Nutrition research
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Randomized Controlled Trial
Ornithine ingestion improved sleep disturbances but was not associated with correction of blood tryptophan ratio in Japanese Antarctica expedition members during summer.
Members of expeditions to Antarctica may show changes in biological and physiological parameters involved in lipid, glucose, and thyroid hormone metabolism as they adapt to the environment; however, alterations in amino acid (AA) levels and sleep among expedition members in Antarctica have yet to be fully elucidated. We hypothesized that there would be alterations of blood AA levels, and ornithine (Orn) ingestion would affect biological parameters and sleep in Japanese expedition members during the summer in Antarctica. Japanese Antarctica Research Expedition members (22 people) who stayed in Antarctica for 3 months from December 2010 were examined, and a randomized double-blind study of Orn ingestion (400 mg/d) for 4 weeks was performed. ⋯ On blood AA analysis, aspartate, Orn, and serine were significantly higher, and alanine and tryptophan (Trp) were significantly lower in Antarctica than in Japan. The Trp ratio, the value of Trp divided by the sum of phenylalanine, tyrosine, and branched-chain AAs, was significantly lower in Antarctica than in Japan. Although sleep deteriorated during the stay in Antarctica, Orn ingestion, to some extent, improved sleep compared with the placebo group in Antarctica, suggesting that Orn is effective for people with heavy physical workloads in places such as Antarctica.
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Randomized Controlled Trial
Folic acid and vitamin B(12) supplementation lowers plasma homocysteine but has no effect on serum bone turnover markers in elderly women: a randomized, double-blind, placebo-controlled trial.
An elevated homocysteine level is a newly recognized risk factor for osteoporosis. Older individuals may have elevated homocysteine levels due to inadequate folate intake and/or lower absorption of vitamin B(12). The aim of this study was to determine whether there is an impact of folic acid and vitamin B(12) supplementation on homocysteine levels and, subsequently, on bone turnover markers in older women with mildly to moderately elevated homocysteine levels. ⋯ The results showed significantly lower homocysteine concentrations in the vitamin group compared to the placebo group (10.6 vs 18.5 μmol/L, P = .007). No significant difference in serum alkaline phosphatase or C-terminal cross-linking telopeptide of type I collagen was found between the vitamin and placebo groups before or after supplementation. The use of folic acid and vitamin B(12) as a dietary supplement to improve homocysteine levels could be beneficial for older women, but additional research must be conducted in a larger population and for a longer period to determine if there is an impact of supplementation on bone turnover markers or other indicators of bone health.
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Randomized Controlled Trial
Flaxseed oil supplementation decreases C-reactive protein levels in chronic hemodialysis patients.
Malnutrition and chronic inflammation in dialysis patients negatively impact their survival prognosis, and nutrients, such as omega-3 oils, are postulated to reduce proinflammatory response. In this randomized, double-blind, multicenter, placebo-controlled trial, we investigated the effects of flaxseed oil (FO) on the inflammatory state of patients with chronic renal failure undergoing renal replacement therapy with hemodialysis (HD). We hypothesized that FO supplementation lowers C-reactive protein (CRP) levels. ⋯ During the study period, 33.3% of the FO group changed from an inflamed to a not-inflamed category, whereas only 16.9% changed in the mineral oil group (P = .04). We conclude that the administration of FO decreases the CRP levels and that inflammation in HD patients appears to be correlated to their body mass index and reduced high-density lipoprotein cholesterol levels. Studies with a larger number of patients and over a longer duration are necessary to corroborate these findings.
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Randomized Controlled Trial
Vitamin D supplementation has no effect on insulin resistance assessment in women with polycystic ovary syndrome and vitamin D deficiency.
Insulin resistance is one of the most common features of polycystic ovary syndrome (PCOS). Some studies suggest that vitamin D deficiency may have a role in insulin resistance; thus, the aim of the current study was to determine the effect of vitamin D supplementation on insulin resistance in women with PCOS and a vitamin D deficiency. We hypothesized that vitamin D supplementation would lower the glucose level and insulin resistance in women with PCOS and a vitamin D deficiency. ⋯ There was a significant increase in insulin secretion in the vitamin D group (P = .01), but this was not significant compared with the placebo group. The fasting serum insulin and glucose levels and the insulin sensitivity and homeostasis model assessment of insulin resistance did not change significantly by the end of the study. We were not able to demonstrate the effect of vitamin D supplementation on insulin sensitivity and insulin resistance in women with PCOS and vitamin D deficiency.
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Randomized Controlled Trial
Green tea extract supplementation gives protection against exercise-induced oxidative damage in healthy men.
The purpose of this study was to evaluate the effects of a long-term (4-week) green tea extract (GTE) supplementation in combination with strength training on selected blood markers of oxidative stress and muscular damage after a short-term exercise in previously untrained men. We hypothesized that GTE supplementation would elevate antioxidant potential and attenuate exercise-induced oxidative stress and muscular damage. Thirty-five male students were exposed to 4 weeks of strength training and received (in a randomized, double-blind design) GTE (n = 17; 640 mg polyphenols/d) or placebo (P; n = 18). ⋯ In term I, the muscular endurance test induced an increase in activity of creatine kinase in plasma after 24 hours of recovery in both the P and GTE groups. In term II, plasma creatine kinase activity after 24 hours of recovery was elevated only in the P group. In conclusion, in previously untrained men, dietary supplementation with GTE (in combination with strength training) enhances the antioxidant defense system in plasma at rest and, in turn, may give protection against oxidative damage induced by both short-term muscular endurance test and long-term strength training.