This is our weekly selection of recently published studies and reviews in nutrition. Here are some of the most interesting findings this week:
- Ketogenic diets don’t cause weight loss irrespective of protein and calorie intake.
- Fructose may be a major cause of metabolic disorders.
- Weight gain during pregnancy increases the risk of excessive weight gain in the child.
- Supplementing with vitamin D has no effect on knee osteoarthritis.
- The human digestive system hosts a variety of viruses that may affect health.
- Supplementing with omega-3 increases the health benefits of exercise in people with metabolic syndrome.
This week we reviewed two articles: one examining the effects of a high-fat ketogenic diet on metabolism and another about the metabolic effects of eating high amounts of fructose.
Review: Do Ketogenic Diets Have a “Metabolic Advantage?”
Article: Energy expenditure and body composition changes after an isocaloric ketogenic diet in overweight and obese men.
Summary: This 2-month metabolic study compared the effects of a high-fat ketogenic diet with a high-carb diet while keeping protein and calorie intake constant.
The ketogenic diet caused a slight, temporary increase in calorie expenditure, which was not considered clinically relevant. However, it significantly improved blood sugar control, causing a 47% drop in insulin levels.
Review: Fructose May be a Major Cause of Metabolic Disorders.
Article: The Sweet Path to Metabolic Demise: Fructose and Lipid Synthesis.
Summary: This was a review on the effects of a high-fructose diet on risk factors for metabolic disorders, such as heart disease and type 2 diabetes.
The review concluded that high fructose intake may increase the risk of heart disease, diabetes and other chronic lifestyle diseases.
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
- Metabolic Syndrome
- Blood Sugar Control and Diabetes
- Heart Health
- Brain and Mental Health
- Digestive Health
- Lung Health
- Bone Health
- Muscles and Physical Performance
- Women’s Health
1. Obesity and Weight Loss
Previous observational studies show that when mothers gain a lot weight during pregnancy their child is at a higher risk of becoming obese.
This observational study supports earlier studies indicating that excessive fat gain during pregnancy may promote weight gain and obesity in early, middle and late childhood.
This observational study suggests that high maternal weight gain during early and mid-pregnancy may increase the risk of excessive weight gain in mid-childhood.
2. Metabolic Syndrome
This was a randomized controlled trial in people with metabolic syndrome on a 24-week, high-intensity exercise program.
The study showed that drinking skim milk enriched with 275 mg of omega-3 fat and 7.5 grams of oleate improved insulin sensitivity, reduced inflammation (CRP levels) and increased HDL-cholesterol levels, compared to a placebo.
3. Blood Sugar Control and Diabetes
Curcumin is the main active ingredient in turmeric, a popular Indian spice. Supplementing with curcumin may have various health benefits. However, research on the effects of curcumin on insulin resistance has provided inconclusive results.
Different doses, treatment times and types of curcumin supplements may affect study results. This review discussed the available evidence and how to improve the potential benefits of curcumin on blood sugar control.
4. Heart Health
Three simple sugars (monosaccharides) are found in your diet: glucose (Glu), fructose (Fru) and galactose (Gal). This randomized, crossover trial compared the effects of these sugars (60 grams of each) on heart function.
The study showed that Glu and Gal caused smaller increases in blood pressure than Fru. Additionally, the increase in heart output and peripheral resistance (an aspect of blood pressure) seen after Glu ingestion was significantly lower after eating Gal.
This was a prospective observational study in individuals at a high risk of developing heart disease. It showed that low to moderate consumption of eggs was not linked to an increased risk of heart disease.
However, eating more than 4 eggs per week was associated with a slightly increased risk (hazard ratio: 0.96) among non-diabetic individuals, when compared with the lowest consumption (less than 2 eggs per week).
Intestinal Microbiota-Generated Metabolite Trimethylamine-N-Oxide and 5-Year Mortality Risk in Stable Coronary Artery Disease: The Contributory Role of Intestinal Microbiota in a COURAGE-Like Patient Cohort.
Previous studies suggest that high circulating levels of trimethylamine N-oxide(TMAO) increase the risk of heart disease. In some people, TMAO levels increase after the consumption of foods that are rich in choline.
This observational study showed that elevated TMAO levels were associated with a higher risk of death among patients with heart disease (stable coronary artery disease).
Hepatocellular carcinoma is the most common type of liver cancer.
This observational study suggests that poor selenium status may increase the risk of hepatocellular carcinoma. In contrast, selenium levels were not linked with the risk of cancer in the bile duct.
6. Brain and Mental Health
Vitamin B12 plays an essential role in neuronal and brain development. This controlled trial examined the effects of supplementing with 50 µg of vitamin B12 daily during pregnancy on neurocognitive outcomes in the child.
Supplementing with vitamin B12 had no significant effects on mental or cognitive function in the child at 9 months of age.
7. Digestive Health
Synbiotics are supplements containing both probiotics and prebiotics (beneficial bacteria and the fiber that nourishes them). This controlled trial examined the effects of supplementing with synbiotics on digestive problems in HIV patients.
Digestive problems are a common complaint among people with HIV and AIDS. The study showed that probiotics plus 6 grams of fructooligosaccharides had no significant effects on digestive symptoms, compared to a placebo (maltodextrin).
Not only is the human digestive system home to billions of bacteria, it also hosts a wide variety of viruses, which are collectively known as the gut virome.
Similarly to gut bacteria, gut viruses may be implicated in chronic diseases and immune disorders. This review discusses the potential role of the gut virome in chronic inflammation and inflammatory bowel disease.
8. Lung Health
This randomized controlled trial examined the effects of supplementing with fish oil on lung function (respiratory performance) in women undergoing chemotherapy for breast cancer.
The study showed that fish oil improved respiratory muscle strength and endurance, compared to a placebo. Supplementing also maintained normal circulating levels of triglycerides, HDL-cholesterol and lactate.
9. Bone Health
Rickets is a bone disorder caused by a dietary deficiency in calcium, vitamin D or phosphate. Individuals with rickets have weak bones, reduced growth and sometimes bone deformities.
This study in Nigerian children with rickets showed that supplementing with 1000 or 2000 mg of calcium daily for 24 weeks was more effective at treating rickets than 500 mg of calcium.
10. Muscles and Physical Performance
Creatine is the most popular supplement used to enhance muscle growth and strength.
This systematic review and meta-analysis of randomized controlled trials concluded that supplementing with creatine effectively improves strength performance in the upper body limbs.
Osteoarthritis is a degenerative joint disease characterized by the breakdown of cartilage in joints. Previous observational studies show that low levels of vitamin D are associated with knee osteoarthritis.
This randomized controlled trial showed that supplementing with 800 IU of vitamin D3 daily for 3 years did not slow the progression of osteoarthritis. It also did not reduce pain, stiffness or functional loss, compared to a placebo.
12. Women’s Health
Supplementing with phytoestrogens, which resemble the female sex hormone estrogen, is popular among women trying to manage their menopausal symptoms. They are mainly found in soy products and nuts.
This meta-analysis of randomized controlled trials suggests that supplementing with phytoestrogens modestly reduces the frequency of hot flashes and vaginal dryness, whereas they have no effects on night sweats.