5.0-7.1 microU/mL, vegetarians: 4.5-5.4, p = 0.03). Omnivores had lower AOPP (omnivores: 0.29-0.36 micromol/g albumin, vegetarians: 0.36-0.52, p = 0.01) and beta-carotene levels than vegetarians, they consumed more calories, proteins, fat and saturated fatty acids, and less fibres, beta-carotene and vitamin C. Multiple regression analysis revealed vitamin E and AOPP levels as the most important independent determinants of MetS RFs. The vegetarian diet seems to exert beneficial effects on MetS RFs associated microinflammation. Whether the vegetarian diet may counteract the deleterious effects of elevated AOPPs and AGEs, remains to be elucidated.

The distinct melatonin rhythm with higher concentrations during the darktime was found in plasma of both control patients and patients with colorectal carcinoma. Moderate surgery did not induce any changes in plasma melatonin levels, but a pronounced increase in both the day- and nighttime melatonin concentrations was found after surgical treatment for colon cancer. The melatonin content in the tumor tissue did not differ from that in the proximal and the distal parts of the resected gut, which were without signs of malignant changes. Neither concentrations of serotonin nor 5-hydroxyindole acetic acid differed among analyzed parts of the gut. Daytime melatonin concentrations in gut tissue (314.7 +/- 87.8 pg/g of wet tissue) were more than ten times higher than the daytime levels in circulation. It was hypothesized that increased levels of this hormone in the gastrointestinal tract may play an important protective role against the development of colorectal cancer via stimulation of the immune system, protection against free radicals, and interaction with fatty acid uptake and metabolism.

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In adults, advanced glycation end products (AGEs) rise slowly in tissues and circulation during aging, and accumulate at an accelerated rate both in diabetes and chronic renal insufficiency (CRI). We aimed to investigate the pattern of AGE accumulation in children/adolescents with CRI and on renal replacement therapy by dialysis and transplantation. Concentrations of fluorescent AGEs, carboxymethyllysine (CML) and lipofuscin-like substance (LFLS, a marker of lipid peroxidation) were followed. Data were obtained from 11 CRI patients on conservative treatment (age 12.6+/-1.7 years, serum creatinine: 205.7+/-17.5 micromol/l), ten patients on renal replacement therapy with dialysis (13.6+/-1.7 years, 698.2+/-48.9 micromol/l) and nine patients after kidney transplantation (15.9+/-1.1 years, 115.9+/-12.0 micromol/l) and comparison made with the data from 28 healthy controls (11.8+/-8.2 years, 44.1+/-8.2 micromol/l). In controls, an age-dependent rise of fluorescent AGE and CML levels was observed. In the CRI group, fluorescent AGEs [0.38+/-0.03x105 arbitrary units (AU)] and CML (369+/-26 ng/ml) concentrations were doubled compared with controls (0.16+/-0.03x105 AU and 189+/-42 ng/ml, respectively) and even higher levels were revealed in dialyzed patients (0.80+/-0.05x105 AU; 650+/-94 ng/ml). Successful kidney transplantation significantly reduced but did not normalize fluorescent AGE levels (0.39+/-0.03 x105 AU), while the decline in CML levels (550+/-47 ng/ml) was insignificant. Plasma LFLS was elevated in CRI (19.6+/- 1.7 AU) and was even higher in dialyzed children (32.0+/-5.3 AU) compared with healthy controls (7.1+/- 1.4 AU). Kidney transplantation did not normalize LFLS levels (20.3+/-5.3 AU), pointing to persistently enhanced lipid peroxidation. Our study provides the first data on enhanced fluorescent AGEs and CML levels in children/adolescents with CRI and on dialysis. Successful renal transplantation decreased but did not normalize AGE levels, probably because of still-impaired renal function with enhanced oxidative stress, as well as the influence of immunosuppressive therapy.