Terry D. Etherton

Polyunsaturated fatty acids in the food chain in the United States

In the United States, intake of n-3 fatty acids is approximately 1.6 g/d ( approximately 0.7% of energy), of which 1.4 g is alpha-linolenic acid (ALA; 18:3) and 0.1-0.2 g is eicosapentaenoic acid (EPA; 20:5) and docosahexaenoic acid (DHA; 22:6). The primary sources of ALA are vegetable oils, principally soybean and canola. The predominant sources of EPA and DHA are fish and fish oils. Intake data indicate that the ratio of n-6 to n-3 fatty acids is approximately 9.8:1. Food disappearance data between 1985 and 1994 indicate that the ratio of n-6 to n-3 fatty acids has decreased from 12.4:1 to 10.6:1. This reflects a change in the profile of vegetable oils consumed and, in particular, an approximate 5.5-fold increase in canola oil use. The ratio of n-6 to n-3 fatty acids is still much higher than that recommended (ie, 2.3:1). Lower ratios increase endogenous conversion of ALA to EPA and DHA. Attaining the proposed recommended combined EPA and DHA intake of 0.65 g/d will require an approximately 4-fold increase in fish consumption in the United States. Alternative strategies, such as food enrichment and the use of biotechnology to manipulate the EPA and DHA as well as ALA contents of the food supply, will become increasingly important in increasing n-3 fatty acid intake in the US population.

Determinants of Erythrocyte Omega‐3 Fatty Acid Content in Response to Fish Oil Supplementation: A Dose–Response Randomized Controlled Trial

Background The erythrocyte membrane content of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which constitutes the omega‐3 index (O3I), predicts cardiovascular disease mortality. The amount of EPA+DHA needed to achieve a target O3I is poorly defined, as are the determinants of the O3I response to a change in EPA+DHA intake. The objective of this study was to develop a predictive model of the O3I response to EPA+DHA supplementation in healthy adults, specifically identifying factors that determine the response. Methods and Results A randomized, placebo‐controlled, double‐blind, parallel‐group study was conducted in 115 healthy men and women. One of 5 doses (0, 300, 600, 900, 1800 mg) of EPA+DHA was given daily as placebo or fish oil supplements for ≈5 months. The O3I was measured at baseline and at the end of the study. There were no significant differences in the clinical characteristics between the groups at baseline. The O3I increased in a dose‐dependent manner (P<0.0001), with the dose of EPA+DHA alone accounting for 68% (quadratic, P<0.0001) of the variability in the O3I response. Dose adjusted per unit body weight (g/kg) accounted for 70% (linear, P<0.0001). Additional factors that improved prediction of treatment response were baseline O3I, age, sex, and physical activity. Collectively, these explained 78% of the response variability (P<0.0001). Conclusions Our findings validate the O3I as a biomarker of EPA+DHA consumption and identify additional factors, particularly body weight, that can be used to tailor EPA+DHA recommendations to achieve a target O3I.

Recent discoveries in inclusive food-based approaches and dietary patterns for reduction in risk for cardiovascular disease.

Purpose of review To discuss new evidence-based dietary recommendations founded on an inclusive food strategy and to address the challenges that are posed by integrating a growing list of heart healthy foods into the diet without increasing energy intake beyond that required to achieve a healthy body weight. Recent findings New food-based dietary recommendations issued by the American Heart Association with the objective of reducing risk for cardiovascular disease (CVD) promote an inclusionary approach. The American Heart Association recommends a variety of foods to target four major goals: achieve a healthy overall diet, achieve a healthy weight, promote desirable lipid levels, and promote desirable blood pressure. Specific foods recommended include fruits and vegetables, grain products (including whole grains), fish, lean meat and poultry, fat-free or low-fat dairy products, and legumes. In addition, the new National Cholesterol Education Program Adult Treatment Panel III recommends reductions in saturated fat and cholesterol and therapeutic dietary options for enhancing LDL-cholesterol lowering, with inclusion of plant stanols/sterols (2 g/day) and increased viscous (soluble) fiber (10-25 g/day). In parallel with the evolution of new dietary recommendations is the expanding list of specific foods that have cardioprotective effects. Additional foods on this list are nuts, soy, legumes, alcohol, tea, and garlic. Summary It will be challenging to include all foods that reduce CVD risk in the diet and still maintain energy control. Strategies are needed that facilitate developing heart healthy dietary patterns that maximally reduce CVD risk.

Dietary stearic acid and risk of cardiovascular disease: Intake, sources, digestion, and absorption

Individual FA have diverse biological effects, some of which affect the risk of cardiovascular disease (CVD). In the context of food-based dietary guidance designed to reduce CVD risk, fat and FA recommendations focus on reducing saturated FA (SFA) and trans FA (TFA), and ensuring an adequate intake of unsaturated FA. Because stearic acid shares many physical properties with the other long-chain SFA but has different physiological effects, it is being evaluated as a substitute for TFA in food manufacturing. For stearic acid to become the primary replacement for TFA, it is essential that its physical properties and biological effects be well understood.

Independent associations of serum concentrations of 25-hydroxyvitamin D and parathyroid hormone with blood pressure among US adults.

Objective Vitamin D deficiency or high levels of parathyroid hormone (PTH) appear to be emerging risk factors for hypertension. This study examined whether serum concentrations of 25-hydroxyvitamin D [25(OH)D] and PTH were independently associated with blood pressure and the presence of hypertension or prehypertension among the United States adults. Methods Cross-sectional data from 7228 participants (aged ≥20 years) in the 2003–2006 National Health and Nutrition Examination Survey were analyzed. The least square means and the regression coefficients of systolic blood pressure, diastolic blood pressure, and pulse pressure across quintiles of serum 25(OH)D and PTH were estimated by conducting multiple linear regression analyses. The adjusted prevalence ratios with 95% confidence intervals for hypertension and prehypertension were estimated using the log-binomial method. Results Among participants not taking blood pressure medications (n = 5414), the mean age- and sex-adjusted systolic and diastolic blood pressure decreased linearly across quintiles of serum 25(OH)D but increased linearly across quintiles of serum PTH (P < 0.001 for all); these relationships remained significant even after extensively adjusting for covariates. Similarly, across quintiles of serum 25(OH)D, the age-adjusted prevalence of hypertension and the adjusted prevalence ratios for both hypertension and prehypertension decreased linearly (P < 0.001 for all). In contrast, the prevalence of hypertension and prehypertension increased nonlinearly (P < 0.05 for both) and the adjusted prevalence ratios for hypertension increased linearly across quintiles of serum PTH (P < 0.001). Conclusion Serum concentrations of 25(OH)D and PTH were independently associated with blood pressure and with the presence of hypertension or prehypertension among the United States adults, though casual relationships remain to be elucidated.

Exogenous pituitary and recombinant growth hormones induce insulin and insulin-like growth factor 1 resistance in pig adipose tissue☆

In the present study, pigs were treated daily for 7 days with exogenous porcine growth hormone (pGH; 70 micrograms/kg BW) in order to determine whether pGH induced insulin and insulin-like growth factor 1 (1GF-1) resistance in pig adipose tissue. In the first experiment, pituitary-derived pGH (ppGH) decreased basal and insulin-stimulated lipogenesis by 50%. Insulin sensitivity decreased more than 90% as the result of pGH treatment. Sensitivity and responsiveness to IGF-1 were decreased 50% by ppGH. In a second experiment, pigs were treated daily (70 micrograms/kg BW) with exogenous pituitary pGH (ppGH) or recombinant pGH (rpGH) for 7 days in order to determine if the effects of pGH were intrinsic properties of the hormone. Both rpGH and ppGH caused similar decreases in basal rates of lipogenesis, insulin- and IGF-1-stimulated lipogenesis, and insulin and IGF-1 responsiveness in pig adipose tissue. In summary, the decrease in adipose tissue growth of pigs treated chronically with pGH is due in large part to the suppression of fatty acid synthesis and a decrease in the ability of insulin to stimulate lipid synthesis in pig adipocytes. These responses are intrinsic properties of pGH since the effects of rpGH mimicked those of ppGH. The role and importance of a decrease in IGF-1 responsiveness remains to be resolved.

Survey of Retail Milk Composition as Affected by Label Claims Regarding Farm-Management Practices

A trend in food labeling is to make claims related to agricultural management, and this is occurring with dairy labels. A survey study was conducted to compare retail milk for quality (antibiotics and bacterial counts), nutritional value (fat, protein, and solids-not-fat), and hormonal composition (somatotropin, insulin-like growth factor-1 [IGF-1], estradiol, and progesterone) as affected by three label claims related to dairy-cow management: conventional, recombinant bovine somatotropin (rbST)-free (processor-certified not from cows supplemented with rbST), or organic (follows US Department of Agriculture organic practices). Retail milk samples (n=334) from 48 states were collected. Based on a statistical analysis that reflected the sampling schema and distributions appropriate to the various response variables, minor differences were observed for conventional, rbST-free, and organic milk labels. Conventionally labeled milk had the lowest (P<0.05) bacterial counts compared to either milk labeled rbST-free or organic; however, these differences were not biologically meaningful. In addition, conventionally labeled milk had significantly less (P<0.05) estradiol and progesterone than organic milk (4.97 vs 6.40 pg/mL and 12.0 vs 13.9 ng/mL, respectively). Milk labeled rbST-free had similar concentrations of progesterone vs conventional milk and similar concentrations of estradiol vs organic milk. Concentrations of IGF-1 in milk were similar between conventional milk and milk labeled rbST-free. Organic milk had less (P<0.05) IGF-1 than either conventional or rbST-free milk (2.73 ng/mL vs 3.12 and 3.04 ng/mL, respectively). The macronutrient profiles of the different milks were similar, except for a slight increase in protein in organic milk (about 0.1% greater for organic compared to other milks). Label claims were not related to any meaningful differences in the milk compositional variables measured. It is important for food and nutrition professionals to know that conventional, rbST-free, and organic milk are compositionally similar so they can serve as a key resource to consumers who are making milk purchase (and consumption) decisions in a marketplace where there are misleading milk label claims.

Effects of Exercise on Plasma Lipids and Lipoproteins of Women

Abstract This review summarizes the cross-sectional and training studies (acute and chronic) that have examined the relationship between exercise and plasma lipid and lipoproteins in women. Because women experience major fluctuations in reproductive hormones throughout the life cycle, the effects of the endogenous sex steroid status on the association between exercise and plasma lipoproteins also are addressed. In general, cross-sectional studies report a positive association between exercise and high density lipoprotein-cholesterol (HDL-C) in both pre- and postmenopausal women. Women on hormone replacement therapy who report exercising have higher HDL-C than sedentary women on hormone replacement therapy. Results from longitudinal training studies have been inconsistent because of experimental design, i.e., inadequate type, duration, and intensity of exercise intervention, lipid measurements made across the menstrual cycle, and studies carried out in women with high baseline HOL-C. Since lipids vary approximately 10-25% throughout the menstrual cycle, menstrual phase should be controlled when determining lipid changes after an exercise intervention. In approximately half of the intervention studies, an increase in HDL-C was demonstrated; the magnitude of the response that can be expected is ≍10%. The responsiveness of pre- versus postmenopausal women to an exercise intervention is unknown. Studies are needed to clarify the interactive effects of exercise and sex hormones on plasma lipoproteins in women of all ages. This information will be useful in developing intervention programs to reduce the risk of coronary heart disease in women.

Mechanisms by which somatotropin decreases adipose tissue growth.

When growing pigs are treated daily with recombinantly derived porcine somatotropin (pST) for 30-60 d there is a dose-dependent decrease in lipid accretion. Maximal doses of pST can reduce lipid accretion by as much as 70%. The reduction in lipid accretion occurs because of a marked decrease in glucose transport and lipogenesis that is the result of a pST-dependent decrease in the ability of insulin to stimulate these processes in the adipocyte; lipolysis is not affected. The decrease in insulin sensitivity is not due to a decrease in insulin binding or insulin receptor kinase activity. Little is understood about the somatotropin (ST) intracellular signal pathway(s) that mediate the biological effects of ST. These effects are chronic rather than acute as was previously believed. This pattern likely reflects that ST decreases transcription of important insulin-responsive genes such as the muscle-adipose tissue transporter gene (GLUT4) and key lipogenic enzymes.

Dietary fat : Assessing the evidence in support of a moderate-fat diet; the benchmark based on lipoprotein metabolism

There is a growing database that has evaluated the effects of varying amounts of total fat on risk factors for cardiovascular disease, diabetes and overweight and obesity. The evidence clearly suggests that extremes in dietary fat should be avoided, and instead a diet moderate in total fat (25-35 % energy) is preferable for the majority of individuals. Moreover, we now appreciate the importance of individualizing dietary fat recommendations within this range of total fat. With respect to cardiovascular disease, a diet higher in total fat (30-35 % energy) affects the lipid and lipoprotein risk profile more favourably than a lower-fat diet; this is also the case for individuals with diabetes, with the added benefit of better glycaemic control. Dietary fibre (> or = 25 g/d) attenuates and even prevents the potentially adverse lipid and lipoprotein effects of a lower-fat diet. With respect to weight control, a moderate-fat diet can be as, or even more, effective than a lower-fat diet, because of advantages with long-term adherence and potentially favourable effects on lipids and lipoproteins. Thus, there is now a convincing scientific basis to advocate a diet moderate in total fat for the majority of individuals. Implicit to this position is that unsaturated fat has numerous beneficial health effects. However, because fat is energy dense, moderation in fat intake is essential for weight control. Consequently, a simple message to convey is to avoid diets that are very low and very high in fat. Moreover, within the range of a moderate-fat diet it is still important to individualize the total fat prescription. Nonetheless, the guiding principle is that moderation in total fat is the defining benchmark for a contemporary diet that reduces risk of chronic disease.