Traditional food resources of indigenous peoples provide a wealth of information on use of unique food species, and their harvest and preparation. In conjunction with a larger study associated with the Northern Contaminants Program, traditional food items most frequently consumed in Inuit, Dene/Metis and Yukon First Nations communities of the Canadian North, were identified following a large-scale dietary assessment that included monitoring and collection of traditional and market foods in five regions of the Canadian North. Fifty out of 200 traditional food samples, collected as eaten, were prioritized for water-soluble vitamin analysis (folate, pyridoxine, riboflavin and niacin) based upon parameters that included frequency of consumption, lack of nutrient data and expectation of nutrient content. This paper reports on contents of selected B vitamins in the prioritized food samples, as eaten and expressed per 100 g of food sample. This is the first report of the levels of these water-soluble vitamins in many of these food sources. This study strongly suggests that traditional foods have the potential to contribute significantly to the water-soluble vitamin requirements of Northern Indigenous Peoples.

Abstract Background Selenium (Se), vitamin C and vitamin E function as antioxidants within the body. In this study, we investigated the effects of reduced dietary Se and L-ascorbic acid (AA) on vitamin C and α-tocopherol (AT) status in guinea pig tissues. Methods Male Hartley guinea pigs were orally dosed with a marginal amount of AA and fed a diet deficient (Se-D/MC), marginal (Se-M/MC) or normal (Se-N/MC) in Se. An additional diet group (Se-N/NC) was fed normal Se and dosed with a normal amount of AA. Guinea pigs were killed after 5 or 12 weeks on the experimental diets at 24 and 48 hours post AA dosing. Results Liver Se-dependent glutathione peroxidase activity was decreased (P < 0.05) in guinea pigs fed Se or AA restricted diets. Plasma total glutathione concentrations were unaffected (P > 0.05) by reduction in dietary Se or AA. All tissues examined showed a decrease (P < 0.05) in AA content in Se-N/MC compared to Se-N/NC guinea pigs. Kidney, testis, muscle and spleen showed a decreasing trend (P < 0.05) in AA content with decreasing Se in the diet. Dehydroascorbic acid concentrations were decreased (P < 0.05) in several tissues with reduction in dietary Se (heart and spleen) or AA (liver, heart, kidney, muscle and spleen). At week 12, combined dietary restriction of Se and AA decreased AT concentrations in most tissues. In addition, restriction of Se (liver, heart and spleen) and AA (liver, kidney and spleen) separately also reduced AT in tissues. Conclusion Together, these data demonstrate sparing effects of Se and AA on vitamin C and AT in guinea pig tissues.

A 90-day feeding study with gerbils was conducted to evaluate the influence of dietary vitamin E levels (25 mg/kg diet, 75 mg/kg, 300 mg/kg, and 900 mg/kg), two levels of dietary methionione (casein or casein+L-methionine (1% w/w)) and two sources of lipid (soybean oil [20%] or soybean oil [4%]+coconut oil [16%, 1:4 w/w]) upon serum lipids (total cholesterol, HDL-cholesterol, LDL-cholesterol). In addition, this study examined the effects of diet-induced hyperhomocysteinemia and supplemental dietary vitamin E on the oxidation of low density lipoproteins. Tissue vitamin E (heart, liver, and plasma) demonstrated a dose response (P< or =0.001) following the supplementation with increasing dietary vitamin E (25, 75, 300, and 900 mg/kg). In addition, tissue vitamin E levels were found to be higher (P< or =0.001) in those animals receiving a combination of coconut oil+soybean oil as compared to the group receiving soybean oil solely. Blood cholesterol profiles indicated an increase (P< or =0.001) in total cholesterol and LDL cholesterol by the influence of saturated fat and supplemental methionine. Low-density lipoprotein cholesterol profile demonstrated a reduction (P< or =0.001) at the higher dietary vitamin E levels (300 and 900 mg/kg) as compared to the 25 mg/kg and 75 mg/kg dietary vitamin E. Plasma protein carbonyls were not influenced by dietary vitamin E nor by supplemental methionine intake. In vitro oxidation of LDL showed that vitamin E delayed the lag time of the oxidation phase (P< or =0.001) and reduced total diene production (P< or =0.001). On the contrary, supplemental methionine decreased (P< or =0.001) the delay time of the lag phase, whereas total diene production was increased (P< or =0.001). Plasma lipid hydroperoxides were significantly reduced (P< or =0.05) with supplemental dietary vitamin E, whereas supplemental L-methionine (1%) resulted in a significant (P< or =0.05) increase in lipid plasma hydroperoxide formation. Plasma homocysteine was elevated (P< or =0.001) with supplemental dietary L-methionine (1%) as well as the inclusion of dietary saturated fat. The present data showed that 1) a combination of dietary lipids (saturated and unsaturated fatty acids) as well as vitamin E and methionine supplementation altered blood cholesterol lipoprotein profiles; 2) in vitro oxidation parameters including LDL (lag time and diene production) and plasma hydroperoxide formations were affected by vitamin E and methionine supplementation; and 3) plasma homocysteine concentrations were influenced by supplemental methionine and the inclusion of dietary saturated fat.

Information on the effects of dietary vitamins involved in homocysteine metabolism on the dietary methionine (Met)-induced hyperhomocysteinemia is limited. Thus, a six-wk study was conducted to investigate the effects of dietary Met with or without adequate vitamins on plasma total homocysteine (tHcy) in rats. Four levels of supplemental L-Met (0, 5, 10 and 20 g/kg) and two levels of vitamins (adequate and deficient in folate plus B-12) were tested in the casein-based diets. The plasma tHcy values in males were higher (p < 0.05) than in females (8.1± 0.6 vs. 6.0±0.6 μmol/L for adequate diet; 66.5± 1.4 vs. 45.5±0.9 μmol/L for folate-B-12 deficient diet). In males, supplementation of the adequate (control) diet with 5, 10 and 20 g/kg Met, increased tHcy to 1.3, 1.9 and 7.9 times control, respectively. In females, the corresponding values were 1.3, 1.7 and 5.6 times control. In rats fed folate-B-12 deficient diets, supplemental Met, however, generally caused reductions in plasma tHcy values in both sexes. These disparate responses to supplementary Met could be partly due to increases in hepatic S-adenosylmethionine (SAM)/S-adenosylhomocysteine (SAH) ratios in folate-B-12 deficient rats.

A pig growth study was conducted to investigate the effects of 2 protein sources (casein and soy protein isolate (SPI); varying in methionine/cysteine ratios) and 2 fat sources (lard and fish oil; varying in n-3 polyunsaturated fatty acids) on the levels of homocysteine and lipids in blood and tissues. The 4 experimental diets (casein-lard, casein-fish oil, SPI-lard, SPI-fish oil) were formulated to contain 22% protein (N X 6.25, from casein or SPI), 10% fat (10% lard or 5% fish oil plus 5% lard) and required levels of minerals and vitamins. Male, weanling, 9 kg Yorkshire pigs (6/diet) were fed the 4 experimental diets for a period of 6 wk. Blood samples were collected before the test and after 2, 4 and 6 wk of test. Samples of tissues (liver, heart and kidneys) were collected before the test and after 6 wk of test.The average fasting baseline value for total (both free and protein bound) homocysteine in plasma of pigs was 11 +/- I umol/l. Plasma homocysteine increased after feeding test diets. At 2 wk of test, pigs fed SPI diets had lower levels of plasma homocysteine (20 to 23 umol/l) than those fed casein diet (30 to 31 umol/l). Differences in plasma homocysteine levels of pigs fed fish oil diets compared to those fed lard diets were however, small. Pigs fed SPI diets also had lower levels of total serum cholesterol (1.26 to 2.11 mmol/l) than those fed casein diets (1.70 to 2.68 mmol/l). Similarly pigs fed fish oil diets had lower levels of serum cholesterol (1.26 to 1.70 mmol/l) than those fed lard diets (2.11 to 2.68 mmol/l). Differences in serum triglycerides of pigs fed experimental diets were small. Analyses for blood samples obtained after 4 and 6 wk of test, and for tissue samples obtained after 6 wk of test were not completed at the time of the preparation of this report.

Values (%) for true digestibility of crude protein and individual amino acids in 20 selected foods were determined by the rat balance (fecal) method. The products were fed as the sole source of protein in diets containing 8% crude protein (N × 6.25). Lowest true protein digestibility values (79–84) were obtained for pinto beans, kidney beans and lentils; intermediate values (89–92) were obtained for chick peas, beef stew, skim milk (over heated), rolled oats, whole wheat cereal, and pea protein concentrate; and highest values (94–100) were obtained for sausage, macaroni-cheese, rice-wheat gluten cereal, skim milk, tuna, soy isolate, peanut butter, chicken frankfurters, beef salami, casein and casein + methionine. In animal foods, peanut butter and soy isolate, the differences between true digestibility of crude protein and most individual amino acids were less than 5%. However, the values for true digestibility of methionine and cystine were up to 44% lower than those of crude protein in pinto beans, kidney beans, lentils, chick peas and pea concentrate. In these legumes, digestibility of crude protein was not a good predictor of digestibility of the limiting amino acids.

Protein efficiency ratio (PER), relative PER (RPER), net protein ratio (NPR) and relative NPR (RNPR) values, and amino acid scores were calculated for 20 food products (casein, casein + Met, beef salami, skim milk, tuna, chicken frankfurters, sausage, heated skim milk, peanut butter, rolled oats, soy isolate, chick peas, pea concentrate, kidney beans, wheat cereal, pinto bean, lentils, rice-wheat gluten cereal, macaroni-cheese, and beef stew). In most cases, PER, RPER, NPR or RNPR ranked the products in the same order and positive correlations among the protein quality methods were highly significant (r=0.98−0.99). Amino acid scores (based on the first limiting amino acid, Lys-Met-Cys, Lys-Met-Cys-Trp or lys-Met-Cys-Trp-Thr) were positively correlated to the PER, RPER, NPR or RNPR data (r=0.61−0.75). Inclusion of the correction for true digestibility of protein improved the correlations between amino acid scores and the indices based on rat growth. The correlations were especially high between Lys-Met-Cys scores (corrected for true digestibility of protein) and PER, RPER, NPR or RNPR (r=0.86−0.91). Inclusion of the correction for true digestibility of individual amino acids did not result in further improvements of the correlations in most cases. It is concluded that adjusting amino acid scores for true digestibility of protein would be sufficient and further correction for digestibility of amino acids would be unnecessary in mixed diets.

Samples of 15 food products and feces obtained by feeding them to rats were analysed for dietary fiber fractions. The food products were added as the sole source of protein in 8% protein diets, making up 8.8–51.6% of the diets. Diets were supplemented with 0.54–5.00% purified cellulose to make them more comparable in total fiber. Fiber analyses of food products revealed that the protein sources provided 0.06–7.27% total dietary fiber. The true protein digestibility in rats was negatively correlated with the total food fiber level (r=−0.69,P<0.01) or with the food cellulose level (r=−0.82,P<0.01) but it was positively correlated (r=+0.81,P<0.01) with the purified cellulose level. No relationship was found between protein digestibility and fiber fermentability. Results indicate that several food fiber fractions and possibly associated substances influenced protein digestibility. Purified cellulose did not have the same physiological behavior as food cellulose from the viewpoint of protein digestibility and fiber fermentability.