Nutritional supplementation for type 2 diabetes: a systematic review

The role of nutritional supplementation is of increasing interest with regard to ocular disease. Randomised controlled trials have demonstrated the effectiveness of supplementation for age-related macular degeneration, and formulations are now being developed for use by people with diabetes and diabetic retinopathy. The aim of this review was to synthesise the evidence for use of nutritional supplementation in type 2 diabetes. MEDLINE and EMBASE databases were searched using a systematic approach. Only double-masked randomised controlled trials were selected. A total of 50 trials were identified as suitable for inclusion. The potential role of alpha-lipoic acid, chromium, folic acid, isoflavones, magnesium, Pycnogenol®, selenium, vitamin C, vitamin E, and zinc in the treatment of type 2 diabetes is discussed. The review of trials identifies positive effects of these nutrients on various outcome measures relating to insulin resistance and cardiovascular factors. Chromium was the most studied supplement, accounting for 16 of the 50 trials. A majority of the trials found a positive effect of chromium on fasting plasma glucose. Isoflavones were found to have a positive effect on insulin resistance and cardiovascular outcome measures, but only when combined with soy proteins. Vitamin E is reported to reduce oxidative stress at levels of 200 mg day-1 or more.

Possible contraindications and adverse reactions associated with the use of ocular nutritional supplements

The role of oxidation in the development of age-related eye disease has prompted interest in the use of nutritional supplementation for prevention of onset and progression. Our aim is to highlight possible contraindications and adverse reactions of isolated or high dose ocular nutritional supplements. Web of Science and PubMed database searches were carried out, followed by a manual search of the bibliographies of retrieved articles. Vitamin A should be avoided in women who may become pregnant, in those with liver disease, and in people who drink heavily. Relationships have been found between vitamin A and reduced bone mineral density, and beta-carotene and increased risk of lung cancer in smoking males. Vitamin E and Ginkgo biloba have anticoagulant and anti-platelet effects respectively, and high doses are contraindicated in those being treated for vascular disorders. Those patients with contraindications or who are considered at risk of adverse reactions should be advised to seek specialist dietary advice via their medical practitioner. © 2005 The College of Optometrists.

An ideal ocular nutritional supplement?

The role of nutritional supplementation in prevention of onset or progression of ocular disease is of interest to health care professionals and patients. The aim of this review is to identify those antioxidants most appropriate for inclusion in an ideal ocular nutritional supplement, suitable for those with a family history of glaucoma, cataract, or age-related macular disease, or lifestyle factors predisposing onset of these conditions, such as smoking, poor nutritional status, or high levels of sunlight exposure. It would also be suitable for those with early stages of age-related ocular disease. Literature searches were carried out on Web of Science and PubMed for articles relating to the use of nutrients in ocular disease. Those highlighted for possible inclusion were vitamins A, B, C and E, carotenoids beta-carotene, lutein, and zeaxanthin, minerals selenium and zinc, and the herb, Ginkgo biloba. Conflicting evidence is presented for vitamins A and E in prevention of ocular disease; these vitamins have roles in the production of rhodopsin and prevention of lipid peroxidation respectively. B vitamins have been linked with a reduced risk of cataract and studies have provided evidence supporting a protective role of vitamin C in cataract prevention. Beta-carotene is active in the prevention of free radical formation, but has been linked with an increased risk of lung cancer in smokers. Improvements in visual function in patients with age-related macular disease have been noted with lutein and zeaxanthin supplementation. Selenium has been linked with a reduced risk of cataract and activates the antioxidant enzyme glutathione peroxidase, protecting cell membranes from oxidative damage while zinc, although an essential component of antioxidant enzymes, has been highlighted for risk of adverse effects. As well as reducing platelet aggregation and increasing vasodilation, Gingko biloba has been linked with improvements in pre-existing field damage in some patients with normal tension glaucoma. We advocate that vitamins C and E, and lutein/zeaxanthin should be included in our theoretically ideal ocular nutritional supplement.

The Effect of nutritional supplementation on subjective and objective measures of visual and retinal function:a random controlled trial

In industrialised countries age-related macular disease (ARMD) is the leading cause of visual loss in older people. Because oxidative stress is purported to be associated with an increased risk of disease development the role of antioxidant supplementation is of interest. Lutein is a carotenoid antioxidant that accumulates within the retina and is thought to filter blue light. Increased levels of lutein have been associated with reduced risk of developing ARMD and improvements in visual and retinal function in eyes with ARMD. The aim of this randomised controlled trial (RCT) was to investigate the effect of a lutein-based nutritional supplement on subjective and objective measures of visual function in healthy eyes and in eyes with age-related maculopathy (ARM) – an early form of ARMD. Supplement withdrawal effects were also investigated. A sample size of 66 healthy older (HO), healthy younger (HY), and ARM eyes were randomly allocated to receive a lutein-based supplement or no treatment for 40 weeks. The supplemented group then stopped supplementation to look at the effects of withdrawal over a further 20 weeks. The primary outcome measure was multifocal electroretinogram (mfERG) N1P1 amplitude. Secondary outcome measures were mfERG N1, P1 and N2 latency, contrast sensitivity (CS), Visual acuity (VA) and macular pigment optical density (MPOD). Sample sizes were sufficient for the RCT to have an 80% power to detect a significant clinical effect at the 5% significance level for all outcome measures when the healthy eye groups were combined, and CS, VA and mfERG in the ARM group. This RCT demonstrates significant improvements in MPOD in HY and HO supplemented eyes. When HY and HO supplemented groups were combined, MPOD improvements were maintained, and mfERG ring 2 P1 latency became shorter. On withdrawal of the supplement mfERG ring 1 N1P1 amplitude reduced in HO eyes. When HO and HY groups were combined, mfERG ring 1 and ring 2 N1P1 amplitudes were reduced. In ARM eyes, ring 3 N2 latency and ring 4 P1 latency became longer. These statistically significant changes may not be clinically significant. The finding that a lutein-based supplement increases MPOD in healthy eyes, but does not increase mfERG amplitudes contrasts with the CARMIS study and contributes to the debate on the use of nutritional supplementation in ARM.

Effect of a fish oil-enriched nutritional supplement on metabolic mediators in patients with pancreatic cancer cachexia

Weight loss in advanced cancer patients is refractory to conventional nutritional support. This may be due to metabolic changes mediated by proinflammatory cytokines, hormones, and tumor-derived products. We previously showed that a nutritional supplement enriched with fish oil will reverse weight loss in patients with pancreatic cancer cachexia. The present study examines the effect of this supplement on a number of mediators thought to play a role in cancer cachexia. Twenty weight-losing patients with pancreatic cancer were asked to consume a nutritional supplement providing 600 kcal and 2 g of eicosapentaenoic acid per day. At baseline and after 3 wk, patients were weighed and samples were collected to measure serum concentrations of interleukin (IL)-6 and its soluble receptor tumor necrosis factor receptors I and II, cortisol, insulin, and leptin, peripheral blood mononuclear cell production of IL-1 beta, IL-6, and tumor necrosis factor, and urinary excretion of proteolysis inducing factor. After 3 wk of consumption of the fish oil-enriched nutritional supplement, there was a significant fall in production of IL-6 (from median 16.5 to 13.7 ng/ml, P = 0.015), a rise in serum insulin concentration (from 3.3 to 5.0 mU/l, P = 0.0064), a fall in the cortisol-to-insulin ratio (P = 0.0084), and a fall in the proportion of patients excreting proteolysis inducing factor (from 88% to 40%, P = 0.008). These changes occurred in association with weight gain (median 1 kg, P = 0.024). Various mediators of catabolism in cachexia are modulated by administration of a fish oil-enriched nutritional supplement in pancreatic cancer patients. This may account for the reversal of weight loss in patients consuming this supplement.

Studies on the composition and nutritional value of the cultivated mushroom, agaricus bisporus (Lange) Sing

The effects of various cultural conditions on the composition and nutritional quality of Agaricus bisporus (Lange) Sing. were investigated. Variation in composition was found between different classes of sample. Sampling techniques were standardised to allow for major variations in the different developmental stages and culture ages. Fruitbodies were found to be of low calorific value but contained protein of high digestibility and quality, containing all the essential amino acids required by man. Quantitative estimates of the sulphur-containing amino acids indicated that fruitbodies were deficient in methionine and cysteine. The extent of water application and the supplementation of conventional substrates with various nitrogen-containing substances, influenced yield and composition, establishing the importance of these two factors in the physiology of fruitbodies and cultural management. Storage conditions influenced composition, high temperatures being deleterious to the nutritional value of fruitbodies. Submerged culture techniques were used to investigate the effects of various nutrients on growth and composition of mushroom mycelium, with special reference to the sulphur-containing amino acids. Yield and composition were greatly affected by the carbon:nitrogen ratio of the medium and by the nitrogen source. Significant increases in mycelial methionine content were observed on the addition of inorganic sulphate, the methionine derivative N-acetyl-L-methionine, and L-methionine. A greater increase in methionine content was obtained when the biomass of a thermophilic bacterium isolated from compost was used as a nitrogen source.

Dietary enrichment by almond supplementation: effects on risk factors for cardiovascular disease

Cardiovascular disease (CVD) is the leading cause of death in Europe responsible for more than 4.3 million deaths annually. The World Health Organisation funded the Monica project (1980s-1990s) which monitored ten million subjects aged 22-6Syrs, and demonstrated that coronary heart disease (CHD) mortality declined over 10 years, was due in two thirds of cases to reduced incidence of CHD (reduced risk behaviours e.g. poor diet and smoking) and one third by improved treatments. Epidemiological evidence suggests diets rich in antioxidants decrease incidence of CVD. Regular consumption of nuts, rich in vitamin E and polyphenols reduces atherosclerosis, an important risk for heart disease. Intervention studies to date using alpha tocopherol (an active component of vitamin E) have not consistently proved beneficial. This thesis aims to investigate the effect of almond supplementation on vascular risk factors in healthy young males (18-3Syrs); mature males and female(>SOyrs); and males considered at increased risk of CVD (18-3Syrs) in a cohort of 67 subjects. The effects of almond intake were assessed after 2Sg/d for four weeks followed by SOg/d for four weeks and compared to a control group which did not consume almonds or change their diet. Cardiovascular risk was assessed by plasma lipid profiles, apolipoprotein A1, plasma nitrates/nitrates, vascular flow, BMl, blood pressure, sVCAM-1 and protein oxidation. Systolic and diastolic blood pressures were reduced in almond supplemented volunteers but not in controls. Dietary monounsaturated fatty acids, polyunsaturated fatty acid content and total dietary fats were increased by almond supplementation. Neither sVCAM-1, venous occlusion plethysmography nor plasma nitrite levels were affected by almond intake in any independent group. No significant changes in plasma lipids, and apolipoprotein A1 were observed. In conclusion almonds supplementation caused a reduction in blood pressure that may be due to increased sensitivity of the baroreceptors after increased monounsaturated fatty acid intake.

The effect of nutritional supplementation on visual function

The aim of this research was to determine the effect of a lutein-based nutritional supplemented on measures of visual function in normal and ARMD-affected eyes. Thirty participants were recruited to the ARMD cohort (aged between 55 and 82 years, mean ± SD: 69.2 ± 7.8) and 46 were recruited into the normal cohort (aged between 22 and 73 years, mean ± SD: 50.0 ± 15.9). Outcome measures were distance (DVA) and near (NVA) visual acuity, contrast sensitivity (CS), photostress recovery time measured with the Eger Macular Stressometer (EMS), central visual function assessed with the Macular Mapping test (MMT), and fundus photography. Reliability studies were carried out for the EMS and the MMT. A change of 14 s is required to indicate a clinically significant change in EMS time, and a change of 14 MMT points is required to indicate a clinically significant change in MMT score. Sample sizes were sufficient for the trial to have 80% power to detect a significant clinical effect at the 5% significance level for all outcome measures in the normal cohort, and for CS in the ARMD cohort. The study demonstrated that a nutritional supplement containing 6mg lutein, 750 mg vitamin A, 250 mg vitamin C, 34 mg vitamin E, 10 mg zinc, and 0.5 mg copper had no effect on the outcome measures over nine or 18 months in normal or ARMD affected participants. The finding that nine months of antioxidant supplementation, in this case, has no significant effect on CS in ARMD-affected participants adds to the literature, and contrasts with previous RCTs, the AREDS and the LAST. This project has added to the debate about the use of nutritional supplementation prior to the onset of ARMD.

Nutritional aspects of cancer

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Tissue protein turnover and its modulation by biochemical, nutritional and physiological factors

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Age-related macular degeneration and nutritional supplementation:a review of randomised controlled trials

Age-related macular degeneration (AMD) is the leading cause of severe vision loss in the developed world. The lack of effective treatment modalities, coupled with evidence supporting an oxidative pathogenesis, has increased interest in the potential preventative role of nutritional supplementation. This article reviews seven randomised controlled trials (RCTs) that have investigated the role of nutritional supplementation in AMD. Three of these trials reported a positive effect of nutritional supplementation on AMD; the Age-related eye study (AREDS), the Lutein Antioxidant Supplementation Trial (LAST), and the oral zinc trial by Newsome et al. (1988). However, the oral zinc trial by Newsome et al. (1988) was unlikely to detect any difference between treatments smaller than 72%, and the AREDS results were based on a subgroup of their study population. Lutein was considered for the AREDS formulation, but was not commercially available at that time. The findings of the LAST support a possible therapeutic role of lutein in AMD. © 2004 The College of Optometrists.