Past Week in Nutrition Science: This is an overview of interesting nutrition research published from Friday, January 29th, to Friday, February 5th, 2016.
Past Week in Nutrition Science (Jan 29th–Feb 5th)
This week, we reviewed two articles. One was published in Obesity, while the other appeared in the American Journal of Clinical Nutrition.
Summary: This was a randomized trial examining how the rate of weight loss, or the degree of calorie reduction, affects weight regain after dieting.
The study showed that the rate of weight loss didn’t have any effects on later weight regain. However, faster weight loss caused a greater loss of lean mass, suggesting that the weight loss quality may be lower.
Summary: This was a randomized, controlled weight-loss trial comparing the effects of two calorie-reduced diets. One provided 35% of calories from protein, while the other provided 15% of calories from protein.
Both groups were also doing high-intensity strength exercises. The study found that the higher-protein group retained more of their lean mass than the lower-protein group. Simply put, the higher-protein diet increased weight loss quality.
New Research From Around the World
Lots of new research came out this week. Here is a summary of the most important papers, organized by subject.
- Obesity and Weight Loss
- Blood Sugar Control and Diabetes
- Heart Health
- Appetite and Eating
- Brain and Mental Health
- Digestive Health
- Kidney Health
- Immune Health
- Bone and Joint Health
- Skin Health
- Vegetarian and Vegan Diets
- Nutrients, Vitamins and Minerals
1. Obesity and Weight Loss
Previous studies have associated green tea extract with weight loss and improvements to bone mineral density (BMD). Yet it is unknown which of the active components of green tea are responsible for these effects.
This 12-month, randomized, controlled trial in overweight or obese women showed that taking decaffeinated green tea extract, containing 843 mg of the antioxidantepigallocatechin gallate, had no effects on body weight or BMD.
Genetic traits play an important role in weight gain and obesity, among both children and adults. This observational study indicates that obesity-promoting genetic traits do not influence weight gain through increased appetite in children.
The risk of obesity and diabetes is increased for children whose mothers were obese or diabetic, which may be due to inherited intestinal bacteria.
This review discusses the possible role of the gut bacteria in this association. It also talks about the factors that affect the development of the gut microbiota in infants.
2. Blood Sugar Control and Diabetes
Previous observational studies have associated vitamin D deficiency with insulin resistance and an increased risk of type 2 diabetes.
This randomized, controlled trial in pre-diabetics showed that supplementing with vitamin D, 20,000 IU per week for 5 years, did not prevent the development of type 2 diabetes.
This large observational study in 120,666 people suggests that high body mass index (BMI) and weight gain in early adulthood may increase the risk of type 2 diabetes after midlife, regardless of current BMI.
Previous animal studies indicate that drinking beverages with artificial sweeteners may increase the risk of diabetes.
This observational study in 12,884 Brazilians found that drinking high amounts of artificially sweetened beverages was associated with diabetes and higher blood sugar levels. However, this did not apply to obese or overweight individuals.
This observational study suggests that eating high amounts of fiber, and low amounts of starch, may improve blood sugar control. Only cereal fiber was associated with lower levels of C-reactive protein, a marker of inflammation.
3. Heart Health
High blood levels of trimethylamine N-oxide (TMAO) are associated with heart disease. This observational study suggests that dairy products may increase TMAO levels, and high levels of TMAO may also increase inflammation.
This scientific review looked at randomized, controlled trials examining the effects of garlic on risk markers for heart disease. It concluded that garlic supplementation has the potential to prevent heart disease.
Garlic contains many healthy plant compounds, such as polysulfides like diallyl disulfide. This scientific review discusses the available evidence linking diallyl polysulfides from garlic with reduced heart disease risk.
Cardiac ectopy (CE) is a condition characterized by a disturbance or irregularities in the heart beat, often described as heart hiccups, jolts or missed beats. CE has been associated with an increased risk of heart disease.
This observational study found no significant links between consuming caffeinated foods, such as coffee, tea and chocolate, and CE.
This observational study suggests that eating a lot of omega-3 alpha-linolenic acid(ALA), mainly from olives and walnuts, reduces the risk of death from all causes.
However, only the intake of long-chain omega-3 fatty acids from fish was associated with a reduced risk of death from heart disease.
Consuming long-chain omega-3 fatty acids (n-3 PUFAs) has consistently been associated with a reduced risk of heart attacks. On the other hand, studies on the association of omega-3 alpha-linolenic acid (ALA) with heart attacks are inconsistent.
This observational study in Chinese adults indicates that high circulating levels of ALA and n-3 PUFAs are associated with a reduced risk of heart attacks.
Glycine is an amino acid found in proteins. Several observational studies have linked low circulating levels of glycine with obesity, high blood pressure and diabetes.
This observational study suggests that low levels of glycine increase the risk of heart attacks in patients with chest pain.
This observational study indicates that low circulating levels of magnesium increase the risk of heart disease and sudden death from a heart attack.
Heart failure occurs when the heart is not able to pump enough blood throughout the body to meet the body’s needs. This meta-analysis of observational studies suggests that eating chocolate does not reduce the risk of heart failure.
Atherosclerosis is a disease of the arteries, the blood vessels that carry blood from the heart. It is characterized by fat accumulation (plaque buildup) on their inner surface, and they may eventually become clogged.
This randomized trial in patients with metabolic syndrome showed that supplementing with aged garlic extract, 2,400 mg per day for 41 days, reduced non-calcified plaques on the inside of the heart arteries.
This meta-analysis of randomized, controlled trials suggests that eating garlic may lower blood pressure in people with high blood pressure. It may also reduce blood cholesterol and strengthen the immune system.
This observational study suggests that those who eat very often may be at an increased risk of high blood pressure and heart disease.
This randomized, controlled trial in 24 men and women with type 2 diabetes showed that drinking red wine, 230–300 ml/day for 4 weeks, increased blood pressure, compared to drinking an equal amount of water.
De-alcoholized red wine did not have similar effects, although there was a non-significant trend towards higher blood pressure when it was compared to water.
This meta-analysis of human trials showed that weight loss causes improvements in the health of the blood vessels (arteries) that carry blood from the heart. These changes may reduce the risk of heart disease.
This 6-month, randomized trial in overweight and obese women found that a calorie-reduced diet providing 35% of calories from protein caused greater improvements in metabolic health, and heart disease risk factors, than a lower-protein diet.
Specifically, the higher protein diet caused greater improvements in the blood lipid profile and insulin sensitivity.
This systematic review and meta-analysis of observational studies indicates that consuming dairy products may be associated with a reduced risk of heart disease.
This human trial showed that eating black raspberries caused some beneficial changes in the cells lining the mouth. Further studies are needed to confirm if this leads to a reduced risk of mouth cancer.
Being overweight or obese may increase the risk of certain cancers, such as breast, pancreatic, colon, thyroid and liver cancer.
This review discusses the potential role of alpha-lipoic acid in the prevention of obesity-related cancers. Alpha-lipoic acid is a type of fat naturally found in the body, but is also sold as a dietary supplement.
This observational study suggests that a high intake of sugar may increase the risk of ovarian cancer in African-American women.
5. Appetite and Eating
This observational study examined the diet quality of participants in the US National Health and Nutrition Examination Survey, using the Healthy Eating Index-2010.
The findings suggest that both higher meal frequency and snack frequency are associated with a healthier diet or better diet quality.
Stress may affect your eating habits. Some people are likely to increase their calorie intake when they are under stress, whereas others eat less. This experiment suggests that different types of stress affect eating in different ways.
Eating at a slower rate increases fullness and has been associated with weight loss. Conversely, eating fast is linked with weight gain and obesity.
This experiment indicates that eating rate is affected by visual feedback. For example, when soup disappears faster or slower than expected, people change their eating rate accordingly.
6. Brain and Mental Health
This systematic review concludes that there are no consistent links between diet and depression during or after pregnancy.
This observational study examined the association of seafood consumption, brain mercury levels and Alzheimer’s disease in elderly people.
The study showed that eating fish, seafood and fish oil was associated with higher levels of mercury in the brain. However, seafood reduced the risk of Alzheimer’s disease, and brain mercury was not associated with brain disorders.
Vitamin D Supplementation Affects the Beck Depression Inventory, Insulin Resistance, and Biomarkers of Oxidative Stress in Patients with Major Depressive Disorder: A Randomized, Controlled Clinical Trial.
This was a randomized, controlled trial in patients with a major depressive disorder. It showed that taking 50,000 IU of vitamin D each week for 8 weeks improved depression and blood sugar control, while reducing oxidative stress.
This observational study in elderly people suggests that a diet high in red meat, potatoes, gravy and butter may increase the risk of a mental decline. However, it was not associated with the speed at which these changes occurred.
This observational study suggests that women who are obese and diabetic before pregnancy are at an increased risk of having children with autism and/or intellectual disabilities.
This observational study in Japanese people indicates that high circulating levels of long-chain omega-3 fats, EPA and DHA, may protect against depression.
7. Digestive Health
Previous studies have shown that many diseases are associated with an imbalance in the gut microbiota.
This study found that the fungal microbiota is imbalanced in people with inflammatory bowel disease. Specifically, there was a higher proportion of Candida albicans and a lower proportion of Saccharomyces cerevisiae, compared to healthy people.
Dairy fat is enclosed in a layer called the milk fat globule membrane (MFGM). However, this does not apply to all dairy fat. The process used to make butter destroys most of the MFGM.
This randomized, controlled trial showed that eating the MFGM increased resistance to a strain of E. coli, a bacterium that may cause mild food poisoning and diarrhea.
Human Milk Oligosaccharides and Synthetic Galactosyloligosaccharides Contain 3′-, 4-, and 6′-Galactosyllactose and Attenuate Inflammation in Human T84, NCM-460, and H4 Cells and Intestinal Tissue Ex Vivo.
The intestines of infants are prone to becoming inflamed, but human milk seems to reduce this risk. This test tube experiment suggests that a type of sugar, galactosyllactose, may contribute to this anti-inflammatory effect.
8. Kidney Health
Many diseases, including chronic kidney disease, have been associated with a gut microbiota that is different from that of healthy people. Certain types of fiber, called prebiotics, can help restore a healthy balance in the gut microbiota.
This review discusses the effects of resistant starch, a type of prebiotic, on the gut microbiota in patients with chronic kidney disease.
9. Immune Health
This review discusses the way garlic may improve immune health. It concludes that supplementing with aged garlic extract may enhance the function of immune cells, partly explaining why garlic consumption may reduce the severity of cold and flu.
10. Bone and Joint Health
Undenatured type II collagen (UC-II) is a type of nutritional supplement used to treat arthritis. This randomized, controlled trial examined its effects on osteoarthritis, which is characterized by the breakdown of cartilage in joints.
This randomized, controlled trial showed that supplementing with UC-II, 40 mg per day for 6 months, significantly improved symptoms in people with osteoarthritis in the knees, compared to a placebo.
11. Skin Health
Human blood contains two main collagen peptides: prolyl-hydroxyproline (PH) and hydroxyprolyl-glycine (HG). Previous test tube experiments indicate that these peptides may improve skin health.
This 8-week, randomized, controlled trial supports earlier studies, suggesting that supplementing with PH and HG may enhance skin moisture and elasticity while reducing wrinkles and roughness.
12. Vegan and Vegetarian Diets
This study in Finnish vegans and non-vegetarians showed that vegans had a lower intake of vitamin B12 and vitamin D, compared to non-vegetarians. Vegans also had lower circulating levels of vitamin D, iodine and selenium.
However, the blood lipid profile of vegans was significantly more favorable, and they had much higher levels of antioxidant isoflavones, mostly derived from soy products.
13. Nutrients, Vitamins and Minerals
People living in high-latitude areas, which get little sunlight during the winter months, are at an increased risk of vitamin D deficiency.
This observational study of native people in Alaska showed that vitamin D levels were affected by season, gender and whether they lived inland or by the coast. The traditional diet also protected against vitamin D deficiency.
Previous studies suggest that calcium and vitamin D supplements may reduce the risk of fractures during initial military training. However, calcium may interfere with iron absorption.
In contrast to previous studies, this randomized, controlled trial indicates that calcium and vitamin D supplements do not affect iron status.