This is an overview of everything new and interesting that happened in nutrition science in the past week, from last Friday (Sep 25th) until today (Oct 2nd).
Past Week in Nutrition Science (Sep 25th – Oct 2nd)
This week, we reviewed two new studies. One was on the effects of saturated fat from meat and cheese on blood lipids, while the other was about the effects of different fruits and vegetables on weight change.
Study: Thorning et al. Diets With High-Fat Cheese, High-Fat Meat, or Carbohydrate on Cardiovascular Risk Markers in Overweight Postmenopausal Women: A Randomized Crossover Trial. American Journal of Clinical Nutrition 2015.
Summary: This randomized controlled trial looked at the effects of saturated fat from high-meat and high-cheese diets on blood lipids and lipoproteins. The control group followed a low-fat, high-carb diet.
In this study, the high saturated fat diets had very little effects, except that they increased HDL cholesterol and apolipoprotein-A1, the lipoprotein that carries HDL cholesterol in the blood.
Study: Bertoia et al. Changes in Intake of Fruits and Vegetables and Weight Change in United States Men and Women Followed for Up to 24 Years: Analysis from Three Prospective Cohort Studies. PLOS Medicine 2015.
Summary: This paper analyzed data from 3 observational studies with a total of 133,468 people. It looked at changes in intake of specific fruits and vegetables and effects on body weight.
They found that all fruits were associated with weight loss, especially berries. Vegetables were also associated with weight loss, except for starchy vegetables like potatoes, corn and peas – which were associated with weight gain.
Vegetables that were both high in fiber and had a low glycemic load (GL) were more strongly associated with weight loss over time.
New Studies From Around The Web
Here is an overview of the most interesting studies, organized by category.
Obesity and Weight Loss
This randomized controlled trial showed that weighing oneself every day with Wi-Fi scales and receiving graphic feedback via e-mail prevented age-related weight gain in young college students. The intervention group lost 0.5 kg (1.1 lb), while the control group gained 1.1 kg (2.4 lbs) over 1 year.
This study suggests that the lipolytic (fat-burning) effects of the hormone leptin are mediated by sympathetic nerves in fat tissue.
This randomized crossover study showed that diet-induced thermogenesis (DIT) was 44% lower in the evening compared to morning, which was mediated by the circadian system (the body’s internal clock). Eating food in the evening or at night may cause weight gain compared to eating it in the morning, when DIT is higher.
This was an analysis from the Minnesota Starvation Experiment looking at metabolic adaptation to severe calorie restriction and subsequent refeeding. We will be reviewing this study in detail next week.
This study found that increased body fat in the abdominal cavity (visceral fat) was linked to increased body dissatisfaction and increased risk of loss-of-control eating. Depositing body fat “centrally” may raise the risk of eating disorders.
This randomized crossover study found that a high-protein breakfast increased metabolism and fat burning and reduced hunger in both normal weight and overweight children.
This study found that males, and those with a higher BMI, under-reported their calorie intake to a greater extent.
This analysis from the Framingham Heart Study Offspring Cohort found that yogurt intake was associated with reduced risk of developing high blood pressure. It also found that total dairy intake and total low-fat/fat-free dairy intake were linked to decreased diastolic blood pressure.
This 24-week randomized controlled trial found that a cholesterol-lowering diet with soy protein, viscous fiber and nuts caused slightly greater reductions in blood pressure than a DASH-type diet.
This 12-month randomized controlled trial found that recommendations to increase fruit and vegetable intake slowed the progression of atherosclerosis in the carotid arteries in individuals with type 1 and type 2 diabetes.
This meta-analysis of 6 observational studies found that drinking sugar-sweetened beverages was linked to a 12% greater risk of developing high blood pressure. Each single serving per day was linked to an 8.2% greater risk.
This observational study found that higher levels of omega-6 fatty acids in the blood were linked to increased stiffness of arteries, while levels of omega-3 fatty acids were linked to decreased stiffness.
Insulin Resistance and Metabolic Syndrome
This meta-analysis of randomized controlled trials found that a paleolithic diet caused greater short-term improvements in symptoms of metabolic syndrome compared to standard nutrition guidelines.
This randomized controlled trial compared modified DASH diets high in either animal or plant protein in overweight adults with metabolic syndrome. Both diets were effective and there was no difference between plant or animal protein.
This analysis from the PREDIMED study found that low-fat dairy, low-fat yogurt, low-fat milk and whole-fat yogurt were linked to decreased risk of metabolic syndrome. However, cheese was linked to increased risk.
Blood Sugar Control and Diabetes
This 52-week randomized controlled trial in 115 obese individuals with type 2 diabetes compared calorie-restricted low-carb and high-carb diets. Both diets caused weight loss and improved blood sugar control. The low-carb diet had greater effects on blood lipids, blood sugar stability and caused a greater reduction in diabetes medication requirements.
This study found that a single serving of caffeinated coffee raised blood sugar levels in overweight men.
This observational study did not find a statistically significant reduction in colorectal cancer based on total fiber intake. However, it did find a reduction in distal colorectal cancer risk and incident colorectal adenoma.
Vegetarian and Vegan Diets
This observational study found that lacto-ovo vegetarians, lacto-vegetarians and vegans had reduced obesity, blood pressure and blood sugar compared to non-vegetarians. However, the vegetarians and vegans had lower HDL levels.
Foods and Food Groups
This randomized crossover trial found that 50 grams of honey, sucrose and high-fructose corn syrup for 14 days had similar effects on inflammation, blood sugar control and blood lipids. All 3 increased blood triglycerides, but only increased blood sugar and inflammatory markers in individuals with insulin resistance.
This meta-analysis of randomized controlled trials found that fish (especially fatty fish) increased blood levels of vitamin D. On average, increased fish intake increased blood levels by 4.4 nmol/mL, but reached 8.3 nmol/L in the longer-term studies.
This systematic review compared different types of whole-grain oats cereals and their effects on blood sugar levels. Steel-cut oats, large-flake oats, muesli and granola had much smaller effects on blood sugar levels than than quick-cooking oats and instant oatmeal.
This study found that palm dates did not change levels of gut bacteria. However, the dates did increase bowel movements and stool frequency and reduced fecal genotoxicity, which may indicate reduced risk of colon cancer.
This randomized controlled trial found no effect of vitamin D supplementation on muscle hypertrophy or muscle strength over 12 weeks in young or elderly individuals. However, there was some difference in muscle quality in elderly and fiber type morphology in young individuals.
Infusing the amino acid leucine into the duodenum of lean men reduced calorie intake by 13%, increased blood levels of cholecystokinin (CCK) and reduced blood sugar and insulin levels.
This randomized controlled trial found that melatonin supplementation for 12 months had no effects on postural balance, risk of falls, muscle strength, quality of life or sleep in postmenopausal women. However, there was a non-significant trend towards improved sleep in women who had sleep disturbances at the beginning of the study.
Effects of a quercetin-rich onion skin extract on 24 h ambulatory blood pressure and endothelial function in overweight-to-obese patients with (pre-)hypertension: a randomised double-blinded placebo-controlled cross-over trial.
This randomized controlled trial found that quercetin from onion skin slightly reduced systolic blood pressure (-3.6 mmHg) in individuals with high blood pressure, but not in individuals with normal blood pressure.
This study found that cocoa flavanols significantly improved endothelial function. They also lowered blood pressure and LDL cholesterol, while increasing HDL cholesterol.
A review that discusses how vitamin E requirements may be increased when people increase their intake of polyunsaturated fatty acids.
This is a review of the effects of the hormone insulin on skeletal muscle protein synthesis and breakdown.
This crossover randomized controlled trial of 12 young men found that dairy protein had a greater effect on muscle protein synthesis in the 0-2 hour post-exercise phase, but there was no net difference over the 0-5 hour post-exercise phase.
This randomized controlled trial found that supplementing with collagen peptides improved body composition and increased muscle strength in elderly men with sarcopenia, when combined with resistance training.
Fertility and Pregnancy
Women with high blood levels of folate and vitamin B12 had much higher (62% and 104%, respectively) rates of successful live births using assisted reproductive technology (ART) treatment.
This study found that overweight, obese and severely obese women had 40%, 80% and 100% greater risk of stillbirth, respectively, compared to lean women.
Aging and Longevity
This study found that a diet with a high dietary inflammation index (DII) was associated with a shortening of telomeres. This indicates that an inflammatory diet can accelerate aging, and that an anti-inflammatory diet may slow aging.