Past Week in Nutrition Science (June 24th – July 1st)

This is our weekly selection of recently published nutrition research.

Here are some of the most interesting findings this week:

Supplementing with L-carnitine may have modest weight loss benefits.
Docosahexaenoic acid (DHA) has stronger anti-inflammatory effects than eicosapentaenoic acid (EPA).
Eating antioxidant-rich chocolate in the morning may reduce some of the negative health effects of sleep deprivation.
The thickness of beverages reduces appetite more than their calorie density.
Eating sucrose leads to faster depletion of liver glycogen after exercise, compared to eating glucose.
Taking multivitamins every day may reduce the risk of major heart disease events in men.
Doctor Sitting At Desk

Research Reviews

This week we reviewed two articles: one meta-analysis on the effects L-carnitine on weight loss and one randomized controlled trial comparing the effects of EPA and DHA on inflammatory markers and blood lipids.

Review: L-Carnitine: Is it Effective for Weight Loss?

Article: The effect of (L-)carnitine on weight loss in adults: a systematic review and meta-analysis of randomized controlled trials.

Summary: This was a systematic review and meta-analysis of randomized controlled trials examining the effects of L-carnitine on weight loss.

The review concluded that supplementing with L-carnitine for one month or longer may promote modest weight loss.

Review: DHA is Better at Reducing Inflammation Than EPA.

Article: Randomized, crossover, head-to-head comparison of EPA and DHA supplementation to reduce inflammation markers in men and women: the Comparing EPA to DHA Study.

Summary: This was a randomized controlled trial comparing the effects of the long-chain fatty acids DHA and EPA on inflammatory markers and blood lipids.

The study showed that DHA had stronger anti-inflammatory effects than EPA. Additionally, it had greater effects on the blood lipid profile.

New Research from Around the World

Many new papers came to our attention this week. Here are summaries of the most interesting or relevant studies, categorized by subject.

Blood Sugar Control and Diabetes
Heart Health
Cancer
Appetite and Eating
Eyes and Vision
Digestive Health
Kidney and Urinary Health
Liver Health
Muscles and Physical Performance
Inflammation
Allergies and Auto-Immune Disorders
Sleep
1. Blood Sugar Control and Diabetes

Effect of a Brown Rice Based Vegan Diet and Conventional Diabetic Diet on Glycemic Control of Patients with Type 2 Diabetes: A 12-Week Randomized Clinical Trial.

This 12-week, randomized controlled trial in Korean diabetics compared the effects of a vegan diet (based on brown rice) and a traditional diabetic diet, recommended by the Korean Diabetes Association, on the levels of HbA1c.

HbA1c is a marker of average blood sugar levels for the preceding three months. The study showed that both diets reduced HbA1c levels, but the decrease was larger in the vegan group.

Genetic susceptibility to diabetes and long-term improvement of insulin resistance and {beta} cell function during weight loss: the Preventing Overweight Using Novel Dietary Strategies (POUNDS LOST) trial.

A high-protein diet is considered beneficial for people with type 2 diabetes and may improve several risk factors for diabetes.

This study showed that individuals with a high genetic risk score for type 2 diabetes benefited more from a high-protein weight-loss diet, compared to others. Similarly, they did not benefit as much from a low-protein weight-loss diet.

Plasma alkylresorcinols, biomarkers of whole-grain wheat and rye intake, and risk of type 2 diabetes in Scandinavian men and women.

Alkylresorcinols (ARs) are a group of phenolic lipids mainly found in cereals, such as wheat, rye and barley. Since they are otherwise rare in nature, their blood levels are used as markers of whole-grain wheat and rye intake.

This observational study showed that levels of total ARs were not associated with a lower risk of type 2 diabetes (T2D). However, based on the levels of rye ARs, it suggests that a high intake of whole-grain rye may protect against T2D.

2. Heart Health

Association between serum calcium concentration and risk of incident and fatal cardiovascular disease in the prospective AMORIS study.

Calcium is a dietary mineral found in high amounts in dairy products. Some previous observational studies have linked high levels of circulating calcium with an increased risk of heart disease.

This large observational study supported earlier studies showing that high levels of calcium were linked with an increased risk of heart disease. However, the cause and effect relationship is unclear.

Dietary phosphatidylcholine and risk of all-cause and cardiovascular-specific mortality among US women and men.

Trimethylamin (TMA) is a compound produced by gut bacteria when they break down certain nutrients, mainly phosphatidylcholine (PC). Previous studies have linked high circulating levels of TMA with an increased risk of heart disease.

This large observational study in US men and women suggests that a high intake of PC is associated with an increased risk of death from heart disease, especially among diabetics. PC is mainly found in eggs, red meat and fish.

Multivitamin Use and the Risk of Cardiovascular Disease in Men.

This observational study in men 40 years of age or older from the Physician’s Health Study suggests that supplementing with multivitamins for 20 years or longer may reduce the risk of major heart disease events.

3. Cancer

Prospective Study of Glycemic Load, Glycemic Index, and Carbohydrate Intake in Relation to Risk of Biliary Tract Cancer.

The glycemic index (GI) is a relative measure of how fast blood sugar levels rise after eating a given amount of a certain type of food. The glycemic load (GL) is a similar measure obtained by multiplying the GI with the amount of food eaten.

This observational study found that eating a lot of foods high on the glycemic index or with a high glycemic load was associated with an increased risk of biliary tract cancer, cancer in the ducts that transport bile into the small intestine.

Plasma Riboflavin and Vitamin B-6, but Not Homocysteine, Folate, or Vitamin B-12, Are Inversely Associated with Breast Cancer Risk in the European Prospective Investigation into Cancer and Nutrition-Varese Cohort.

This observational study showed that high circulating levels of vitamin B6 and riboflavin were associated with a lower risk of breast cancer, especially in premenopausal women.

Markers of Vitamin D Exposure and Esophageal Cancer Risk: A Systematic Review and Meta-analysis.

This systematic review and meta-analysis of observational studies concluded that there are no consistent associations between vitamin D intake and cancer in the esophagus, the tube that connects the mouth to the stomach.

Dietary Fat Intake During Adolescence and Breast Density Among Young Women.

This prospective observational study measured fat intake and breast density in women when they were 10–18 years old and again when they were 25–29 years old.

A higher intake of saturated fat and a lower intake of mono and polyunsaturated fats during adolescence were linked with higher breast density 15 years later. These changes might affect breast cancer risk, but further studies are needed.

4. Appetite and Eating

Empty calories and phantom fullness: a randomized trial studying the relative effects of energy density and viscosity on gastric emptying determined by MRI and satiety.

This study tested the effects of dairy-based drinks, varying in viscosity (thickness) and calorie density, on fullness (satiety) and the rate of stomach emptying.

It showed that high viscosity reduced stomach emptying less than high-calorie density. However, highly viscous drinks were more effective at reducing self-perceived fullness.

5. Eyes and Vision

Association of low oleic acid intake with diabetic retinopathy in type 2 diabetic patients: a case–control study.

Diabetic retinopathy (DR), also known as diabetic eye disease, is a complication of diabetes characterized by damage to the retina of the eye. It may eventually lead to blindness.

This observational study showed that DR was associated with a low dietary intake of fiber, monounsaturated fatty acids (MUFAs), palmitic acid and oleic acid.

6. Digestive Health

From Dietary Fiber to Host Physiology: Short-Chain Fatty Acids as Key Bacterial Metabolites.

Growing evidence links the gut microbiota — the bacteria that inhabit our digestive tract — with body function and disease. Simply put, the types of bacteria that live in your gut produce compounds that affect your body.

These include short-chain fatty acids (SCFAs). This scientific review discusses the potential role of SCFAs in health and disease.

Serum 25-hydroxyvitamin D concentration is inversely associated with mucosal inflammation in patients with ulcerative colitis.

Ulcerative colitis (UC) is a type of inflammatory bowel disease characterized by inflammation and small ulcers in the lining of the colon. Bloody diarrhea is the main symptom of an active disease.

This observational study in 230 people with UC showed that low circulating levels of vitamin D were associated with greater disease severity.

7. Kidney and Urinary Health

Serum Magnesium Levels and Hospitalization and Mortality in Incident Peritoneal Dialysis Patients: A Cohort Study.

Peritoneal dialysis (PD) is a procedure used to clean the blood of patients with severe chronic kidney disease.

This observational study in patients undergoing PD showed that low circulating magnesium levels were associated with a higher risk of hospitalization.

8. Liver Health

Vitamin D Deficiency Is Associated With Increased Risk of Non-alcoholic Steatohepatitis in Adults With Non-alcoholic Fatty Liver Disease: Possible Role for MAPK and NF-κB?

Non-alcoholic fatty liver disease (NAFLD) is characterized by an accumulation of fat in the liver. It is associated with metabolic syndrome. If untreated, it may damage the liver over time, leading to a serious condition known as cirrhosis.

This observational study found that vitamin D deficiency is common in patients with NAFLD. It was also associated with greater disease severity.

9. Muscles and Physical Performance

The effects of phosphatidic acid supplementation on strength, body composition, muscular endurance, power, agility, and vertical jump in resistance trained men.

Studies show that phosphatidic acid (PA) promotes muscle protein formation, potentially increasing muscle mass and strength. MaxxTOR(R) is a supplement that mainly contains PA but also leucine, HMB and vitamin D3.

This randomized controlled trial in 18 strength-trained men showed that supplementing with MaxxTOR(R) for 8 weeks, while strength training three times per week, increased lean body mass and strength, compared to a placebo.

Sucrose ingestion after exhaustive exercise accelerates liver, but not muscle glycogen repletion compared with glucose ingestion in trained athletes.

The body stores carbs in the form of glycogen (long chains of glucose), mainly in the liver and muscles. High glycogen stores are very important for long-distance athletes, who sometimes experience glycogen depletion, referred to as “hitting the wall.”

This study in trained male cyclists showed that eating sucrose led to faster depletion of liver glycogen after exercise, compared to eating glucose. However, glycogen depletion in muscles was similar after eating glucose and sucrose.

10. Inflammation

Paleolithic and Mediterranean Diet Pattern Scores Are Inversely Associated with Biomarkers of Inflammation and Oxidative Balance in Adults.

This observational study suggests that Paleolithic and Mediterranean dietary patterns are associated with lower levels of systemic inflammation and oxidative stress.

Breastfeeding and Risk of Kawasaki Disease: A Nationwide Longitudinal Survey in Japan.

Kawasaki disease is a rare autoimmune condition, most often seen in Asian children under 5 years of age. It is a common cause of heart disease in children, causing inflammation throughout the body and affecting blood vessels and skin.

This observational study in Japanese children showed that breastfeeding was associated with a reduced risk of hospitalization due to Kawasaki disease, compared to formula feeding.

11. Allergies and Auto-Immune Disorders

Prenatal Fish Oil Supplementation and Allergy: 6-Year Follow-up of a Randomized Controlled Trial.

Previous randomized controlled trials suggest that supplementing with long-chain omega-3 fatty acids in pregnancy may reduce the risk of allergies in the child. The affected allergies were characterized by an immunoglobin E (IgE) response.

This study suggests that maternal long-chain omega-3 supplementation has no effect on the risk of IgE-associated allergies when the child is 6 years old.

12. Sleep

Flavanol-rich chocolate acutely improves arterial function and working memory performance counteracting the effects of sleep deprivation in healthy individuals.

This study examined whether eating chocolate rich in cocoa antioxidants (flavanols) could reduce some of the adverse effects of sleep deprivation.

The study showed that eating flavonol-rich chocolate reduced some of the negative health effects of sleep deprivation. Specifically, it reduced blood pressure and improved blood vessel function and working memory in women.