Nutrition News, May 19th

Smiling chef preparing a salad in the kitchen

This is our weekly selection of recently published studies and reviews in nutrition. Here are some of the most interesting findings this week:

  • Olive oil may reduce the risk of type 2 diabetes and benefit those who are already diabetic.
  • Walnut oil improves the blood lipid profile, potentially reducing the risk of heart disease.
  • Galacto-oligosaccharide supplements, a type of prebiotic fiber, may increase the abundance of beneficial bifidobacteria in the gut by 400%.
  • Oxygenated water might improve recovery after exercise.
  • Nicotinamide Mononucleotide (NMN) testing in humans shows link between brain NAD+ and disease


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
  2. Blood Sugar Control and Diabetes
  3. Heart Health
  4. Cancer
  5. Digestive Health
  6. Lung Health
  7. Bone Health
  8. Muscles and Physical Performance
  9. Longevity and Healthy Aging
  10. Vitamins, Minerals and Other Nutrients

1. Obesity and Weight Loss

Protein intake and dietary glycemic load of 4-year-olds and association with adiposity and serum insulin at 7 years of age: sex-nutrient and nutrient–nutrient interactions.

This observational study in 1,999 children found that a high protein intake at age four was associated with a higher body mass index (BMI) at age seven.

The study also showed that a high protein intake was linked to higher fasting insulin levels in boys. Additionally, high dietary glycemic load was associated with an increased risk of fat gain in boys only.

2. Blood Sugar Control and Diabetes

Chocolate intake and diabetes risk in postmenopausal American women.

This observational study in 92,678 postmenopausal American women found no significant association between long-term chocolate intake and the risk of type 2 diabetes.

However, a moderate intake of chocolate reduced the risk in two subgroups of women — those who were younger than 65 and those whose physical activity was below median.

Olive oil in the prevention and management of type 2 diabetes mellitus: a systematic review and meta-analysis of cohort studies and intervention trials.

This meta-analysis and review of observational and controlled studies concluded that a high intake of olive oil may reduce the risk of type 2 diabetes by 16%. It may also improve blood sugar control in people who are already diabetic.

3. Heart Health

A systematic review and meta-analysis of randomized controlled trials of the effect of konjac glucomannan, a viscous soluble fiber, on LDL cholesterol and the new lipid targets non-HDL cholesterol and apolipoprotein B.

Glucomannan is a soluble dietary fiber produced from konjac root.

This meta-analysis of 12 controlled studies concluded that glucomannan supplements reduce LDL and non-HDL cholesterol levels, possibly reducing the risk of heart disease.

Circulating cadmium concentration and risk of aortic aneurysms: A nested case-control study within the Malmö Diet and Cancer cohort.

Aortic aneurysm (AA) is when the aorta, the body’s main artery, dilates or enlarges 1.5 times its normal size. It normally does not cause any symptoms, but it increases the risk of aortic rupture, which causes massive internal bleeding.

This observational study in 30,447 middle-aged, Swedish adults showed that high circulating cadmium levels were associated with a 250% increased risk of AA in current or ex-smokers.

Can sesame consumption improve blood pressure? A systematic review and meta-analysis of controlled trials.

This meta-analysis of eight controlled studies including 843 participants concluded that eating sesame seeds can reduce blood pressure. However, the evidence was considered weak and better designed studies need to confirm the effect.

The effect of a low salt diet on blood pressure and some hormones and lipids in people with normal and elevated blood pressure.

This Cochrane review and meta-analysis of controlled studies concluded that reducing high sodium intake down to 3.8 grams of salt per day (66 mmol/day) decreased blood pressure in white people with high blood pressure (hypertension).

Specifically, it decreased systolic blood pressure by 5.5 mm and diastolic blood pressure by 2.9 mm, on average. Some studies suggest that sodium reduction may be even more effective in Asian and black people.

Effects of walnut oil on lipid profiles in hyperlipidemic type 2 diabetic patients: a randomized, double-blind, placebo-controlled trial.

This was a controlled study in 100 diabetic people aged 35–75 who had elevated blood lipid levels (hyperlipidemia).

The study showed that taking 0.45 ounces (15 milliliters) of walnut oil for three months improved the blood lipid profile by reducing levels of triglycerides, LDL cholesterol and the total cholesterol to HDL cholesterol ratio.

4. Cancer

Association between phytosterol intake and colorectal cancer risk: a case-control study.

Phytosterols are plant compounds that resemble cholesterol in structure. They are found in high amounts in vegetable oils.

This observational study in 3,615 Chinese adults found that a high total phytosterol intake was associated with a 50% lower risk of colorectal cancer. However, one type of phytosterol called stigmasterol was linked to an increased risk in women.

5. Digestive Health

Oral Supplementation with Bovine Colostrum Decreases Intestinal Permeability and Stool Concentrations of Zonulin in Athletes.

Intestinal permeability describes the ability of the gut wall to control what compounds can slip through and into the blood. Vigorous exercise may increase IP. Abnormally high IP has been associated with various chronic diseases.

This was a controlled study in 16 training athletes, most of whom had high IP. It found that supplementing with 500 mg of cow colostrum for 20 days reduced intestinal permeability.

Supplementation of Diet with Galacto-oligosaccharides Increases Bifidobacteria, but not Insulin Sensitivity, in Obese Prediabetic Individuals.

Galacto-oligosaccharides (GOS) are a category of prebiotic fiber that may improve the growth of beneficial gut bacteria, such as bifidobacteria.

This controlled study in 44 overweight or obese, prediabetic adults aged 45–70 showed that taking 15 grams of GOS per day for three months caused a five-fold increase in the abundance of bifidobacteria in the gut.

6. Lung Health

Longitudinal study of diet quality and change in asthma symptoms in adults, according to smoking status.

Asthma is a lung condition characterized by narrowing of the passages in the lungs, which may cause difficulties breathing. Asthma attacks can be triggered by physical exertion or particles in the air.

This observational study showed that a better dietary quality, estimated using the Alternative Healthy Eating Index 2010, was associated with a lower risk of asthma in people who had never smoked.

Association between lutein intake and lung function in adults: the Rotterdam Study.

Lutein is an antioxidant found in high amounts in many vegetables, such as kale, spinach, turnip greens, watercress, romaine lettuce, zucchini and Brussels sprouts.

This observational study in 4,402 adults aged 45–79 found no significant links between lutein intake and lung function. However, there were some indications of improved lung function in smokers.

7. Bone Health

Cadmium exposure and osteoporosis: a population-based study and benchmark dose estimation in southern China.

Cadmium (Cd) is a toxic heavy metal. Sources of cadmium include tobacco smoke, airborne dust and some grains and vegetables.

This observational study in 1,116 Chinese adults found that high urinary Cd levels were associated with lower bone mineral density, increasing the risk of osteoporosis.

Dietary protein and bone health: a systematic review and meta-analysis from the National Osteoporosis Foundation.

This meta-analysis of controlled studies concluded that a high protein intake doesn’t impair bone mineral density (BMD). In fact, high protein intake may improve BMD in most bones.

8. Muscles and Physical Performance

Ingestion of oxygenated water enhances lactate clearance kinetics in trained runners.

Oxygenated water is a type of bottled water with high levels of dissolved oxygen. Some people consume OA to improve their exercise and sports performance, but evidence of its effectiveness is lacking.

This crossover study in trained male runners found that OA didn’t improve exercise performance. However, it seemed to improve recovery after exercise by increasing the clearance of lactate.

9. Longevity and Healthy Aging

Hb level, iron intake and mortality in Chinese adults: a 10-year follow-up study.

This observational study followed 8,291 Chinese adults for 10 years. It showed that both low and high iron intake was associated with an increased risk of death from any cause in women, but not in men.

10. Vitamins, Minerals and Other Nutrients

Effects of the flavonol quercetin and α-linolenic acid on n-3 PUFA status in metabolically healthy men and women: a randomised, double-blinded, placebo-controlled, crossover trial.

Your body may convert alpha-linolenic acid (ALA) into long-chain omega-3 fatty acids (DHA and EPA), which have been linked with several health benefits. However, this conversion is not efficient.

This crossover study 74 healthy adults showed that taking ALA for eight weeks increased ALA levels by 56–69% and EPA levels by 26–37%, but it didn’t raise DHA levels. Taking 190 mg of quercetin per day with ALA had no effects.

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