Kari D. Hecker

Biological correlates of day-to-day variation in flow-mediated dilation in individuals with Type 2 diabetes: a study of test-retest reliability

Aims/hypothesisDysfunction of the vascular endothelium is commonly observed in Type 2 diabetes, and endothelial function may be an important outcome for clinical trials in diabetic samples. However, the most commonly used non-invasive test of endothelial function (flow-mediated dilation [FMD]) is technically challenging to perform, and no previous studies have carefully examined the reproducibility of FMD measurements in individuals with Type 2 diabetes. In this study, we tested the hypothesis that larger day-to-day changes in insulin and glucose are associated with larger fluctuations in FMD.MethodsUltrasound was used to measure the FMD (% change from baseline diameter) of the brachial artery in 18 healthy adults with Type 2 diabetes on three separate occasions, in the absence of changes to diet, activity level or medications. The CV and mean deviations between pairs of FMD scores in the same individual were used as the primary outcome variables.ResultsThe CV for FMD (29.7%) was higher than the level traditionally accepted for biochemical assays. However, this CV estimate is within the low range of published values for FMD in healthy individuals. FMD scores were not significantly correlated with glucose or insulin levels. However, subjects with the largest variability in FMD also showed the largest fluctuations in glucose (r=0.52), insulin (r=0.47) and heart rate (r=0.48) (p≤0.05).Conclusions/interpretationFMD can be reliably measured in individuals with Type 2 diabetes, and population-specific data on reliability is critical for the design of adequately powered studies of endothelial function.

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.

CHAPTER 18 – Dietary Macronutrients and Cardiovascular Risk

Cardiovascular disease (CVD) is the leading cause of death in the United States accounting for more deaths than all other causes combined. Numerous risk factors for CVD are identified, many of which are modifiable by diet and lifestyle practices. Major modifiable risk factors include cigarette smoking, elevated total and low-density lipoprotein (LDL) cholesterol levels, overweight and obesity, hypertension, diabetes mellitus, and a sedentary lifestyle. Other important risk factors that are modifiable by diet are a low level of high-density lipoprotein cholesterol, elevated levels of triglycerides, lipoprotein, insulin, hypertension, altered hemostatic factors, and small, dense LDL particles. This chapter reviews the understanding of how changes in the macronutrient profile of the diet affect CVD risk status. It describes various low saturated fatty acids (SFA) and cholesterol diets that differ in macronutrient content and present the plasma lipid and lipoprotein responses that are reported for these diets. This, chapter highlights the effect of various low SFA , low-cholesterol diet options with differentmacronutrient profiles on newly defined CVD risk factors.

Oils and Fats in the Prevention and Treatment of Cardiovascular Disease

For the first time, Dietary Reference Intakes (DRIs) for macronutrients have been established by the National Academies’ Institute of Medicine for the United States and Canada (1). This science-based report makes new recommendations for energy, carbohydrates, fiber, fat, fatty acids, cholesterol, protein, and amino acids. The DRI Report embraces the philosophy of making dietary recommendations that assure a nutritionally adequate diet, promote good health, prevent chronic disease, and avoid overconsumption. Recommendations suggest that adults should consume a diet that provides 45% to 65% of their calories from carbohydrates, 10% to 35% from protein, and 20% to 35% from fat. The report advises that saturated fat, trans fat, and cholesterol be as low as possible. Because polyunsaturated fatty acids (PUFAs) are essential nutrients, the DRI Report recommends 17 g/d for men and 12 g/d for women of linoleic acid (C 18:2), an omega-6 PUFA. For cs-linolenic acid (ALA), an omega-3 fatty acid, 1.6 and 1.1 g/d should be consumed by men and women, respectively. The recommendations for PUFA are based on average intakes in the United States. For simplicity, the report recommends that 5% to 10% of calories come from PUFA and 0.6% to 1.2% come from ALA. Importantly, approx 10% of omega-3 fatty acid intake can come from long-chain, highly unsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Because of the total fat recommendation and the guidance provided about saturated fat, trans fat, and PUFA intake, the balance will be derived from monounsaturated fatty acids (MUFAs). The range of total fat from 20% to 35% of calories recognizes that healthy diets can be planned over a reasonably broad range of fat intake, as long as saturated fat, trans fat, and cholesterol are kept as low as possible. This range in total fat reflects the health benefits of unsaturated fat in the context of a nutritionally adequate diet that promotes a healthy weight. The range of all macronutrients acknowledges that there are many healthy diets with respect to macronutrient profiles, as long as each diet meets the specific recommendations made in the DRI Report for saturated fat, trans fat, cholesterol, total fiber (38 g/d for men and 25 g/d for women), and added sugar (a maximum of 25% or fewer calories from added sugars).