Past Week in Nutrition Science (Feb 26th–March 4th)

This is an overview of interesting nutrition research published from Friday, February 26th, to Friday, March 4th, 2016.

Male Doctor Thinking With Apple

Research Reviews

In the past week, we reviewed two articles: one published in the British Journal of Nutrition and the other from Appetite.

Review: Organic Meat is Higher in Omega-3 and Polyunsaturated Fat.

Article: Composition differences between organic and conventional meat: a systematic literature review and meta-analysis.

Summary: This study compared the fat content of organic and non-organic meat.

The main results were that organic meat was higher in polyunsaturated fat, including omega-3 and omega-6, and monounsaturated fat. Since meat is a small dietary source of these nutrients, the health relevance of the findings is unclear.

Review: For Food Addicts, Mood Affects Attention to Junk Food.

Article: A sad mood increases attention to unhealthy food images in women with food addiction.

Summary: This experiment examined the effects of watching a sad film on attention to unhealthy foods among women with and without food addiction.

The study found that only women who were food addicts increased their attention to unhealthy foods when sad, whereas women without food addiction did not.

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.

1. Obesity and Weight Loss

Characterization of the Gut Microbial Community of Obese Patients Following a Weight-Loss Intervention Using Whole Metagenome Shotgun Sequencing.

Observational studies have shown that the gut microbiota of obese people is different from that of normal-weight people. This study found that a 52-week weight loss program led to changes in the gut bacteria of obese individuals.

However, the gut microbiota gradually returned to initial levels after the program finished, except for levels of Akkermansia, which remained elevated for 2 years.

Maternal plasma PUFA concentrations during pregnancy and childhood adiposity: the Generation R Study.

This observational study found that lower intakes of omega-3 fat and higher intakes of omega-6 fat during pregnancy are linked to more body fat in the child.

Dairy consumption in association with weight change and risk of becoming overweight or obese in middle-aged and older women: a prospective cohort study.

This prospective observational study of middle-aged and elderly women suggests that eating dairy products may reduce their risk of weight gain or obesity. However, this only applied to full-fat dairy products, and not low-fat dairy.

A randomized trial of high-dairy-protein, variable-carbohydrate diets and exercise on body composition in adults with obesity.

This randomized, controlled trial of overweight or obese people examined the effects of different amounts of protein (P), carbs (C) and fat (F) on weight loss during a 16-week, high-protein weight-loss program with exercise training.

The diets were as follows: 1) 40% C, 30% P and 30% F; 2) 55% C, 30% P and 15% F; or 3) 55% C, 15% P and 30% F. Weight loss, fat loss and changes in lean mass were similar in all groups.

Association between Maternal Fish Consumption and Gestational Weight Gain: Influence of Molecular Genetic Predisposition to Obesity.

This observational study in Danish women found no significant association between fish consumption and weight gain during pregnancy.

2. Blood Sugar Control and Diabetes

Consumption of dairy foods and diabetes incidence: a dose-response meta-analysis of observational studies.

This meta-analysis of observational studies showed that a high intake of dairy products was associated with a lower occurrence of type 2 diabetes.

When individual dairy products were examined separately, yogurt (80 grams/day) appeared to be especially protective. Eating ice cream (10 grams/day) was also linked with a reduced risk, but higher quantities did not provide an added benefit.

Roasting intensity of naturally low-caffeine coffee modulates glucose metabolism and redox balance in humans.

This small, randomized, crossover study showed that drinking 4 cups of dark-roasted coffee per day, for one week, improved blood sugar control, antioxidant status and omega-3 levels in red blood cells, compared to drinking light-roasted coffee.

3. Heart Health

Flavonoid intake and incident hypertension in women.

This observational study in French, middle-aged women suggests that a higher intake of antioxidant flavonoids may protect against high blood pressure.

Plasma levels of marine n-3 fatty acids and cardiovascular risk markers in renal transplant recipients.

This observational study in Norwegian kidney transplant recipients found that high circulating levels of omega-3 fatty acids were linked to a lower resting heart rate, lower blood sugar and triglyceride levels, and higher HDL-cholesterol levels.

Vegetarianism, low meat consumption and the risk of lung, postmenopausal breast and prostate cancer in a population-based cohort study.

This observational study suggests that vegetarians, pescetarians and those who eat meat once per week are not at a reduced risk of developing breast or prostate cancer, compared to people who consume meat every day.

Serum magnesium is inversely associated with coronary artery calcification in the Genetics of Atherosclerotic Disease (GEA) study.

This observational study in Mexican women suggests that low circulating levels of magnesium may increase the risk of high blood pressure, type 2 diabetes and calcification in arteries.

Consumption of Fish Oil Providing Amounts of Eicosapentaenoic Acid and Docosahexaenoic Acid That Can Be Obtained from the Diet Reduces Blood Pressure in Adults with Systolic Hypertension: A Retrospective Analysis.

This randomized, controlled trial suggests that the long-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may reduce blood pressure in people with isolated systolic hypertension.

EPA and DHA had significant effects even at daily doses as low as 0.7 grams. Conversely, doses ranging from 0.7 grams/day and 1.8 grams/day had no effects on blood pressure in people with healthy blood pressure levels.

4. Cancer

Adherence to the Dietary Approaches to Stop Hypertension-style diet in relation to glioma: a case–control study.

Glioma is a type of cancer that starts in the brain or spinal cord, arising from the cells (glial cells) that insulate nerves.

This observational study in Iranian adults suggests that a high consumption of red meat and salt may increase the risk of glioma. Conversely, a diet rich in legumes, nuts and fruit was linked with a lower risk of glioma.

Dietary risk factors for colorectal cancer in Brazil: a case control study.

This observational study in Brazilian adults indicates that a high meat intake may increase the risk of colon cancer.

5. Appetite and Eating

Comparison of short-term energy intake and appetite responses to active and seated video gaming, in 8–11-year-old boys.

This study in 8–11 year old boys compared the effects of seated and active video gaming on appetite and calorie intake.

The study showed that calorie intake was lower during active video gaming. However, one hour after the gaming session had stopped, calorie intake was the same in both groups. Self-rated appetite did not differ at any point.

6. Brain and Mental Health

Vitamin B-12 concentration, memory performance, and hippocampal structure in patients with mild cognitive impairment.

This observational study found that vitamin B12 levels that were on the lower end of the normal range were associated with poorer memory in patients with mild cognitive impairment.

7. Digestive Health

Probiotics for the Prevention of Antibiotic-Associated Diarrhea in Children.

This article discusses the recommendations of the Working Group on Probiotics of the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition for the use of probiotics to treat antibiotic-associated diarrhea in children.

This group recommends using Lactobacillus rhamnosus and/or Saccharomyces boulardii. Other probiotic strains have been tested, but the evidence is lacking.

8. Kidney and Urinary Health

The effects of a high protein diet on indices of health and body composition – a crossover trial in resistance-trained men.

This randomized, crossover study in healthy, strength-trained men who increased their daily protein intake showed that consuming 2.6 to 3.3 g/kg/day of protein for 4 months had no effects on blood lipids or markers of kidney or liver function.

The findings suggest that increasing the daily protein intake to over four times the recommended daily allowance has no adverse effects on kidney or liver function.

9. Bone Health

Associations of breast-feeding patterns and introduction of solid foods with childhood bone mass: The Generation R Study.

This observational study suggests that 6-year-old children who were breast-fed have a higher bone mass, compared to children who were never breast-fed.

However, those children who were exclusively breast-fed for at least 4 months had lower bone mass than children who were breast-fed while being allowed to eat other foods at the same time.

Serum concentrations of 25-hydroxyvitamin D and its association with bone mineral density and serum parathyroid hormone levels during winter in urban males from Guiyang, Southwest China.

This observational study in adult men from Southwest China showed that circulating levels of vitamin D were generally low during the winter months.

It also found that when levels of vitamin D were adequate, or around 30 and 50 nmol/L, bone health tended to be better.

Maternal gestational vitamin D supplementation and offspring bone health (MAVIDOS): a multicentre, double-blind, randomised placebo-controlled trial.

This randomized, controlled trial showed that supplementing with vitamin D during pregnancy did not increase bone mineral content in the child.

10. Muscles and Physical Performance

Monthly High-Dose Vitamin D Treatment to Prevent Functional Decline.

This randomized, controlled trial examined the effects of supplementing with different amounts of vitamin D on physical function in people 70 years and older.

Three monthly doses were tested: 24,000 IU, 60,000 IU and 24,000 IU plus 300 µg of calcifediol. The study showed that a dose of 24,000 IU/month was more effective in improving physical function and reducing the risk of falls, compared to higher doses.

Effects of combined β-hydroxy-β-methylbutyrate (HMB) and whey protein ingestion on symptoms of eccentric exercise-induced muscle damage.

This randomized trial examined the effects of supplementing with β-hydroxy-β-methylbutyrate (HMB), 3 grams/day, and whey protein, 36.6 grams/day, on markers of muscle damage after strength training.

The study showed that HMB and whey protein did not decrease soreness, the loss of muscle strength or markers of muscle damage, compared to supplementing with HMB or whey protein alone.

11. Allergies and Auto-Immune Disorders

Gluten Introduction and the Risk of Coeliac Disease: A Position Paper by the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition.

The time at which gluten is introduced into the diet of infants may affect their risk of developing gluten intolerance. This paper discusses the available evidence, which applies to infants who are genetically predisposed to developing gluten intolerance.

Based on observational data, infants should not eat gluten until they are at least 4 months old. Gluten should also be introduced slowly.

High-Fat and Low-Carbohydrate Diets Are Associated with Allergic Rhinitis But Not Asthma or Atopic Dermatitis in Children.

Allergic rhinitis, or hay fever, is characterized by an itchy, runny nose, as well sneezing and watery eyes. It is caused by an allergic reaction to particles in the air, such as dust or pollen.

This observational study in Korean children suggests that high-carb or high-fat diets may increase the risk of hay fever. Conversely, the study found no significant links between diet and asthma or eczema.

12. Infections and Immune Health

Role of Vitamin D in Hospitalized Children With Lower Tract Acute Respiratory Infections.

This observational study in hospitalized children with lung infections found that low levels of circulating vitamin D were linked with more severe infections.

However, it is unclear whether low levels of vitamin D made the infections worse, or if the infections depleted vitamin D levels. Randomized, controlled trials are needed.

13. Pregnancy and Infant Health

Maternal Serum Zinc Concentration during Pregnancy Is Inversely Associated with Risk of Preterm Birth in a Chinese Population.

This observational study in pregnant mothers in China indicates that high zinc levels may protect against preterm birth.

14. Men’s Health

Analysis of Gut Microbiome Reveals Significant Differences Between Men with Chronic Prostatitis/Chronic Pelvic Pain Syndrome and Controls.

Chronic pelvic pain syndrome (CPPS) is a condition characterized by inflammation in the prostate. This inflammation may be caused by infections (prostatitis), but the majority of cases are due to unexplained, chronic inflammation.

This study showed that patients with CPPS have significantly lower diversity in the gut microbiota, compared to healthy people. The findings suggest that an imbalanced gut microbiota may be involved in CPPS.

15. Contaminants and Food Safety

Microbial Safety of Wood in Contact with Food: A Review.

Four basic groups of materials are generally used in food packaging: plastic, glass, metal and wood. Concerns have been raised that wood packaging may reduce food hygiene and safety.

However, this review concludes that wood is a safe material for food packaging. The rough surface of wood is unfavorable to microbes and may even contain anti-microbial substances that limit the growth of disease-causing bacteria.

16. Vitamins, Minerals and Other Nutrients

Higher PUFA and n -3 PUFA, conjugated linoleic acid, α -tocopherol and iron, but lower iodine and selenium concentrations in organic milk: a systematic literature review and meta- and redundancy analyses.

This systematic review and meta-analysis showed that organic milk is, on average, higher in polyunsaturated fat, omega-3 fat, conjugated linoleic acid, vitamin E and iron, compared to milk that’s not produced according to organic standards.

However, organic milk was also significantly lower in iodine and selenium. Explaining this, cows tend to be grass-fed or pasture-raised on organic farms, whereas conventional farms more often use concentrated feeds based on grains and legumes.

Dietary intake and food contributors of polyphenols in adults and elderly adults of Sao Paulo: a population-based study.

This observational study suggests that coffee is the main source of antioxidant polyphenols in the diet of young and elderly adults in Brazil. Other significant sources of polyphenols were citrus fruits and tropical fruits.

Added sugar intake that exceeds current recommendations is associated with nutrient dilution in older Australians.

This observational study in elderly Australians found that a low intake of added sugar was linked with a higher intake of protein, vitamin C, vitamin E, zinc, fruit, vegetables, fish and alcohol.

Evidence from a Randomized Trial That Exposure to Supplemental Folic Acid at Recommended Levels during Pregnancy Does Not Lead to Increased Unmetabolized Folic Acid Concentrations in Maternal or Cord Blood.

High intake of folic acid from fortified food and supplements has been associated with elevated levels of un-metabolized folic acid (UFA) in the blood. There is some observational evidence linking high levels of UFA with increased cancer risk.

This randomized, controlled trial in pregnant women suggests that supplemental folic acid, at the recommended level of 400 µg/day, does not lead to increased levels of un-metabolized folic acid in the circulation or cord blood.