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04.12.2013

hooked leaves kill bedbugs

The New York Times covers this paper on how bean leaves help fight bedbug infestations. The leaves in question have tiny hooks that trap the bedbugs’ legs as they crawl over them. Using these leaves are a common folk remedy for getting rid of bedbugs in Eastern Europe. From the New York Times :

The first task was to determine exactly how the hooks — the technical name is trichomes — worked. The process was viewed through an electron microscope, Dr. Loudon said. “The foot comes down onto the surface, but as it’s lifting up, it’s catching on these hooks,” she said. “The point is pointing down. So all of their legs get impaled.”

“And as soon as one leg gets caught,” she added, “they are rapidly moving legs around and try to get away on the surface. That’s when they get multiply impaled.”

…

On the natural leaves, bugs were snagged, on average, after six steps, or locomotory cycles. (In one cycle, each of the insect’s six legs moves once.) Once stuck, they tried to free themselves, but they usually ended up just flailing in place around the impaled limb.

04.10.2013

vitamin d holds up under scrutiny

Six studies confirm the health benefits of vitamin D

We often see headlines mentioning a chemical or vitamin has astonishing new health benefits, only to have those claims fall apart under more thorough investigation. Vitamin D is looking like it might be an exception. Science News highlights six studies on the vitamin’s health benefits:

An analysis of 24 clinical trials in children finds that kids getting vitamin D supplements had a 47 percent reduced risk of dental caries, researchers report in Nutrition Reviews.

A study of 242 healthy adults getting daily calcium supplements shows that those who also took modest vitamin D supplements of 800 IU per day saw their blood pressure decrease. Their top blood pressure number fell by 10 points on average after a year and their bottom BP number fell by four points. Writing in Nutritional Influences on Bone Health, the researchers also report that the vitamin D folks saw their heart rate decline from 74 to 70 beats per minute. The calcium-only group saw no improvement on average.
A 28-year study in which Danish scientists monitored the health of nearly 10,000 people finds that those who developed a tobacco-related cancer during that time had vitamin D levels at the study outset of 14.8 nanograms per milliliter of blood on average, compared with 16.4 ng/ml on average for everyone else. That report shows up in Clinical Chemistry.
BMJ reports in a review of 31 studies that pregnant women with vitamin D levels of less than 30 ng/ml had an increased risk of developing a complication such as preeclampsia or gestational diabetes.
Low vitamin D levels may hamper metabolism in blacks. A study in Nutrition Research finds that adult blacks averaged vitamin D of only 14.6 6 ng/ml compared with 25.6 ng/ml on average in whites. Blacks were also more likely to have insulin resistance, a condition in which cells fail to use the hormone insulin efficiently to process glucose. But when researchers compared groups with similar vitamin D levels, the differences in insulin resistance disappeared. That suggests that the higher burden of insulin resistance in blacks is at least in part the result of low vitamin D, they conclude.
Very low vitamin D might be linked to suicide risk. An analysis of military service members finds that people who committed suicide appear to have similar vitamin D levels on average compared with those who don’t. But a closer look finds that people with the very lowest levels, less than 15 ng/ml, were roughly twice as likely to commit suicide as people with vitamin D ranging from 17 to 41 ng/ml. That study appears in PLoS One.

04.09.2013

red meat linked to cardiovascular disease

Carnitine, found in red meat and some energy drinks, has been linked to cardiovascular disease in a new study.

Consuming lots of red meat has long been thought to increase the chances of developing cardiovascular diseases. Researchers now believe they have evidence that a molecule called carnitine found in red meat is likely a key player in the link between the two. From The New Scientist:

Some bacteria in the intestine use carnitine as an energy source, breaking it down and producing a waste product called trimethylamine (TMA). The liver converts this into another substance, trimethylamine-N-oxide (TMAO), which is excreted in urine.

In mice, high levels of dietary carnitine shifted the types of bacteria present in the gut and increased the volume of TMAO produced tenfold. “Imagine a Petri dish full of bacteria,” says Hazen. “If you start feeding them carnitine, the ones that like carnitine more will reproduce and those that don’t will decrease.”

TMAO levels matter because the substance increases the uptake of “bad” cholesterol and prevents its destruction by macrophages – white blood cells – in artery walls. This causes a build-up of plaque that can lead to atherosclerosis.

In further tests, Hazen’s team found that meat-eaters produced higher levels of TMAO than vegans or vegetarians after they were fed carnitine, suggesting that they had more TMA-producing bacteria in their gut. “I’m not telling people to cut out red meat,” Hazens says. “But cut down the frequency and portion sizes.”

As a check, the researchers looked at the blood levels of carnitine and TMAO in human blood samples and determined whether there was a link to cardiovascular disease. And there was. From Scientific American:

[E]ven when they took l-carnitine supplements, vegans and vegetarians made far less TMAO than meat eaters. Fecal studies showed that meat eaters and non-meat eaters also had very different types of bacteria in their guts. Hazen says that a regular diet of meat probably encourages the growth of bacteria that can turn l-carnitine into TMAO.

To further make the case, researchers checked the levels of l-carnitine in the blood of nearly 2,600 people who were having elective heart check-ups. By itself, the nutrient didn’t seem to make a difference. However, people who had high levels of both l-carnitine and TMAO were prime targets for heart disease, further evidence that it’s the bacterial alchemy — not the l-carnitine alone — that poses the real threat.

The original research is published in Nature Medicine.