This is our weekly selection of recently published studies and reviews in nutrition. Here are some of the most interesting findings this week:
- Barley beta-glucan may help you lose weight.
- Replacing saturated fat with polyunsaturated fat (mostly omega-6) may not affect heart disease risk.
- Low-quality, oxidized fish oil doesnâ€™t have as many benefits as high-quality fish oil.
- Prunes may reduce bone loss in postmenopausal women.
- Synbiotic supplements may improve the symptoms of rheumatoid arthritis.
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.
- Obesity and Weight Loss
- Blood Sugar Control and Diabetes
- Heart Health
- Brain and Mental Health
- Bone Health
- Muscles and Physical Performance
- Longevity and Healthy Aging
1. Obesity and Weight Loss
Flavonoids are a category of antioxidants found in virtually all plant-derived foods, especially fresh vegetables, fruits, legumes and whole grains.
This observational study in 9,551 US adults found that those who consumed a lot of flavonoids were less likely to be obese. Additionally, a high flavonoid intake was associated with lower levels of C-reactive protein, which is a marker of inflammation.
Effects of high beta-glucan barley on visceral fat obesity in Japanese subjects: a randomized double blind study.
Barley beta-glucan is a water-soluble, viscous fiber thatâ€™s similar to oat beta-glucan, which has been linked to various health benefits.
This controlled study in 100 Japanese adults showed that eating a diet high in barley beta-glucan, or 4.4 grams per day for three months, led to greater weight loss than garcinia cambogia which doesn’t contain any beta-glucan.
2. Blood Sugar Control and Diabetes
This controlled study in 65 vitamin D-deficient, overweight or obese adults showed that a one-time 100,000-IU dose of cholecalciferol followed by a 4000-IU daily dose of cholecalciferol for four months did not affect insulin sensitivity or production.
3. Heart Health
This observational study in 9,370 Korean adults showed that a moderate intake of unprocessed meat and regular consumption of poultry was linked to a reduced risk of heart disease.
High intake of unprocessed meat was not significantly associated with the risk of heart disease.
Low-fat dietary pattern and cardiovascular disease: results from the Womens Health Initiative randomized controlled trial.
This controlled study in 48,835 postmenopausal women aged 50â€“79 found that following a low-fat diet consisting of 20% of calories from fat for eight years did not affect the risk of heart disease overall, compared to a usual diet.
However, women without prior heart disease appeared to benefit from the diet, although the health improvements were offset by an increased risk of stroke.
The effect of replacing saturated fat with mostly n-6 polyunsaturated fat on coronary heart disease: a meta-analysis of randomised controlled trials.
This meta-analysis of controlled studies concluded that replacing saturated fat with polyunsaturated fat (mostly omega-6) probably doesnâ€™t reduce the risk of heart disease, death from heart disease or death from any cause.
Some previous meta-analyses have concluded that replacing saturated fat with omega-6 fat has benefits for heart health. However, the researchers pointed out that they may have included inadequately controlled studies.
High-quality fish oil has a more favourable effect than oxidised fish oil on intermediate-density lipoprotein and LDL subclasses: a randomised controlled trial.
Numerous studies show that taking fish oil supplements may reduce the risk of heart disease. However, not all fish oil is the same.
This controlled study in 54 adults showed that high-quality fish oil caused a greater reduction in the levels of LDL particles, total blood lipids and cholesterol than low-quality, oxidized fish oil.
Dietary polyphenol intake and risk of hypertension in the Polish arm of the HAPIEE study.
Polyphenols are a large and diverse group of antioxidants that is found in most plant-derived foods. A high intake of polyphenol-rich foods has been linked to a variety of health benefits.
This observational study in 2,725 Polish adults showed that a high intake of polyphenols was linked to a 31% lower risk of developing abnormally high blood pressure (hypertension).
This meta-analysis of 17 observational studies showed that a high intake of calcium was associated with a 20% lower risk of cancer in the esophagus.
Calcium appeared to be most protective against esophageal squamous cell cancer in Asian populations.
Dietary Intake of Meat Cooking-Related Mutagens (HCAs) and Risk of Colorectal Adenoma and Cancer: A Systematic Review and Meta-Analysis.
This review and meta-analysis of observational studies concluded that contaminants that form when meat is cooked at a high temperature may be responsible for meatâ€™s association with an increased risk of colon cancer.
5. Brain and Mental Health
Multiple sclerosis (MS) is a neurodegenerative disease. Itâ€™s characterized by a variety of neurological symptoms, ranging from impaired memory and mental problems to impaired eyesight, muscle weakness and lack of coordination.
This review concluded that a high intake of vitamin D may reduce the risk of MS and improve symptoms. Additionally, a few studies show that low vitamin B12 levels are associated with worsened MS symptoms.
6. Bone Health
Previous studies in rats and postmenopausal women suggest that eating dried plums (prunes) is an effective way to prevent bone loss (osteoporosis), potentially reducing the risk of fractures.
This follow-up study found that postmenopausal women who ate 100 grams of prunes every day for one year retained higher bone mineral density five years later, compared to the placebo group.
Vegetable and Fruit Intake and Fracture-Related Hospitalisations: A Prospective Study of Older Women.
This observational study in 1,468 older, postmenopausal women found that a high self-reported intake of vegetables was linked to a lower risk of bone fractures. In contrast, fruit intake was not associated with fracture risk.
When the researchers looked at different vegetable types, onions and cruciferous vegetables appeared to be the most protective. For instance, a high intake of cruciferous vegetables reduced fracture risk by 28%, compared to low intake.
7. Muscles and Physical Performance
This observational study in 50 older, elite athletes found that a higher protein intake was associated with greater muscle strength.
Synbiotics are supplements containing both probiotics and prebiotics (beneficial bacteria and the fiber that nourishes them). Their anti-inflammatory effects might benefit people with rheumatoid arthritis (RA).
This two-month, controlled study in 54 adults with RA found that daily synbiotic supplements significantly improved insulin sensitivity, reduced levels of the inflammatory marker C-reactive protein (CRP) and alleviated the symptoms of RA.
Dietary and Supplemental Vitamin C and D on Symptom Severity and Physical Function in Knee Osteoarthritis.
Previous observational studies indicate that high levels of vitamins C and D may reduce pain and improve function in people with knee osteoarthritis (KO).
This observational study in people with KO found that vitamin D supplements were strongly linked to better function. However, high vitamin D levels were associated with greater pain, whereas vitamin C wasnâ€™t linked to any measures of KO.
Cardamom is a spice thatâ€™s commonly used in Indian cuisine.
This controlled study in 80 overweight or obese, pre-diabetic women found taking 3 grams of cardamom supplements per day for two months significantly reduced markers of inflammation (CRP and IL-6) and oxidative stress (malondialdehyde).
10. Longevity and Healthy Aging
This observational study in 103,256 Swedish adults showed that eating a lot of non-fermented dairy (ND) and butter was linked to a 32% greater risk of death from any cause, compared to eating ND only once per week.
The risk of death was lower among those who consumed mostly medium or low-fat milk. In contrast, fermented milk products, such as yogurt and cheese, were associated with a lower risk of death.