Past Week in Nutrition Science: This is an overview of interesting nutrition research published from Friday, Nov 27th, to Friday, Dec 4th.
Past Week in Nutrition Science (Nov 27th–Dec 4th)
As usual, we reviewed two articles this week. One was recently published in Cell, while the other appeared in Appetite.
Summary: This study examined which factors caused individual variability in blood sugar responses after identical meals. The authors also developed an algorithm to predict blood sugar responses.
The study showed that the rise in blood sugar after meals is highly variable between individuals. This is explained by multiple factors, such as the types of bacteria present in people’s digestive system.
Summary: Garlic may improve the smell of men’s armpit sweat, reducing its intensity, as rated by women. Sweat that smelled less strong was considered more attractive.
Hypothetically, this may be because garlic’s antibiotic properties reduce the growth or activity of the skin bacteria responsible for sweat-related body odor.
New Research From Around the World
Tons of new research articles were published this week. As usual, we categorize the articles by subject.
- Obesity and Weight Loss
- Blood Sugar Control and Diabetes
- Heart and Vascular Health
- Appetite and Eating
- Brain and Mental Health
- Digestion and Gut Health
- Bone Health
- Eyes and Vision
- Infant Health
- Sports Nutrition
- Nutrients, Vitamins and Minerals
1. Obesity and Weight Loss
This observational study suggests that temporarily encouraging weight gain in 12–18 month old children, in an interventional study, does not make them more likely to be overweight 15 years later.
Also, they were not more likely to have high blood pressure or to have worse blood lipid profiles, compared to children who were not encouraged to gain weight.
This cross-sectional observational study suggests that eating often — high meal and snacking frequency — makes US adults more likely to be overweight or obese. Eating frequency was also associated with abdominal obesity.
2. Blood Sugar Control and Diabetes
This trial in overweight and obese adults showed that following a high-fat, high-saturated-fat diet for 4 weeks reduced insulin sensitivity, even without weight gain. This suggests a high-fat diet may contribute to the development of type 2 diabetes.
This observational study suggests that taking chromium supplements may reduce the risk of type 2 diabetes.
Previous research indicates that low circulating levels of vitamin D are associated with insulin resistance. This observational study suggests that central or abdominal obesity is mainly responsible.
This randomized controlled trial found that taking fish oil, 6 grams every day for 9 months, did not improve blood sugar control for those with impaired blood sugar control.
This randomized controlled trial in pregnant women showed that taking selenium supplements, 60 µg per day from the 12th week of pregnancy until delivery, had no effects on the hormone adiponectin, which is a marker of insulin resistance.
These findings suggest that moderate selenium supplementation does not increase the risk of type 2 diabetes during pregnancy.
3. Heart and Vascular Health
This randomized controlled trial showed that supplementing with vitamin D3, 20 µg per day for 12 weeks, did not improve risk factors for heart disease in German people with inadequate vitamin D levels.
This scientific review discusses the association of constipation and poor health. It concludes that chronic constipation may be linked with several diseases, including heart disease and increased risk of death.
Previous studies indicate that soy protein may lower LDL-cholesterol, a risk factor for heart disease.
This randomized controlled trial examined whether soy flour had similar effects. The study showed that taking 12.5 or 25 grams of soy protein from soy flour daily for 6 weeks did not reduce LDL-cholesterol or other risk factors for heart disease.
This observational study in Korean women suggests that eating fried food frequently may increase the chance of high blood pressure.
Poor blood sugar control may promote the formation of glyceraldehyde, which promotes the formation of unhealthy compounds known as glyceraldehyde-derived advanced glycation end products (glycer-AGEs).
This prospective observational study suggests that high levels of circulating glycer-AGEs may increase the risk of rectal cancer. However, glycer-AGEs were not linked with colon cancer.
This observational study in Chinese adults suggests that folate and vitamin B6 may protect against cancer in the upper part of the pharynx.
This observational study in Italian women indicates that eating a diet that promotes inflammation may increase the risk of cancer in the endometrium, the inner lining of the uterus.
Carotenoids are a class of antioxidant pigments found in plants. The best known carotenoid is beta-carotene, which can be changed into vitamin A in the body.
This observational study in Chinese women suggests that high circulating levels of the carotenoids alpha-carotene, beta-carotene, lycopene, lutein and zeaxanthin may protect against breast cancer.
5. Appetite and Eating
Some studies suggest that monosodium glutamate (MSG) may increase the feeling of fullness in normal-weight adults. However, not all studies have provided consistent results.
This randomized controlled trial showed that 200 ml of vegetable soup with 1 gram of MSG reduced subsequent calorie intake, compared to the same soup without MSG.
6. Brain and Mental Health
This scientific review discusses the possibility that toxicants or micronutrients in the pregnant mother‘s diet may increase the risk of autism in the child.
Previous studies have identified vitamin D deficiency as a risk factor for mental impairment. This observational study examined this association in peritoneal dialysis patients.
Peritoneal dialysis is a mechanical process that helps clean the blood of patients with poor kidney function. The study found that vitamin-D-deficient peritoneal dialysis patients had an increased risk of cognitive impairment.
This study showed that autistic Canadian children had lower levels of certain fatty acids in their red blood cells, compared to healthy children.
These fatty acids were docosahexaenoic acid (DHA), arachidonic acid and the ratio of omega-3 and omega-6 fatty acids.
This observational study in Tanzanian children indicates that chronic malnutrition may cause delays in brain and mental development.
This controlled, crossover trial showed that a single, 800-mg dose of wild green oat extract temporarily improved mental performance in healthy adults, aged 40 to 65 years.
7. Digestion and Gut Health
This study in mice with colitis suggests that potato fiber may reduce intestinal inflammation, possibly by promoting the formation of short-chain fatty acids.
This small, crossover trial in overweight men showed that casein, the most abundant type of milk protein, affects fat digestion and reduces the rise in circulating triglycerides after a meal.
In this randomized crossover study, bread with gluten and bread without gluten had similar effects on digestive function.
This mouse study indicates that cold exposure may change the composition of gut bacteria. The authors called the resulting microbiota the “cold microbiota.”
Transplanting the cold microbiota into other mice resulted in changes associated with adaptation to cold environments. This study shows that the gut bacteria play an important role in how animals adapt to their environment.
This study examined the effects of eating oatmeal porridge, 60 grams daily for a week, on the activity of gut bacteria.
The results suggest that oatmeal porridge may have prebiotic properties, possibly stimulating the growth of beneficial gut bacteria.
8. Bone Health
This randomized controlled trial in 9–11 year old girls showed that taking zinc supplements, 9 mg every day for 4 weeks, increased bone formation. However, it is unclear whether this results in improved bone strength.
This was a randomized trial in lactating Chinese women. The study showed that taking 300 or 600 mg of calcium for 12 months did not have any effects on bone density.
This observational study in Chinese adults showed that high circulating levels of vitamin E were associated with higher bone density in women, but not in men.
9. Eyes and Vision
Retinopathy of prematurity (ROP) is a disease that affects the retinas of premature children. It may result in impaired vision or blindness. This meta-analysis of observational studies concludes that breastfeeding may help prevent ROP.
10. Infant Health
Insulin-like growth factor (IGF-1) is a hormone that promotes growth in children. Previous studies have shown that a high protein intake may increase circulating IGF-1 levels.
This study in infants indicates that a high-protein diet alone is not sufficient to raise IGF-1 levels. Instead, specific amino acids, such as free tryptophan and phenylalanine, are more important.
This randomized crossover study indicates that the probiotic Bifidobacterium animalissubsp. lactis BB-12 may reduce systemic inflammation in healthy adults.
Taking B. animalis in yogurt, especially when added before fermentation, was more effective than B. animalis in capsules.
12. Sports Nutrition
This randomized, controlled crossover trial suggests that drinking beetroot juice, rich in nitrate, does not reduce oxygen uptake during exercise at a high altitude, compared to beetroot juice without nitrate.
13. Nutrients, Vitamins and Minerals
This cross-sectional, observational study in Chinese adults indicates that high abdominal fat may increase the risk of vitamin D deficiency.
Cadmium is a toxic heavy metal. Its absorption is possibly related to zinc intake.
This observational study suggests that a high dietary intake of zinc, and high circulating levels of zinc, may promote the absorption and accumulation of cadmium in the body. However, the health relevance of this is unclear.