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SUBJECT: AJCN Oct 2012
OBESITY SECTION 1. Why eating carbs is so dangerous - The search for lifestyle changes that will slow the obesity epidemic and its adverse sequelae has turned to dietary sugar. A substantial number of calories come from beverages and desserts made with sucrose or high-fructose corn syrup, which are absorbed as a mixture of glucose and fructose. But apart from weight gain from excess sweet calories, what are the specific metabolic consequences that are harmful to health?
The best-documented adverse effect known for decades is the dyslipidemia that develops with the ingestion of large amounts of sugar, even when substituted calorie for calorie for fat (1). An important mechanism is de novo lipogenesis (DNL), the synthesis of the SFA palmitate, from glucose, fructose, or both. There is a marked increase in DNL after excess carbohydrate calories (2) or the isocaloric substitution of dietary glucose or mixed sugars for starch, complex carbohydrate, or fat (1, 3). Although the absolute quantity of synthesized fat is small, there are large increases in plasma triglyceride concentrations and the ratio of palmitate to the essential fatty acid linoleate (lipogenic index). Triglyceride synthesis and secretion by the liver is increased by the generation of palmitate, glycerol (the backbone of triglyceride), and malonyl coenzyme A (an intermediate that inhibits fatty acid oxidation and channels fatty acids into triglyceride). The fructose component of dietary sugar is particularly lipogenic because of its uniquely high first-pass clearance by the liver. Increased plasma VLDL triglyceride, via cholesterol ester exchange protein, produces the full spectrum of lipid abnormalities (high triglycerides, small dense LDL, and low HDL) that accelerate atherosclerosis. Conversely, DNL and triglyceride synthesis are rapidly suppressed during weight loss (2). The current study by Sevastianova et al (4) in this issue of the Journal expands the lipogenic effects of dietary sugar beyond dyslipidemia to include fatty liver.
2. Dairy Calories have the same effect as any food on weight loss - A more rigorous meta-analysis (10) reviewed the findings from intervention trials with or without energy restriction that have compared weight loss and fat loss. The addition of dairy to diets promotes neither weight gain nor weight loss. However, energy-restricted diets containing dairy promoted weight loss but were not superior compared with other forms of caloric restriction. But many components of dairy have potential benefits. The high calcium in cheese might decrease fat absorption by promoting the formation of insoluble calcium soaps with fatty acids (4), but this effect has been shown to be trivial (5). A large amount of attention in the past decade was focused on conjugated linoleic acid (CLA) and its purported weight-loss effects. However, the intake of CLA provided by dairy is ∼0.1 g/d, much less than the amounts (2–4 g/d) tested in weight-loss trials, which showed no convincing effects (6). More recently, branched-chain amino acids (valine, leucine, isoleucine), which are enriched in the whey fraction, have been proposed to have anabolic effects acting via the insulin-like growth factor axis and mammalian target of rapamycin complex 1 signaling pathway (7, 8).
3. Irregular sleep times promote obesity -The main effect of circadian misalignment, either phase advanced or phase delayed, is a concomitant disturbance of the glucose-insulin metabolism and substrate oxidation, whereas the energy balance or sleep is not largely affected. Chronically eating and sleeping at unusual circadian times may create a health risk through a metabolic disturbance.
4. Key to postpartum weight loss is restricting Calories, not exercise - Dietary treatment provided clinically relevant weight loss in lactating postpartum women, which was sustained at 9 mo after treatment. The combined treatment did not yield significant weight or body-composition changes beyond those of dietary treatment alone.
HEART DISEASE 5. Balancing fish and mercury - Exposure to methylmercury was associated with increased risk of MI, and higher S-PUFA concentrations were associated with decreased risk of MI. Thus, MI risk may be reduced by the consumption of fish high in PUFAs and low in methylmercury.
6. Be pear, not an apple shaped, if overweight - Ethnic differences in cardiometabolic risk (CMR) may be related to patterns of ethnic-specific body fat distribution.
7. Upper limit for leucine is 35g/day - Leucine has been suggested to improve athletic performance. Therefore, the branched-chain amino acids (BCAAs), especially leucine, are popular as dietary supplements in strength-training athletes; however, the intake of leucine in excess of requirements raises concerns regarding adverse effects.
9. Two daily portions of berries lowers BP - These data, which include direct measures of arterial stiffness and thickness, suggest that higher intake of anthocyanins and flavones are inversely associated with lower arterial stiffness. The intakes of anthocyanins associated with these findings could be incorporated into the diet by the consumption of 1–2 portions of berries daily.
10. Iron excess modestly increases endometrial cancer - Our study suggests a modest positive association between heme iron, total iron, and liver intakes and endometrial cancer risk.
11. Meat, milk and eggs increase prostate cancer risk - Meat, milk, and eggs have been inconsistently associated with the risk of advanced prostate cancer. These foods are sources of choline. Of the 47,896 men in our study population, choline intake was associated with an increased risk of lethal prostate cancer.
12. Physicians Health Study finds metabolites of EPA and DHA are what lowers heart disease risk - Our data are consistent with an inverse and nonlinear relation of plasma phospholipid ALA and DPA, but not EPA or DHA, with HF risk. Fish consumption greater than once per month was associated with a lower HF risk.
- Roc, Nutrition Investigator