This is our weekly selection of recently published studies and reviews in nutrition. Here are some of the most interesting findings this week:
- Zinc supplements may improve wound healing in people with diabetic ulcers.
- Obese children and adolescents are more likely to be depressed than their normal-weight counterparts.
- Iron deficiency anemia is associated with a greater risk of deafness.
- Chlorogenic acid may help people fall asleep.
New Research From Around the World
Lots of recent 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
This observational study in 240 adults with metabolic syndrome showed that intake of berberine was associated with weight loss, dietary quality or metabolic factors.
This observational study in 4,830 mothers and their children found that a higher intake of omega-3 fatty acids during pregnancy (estimated by measuring their levels in cells) was associated with lower fat mass in their children six years later.
This crossover study in 15 overweight, adult women showed that eating 25 mL of virgin coconut oil (VCO) as part of a mixed breakfast did not affect the amount of calories burned, compared to extra virgin olive oil (EVOO).
Additionally, VCO didn’t cause any adverse changes in blood lipids or insulin sensitivity, compared to EVOO. However, VCO did not suppress hunger and fullness as much as EVOO.
2. Blood Sugar Control and Diabetes
This controlled study in 60 patients with diabetic foot ulcers showed that taking 220 mg of zinc sulfate supplements daily for three months significantly reduced ulcer size, compared to a placebo.
In addition, zinc supplements significantly improved blood sugar, insulin, insulin sensitivity, antioxidant status and HDL cholesterol levels.
This observational study in 2,818 middle-aged people showed that a higher intake of glucose was linked to higher insulin sensitivity. In contrast, fructose and sucrose were not significantly associated with insulin sensitivity.
This observational study in 2,332 Finnish men aged 42–60 found that plant and egg proteins were linked to a lower risk of type 2 diabetes, whereas other protein sources were not.
The study also estimated that replacing 1% of calories from animal protein with calories from plant protein was associated with an 18% reduced risk of type 2 diabetes.
3. Heart Health
The glycemic index (GI) is a relative measure of the extent to which foods raise blood sugar levels.
This review and meta-analysis of 14 controlled studies including a total of 1,097 participants concluded that a lower-glycemic diet may reduce blood pressure, potentially reducing the risk of heart disease.
This observational study in 190,949 Americans with various ethnic backgrounds showed that a higher dietary quality was associated with a significantly lower risk of colorectal cancer.
5. Brain and Mental Health
This meta-analysis of 18 observational studies including a total of 51,272 participants concluded that obese children and adolescents are more likely to be depressed, or vice versa, than normal-weight children or adolescents.
Specifically, obesity was associated with a 34% greater risk of depression. In contrast, overweight was not significantly linked to depression.
This observational study in 305,339 US adults found that iron deficiency anemia was associated with a greater risk of hearing loss.
7. Digestive Health
Necrotising enterocolitis (NE) is an inflammatory digestive disease that’s common among preterm infants. The risk of death is quite high.
This Cochrane review and meta-analysis of controlled studies concluded that adding arginine supplements to a preterm infant’s diet may reduce the risk of NE.
Inflammatory bowel disease, including Crohn’s disease (CD) and ulcerative colitis (UC), is characterized by inflammation in the digestive tract. Symptoms include stomach pain, diarrhea and weight loss.
This meta-analysis of observational studies showed that folate levels were significantly lower in people with UC, compared to those who were healthy. However, similar associations were not found in people with CD.
Oats are generally considered safe for people with celiac disease (CD). However, oatmeal may be contaminated with wheat in the factory, and some patients with CD may be sensitive to avenin, a protein found in oats.
However, this review and meta-analysis of controlled and observational studies concluded adding oats to a gluten-free diet has no adverse effects in people with CD.
8. Muscles and Physical Performance
This prospective observational study in very old adults found that low vitamin D levels were associated with a greater decline in muscle strength over the following five years. The association was stronger in men than women.
Acid-producing diets have been linked to an increased risk of disease.
This observational study in 2,176 Japanese women aged 65–94 found that a higher dietary acid load was associated with greater frailty, especially slowness and weakness, as well as low physical activity.
9. Skin Health
Rosacea is an inflammatory skin condition that causes redness and swelling of the face.
This observational study in 82,737 US women showed that a high alcohol intake was associated with an increased risk of rosacea.
Effects of subacute ingestion of chlorogenic acids on sleep architecture and energy metabolism through activity of the autonomic nervous system: a randomised, placebo-controlled, double-blinded cross-over trial.
Chlorogenic acid (CA) is the most abundant polyphenol antioxidant in coffee.
This controlled study in nine healthy adults found that taking 600 mg of CA supplements daily for five days increased fat burning and reduced the time it took them to fall asleep at night. However, it didn’t affect sleep in other ways.
11. Contaminants and Food Safety
Cholesterol in food is susceptible to oxidation during storage and cooking, forming oxysterols. Previous studies indicate that oxysterols may promote inflammation and oxidative stress.
This study showed that greater amounts of oxysterols formed in meat cooked at 482°F (250 °C) than 356°F (180 °C). It also found that freezing meat or the addition of marjoram doesn’t completely prevent their formation during storage or cooking.
12. Vitamins, Minerals and Other Nutrients
Soy products are rich in antioxidants known as isoflavones. This controlled study in breastfeeding women showed that drinking 250 mL of a soy drink every day for six days significantly increased the levels of isoflavones in breast milk.
In contrast, drinking 300 mL of decaffeinated black tea didn’t significantly affect the antioxidant content of breast milk.