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.

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.

gut microbes help people lose weight

Gut bacteria can effect weight loss

Gut bacteria keep proving how important they are in helping us maintain good health. Studies have shown that exposure to the right gut bacteria can ward off infection from harmful bacteria like C. difficile. Studies have also linked gut bacteria exposure to development of chronic diseases like asthma and Chron’s disease. Yesterday, the New York Times reported on two studies that together link gut microbe exposure to the weight loss.

In one study, people who are overweight were found to be more likely to have a certain microbe named Methanobrevibacter smithii in their gut. The scientists believe this microbe is better at squeezing nutritional value out of foods and makes it harder for people to lose weight:

The study involved 792 people who had their breath analyzed to help diagnose digestive orders. They agreed to let researchers measure the levels of hydrogen and methane; elevated levels indicate the presence of a microbe called Methanobrevibacter smithii. The people with the highest readings on the breath test were more likely to be heavier and have more body fat, and the researchers suspect that the microbes may be at least partly responsible for their obesity.

This type of organism may have been useful thousands of years ago, when people ate more roughage and needed all the help they could get to squeeze every last calorie out of their food. But modern diets are much richer, said an author of the study, Dr. Ruchi Mathur, director of the diabetes outpatient clinic at Cedars-Sinai Medical Center in Los Angeles.

In the other study, scientist examined the effects of gastric bypass surgeries on the microbiota of mice. The scientist gave one group of mice the surgery and saw their microbiome change significantly while they lost weight. They compared this result to mice who had their intestines surgically separated and stitched back together. This group of mice showed little change in their microbial flora. Implanting the fecal matter from the mice who received the gastric bypass into another set of mice caused the new group to lose weight as well:

the researchers used mice, which they had fattened up with a rich diet. One group had gastric bypass operations, and two other groups had “sham” operations in which the animals’ intestines were severed and sewn back together. The point was to find out whether just being cut open, without having the bypass, would have an effect on weight or gut bacteria. One sham group was kept on the rich food, while the other was put on a weight-loss diet.

In the bypass mice, the microbial populations quickly changed, and the mice lost weight. In the sham group, the microbiota did not change much — even in those on the weight-loss diet.

Next, the researchers transferred intestinal contents from each of the groups into other mice, which lacked their own intestinal bacteria. The animals that received material from the bypass mice rapidly lost weight; stool from mice that had the sham operations had no effect.

Exactly how the altered intestinal bacteria might cause weight loss is not yet known, the researchers said. But somehow the microbes seem to rev up metabolism so that the animals burn off more energy.

Check out the human study here at the Journal of Clinical Endocrinology and Metabolism. The study on mice appars here at Science Translational Medicine.

is the paleo diet scientific?

The paleo diet recommends eating a diet rich in meats, seafood, vegetables, fruits, and nuts while avoiding refined grains and sugars. The thinking is that the human body is best served on a diet that mimics what hunter-gatherers ate. Laura Miller argues that the diet is not scientific in Salon:

For this reason, generalizations about the typical hunter-gatherer lifestyle are spurious; it doesn’t exist. With respect to what people ate (especially how much meat), the only safe assumption was “whatever they could get,” something that to this day varies greatly depending on where they live. Recently, researchers discovered evidence that people in Europe were grinding and cooking grain (a paleo-diet bugaboo) as far back as 30,000 years ago, even if they weren’t actually cultivating it. “A strong body of evidence,” Zuk writes, “points to many changes in our genome since humans spread across the planet and developed agriculture, making it difficult at best to point to a single way of eating to which we were, and remain, best suited.”…

Furthermore, the fossil record of the Stone Age is so small and necessarily incomplete that its ability to tell us about paleolithic society is severely limited. Consider this: For all we know, the first tools were not stone implements but woven slings designed to allow a mother to carry an infant while foraging; it’s just that stone happens to survive longer than fibers.

drunk on alcohol and caffeine

How does mixing a caffeinated drinks like coffee or cola with alcohol change your level of drunkeness?

This month’s Scicurious column on Scientific American examines the interaction between caffeine and alcohol when we’re drinking. As you know alcohol is a depressant and caffeine is a stimulant. Does the combination of the two cancel each other out? Or is there a more complex interaction. An excerpt:

Consuming alcohol results in one set of effects, and consuming caffeine results in a completely different set of effects. When used in moderation, both alcohol and caffeine consumed alone can have positive outcomes. Despite this, most of us have experienced very negative consequences from consuming too much of either beverage. What about alcohol and caffeine together? When alcohol and caffeine are combined, the effects and ultimate results become much more complicated.

Alcohol drinkers who also consume caffeine feel awake, talkative, and stimulated for a much longer period of time compared to when they drink alcohol alone. However, the added caffeine does not make you less drunk or less likely to go home with a grenade. Furthermore, the sedation that always accompanies drinking alcohol is often muted, or experienced much later when caffeine is in the picture.

Click the link for much, much more.

cavemen had fewer cavities

The teeth of this Egyptian skull are healthier than the teeth of most people living today.

Science magazine reports on pre-historic dental hygiene. Compared to modern mouths, the mouth’s of cavemen seem to have been colonized by fewer bacteria that cause tooth decay. The switch to agriculture and a diet that includes lots of sugars and refined carbohydrated seem to correspond to a surge in these types of bacterial species:

With these data, they charted the spectrum of bacterial species within the human mouth over the past 7500 years. Hunter-gatherers had fewer species that cause cavities and periodontal disease, and different percentages of all 15 phyla of bacteria found in modern teeth, plus some unclassified bacteria. Early farmers showed a sharp increase in bacteria that cause tooth decay, such as a Veillonellaceae strain, and a dramatic surge inPorphyromonas gingivalis, which causes periodontal disease.

The first significant sample of S. mutans turned up around 4300 years ago in the Bronze Age in Yorkshire, U.K. Overall bacterial diversity, including higher levels of S. mutans and P. gingivalis, seemed to stabilize through the Bronze Age and medieval period. Then, sometime in the past 400 years, the diversity of bacteria within each tooth dropped sharply once again. Modern samples and preliminary data from the mid-19th century show an oral environment even more dominated by S. mutans. Cooper concludes that the change occurred with the Industrial Revolution, about 1850 in England, when cavities also increased and refined sugars entered the diet. “Sugar and flour caused everything to go berserk,” he says.

More here and here.
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drunk on diet soda

Some people may get drunker when mixing alcohol with diet sodas compared to regular soda

A new (and small) research study suggests that mixing diet soda with alcoholic beverages can lead to greater intoxication than having alcohol with a sugared mixer.  NPR’s Allison Aubrey spoke with the researcher about the findings:

So what was the motivation for the new study? “I wanted to know if the choice of a mixer could be the factor that puts a person above or below the legal limit,” writes Marczinski, who’s a professor at Northern Kentucky University.

And it turns out, diet soda might just push you past that tipping point. Marczinski’s study found that the average BrAC was .091 (at its peak) when subjects drank alcohol mixed with a diet drink. By comparison, BrAC was .077 when the same subjects consumed the same amount of alcohol but with a sugary soda.

“I was a little surprised by the findings, since the 18% increase in BrAC was a fairly large difference,” Marczinski tells The Salt via email.

Marczinski says she also wanted to determine if the volunteers in her study (eight women, eight men) would notice any differences between the two mixers. Not so much, it turns out.

The subjects didn’t report feeling more impaired or intoxicated after drinking the diet soda mixer, compared to the sugary soda. Experts say this may put them at an increased risk of drinking and driving.

 

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eat earlier. lose weight.

Can eating earlier lunches help you lose weight? Maybe. A study of 420 adults in Boston and Spain seems to suggest so. From the abstract in the International Journal of Obesity:

Late lunch eaters lost less weight and displayed a slower weight-loss rate during the 20 weeks of treatment than early eaters (P=0.002). Surprisingly, energy intake, dietary composition, estimated energy expenditure, appetite hormones and sleep duration was similar between both groups. Nevertheless, late eaters were more evening types, had less energetic breakfasts and skipped breakfast more frequently that early eaters (all; P<0.05). CLOCK rs4580704 single nucleotide polymorphism (SNP) associated with the timing of the main meal (P=0.015) with a higher frequency of minor allele (C) carriers among the late eaters (P=0.041). Neither sleep duration, nor CLOCK SNPs or morning/evening chronotype was independently associated with weight loss (all; P>0.05).

Early eaters lost an average of 22lbs compared to 16.5lbs for later eaters.

 

how camels survive in the desert

An Arabian Camel

Genomic studies are helping researchers determine what is unique about these dessert dwelling mammals. It turns out it is mostly their metabolism. From Scientific American:

Camels, as ruminants like cattle and sheep, digest food by chewing the cud. But many of the Bactrian genome’s rapidly evolving genes regulate the metabolic pathway, suggesting that what camels do with the nutrients after digestion is a whole different ball game. “It was surprising to me that they had significant difference in the metabolism,” says Kim Worley, a molecular geneticist at Baylor College of Medicine in Houston, Texas. The differences could point to how Bactrians produce and store energy in the desert.

The work shows that camels can withstand massive blood glucose levels owing in part to changes in genes that are linked to type II diabetes in humans. The Bactrians’ rapidly evolving genes include some that regulate insulin signaling pathways, the authors explain. A closer study of how camels respond to insulin may help to unravel how insulin regulation and diabetes work in humans. “I’m very interested in the glucose story,” says Brian Dalrymple, a computational biologist at the Queensland Bioscience Precinct in Brisbane, Australia.

The researchers also identified sections of the genome that could begin to explain why Bactrian camels are much better than humans at tolerating high levels of salt in their bloodstreams. In humans, the gene CYP2J controls hypertension: suppressing it leads to high blood pressure. However, camels have multiple copies of the gene, which could keep their blood pressure low even when they consume a lot of salt, suggest the authors of the latest work.

The study appears in Nature Communications.

how much meat did cavemen eat?

It turns out that cavemen might not have chomped away on gigantic bison burgers as we often think.  It had been estimated that protein intake made up 60-80 percent of the caveman’s diet.  A new study suggests that this is wrong as only about 45 percent of the modern diet consists of protein. And that is protein of any type, not just from meat.  From Scientific American:

 [M]any studies estimate that between 60 and 80 percent of the prehistoric human diet came from proteins, with most of that from animal sources.

That was surprising because no more than 45 percent of modern diets come from protein of any type.

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That contradiction led O’Connell to wonder if the offset was wrong because it relied on animal estimates, not humans.

To find out, her team took human blood samples from a study where scientists meticulously re-created people’s usual diets, measured exactly how much they ate over a week, and took precise samples of each meal. By comparing the nitrogen isotope ratios in the food and human blood samples, they were able to estimate how much heavy nitrogen the human body stores. (They then extrapolated their estimate for blood samples to human hair and to bone.)

Previous estimates based on animal studies were too small and thus inflated how much animal protein our ancient ancestors ate, she said.

Instea
“We are suggesting that animal proteins would be less important overall and that’s particularly true for interpretations of Neolithic farmers,” she said. “What that would mean is that they are having more of a balance of animal and plant proteins in their diet, suggestive of a mixed existence strategy.”d, the first farmers, who lived around 12,000 years ago, likely ate no more than 40  to 50 percent of their protein from animal sources. Those people ate a diet more similar to subsistence farmers in modern-day India or China, O’Connell said. Hunter-gatherers from the Paleolithic period also ate less meat, she added.