Fish-based Diet Research Articles

Methylmercury and the Developing Brain

We reported that prenatal exposure to methylmercury causes cognitive impairment in an estimated 316,588 children born in the United States each year, costing this nation $8.7 billion annually in lost productivity (Trasande et al. 2005). Each year, this exposure also causes an estimated 1,566 cases of mental retardation (Trasande et al. 2006). The principal (70%) source of the mercury that enters the bodies of American children is combustion of coal in electricity-generating plants. In their reanalysis of our data, Griffiths et al. (2007) made a series of incorrect judgments and poorly considered assumptions, each of which diminishes the import of our findings. We note the following errors in their analysis: First, Griffiths et al. (2007) incorrectly used a linear model to relate cognitive function to prenatal methylmercury exposure, despite the National Research Council’s (NRC) clear finding that a logarithmic model provides a better statistical fit. The NRC, in their examination of the Faroe Islands cohort study, the study on which they place greatest reliance, stated that “[b]ecause these calculations necessitate extrapolating to estimate the mean response at zero exposure level,” logarithmic models “lead to lower estimates of the Benchmark Dose (BMD) than linear or K-power models” (NRC 2000, p. 294). Recent analyses of early childhood lead exposure further corroborate the validity of logarithmic models in representing subclinical dose–response relationships of neuro-developmental injury (Canfield et al. 2003). Second, Griffiths et al. (2007) unwisely based their analysis on potentially biased data from the Seychelles cohort study. By contrast, our model (Trasande et al. 2005), like that of the NRC, is based primarily on Faroes data. We chose not to use Seychelles data because of concern that the tests of neurobehavioral function used there were not well validated for a non-American population and therefore may not have been sensitive to detect cognitive impairment (Landrigan and Goldman 2003). Another major potential source of bias in the Seychelles study, not acknowledged by Griffiths et al. (2007), is that it fails to consider the potentially beneficial nutrients found in the fish-based diet of the Seychelles. These nutrients, omega-3 fatty acids in particular, may partially offset the toxicity of methylmercury. Indeed, if maternal fish intake is taken into account in the Seychelles cohort, as recently was done, the estimate of methylmercury toxicity increases (Budtz-Jorgensen et al. 2007). Griffiths et al. (2007) cited previous meta-analyses of the Faroes, Seychelles, and New Zealand studies by Ryan (2005) in applying IQ decrements of 0.13–0.18 points/ppm hair mercury, but these are likely underestimates, and further invalidate the analysis of Griffiths et al. Third, in attributing mercury deposition to sources of emission, Griffiths et al. (2007) relied inexplicably and without justification on a mathematical model that posits that only 16% of deposits are attributable to American sources. They ignored empiric data from the U.S. Environmental Protection Agency (EPA)-sponsored Steubenville study, which found that 80–90% of mercury emissions deposit within 30–50 miles of the source (U.S. EPA 2007); and from the Electric Power Research Institute, which estimated that 30% of mercury deposits are attributable to American sources (Seigneur et al. 2004). Fourth, Griffiths et al. (2007) incorrectly assumed that reductions in mercury emissions from power plants do not result in any reduced levels of fish contamination until after 15 years. This is not correct. Reductions in power-plant emissions in 2008 will, in fact, begin immediately to minimize methylmercury body burden among children born to women in 2008, and the degree of reduction will increase further in subsequent years, perhaps through 2038, thus reducing the number of children damaged, the severity of the prenatal brain damage in these children, and the resulting economic burden. Finally, Griffiths et al. (2007) incorrectly based their estimate of the economic value of a child’s social productivity on the 1992 Current Population Survey rather than on the currently available 2005 data set. This miscalculation substantially underestimates the economic impact of methylmercury on the developing brain. Viscusi and Aldy (2004) estimated that this value is currently on the order of $4–9 million/child, a value far greater than that used by Griffiths et al., and greater even than our estimate.

Spatio-temporal variation in diet may affect condition and abundance of juvenile European hake in the Gulf of Lions (NW Mediterranean)

Variations in space and time of juvenile hake diet (5 to 19 cm total length, TL) were investigated in the Gulf of Lions (NW Mediterranean) and related to variation in C and N stable iso- tope ratios, condition and abundance. Crustaceans (mysids and euphausiids) dominated the diet of the smallest juvenile hake (5 to 9 cm TL), and fishes (sardines and anchovies) of the largest juveniles (15 to 19 cm TL). The transition from a crustacean- to a fish-based diet occurred in medium-sized juveniles (10 to 14 cm TL), which preyed on both crustaceans and fishes (gobiids). These juveniles preyed on fishes when living in shallow waters (30 to 50 m), and crustaceans when located in deep waters (70 to 150 m). Although hake diet did not change over time in shallow waters (fish-based diet), in deep waters it was dominated by mysids and euphausiids in 2002 and natantids in 2003. In the size range analysed, no correlation was found between juvenile hake length and their δ 13 C and δ 15 N val- ues, but a significant correlation with depth was observed, with higher values in shallow waters. The condition factor of medium-sized juveniles did not vary with depth in 2002, but was significantly lower in deep waters in 2003 when they fed on natantids instead of small crustaceans. Abundance of juvenile hake in the Gulf of Lions drastically decreased from 2002 to 2003, particularly in deep waters. The lower condition factor of juvenile hake in deep waters in 2003, probably owing to a lack of suitable food, might have negatively affected their survival. These results support the hypothesis that food resources influence condition and survival of juvenile hake when settled, and thus affect NW Mediterranean fisheries.

The effect of dietary chitin supplementation on the survival and immune reactivity of the shore crab, Carcinus maenas

Adult male shore crabs (Carcinus maenas) were maintained on a fish-based diet supplemented with 0, 5 or 10% chitin for 11 weeks. Significantly greater mortality was found during this period in the control group (0% chitin) than those fed 10% chitin. Crabs fed 5 or 10% chitin had lower numbers of cultivatable bacteria in the hepatopancreas than those on the basal diet alone. The addition of chitin had no significant effect on the serum concentrations of protein and glucose, and the levels of glycogen in the hepatopancreas. The total number of circulating hemocytes in the blood was unaffected by the addition of chitin to the diet, however, at week 6 there were significantly more hyaline hemocytes in those crabs fed 10% chitin than the control group. The in vitro phagocytic activity of hemocytes was unaffected by chitin supplementation and crabs challenged with Vibrio alginolyticus showed a similar pattern of susceptibility in the three dietary groups (0, 5 or 10% chitin). Overall although crabs on a chitin-supplemented diet showed greater survival, this was not explained in terms of elevation in the cellular defences of these animals. The enhanced survival of crabs-fed chitin is probably as a result of the removal of potentially pathogenic bacteria from the hepatopancreas. Because chitin appears to 'purge' bacteria from the gut, this may prove to be a useful addition to diets on animals undergoing oral probiotic treatment.

Lack of oxidative stress in a selenium deficient area in Ivory Coast

Previous studies have described an important selenium deficiency in a mountain region (Glanle) in the west of Ivory Coast. To assess the antioxidant capacity of subjects from a selenium deficient area in Ivory Coast (Glanle region). This study involved 57 subjects, 18 to 69 years old, living in the Glanle region and 56 healthy controls living in the southern coastal region (Bodou). In the Glanle region families consume basically a vegetarian and crude palm oil diet, whereas in the Bodou region, families eat a fish-based diet with principally refined palm oil. Fasting blood samples were collected to assess the following parameters: lipid status (plasma total lipids; total-, HDL and LDL-cholesterol; triglycerides; phospholipids; fatty acid composition), plasma protein status (total protein, albumin, transthyretin, orosomucoid, CRP, transferrin), antioxidant capacity (plasma selenium, uric acid, retinol, alpha-tocopherol and tocotrienols levels, plasma seleno-glutathione peroxidase (GSHPx) activity) and oxidative stress markers (malondialdehyde (MDA) and advanced oxidation protein products (AOPP)). The mountain region samples (Glanle) were characterized by significantly lower plasma albumin, total-, HDL- and LDL-cholesterol, retinol and selenium levels, plasma PUFA content and GSHPx activity, but significantly higher alpha-tocopherol index and total tocotrienol level, than controls from the coastal area (Bodou). These results suggest a higher exposure risk to oxidative stress for the mountain region subjects. However, the absence of oxidative damage in this group provides evidence of a selenium independent protection mechanism against oxidative stress. This protection is related to lower plasma LDL cholesterol and PUFA content, and to higher alpha-tocopherol index, delta and total tocotrienols. The long-term consumption of crude palm oil could be considered as an effective protective factor against oxidative stress.

Dietary lipid enhancement of broodstock reproductive performance and egg and larval quality in Atlantic halibut ( Hippoglossus hippoglossus)

Two series of experiments were conducted to assess whether the trash fish-based diet traditionally used by the industry for broodstock halibut could be replaced by a formulated pelleted feed and to investigate the effects of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and arachidonic acid (AA) on halibut fecundity, blastomere morphology and fertilisation and hatching rates. In the first experiment, two formulated broodstock feeds (one containing Krill meal and one supplemented with tuna orbital oil, which provided higher dietary levels of DHA and AA), gave similar performances (Relative fecundity 9557±3462 and 10,551±2166, fertilisation rate 40.0±6.4% and 40.0±9.1%, respectively) to that of a fish fed a trash fish-based diet (Relative fecundity 11,782±1873, fertilisation rate 41.0±4.0%). In a second experiment, the spawning performance and egg quality of two groups of broodstock maintained on two formulated diets, each containing different levels of AA (1.8% and 0.4%) was compared over two successive spawning seasons. The diet with the higher (1.8%) level of AA resulted in significantly higher ( p<0.05) fertilisation rates (59.0±5.8%), blastomere morphology scores (14.2±0.4) and hatching rates (51.0±3.6%) compared to those on the 0.4% AA diet (31.0±4.9%, 12.5±0.3 and 28.0±5.7%, respectively). The eggs selectively accumulated DHA up to 30% of the total fatty acids. DHA/EPA and EPA/AA ratios of 2 and 4 in the eggs respectively were associated with improved egg and larval quality, similar to that achieved by fish maintained on the trash fish-based diets.

Effects of beef- and fish-based diets on the kinetics of n−3 fatty acid metabolism in human subjects

The quantity and type of dietary polyunsaturated fatty acids (PUFAs) can alter essential fatty acid metabolism in humans. Diets rich in 20- and 22-carbon PUFAs may inhibit desaturase expression or activity and decrease the synthesis of long-chain unsaturated fatty acids. It was theorized that the fat content of a fish-based diet would inhibit the kinetics of the in vivo metabolism of n-3 fatty acids compared with a beef-based diet. A compartmental model was used to determine the coefficients of the kinetic rate constants from the plasma concentration time curves of pentadeuterated (d(5)) 18:3n-3, 20:5n-3, 22:5n-3, and 22:6n-3 of 10 subjects who subsisted on 3 diets with different long-chain PUFA contents. For 3 wk, subjects reported their food intake from their usual diets and then consumed a beef-based diet for 3 wk and then a fish-based diet for an additional 3 wk. Subjects consumed 1 g d(5)-18:3n-3 ethyl ester at weeks 3, 6, and 9. Blood was drawn over 168 h and the plasma analyzed for fatty acids. The coefficients of the kinetic constants of n-3 fatty acid metabolism and the percentage utilization of the substrates were determined. Across all diets, < 1% of plasma 18:3n-3 was utilized for long-chain PUFA synthesis. There was a 70% reduction in the value of the rate constant coefficient that regulated transfer of the isotope from the 22:5n-3 compartment to 22:6n-3 when the fish-based diet was compared with the beef-based diet. The turnover rate of plasma d(5)-22:6n-3 also decreased. The primary effect of a fish-based diet on the kinetics of n-3 metabolism involves processes that inhibit the synthesis of 22:6n-3 from 22:5n-3. These processes may involve a system of feedback control mechanisms responsive to the plasma concentration of 22:6n-3.

Cardiovascular disease risk factors and n−3 fatty acid status in the adult population of James Bay Cree , ,

Canadian native populations, which traditionally consume large amounts of fish, have lower rates of mortality from heart disease than do Canadian nonnative populations, which have low fish intakes. Fish oils rich in n-3 fatty acids may have a protective effect against cardiovascular disease (CVD) risk factors. The purposes were to examine the profile of plasma phospholipid concentrations of the n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) among James Bay Cree and to verify the relation between these concentrations and CVD risk factors. The study population consisted of 917 subjects aged 18-74 y who participated in the 1991 Santé Québec Health Survey. Data were obtained through home interviews and clinic visits. Plasma samples were analyzed for phospholipid fatty acid composition. The mean fish consumption on the day before the survey was 60 g among the adult Cree population. Expressed as a percentage of total fatty acids, relative concentrations of EPA and DHA were 0.65% and 2.80%, respectively. n-3 Fatty acids were higher among coastal residents than among inland residents. A positive association was observed between plasma HDL and n-3 fatty acids. EPA and EPA+DHA were inversely associated with triacylglycerols. Among subjects aged 50-74 y, an inverse association between EPA and EPA:AA and total:HDL cholesterol was observed. n-3 Fatty acids may favorably influence some CVD risk factors. The Cree population must be encouraged to maintain their traditional fish-based diet, which may be one of the factors protecting them against mortality from CVD.

Fatty acid signature analysis from the milk of Antarctic fur seals and Southern elephant seals from South Georgia:implications for diet determination

Fatty acid signature analysis (FASA) makes use of specific fatty acids, as well as entire profiles, to study dietary relationships at different trophic levels. Previously, FASA has been used in marine ecosystems in which diet determination by more direct methods is difficult and sometimes misleading. This study examined fatty acid profiles in milk from 2 species of pinniped from the Southern Ocean that were expected to have highly contrasting diets. Milk samples were collected from Antarctic fur seals Arctocephalus gazella in 3 consecutive years, from 1991 to 1993 (n = 72), and from Southern elephant seals Mirounga leonina in 1988 (n = 53) at South Georgia. Lipids were extracted and fatty acid profiles determined by temperature-programmed gas chromatography. Possible prey species collected from waters around South Georgia were also analysed. Cluster analysis as well as classification and regression trees (CART) indicated that profiles from fur seals and elephant seals were significantly different. Southern elephant seal data could be distinguished from Antarctic fur seals by lower levels of the fatty acids 16:4 n1, 18:2 n6, 18:4 n3, 18:4 n1 and 20:5 n3 and by higher levels of 18:0, 18:1 n9/ n11 (i.e. 18:1 n9 co-eluting with 18:1 n11) and 20:1 n9. Fatty acid signatures from the milk of Antarctic fur seals were closest to krill and fish species that were also known to feed on krill. Southern elephant seal fatty acid profiles were closest to species that are not known as krill predators such as larger notothenids and myctophids. The fatty acid profiles of Antarctic fur seals showed considerable inter- and intra-annual variability, which was congruent with diet variability detected using scat analyses. Southern elephant seals showed little variation in profile through lactation. In contrast to previous diet analyses based on examination of stomach contents, the results from FASA were consistent with a fish-based diet for Southern elephant seals.

Microbiology and chemical composition of a typical product from Alosa fallax lacustris

Twaire, Alosa fallax lacustris, is the basic ingredient of a typical iscine product locally called “missol-tini”, prepared on the shores of Lake Corno. The artisan technokgy provides an optimal hygienic and nutritional product. When preserved, there is a total absence of contaminating microorganisms; lac-tobacilli and halophilous represent harmless bacteria. The food value lies in the high protein content with a notable lipid presence, plus the significant presence of polyunsaturated fatty acids. These attributes make “missoltini” a complementary component in any fish-based diet, such diets having long been recognized as valid in the prevention of cardiovascular disease.

Erythrocyte eicosapentaenoic acid versus docosahexaenoic acid as a marker for fish and fish oil consumption

The fatty acid composition of erythrocyte membranes was investigated in 21 healthy men after 6 wk of varying intakes of eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3). In one experiment, 12 subjects were fed three diets in a 3 × 3 crossover design: an essentially fish-free control diet, a fish diet (0.15 g EPA/d, 0.41 g DHA/d) and the same fish-based diet supplemented with 5 g/d fish oil (Fish + Oil: 0.99 g EPA/d, 0.99 g DHA/d). A 6 wk wash-out period was allowed between each diet. In another experiment, 11 subjects were supplemented with 5 g/d fish oil alone for 6 wk (0.84 g EPA/d, 0.48 g DHA/d). After fish or fish oil feeding, the percent proportion of EPA and DHA in the erythrocyte membranes rose at the expense of linoleic and arachidonic acids. After 6 wk on the fish-based diets, EPA incorporation approached saturation, with the incremental increases being proportional to the amounts supplied by the diets. In contrast, parallel increases were observed for erythrocyte DHA even though the Fish + Oil diet was supplying twice as much DHA as the fish alone diet. These observations imply different metabolic rates for EPA and DHA and their importance is discussed in terms of the value of erythrocyte EPA versus DHA as markers for fish and fish oil consumption.

Fish and fish oil intake: Effect on haematological variables related to cardiovascular disease

To investigate the effects of practical amounts of n-3 highly-unsaturated fatty acids (HUFA) on a number of parameters involved in haemostasis, 12 healthy men were fed three diets in a 3×3 cross-over design. The diets, fed as the evening meal for 6-week periods, were: Control diet (essentially fish-free), Fish diet (200 g/d of lean Australian fish flesh) and the same fish-based diet but supplemented with 5 g/d fish oil (Fish+Oil). The diets supplied about 0, 0.6, and 2.0 g n-3 HUFA/d, respectively. Relative to the Control diet, the number of circulating leukocytes was significantly reduced after both the Fish and Fish+Oil diets (by 13% and 15%, respectively). This reduction occurred in the number of neutrophils, although this did not reach significance on the Fish diet alone. Platelet count fell on the Fish+Oil diet (by 6%) but not on the Fish diet alone. There was an apparent enhancement of fibrinolytic potential after both fish-containing diets, which tended to be accentuated with the fish oil supplementation. The mechanisms underlying some if not all of these observations may be eicosanoid-mediated as indicated by a diminution in the platelet arachidonic acid (20:4n-6) to eicosapentaenoic acid (20:5n-3) ratios after the Fish+Oil (13.7±1.8) and Fish (34.4±8.9) diets relative to the Control diet (66.1±15.6). These data suggest that a practical amount of lean fish can improve certain haematological parameters implicated in the etiology of cardiovascular disease.

A mixed Australian fish diet and fish-oil supplementation: impact on the plasma lipid profile of healthy men

Twelve healthy men were fed in turn three diets for 6 wk each in a 3 x 3 randomized block design: a control diet (essentially fish free), a fish diet (200 g lean Australian fish flesh/d), and the same fish-based meal but supplemented with 5 g fish oil/d. Dietary eicosapentaenoic acid [EPA, 20: 5n-3 (omega-3)] was strongly associated with erythrocyte membrane EPA (r = 0.908 at 6 wk), strengthening its value as a measure of compliance in fish and fish-oil feeding trials. On the fish diet, subjects had increased incorporation of n-3 polyunsaturated fatty acids (PUFAs) at the expense of n-6 PUFAs in their erythrocyte membranes. When the fish-based diet was supplemented with fish oil (5 g/d), there was a significant lowering of plasma triacylglycerol (-0.16 +/- 0.24 mmol/L; mean +/- SD). No change in plasma total cholesterol was detected although the fish + oil diet produced a reduction in very-low-density-lipoprotein cholesterol (-0.24 +/- 0.26 mmol/L).

Preparation magnetic and optical properties of ferrimagnets in the RbMgF 3RbCoF 3 system

Brachial-ankle pulse wave velocity (baPWV) and ratio of plasma eicosapentaenoic acid to arachidonic acid (EPA/AA ratio) are surrogate markers for coronary artery disease (CAD). We aimed to evaluate the effects of a fish-based diet and administration of EPA on baPWV and plasma EPA/AA ratio.The changes in baPWV and plasma EPA/AA ratio were compared before and after a 6-month fish-based diet in 191 patients with cardiovascular risk factors. A fish-based diet resulted in significant increment of plasma EPA/AA ratio (0.40 ± 0.18 vs. 0.49 ± 0.27, p < 0.001), with baPWV remaining unchanged. Multivariate analysis revealed that systolic blood pressure (SBP) (6-month SBP-baseline SBP) and CAD were positively associated with increased baPWV (CAD: odds ratio = 2.040, p = 0.0436, SPB: odds ratio = 1.056, p = 0.0003). When the patients were divided into three groups: CAD, low-risk, and high-risk with no prior history of CAD according to the number of risk factors at baseline, comparison among the three groups disclosed an inter-group difference in the magnitude of change in baPWV (low-risk: −35 ± 164 cm/s, high-risk: −14 ± 190 cm/s, CAD: 39 ± 164 cm/s, p = 0.0071 for trend). In 191 patients who had received a 6-month fish-based diet, 21 patients (primarily CAD patients) sequentially received high purity EPA (1800 mg/day) for 6 months. It resulted in marked increment of plasma EPA/AA ratio (0.65 ± 0.57 vs. 1.19 ± 0.46, p < 0.001), accompanied by significant reduction in baPWV (1968 ± 344 cm/s vs. 1829 ± 344 cm/s, p = 0.0061). There was a significant negative correlation between changes in baPWV and changes in plasma EPA/AA ratio in patients with a fish-based diet and sequential administration of EPA (r = −0.446, p = 0.017).A fish-based diet was effective against increased baPWV only in low-risk patients, with slight increment of plasma EPA/AA. In high-risk patients and CAD patients, administration of EPA for preventing progression of baPWV endorsed the validity of high purity EPA administration recommended in the current guidelines.