This is an overview of interesting nutrition research published from Friday, May 6th, to Friday, May 13th, 2016. Some of the more interesting topics this week:
- Extreme weight loss causes extreme metabolic slowdown.
- Can yogurt help you lose weight? The surprising truth.
- How breastfeeding is linked to a reduced obesity risk.
- Do high-fat dairy products protect against diabetes?
- Does dietary cholesterol increase the risk of breast cancer?
- Dietary supplements against depression — an evidence-based review.
This week we reviewed two papers: one about how calorie restriction affects metabolic slowdown, and the other about how yogurt affects weight.
Summary: This study checked in on former contestants of The Biggest Loser TV show, 6 years later. It examined how rapid weight loss affects long-term metabolism.
It found that extreme weight loss caused long-term metabolic slowdown. However, the study did not include a control group, which makes the results difficult to interpret.
Summary: This systematic review and meta-analysis examined how conventional yogurt affects weight, and suggests that it may have modest weight loss benefits.
New Research From Around the World
Lots of new 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
- Appetite and Eating
- Brain and Mental Health
- Kidney and Urinary Health
- Bone Health
- Muscles and Physical Performance
- Infections and Immune Health
1. Obesity and Weight Loss
This review concluded that depressive symptoms were linked with behaviors that tend to cause obesity in children.
Specifically, children who were depressed engaged in less physical activity, had a poor diet and spent more time in front of the TV or computer.
This observational study suggests that breastfeeding for a long time may reduce the risk of obesity at age 2. The study found that for every extra week a child was breastfed, the risk of obesity decreased by 0.82%.
2. Blood Sugar Control and Diabetes
Dairy fat contains a few types of fat that are rare in nature. These include pentadecanoic acid, margaric acid and trans-palmitoleic acid.
This observational study found that higher circulating levels of these fats were associated with a lower risk of type 2 diabetes. The findings suggest that eating a lot of dairy may protect against the development of type 2 diabetes.
This meta-analysis of observational studies suggests that both low and high levels of selenium are associated with an increased risk of type 2 diabetes. Conversely, normal levels of selenium were not linked with diabetes.
3. Heart Health
Orthostatic hypotension (OH) is what occurs when your blood pressure drops if you suddenly stand up or stretch. It can lead to dizziness, dimmed vision or fainting, and is common among elderly people.
This systematic review and meta-analysis suggests that low circulating levels of vitamin D may increase the risk of OH.
This observational study indicates that high circulating levels of zinc are associated with a higher risk of high blood pressure in men, increasing the risk of heart disease.
This systematic review and meta-analysis indicates that a high dietary intake of cholesterol is associated with an increased risk of breast cancer.
Estradiol is the main female sex hormone. High levels of estradiol may promote certain types of cancer, mainly breast cancer and endometrial cancer.
This observational study found that the Western diet (especially egg and meat intake) is associated with higher levels of estradiol, possibly increasing breast cancer risk.
5. Appetite and Eating
Food addiction is when people can’t control what they eat and compulsively overeat. It often involves high-fat and/or high-sugar foods, and is associated with obesity.
Many obese individuals believe themselves to be food addicts. This observational study suggests this belief makes people more concerned about their calorie intake. As a result, they tend to eat less, but the long-term effects are unknown.
Picky eating habits are common in children. Also common is food neophobia, which is when children are unwilling to eat foods they haven’t tried before.
This systematic review of observational studies concluded that food neophobia is not linked with weight status. Conversely, the association of picky eating is unclear, since the definition differed between studies.
6. Brain and Mental Health
This randomized controlled trial showed that supplementing with 2 grams of green tea powder every day for 12 months did not affect mental function in elderly, Japanese people. However, it did reduce oxidative stress.
Some nutrients may improve your response to antidepressant medications. This systematic review suggests that S-adenosylmethionine, methylfolate, omega-3 fats and vitamin D may reduce depressive symptoms when taken with antidepressants.
This study suggests that a single cup of tea has no effects on mood, compared to a glass of water.
7. Kidney and Urinary Health
Polycystic kidney disease (PKD) is a genetic disorder characterized by cysts that grow on the kidneys. The main symptoms are high blood pressure, abdominal pain, blood in urine and excessive urination. Eventually, it leads to kidney failure.
This mouse study suggests that calorie restriction may slow the progression of PKD.
8. Bone Health
Advanced glycation end products (AGEs) are a group of compounds that form in your body when sugar reacts with protein. High blood sugar levels promote formation.
This observational study suggests that AGEs may be responsible for the bone deterioration and osteoporosis seen in some people with type 2 diabetes.
9. Muscles and Physical Performance
Mangosteen is a fruit that mainly grows in Southeast Asia. This randomized controlled trial found that drinking 250 ml of mangosteen juice one hour before exercise did not reduce fatigue during exercise.
This was a randomized controlled trial in frail, elderly adults. It showed that taking leucine, vitamin D and medium-chain triglycerides for 3 months improved muscle strength and function more than leucine, vitamin D and long-chain triglycerides.
10. Infections and Immune Health
Natural killer cells are your immune system’s first line defence against viral infections and cancer. Growing evidence suggests resveratrol may improve their function.
Resveratrol is an antioxidant found in plants like red grapes and blueberries. This review discusses the evidence linking resveratrol to improved immune function.