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The effects of fish consumption and n-3 fatty acids on type 2 diabetes mellitus (T2DM) have recently been debated. We explored the risk of T2DM in relation to consumption of lean fish, fatty fish, fish products and total fish as well as cod liver oil supplements in a representative sample of Norwegian women. This was a prospective population based cohort study in 33740 women free of T2DM, stroke, angina or heart attack and with detailed information on important co-variates and dietary intake at baseline. Risk ratios and corresponding 95% CI were estimated using Poisson regression with log-person time as offset. Lean fish consumption was inversely associated with T2DM compared to zero intake. Risk ratios and 95% CI for intake of 75 and 100 g lean fish per day were 0.71 (0.51, 0.98) and 0.67 (0.46, 0.98), respectively. There was no effect of intake of fatty fish, fish products, total fish or use of cod liver oil supplements on the risk of T2DM. Lean fish consumption of 75-100 g/d had a beneficial effect on T2DM. It remains unclear whether lean fish in itself has a protective effect on T2DM or that lean fish consumers have a protective life-style that we were not able to take into account in this study. Unfavorable effects of fatty fish consumption or use of cod liver oil supplements on T2DM were not observed.

Objective. Docosahexaenoic acid (DHA, 22:6 n-3) is considered an essential fatty acid for the fetus and newborn infant, but the optimal level of supply is not known. We studied the effect of supplementing pregnant and lactating women with marine n-3 polyunsaturated fatty acids (PUFAs) as compared to n-6 PUFAs related to maternal and infant lipid levels. Study design. Five hundred and ninety pregnant women in weeks 17-19 of pregnancy were recruited. They were given either 10 mL cod liver oil (n-3 PUFAs) or corn oil (n-6 PUFAs) daily until three months after delivery, and 341 women took part in the study until giving birth. Results. Maternal supplementation with cod liver oil increased the concentration of DHA in maternal as well as infant plasma and umbilical tissue phospholipids, as compared to corn oil. The maternal plasma triacylglycerol increase during pregnancy was less pronounced in women supplemented with cod liver oil as compared to corn oil. The concentration of high-density lipoprotein (HDL)-cholesterol was unchanged during pregnancy in the cod liver oil group, whereas it decreased in the corn oil group, promoting a greater increase in the ratio of total cholesterol HDL-cholesterol in the corn oil group. Conclusion. Maternal supplementation with n-3 fatty acids during pregnancy and lactation provides more DHA to the infant and reduces maternal plasma lipid levels compared to supplementation with n-6 fatty acids.

Vitamin D deficiency occurs worldwide. Winter season and high Body Mass Index (BMI) are associated with low levels of serum 25-hydroxyvitamin D (25(OH)D). We estimated the prevalence of vitamin D deficiency in a Norwegian adult population and examined factors associated with vitamin D deficiency. A cohort of 25 616 adults (19–55 years) who participated in both the second and third Nord-Trøndelag Health Study (HUNT 2 (1995–1997) and HUNT 3 (2006–2008)) was established in a previous study. A 10% random sample of the cohort population was recruited for serum 25(OH)D measurements (n=2584), which was used for the current cross-sectional study. Vitamin D deficiency was defined as serum 25(OH)D level <50 nmol/L. The overall prevalence of vitamin D deficiency was 40%, but varied by season (winter: 64%; summer: 20%). Winter season (adjusted prevalence ratio (PR): 3.16, 95% CI 2.42 to 4.12) and obesity (BMI ≥30.0 kg/m2) (PR: 1.74, 95% CI 1.45 to 2.10) were strongly associated with prevalent vitamin D deficiency. Current smoking also demonstrated an increased PR (1.41, 95% CI 1.21 to 1.65). Daily intake of cod liver oil (PR: 0.60, 95% CI 0.41 to 0.77), increased physical activity (PR: 0.80, 95% CI 0.68 to 0.95) and more frequent alcohol consumption (PR: 0.76, 95% CI 0.60 to 0.95) were associated with a reduced PR. The prevalence of vitamin D deficiency was high in Norwegian adults. Winter season, high BMI and current smoking were positively associated, and intake of cod liver oil, increased physical activity and more frequent alcohol consumption were inversely associated with vitamin D deficiency.

Background: The role of dietary fish and n-3 polyunsaturated fatty acids (n-PUFAs) in the primary prevention of allergic diseases remains uncertain. The aim of this study was to investigate associations between the consumption of fish and cod liver oil (rich in n-PUFAs) from pregnancy to the first two years of life, and parental reported allergic diseases at six years of age. Methods: We used data from the Prevention of Allergy among Children in Trondheim study and included mother-infant pairs who had submitted questionnaires detailing both maternal or infant diet and allergic disease at six years of age. Results: Eating fish at least once a week at one year of age was associated with a 28%, 40% and 34% reduction in the odds of current eczema, asthma, and wheeze at six years of age. Cod liver oil consumption at least four times per week at one year of age tended to be associated with a lower risk of allergy-related outcomes at six years. We found no consistent associations between allergy-related outcomes and fish or cod liver oil consumption by mothers. Conclusion: The preventive effect of fish consumption is best achieved by increasing dietary fish in the first year of life.

Background Cod liver oil is an important source of vitamin D, but also contains other fat-soluble components such as vitamin A. Before 1999, the cod liver oil formula in Norway contained a high concentration of vitamin A (1000 µg per 5 ml). High vitamin A status is associated with increased risks of several chronic diseases. Objective To investigate the association between cod liver oil intake and asthma development. Methods In the Nord-Trøndelag Health Study, a total of 25 616 Norwegian adults aged 19–55 years were followed up from 1995–1997 to 2006–2008. Current analysis based on 17 528 subjects who were free of asthma and had complete information on cod liver oil intake at baseline. Cod liver oil intake was defined as daily intake ≥1 month during the year prior to baseline. Incident asthma was reported as new-onset asthma during the 11-year follow-up. Results Of the 17 528 subjects, 18% (n=3076) consumed cod liver oil daily for ≥1 month over the past year. Cod liver oil intake was significantly associated with incident asthma with an OR of 1.62 (95% CI 1.32 to 1.98) after adjustment for age, sex, daily smoking, physical activity, education, socio-economic status, family history of asthma, and body mass index (BMI). The positive association was consistent across age (<40/≥40 years), sex (men/women), family history of asthma (yes/no) and BMI subgroups (<25/≥25 kg/m2). Conclusions Intake of cod liver oil with high vitamin A content was significantly associated with increased incidence of adult-onset asthma.

A relationship between the latitude related distribution of multiple sclerosis (MS) and exposure to sunlight has long been considered. Higher sun exposure during early life has been associated with decreased risk of MS. Since Norway is an exception to the latitude gradient of MS prevalence, we tested here whether sunlight exposure or vitamin D-related dietary factors in childhood and adolescence are associated with the risk of MS. Retrospective recall questionnaire data from 152 MS patients and 402 population controls born at and living at latitudes 66-71 degrees N were analysed by means of conditional logistic regression analysis accounting for the matching variables age, sex, and place of birth. Increased outdoor activities during summer in early life were associated with a decreased risk of MS, most pronounced at ages 16-20 years (odds ratio (OR) 0.55, 95% CI 0.39-0.78, p = 0.001, adjusted for intake of fish and cod-liver oil). A protective effect of supplementation with cod-liver oil was suggested in the subgroup that reported low summer outdoor activities (OR 0.57, 95% CI 0.31-1.05, p = 0.072). Consumption of fish three or more times a week was also associated with reduced risk of MS (OR 0.55, 95% CI 0.33-0.93, p = 0.024). Summer outdoor activities in childhood and adolescence are associated with a reduced risk of MS even north of the Arctic Circle. Supplemental cod-liver oil may be protective when sun exposure is less, suggesting that both climate and diet may interact to influence MS risk at a population level.

We investigated how cod liver oil influences the amount of essential fatty acids in mothers' breast milk. Lactating mothers (n =22) were randomized into four groups 3-8 weeks after parturition. They were supplemented for 14 days with 0, 2.5, 5 and 10 ml cod liver oil (7.7 g eicosapentaenoic acid (EPA, 20:5n-3), 10.2 g docosahexaenoic acid (DHA, 22:6n-3) and 22.9 g n-3 fatty acids in total per 100 ml). In maternal plasma phospholipids there was an increase in the content of EPA and DHA in the group supplemented with 10 ml cod liver oil daily (P < or = 0.05). DHA concentrations in breast milk pre-supplementation ranged from 0.15 to 1.56 wt% and increased in all supplemented groups (P< or =0.05). The concentration of EPA in breast milk increased in the groups supplemented with 5 or 10 ml cod liver oil (P< or =0.05), whereas the concentration of arachidonic acid (AA, 20:4n-6) did not change in any of the supplemented groups. Total intake of DHA adjusted to body mass index (BMI), correlated to DHA concentrations in plasma (r = 0.49, P = 0.02) and breast milk (r = 0.45, P = 0.04). The concentration of tocopherol did not change during the supplementation period, neither in plasma nor in breast milk. Dietary intake of DHA is reflected in the concentration of DHA in breast milk, without affecting the concentration of AA or tocopherol.

The aim of the present study was to examine the effect of a single high-fat meal with different fat quality on circulating inflammatory markers and gene expression in peripheral blood mononuclear cells (PBMC) to elucidate the role of fat quality on postprandial inflammation. A postprandial study with fourteen healthy females consuming three test meals with different fat quality was performed. Test days were separated by 2 weeks. Fasting and postprandial blood samples at 3 and 6 h after intake were analysed. The test meal consisted of three cakes enriched with coconut fat (43 % energy as saturated fat and 1 % energy as α-linolenic acid (ALA)), linseed oil (14 % energy as ALA and 30 % energy as saturated fat) and cod liver oil (5 % energy as EPA and DHA and 5 % energy as ALA in addition to 31 % energy as saturated fat). In addition, ex vivo PBMC experiments were performed in eight healthy subjects investigating the effects of EPA and ALA on release and gene expression of inflammatory markers. The IL-8 mRNA level was significantly increased after intake of the cod liver oil cake at 6 h compared with fasting level, which was significantly different from the effect observed after the intake of linseed cake. In contrast, no effect was seen on circulating level of IL-8. In addition, ALA and EPA were shown to elicit different effects on the release and mRNA expression levels of inflammatory markers in PBMC cultured ex vivo, with EPA having the most prominent pro-inflammatory potential.

In this long‐term study, we wanted to explore the effect of dietary supplementation of seal oil (SO) as compared cod‐liver oil (CLO) on subjects with moderate hypercholesterolemia. The test parameters included fatty acid composition in serum, blood lipids, platelet aggregation, and the activity of blood monocytes. After a run‐in period of 6 mon, 120 clinically healthy hypercholesterolemic (7.0–9.5 mmol/L; 270–366 mg/dL) subjects were randomly selected to consume either 15 mL of SO or CLO daily for 14 mon followed by a 4‐mon wash‐out period. A third group was not given any dietary supplement (control). Consumption of marine oils (SO and CLO) changed the fatty acid composition of serum significantly. Maximal levels were achieved after 10 mon. No further changes were seen after 14 mon. A wash‐out period of 4 mon hardly altered the level of n−3 fatty acids in serum. Addition of SO gave 30% higher level of eicosapentaenoic acid, as compared to CLO. Subjects taking SO or CLO had lower whole‐blood platelet aggregation than the control group. Neither SO nor CLO had any effects on the levels of serum total cholesterol, high‐density lipoprotein cholesterol, postprandial triacylglycerol, apolipoproteins A1 and B100, lipoprotein (a), monocyte function expressed as monocyte‐derived tissue factor expression, and tumor necrosis factor.

Cod liver oil is a traditional source of vitamin D in Iceland, and regular intake is recommended partly for the sake of bone health. However, the association between lifelong consumption of cod liver oil and bone mineral density (BMD) in old age is unclear. The present study attempted to assess the associations between intake of cod liver oil in adolescence, midlife, and old age, and hip BMD in old age, as well as associations between cod liver oil intake in old age and serum 25-hydroxyvitamin D (25(OH)D) concentration. Participants of the Age, Gene/Environment Susceptibility–Reykjavik Study (age 66–96 years; n 4798), reported retrospectively cod liver oil intake during adolescence and midlife, as well as the one now in old age, using a validated FFQ. BMD of femoral neck and trochanteric region was measured by volumetric quantitative computed tomography, and serum 25(OH)D concentration was measured by means of a direct, competitive chemiluminescence immunoassay. Associations were assessed using linear regression models. No significant association was seen between retrospective cod liver oil intake and hip BMD in old age. Current intake of aged men was also not associated with hip BMD, while aged women with daily intakes had z-scores on average 0·1 higher, compared with those with an intake of < once/week. Although significant, this difference is small, and its clinical relevance is questionable. Intake of aged participants was positively associated with serum 25(OH)D: individuals with intakes of < once/week, one to six time(s)/week and daily intake had concentrations of approximately 40, 50 and 60 nmol/l respectively (P for trend < 0·001).