Past Week in Nutrition Science: This is an overview of interesting studies published on nutrition from Friday, Oct 23rd, to Friday, Oct 30th, 2015.
TYPE OF DIETARY FAT AND THE BENEFITS OF VITAMIN D
This week we reviewed two research papers, one published in Diabetes and one from the British Journal of Nutrition.
Summary: This randomized trial compared the effects of eating high amounts of saturated fat or polyunsaturated fat.
The study found that high amounts of saturated fat from palm oil led to a greater increase in visceral fat than polyunsaturated fat from sunflower oil. Additionally, sunflower oil led to an almost three times greater increase in lean body mass.
Summary: This randomized trial examined the effects of daily vitamin D supplements on body fat and blood sugar control. It also compared the response of different genotypes to vitamin D supplements.
The study showed that not all people benefit equally from vitamin D supplements. While vitamin D may promote weight loss and improve blood sugar control in some people, others do not achieve similar benefits. This depends on people’s genes.
OTHER RESEARCH FROM AROUND THE WORLD
As usual, many papers were published this week, ranging from randomized controlled trials to scientific reviews.
Below is an overview of the most interesting nutrition research, categorized by subject.
OBESITY AND WEIGHT LOSS
This observational study in children found that consuming both sugar-sweetened and artificially sweetened beverages is associated with body fat gain in the UK.
Weight loss causes the body to start conserving energy — a condition called “starvation mode.” This 8-week trial found that weight loss causes changes in the levels of specific proteins involved in the metabolism of fat cells.
Inulin is a type of fermentable dietary fiber. Animal studies indicate that fermentable dietary fiber may promote weight loss.
This 18-week randomized controlled trial found that inulin supplementation improves the effectiveness of a weight loss diet, compared with cellulose. Additionally, inulin caused a greater reduction in liver and muscle fat.
This meta-analysis of randomized controlled trials showed that during a calorie deficit, high-fat diets lead to greater weight loss, compared to low-fat diets. Low-fat diets lead to greater weight loss only when compared to a “usual” diet.
Overall, there is no evidence to support low-fat diets over other types of weight loss diets.
This trial investigated whether individual responses to fasting and overfeeding were associated with future changes in body weight.
The study found that those who had a greater reduction in calories burned during a 24-hour fast were more likely to have gained weight 6 months later. Simply put, those who are better at conserving energy are predisposed to weight gain.
Sustained low-grade inflammation is associated with metabolic syndrome, which is a cluster of health conditions including central obesity, diabetes, insulin resistance, hypertension and a poor blood lipid profile.
This meta-analysis of randomized controlled trials suggests that low-fat and low-carb diets may be effective against inflammation.
This trial in obese children with metabolic syndrome found that reducing dietary fructose for 9 days improved blood pressure, glucose tolerance, and circulating levels of triglycerides, LDL-cholesterol and insulin.
Acute coronary syndrome (ACS) is a term for any conditions that suddenly reduce blood flow to the heart. Low ratios of omega-3/omega-6 fatty acids have previously been implicated in the development of ACS.
This observational study supported earlier findings. It found that low ratios of omega-3/omega-6 fatty acids increased the risk of early ACS in men, but not in women.
This observational study suggests that eating high amounts of red and/or processed meat may increase the risk of heart disease in women. These associations were stronger for processed meat.
BLOOD SUGAR CONTROL AND TYPE 2 DIABETES
This small cross-over experiment in men found that taking 500 mg of phosphorus with 75 g of glucose reduced subsequent blood sugar levels and insulin, and improved insulin sensitivity, compared with the ingestion of glucose alone.
Previous observational studies indicate that low circulating levels of vitamin B6 may increase the risk of kidney cancer.
This observational study supports previous studies. Additionally, it found low levels of vitamin B6 to be associated with increased risk of death from kidney cancer.
This study in children found that probiotic supplementation caused a significant improvement in the digestive environment by increasing the numbers of beneficial bacteria, while reducing undesirable species of bacteria.
However, 6 months after the supplementation stopped, the digestive environment had returned back to its original state.
Vitamin D deficiency is a common problem in children with inflammatory bowel disease.
This study showed that taking a single, high dose of vitamin D3 maintained an adequate vitamin D status for at least 6 months in children with inflammatory bowel disease.
BRAIN HEALTH AND FUNCTION
This observational study found no association between vitamin D status at birth and attention deficit/hyperactivity (ADHD) disorder later in life, compared with children without ADHD.
This observational study in Swiss vegans, vegetarians and non-vegetarians suggests that all three diets can fulfill dietary requirements for vitamins and minerals. However, they need to be well-balanced and supplements are necessary in some cases.
Non-vegetarians had the lowest intakes of magnesium, vitamin C, vitamin E, niacin and folic acid. Conversely, vegans consumed low amounts of calcium, and had very low intakes of vitamin D and B12.
VITAMINS AND MINERALS
MTHFR is an enzyme that serves an essential function in folate metabolism. In some people, MTHFR is slightly different, making them predisposed to folate deficiency. These people are of the MTHFR 677TT genotype.
This meta-analysis supports previous studies. Those with the MTHFR 677TT genotype had higher homocysteine levels in blood, less folate and did not respond as well to folate supplementation, compared to other people.
This review discusses the addition of illegal substances to dietary supplements. They are most frequently added to supplements intended for weight loss, muscle building and improved exercise performance. This is a rising health concern.
Punicic acid is polyunsaturated fatty acid, categorized as a conjugated linoleic acid (CLA). Pomegranate seeds are the main dietary source of punicic acid.
This review discusses the potential health benefits of punicic acid. It is considered more potent than ordinary CLAs, and some studies indicate that it may help prevent diabetes, obesity and cancer.