Pot smokers don't puff away lung health: study

NEW YORK (Reuters Health) - A few hits on the bong now and then don't seem to have any detrimental effects on lung health, suggests a new study.

Researchers found that multiple measures of lung function actually improved slightly as young people reported using more marijuana -- at least up to a couple thousand lifetime joints.

"There's no doubt, if you've watched a Harold & Kumar movie, marijuana triggers a cough," said Dr. Stefan Kertesz, from the University of Alabama at Birmingham, who worked on the new study. But questions have remained about the drug's longer-term effect on lung functioning.

"Previous studies have had mixed results," Kertesz explained. "Some have hinted at an increase in lung air flow rates and lung volume (with marijuana smoking), and others have not found that. Others have found hints of harm."

While marijuana smoke has a lot of the same toxins as cigarette smoke, he added, people who use pot tend to smoke fewer joints each day than tobacco users smoke cigarettes. That and the method of inhaling may offer some relative lung protection, researchers have proposed.

Still, the findings don't let marijuana off the hook for long-term health consequences.

"I think a lot more work will need to be done to make any blanket statements about safety," said Dr. Jeanette Tetrault, a substance abuse researcher at the Yale School of Medicine in New Haven, who wasn't tied to the new research.

"These are only two measures of pulmonary function and don't really paint the entire picture" of the potential effects of marijuana on the lungs, she told Reuters Health.

The new data come from a long-term study of more than 5,000 young adults in Oakland, Chicago, Minneapolis and Birmingham. From 1985 until 2006, researchers regularly asked participants about their past and current use of cigarettes and marijuana. They also tested how much air their lungs could hold and the maximum rate of air flow out of their lungs.

Not surprisingly, the researchers found that the more cigarettes their participants smoked or had smoked in the past, the worse their lungs performed on both tests, Kertesz's team reported Tuesday in the Journal of the American Medical Association.

But at least at moderate levels of pot smoking, that didn't seem to be the case -- in fact, the trend was reversed.

Lung volume and air flow rates both increased with each "joint-year" -- the equivalent of 365 joints or pipe bowls -- participants said they'd ever smoked, up until about seven joint-years, or some 2,555 joints.

It was a small overall improvement, though. Lung airflow -- measured by how much air people could blow out in one second -- was no more than 50 milliliters higher in pot smokers compared with non-smokers. The average value for a healthy male is four liters, according to Kertesz.

"It's a very real increase... but it's so small that I don't think that a person would feel a benefit in terms of their breathing," Kertesz said.

"Is this a real increase in lung health? That's the other question. We don't know exactly what's happening inside all of the airways of the individuals who are measured."

One explanation, he said, could be that deep breaths taken by pot smokers when they're inhaling could train them to do well on a test of lung function that involves breathing in and blowing out air as quickly as possible.

That wouldn't necessarily mean their lungs are better off for marathon running, for example.

At the highest levels of pot smoking -- using marijuana more than 20 times in a month, or having over 10 lifelong joint-years worth of smoking -- lung function seemed to decline again, but the researchers noted that there weren't enough heavy marijuana users in their study population to be sure of that.

The study was funded by the National Institute on Drug Abuse and the National Heart, Lung, and Blood Institute.

Of course, researchers said, the new findings don't mean people should reach for the bong to boost their lung capacity.

Pot might irritate the lungs in the short term and cause problems for people with asthma, they said. And there's more to consider besides breathing -- like traffic accidents and problems on the job or at school while under the influence.

Whether pot smoking may increase the risks of certain types of cancer is still controversial.

But it's unlikely that it puts users at risk of chronic obstructive pulmonary disease, or COPD, as smoking does, according to Dr. Donald Tashkin, who studies the effects of marijuana on the lungs at the University of California, Los Angeles but wasn't involved in the new study.

When it comes to diminished lung function, "This particular potential complication of marijuana smoking doesn't appear to be an important risk," he told Reuters Health.

"Therefore, people who are using marijuana for medicinal purposes or recreationally at least could be reassured that they're not harming their lungs in this way."

SOURCE: http://bit.ly/xky86a Journal of the American Medical Association, online.

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Natural trans fat may not boost 'bad' cholesterol

NEW YORK (Reuters Health) - The artificial trans fats that once abounded in processed foods have become notorious for their undesirable effects on cholesterol levels. But a small clinical trial suggests that natural trans fats may not do the same damage.

When 61 healthy women followed a diet with a hefty dose of natural trans fats for four weeks, researchers found there were no changes in the women's LDL ("bad") cholesterol and only small changes in HDL, or "good," cholesterol, in some women.

So-called industrial trans fat was once widely used in crackers, chips and other baked or fried processed foods, but the other kind of trans fat occurs naturally in meat and dairy products.

It's known that industrial trans fats tend to raise people's levels of LDL cholesterol, while also lowering HDL cholesterol -- a double whammy against heart health.

But much less research has gone into the possible effects of natural trans fat.

And since food manufacturers have been removing the artificial kind from their products, the natural variety is becoming our main source of dietary trans fat, said Benoit Lamarche, a professor of food sciences and nutrition at Laval University in Quebec, Canada.

"The question is, 'is this a problem?'" said Lamarche, the senior researcher on the new paper. "This study suggests it's not."

Among overweight women in the study, however, HDL cholesterol declined -- by an average of five percent, though the average HDL level remained in the desirable range.

Since HDL cholesterol is heart-healthy, that's a potential concern, Lamarche told Reuters Health.

But on balance, he said, "we don't see what we see with industrial trans fats."

"The effects seem to be different, particularly with LDL," Lamarche said.

So does that mean a healthy, normal-weight woman can eat all the meat and butter she wants?

No, according to Lamarche, whose study was funded by Dairy Farmers of Canada, Dairy Australia, Agriculture and Agri-Food Canada and the Canadian Dairy Commission.

"This doesn't change the nutritional guidelines," he said, noting that the conventional advice is to avoid trans fats and limit saturated fat.

Saturated fat, found mainly in meat and dairy, can boost LDL cholesterol. But unlike trans fat, it does not lower HDL. The American Heart Association says people should keep saturated fat to less than seven percent of their total daily calories. (That's 140 calories if you eat 2,000 calories in a day.)

It's also always tough to know exactly how any single nutrient might affect a person's health in real life.

In studies like the current one, diets are carefully controlled to try to pinpoint a nutrient's effects.

In this case, Lamarche's team used a butter enriched with natural trans fats to substantially boost the women's intake over four weeks -- equivalent to what you'd get if you downed eight servings of dairy products in a day.

The women spent another four weeks using a "control" butter with about one-third the amount of trans fat. All of the other diet components -- from calories to protein, to fiber and other types of fat -- were kept the same between the two diets.

Studies like that are important for understanding the specific effects of natural trans fats, said David J. Baer, a researcher at the U.S. Department of Agriculture who wrote an editorial published with the study.

But there are still questions, Baer told Reuters Health. Only a handful of studies have tested the potential short-term effects of consuming natural trans fats. And, Baer said, those studies have involved different "doses" of the fats, different approaches to adding them to the diet and different groups of people.

The only previous study that included women found that natural trans fats did boost women's LDL (but not men's). However, Baer pointed out, it used a higher daily allotment of the fats than the current study did.

So for now, Baer said, "it's hard to make a blanket statement" about natural trans fats.

He noted that some researchers believe the point is moot. If you follow conventional wisdom and limit saturated fat, you'll end up with little natural trans fat in your diet.

On the other hand, some researchers are looking at ways to boost the concentration of one natural trans fat in dairy products -- known as conjugated linoleic acid, or CLA. Animal research has suggested CLA can be heart-healthy and promote fat loss.

That could be done by changing how dairy cows are fed.

"If you want to produce a high-CLA product," Baer said, "it will probably have more of the other trans fats too."

So that, he noted, is one additional reason for studying the potential health effects of natural trans fats.

SOURCE: http://bit.ly/AxaO9v American Journal of Clinical Nutrition, online.

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