This is our weekly selection of recently published nutrition research.
Here are some of the most interesting findings this week:
Regional light pollution is associated with higher obesity rates.
Older people’s protein requirements may be underestimated.
Aspartame is associated with impaired blood sugar control in obese individuals.
Too much sodium may increase the risk of heart disease in people with high blood pressure.
Textured foods reduce appetite more than simple-textured foods.
Caffeine temporarily helps you get things done and achieve your goals.
This week we reviewed one study examining the association of outdoor light pollution with regional obesity rates and another assessing the protein requirements of older people using a new technique.
Review: Does Night-Time Light Make People Fat?
Article: Does artificial light-at-night exposure contribute to the worldwide obesity pandemic?
Summary: This was an observational study examining the association of outdoor, artificial light levels with obesity rates.
The study found that higher regional light levels were linked with increased obesity rates. The causality of this association is unknown. The authors speculated that light might promote weight gain by impairing people’s sleep and disrupting the body clock.
Review: Do Recommendations Underestimate People’s Protein Requirements?
Article: Dietary Protein Requirement of Men >65 Years Old Determined by the Indicator Amino Acid Oxidation Technique Is Higher than the Current Estimated Average Requirement.
Summary: This study evaluated the protein requirements of older people using a new and potentially more accurate technique.
It suggests that the official recommendations for protein intake may underestimate protein requirements by 30%. However, further studies are needed before the current recommendations can be changed.
New Research from Around the World
Lots of new papers came to our attention this week. Here are summaries of the most interesting or relevant studies, categorized by subject.
Obesity and Weight Loss
Blood Sugar Control and Diabetes
Appetite and Eating
Brain and Mental Health
Muscles and Physical Performance
Pregnancy and Infant Health
1. Obesity and Weight Loss
Vitamin D and body composition in the elderly.
This observational study in elderly people showed that low circulating levels of vitamin D were associated with a greater fat mass. However, the causality of this association is unknown.
It is unlikely that vitamin D deficiency causes obesity. Instead, higher amounts of fat mass may bind to vitamin D, reducing its blood levels. Further studies are needed.
Efficacy of an orlistat-resveratrol combination for weight loss in subjects with obesity: A randomized controlled trial.
This 6-month, randomized controlled trial in obese adults on a calorie-reduced diet showed that supplementing with a combination of resveratrol and orlistat caused significantly more weight loss than orlistat or resveratrol alone.
Resveratrol is an antioxidant found in plant foods, such as the skin of red grapes and blueberries, whereas orlistat is a pharmaceutical weight loss drug that blocks the absorption of dietary fat.
2. Blood Sugar Control and Diabetes
Effects of wheat bran extract rich in arabinoxylan oligosaccharides and resistant starch on overnight glucose tolerance and markers of gut fermentation in healthy young adults.
Arabinoxylan oligosaccharides (AXOs) are a type of prebiotic fiber found in wheat bran.
This randomized crossover study in healthy adults showed that eating bread enriched with AXOs in the evening improved insulin sensitivity in the morning.
Aspartame intake is associated with greater glucose intolerance in individuals with obesity.
Aspartame is a common artificial sweetener. This observational study showed that a higher intake of aspartame was associated with impaired obesity-related blood sugar control. The causality of this association is unclear.
3. Heart Health
Associations of urinary sodium excretion with cardiovascular events in individuals with and without hypertension: a pooled analysis of data from four studies.
This large observational study showed that a higher sodium intake was linked with increased systolic blood pressure and an increased risk of heart disease events and death in people with high blood pressure (hypertension).
However, a similar association was not seen in people without hypertension. Additionally, low sodium intakes were linked with an increased risk of heart disease events and death, regardless of people’s blood pressure.
Potassium supplementation and heart rate: a meta-analysis of randomized controlled trials.
This meta-analysis of randomized controlled trials showed that supplementing with 2–3 grams of potassium per day is unlikely to increase heart rate in healthy adults.
In contrast, previous studies have indicated that increased potassium intake may lower blood pressure.
Soy milk powder supplemented with phytosterol esters reduced serum cholesterol level in hypercholesterolemia independently of lipoprotein E genotype: A random clinical placebo-controlled trial.
Phytosterols are a group of plant compounds found in oils and fat. They have a structure similar to cholesterol.
This randomized controlled trial in older Chinese people found that supplementing with 2 grams of phytosterols per day for 6 months reduced circulating levels of cholesterol by 9.3%. However, the health benefits are debatable.
Impact of flavonoid-rich black tea and beetroot juice on postprandial peripheral vascular resistance and glucose homeostasis in obese, insulin-resistant men: a randomized controlled trial.
Vascular resistance (VR) is the force needed to keep the blood flowing through your veins. It mainly depends on how narrow or dilated your veins are. High VR is an aspect of high blood pressure.
This randomized controlled trial in obese, insulin-resistant men found that drinking 100 ml of black tea or beetroot juice, combined with 75 grams of glucose, reduced VR, compared to a placebo. The tea also decreased their rise in insulin.
Impact of menaquinone-4 supplementation on coronary artery calcification and arterial stiffness: an open label single arm study.
Arterial stiffness is a measure of the blood vessels’ ability to expand or contract. It specifically refers to the arteries, the blood vessels that carry blood from the heart. Increased arterial stiffness is associated with an elevated risk of heart disease.
This study showed that supplementing with 45 mg of menaquinone-4 (vitamin K2) per day for 1 year did not affect arterial stiffness.
Dairy Consumption and Risk of Stroke: A Systematic Review and Updated Dose-Response Meta-Analysis of Prospective Cohort Studies.
This systematic review and meta-analysis of observational studies suggests that drinking milk and eating cheese may reduce the risk of stroke. However, total intake of dairy products, yogurt or butter was not significantly linked with the risk of stroke.
The Geriatric Nutritional Risk Index Predicts Survival in Elderly Esophageal Squamous Cell Carcinoma Patients with Radiotherapy.
Esophageal squamous cell carcinoma (ESCC) is a type of cancer that forms in the esophagus, the tube that connects the mouth to the stomach.
This observational study showed that a favorable score on the Geriatric Nutritional Risk Index was associated with better treatment outcomes in older people undergoing radiotherapy to treat ESCC.
5. Appetite and Eating
Satiety effects of psyllium in healthy volunteers.
Psyllium husk is a type of fiber commonly used to treat constipation and the main active component in Metamucil. Like other bulk-producing types of fiber, it may be used to promote fullness.
This randomized controlled trial found that 3.4–10.2 grams of psyllium taken before meals significantly reduced hunger and the desire to eat and increased fullness. These findings suggest that psyllium may be effective at reducing calorie intake.
Increased textural complexity in food enhances satiation.
This randomized crossover trial showed that eating food with complex textures reduced appetite and calorie intake, compared to foods with simple textures.
This is likely due to the fact that people tend to spend more time chewing textured food, which promotes a decrease in appetite.
Pleasure as an ally of healthy eating? Contrasting visceral and Epicurean eating pleasure and their association with portion size preferences and wellbeing.
There are two distinct types of eating-related pleasures. One is visceral eating pleasure (VEP), which is triggered by hunger, smell, cravings or other emotional urges. Too much VEP is linked to overeating and weight gain.
The other is Epicurean eating pleasure (EEP), which is the appreciation of the cultural, aesthetic or symbolic value of food. Unlike VEP, EEP is associated with health and smaller food portions and not linked with a higher body mass index.
Calorie Underestimation When Buying High-Calorie Beverages in Fast-Food Contexts.
This study asked 1,877 adults and 1,178 adolescents visiting fast food restaurants to estimate the calories in the food they ordered. It showed that people significantly underestimated the calorie content of their food.
This especially applied to high-calorie beverages. The findings indicate that high-calorie beverages, such as sugar-sweetened soft drinks, significantly contribute to calorie underestimation and overeating.
6. Brain and Mental Health
Milk intake during pregnancy is inversely associated with the risk of postpartum depressive symptoms in Japan: The Kyushu Okinawa Maternal and Child Health Study.
Postpartum depression affects some women in the first few months after childbirth. This observational study in Japanese women suggests that drinking milk during pregnancy is linked with a lower risk of postpartum depression.
Investigating the effects of caffeine on executive functions using traditional Stroop and a new ecologically-valid virtual reality task, the Jansari assessment of Executive Functions (JEF©).
Executive function is a term used to describe the mental skills that help you achieve your goals. These include attention, working memory, reasoning and problem solving, to name a few.
This study suggests that caffeine, the stimulant found in coffee, may improve many aspects of executive function, such as planning, creative thinking and reaction time.
From gut dysbiosis to altered brain function and mental illness: mechanisms and pathways.
Gut dysbiosis is when there is an unhealthy imbalance in the bacterial community of the digestive system. This review discusses how dysbiosis may possibly affect brain function, causing depression and other psychiatric disorders.
7. Muscles and Physical Performance
Anabolic effects of leucine-rich whey protein, carbohydrate, and soy protein with and without β-hydroxy-β-methylbutyrate (HMB) during fasting-induced catabolism: A human randomized crossover trial.
β-hydroxy-β–methylbutyrate (HMB) is a common supplement used to increase muscle strength and performance and reduce recovery time after training. It is also formed in the body as a metabolite of leucine, an essential amino acid.
This randomized controlled trial found that supplementing with a leucine-rich whey protein beverage or soy protein enriched with 3 grams of HMB improved muscle maintenance after 36 hours of fasting, compared to carbs or soy protein alone.
8. Pregnancy and Infant Health
Vitamin supplementation for preventing miscarriage.
This Cochrane review concluded that supplementing with vitamins before pregnancy or during early pregnancy does not prevent miscarriage. However, taking multivitamins along with iron and folic acid may reduce the risk of stillbirth.
Decreased serum vitamin D levels in early spontaneous pregnancy loss.
This observational study showed that a vitamin D deficiency was associated with pregnancy loss (miscarriage) in the first trimester of pregnancy.
Association between lutein intake and lutein concentrations in human milk samples from lactating mothers in South Korea.
Lutein is an antioxidant found in high amounts in many vegetables, such as kale, spinach, turnip greens, watercress, romaine lettuce, zucchini and Brussels sprouts.
This observational study in lactating South Korean mothers showed that a high intake of lutein-rich foods was linked with increased lutein levels in breast milk, suggesting that it may also benefit the infant.