Past Week in Nutrition Science: This is an overview of interesting nutrition research published from Friday, Nov 20th, to Friday, Nov 27th
Past Week in Nutrition Science (Nov 20th–Nov 27th)
This week, we reviewed two articles: one from Lancet Diabetes and Endocrinology, and one published in JAMA.
Summary: This was a meta-analysis of randomized controlled trials examining the effectiveness of low-fat diets on weight loss. It also compared low-fat diets with low-carb and other, higher-fat diets.
The main finding was that low-fat diets may be effective for weight loss. However, they are not as effective as low-carb diets or other, higher-fat diets.
Summary: This randomized, controlled crossover study examined the effects of an energy drink on heart function, blood pressure, heart rate and blood sugar.
The study showed that the energy drink caused a sudden increase in blood pressure and a greater rise in the stress hormone norepinephrine, compared to a placebo. The authors concluded that these changes might increase the risk of heart disease.
New Research From Around the World
Lots of new research was published this week. Below is a selection of the most interesting papers, categorized by subject.
- Obesity and Weight Loss
- Blood Sugar Control and Diabetes
- Heart and Vascular Health
- Appetite and Eating
- Mental Health
- Digestive Health
- Liver and Kidney Health
- Sports Nutrition
1. Obesity and Weight Loss
Respiratory quotient (RQ) is the ratio of carbon dioxide formation to oxygen absorption in cells. This experiment showed that a high RQ predicted body fat and weight gain for 1 year, in young adults.
This observational study indicates that good sleep and a high-quality diet may reduce the risk of obesity in children.
This mouse experiment investigated how fiber supplements affect a high-calorie diet. It found that taking soy pod fiber for 30 days prevented weight gain by decreasing fat and sugar absorption. There was also a shift in the gut microbiota.
Intermittent fasting, or intermittent calorie restriction, is a dietary pattern characterized by alternating cycles of fasting and eating. This scientific review concludes that intermittent fasting is an effective weight loss strategy.
This 12-week, randomized controlled trial found that replacing sugar-sweetened beverages with artificially-sweetened beverages decreased liver fat.
However, the dietary replacement did not cause changes in body weight, visceral fat or other aspects of metabolic health.
2. Blood Sugar Control and Diabetes
This was a small, randomized, controlled crossover trial in patients with type 2 diabetes.
It showed that taking resveratrol supplements, 500 mg twice daily for 5 weeks, did not improve blood glucose control and body weight, and had no effects on stomach emptying or calorie intake.
Amla, scientifically known as Emblica officinalis, is an herb used by alternative medicine practitioners. One of its active constituents is ellagic acid, which promotes insulin release after sugar consumption, thus increasing blood sugar control.
This animal study shows that giving rats supplements with amla and ellagic acid, 250 or 500 ml per kg of body weight, may have beneficial effects on type 2 diabetes.
This large study showed that foods do not affect blood sugar levels the same in all individuals. In fact, there was a high variability in this response, suggesting that general dietary recommendations have limited value.
Instead, personalized dietary plans appear to be much more effective.
3. Heart and Vascular Health
This randomized, controlled trial found that drinking nitrate-rich beetroot juice, every day for 6 weeks, improved the health and function of blood vessels, compared to nitrate-depleted beetroot juice.
Previous studies indicate that fat gain and obesity may increase the chance of atherosclerosis, a disease that restricts blood flow in arteries.
This randomized controlled trial showed that weight loss may be an effective treatment for atherosclerosis.
Flow-mediated dilation is a measure of endothelial dysfunction (ED), which causes the inner lining of blood vessels to constrict or dilate too much. ED can contribute to hypertension.
This experiment suggests that high-fat meals lead to ED in African American women.
Previous research indicates that vitamin D deficiency may increase the risk of heart disease. This observational study in people with hypertension supports this.
People who had the lowest levels of vitamin D were most likely to experience heart attacks or other serious heart disease events.
Association of Fruit and Vegetable Consumption During Early Adulthood With the Prevalence of Coronary Artery Calcium After 20 Years of Follow-Up: The Coronary Artery Risk Development in Young Adults (CARDIA) Study.
This observational study suggests that a high intake of fruit and vegetables in early adulthood may reduce the risk of atherosclerosis in blood vessels supplying the heart.
Previous studies on the association of protein intake and stroke have provided inconsistent results.
This observational study did not find any link between protein intake and stroke. However, it indicates that high red meat consumption may increase the risk of stroke.
Heart attacks happen when blood flow to the heart is impaired. Interestingly, obese and overweight people are at a lower risk of dying after a heart attack, compared to normal-weight people. This is known as the obesity paradox.
This observational study found a similar association. Excess body fat appeared to increase life expectancy after a heart attack.
This observational study in Chinese people suggests that a high intake of alcohol and processed foods may increase the chance of getting esophageal cancer. Conversely, a diet rich in fruit and vegetables reduced the risk of esophageal cancer.
This prospective observational study suggests that a high intake of saturated fat may increase the risk of epithelial ovarian cancer.
This 5-year, prospective observational study indicates that high intake of red and processed meat does not predict a higher risk of death from colorectal cancer.
This huge, prospective observational study suggests that high intake of vegetables may reduce the risk of breast cancer. In contrast, fruit consumption was not associated with breast cancer risk.
This observational study was a part of the PREDIMED trial. It suggests that the Mediterranean diet, supplemented with virgin olive oil, may reduce the risk of breast cancer.
This meta-analysis of observational studies showed that a diet with a high glycemic index or glycemic load is associated with an increased risk of breast cancer.
5. Appetite and Eating
This experiment suggests that those who reduce their sugar intake may gradually experience an increased sensitivity to the sweet taste of sugar. More studies are needed to find out if this changes the preference for sweet foods.
This experiment suggests that gut bacteria, such as E. coli, may be involved in the control of satiety (fullness).
6. Mental Health
The glycemic index (GI) is a measure of the extent to which foods raise blood sugar levels after eating.
This observational study suggests that foods high on the glycemic index may increase the risk of depression. Conversely, a high glycemic load reduced the risk of mental disorders and anxiety.
7. Digestive Health
Synbiotics are nutritional supplements that contain both probiotics and prebiotics.
This randomized, controlled trial in cancer patients receiving chemotherapy showed that taking synbiotic supplements reduced the risk of diarrhea. They also helped maintain the numbers of lymphocytes, a type of white blood cells.
This study showed that reducing the intake of FODMAPs may improve symptoms in people with irritable bowel syndrome. This was also associated with a beneficial change in the density of the endocrine cells lining the colon.
Effect of inulin and fructo-oligosaccharide on the prevention of acute radiation enteritis in patients with gynecological cancer and impact on quality-of-life: a randomized, double-blind, placebo-controlled trial.
Radiotherapy for cancer in the abdominal region may negatively affect gut bacteria.
This randomized controlled trial in women receiving radiotherapy found that supplementation with prebiotics improved stool consistency and regularity, indicating better digestive health.
8. Liver and Kidney Health
This mouse study indicates that vitamin E supplements may slow the development of non-alcoholic fatty liver disease caused by the surgical removal of part of the liver.
This test-tube experiment suggests that isoliquiritigenin, one of the active constituents of licorice, may help protect the liver against oxidative damage.
In patients with dysfunctional kidneys, hemodialysis is a mechanical procedure that helps clean the blood and remove excess fluid.
This observational study indicates that high levels of circulating magnesium may increase the risk of sudden death in patients undergoing hemodialysis.
This mouse study showed that high circulating folate levels increased the risk of death after a malaria infection.
This randomized controlled trial in elderly people found that supplementation with the probiotic Lactobacillus casei, once daily for 6 months, decreased the frequency of fever and improved digestive health.
10. Sports Nutrition
Withania somnifera is a plant, often known as ashwagandha, used in traditional herbal medicine. This randomized controlled trial in young men showed that 300 mg of ashwagandha root, twice daily for 8 weeks, increased muscle mass and strength.