Why Your Sperm Hate Second-Hand Smoke

— By Jen Quraishi

| Tue Jul. 19, 2011 2:09 PM PDT

OFP Niota/Flickr

Over the past week, there's been a bunch of science stories about the dangers of smoking and second-hand smoke to babies and teens. I don't think this represents a bona-fide trend, but it is interesting all these reports came out so close together.

This study, conducted by Stanford University researchers, found that even small exposure to second-hand smoke damages the DNA in sperm cells, which could lead to reproductive difficulties. Surprisingly, the effects of heavy second-hand smoke inhalation could be just as bad as smoking itself to men's sperm. One fertility expert has recommended men stop smoking in the three months before trying to conceive.

Pregnant women, on the other hand, have been cautioned for some years not to smoke because it leads to premature or underweight babies. University College London found an even more compelling rationale: a new study that links birth defects like missing limbs, clubfoot, and cleft palate to maternal smoking. Another report, this one from Peking University in China, tied severe and fatal fetal conditions like spina bifida and anencephaly to second-hand smoke inhalation. Approximately 20% of women smoke during pregnancy, especially if they are poor or are teenagers.

Even non-pregnant teens may want to steer clear of smokers if they can: New York University researchers found that exposure to second-hand smoke is tied to hearing loss in teenagers. Dr. Anil Lalwani, who worked on the report, says that this could explain some of the other problems tied to kids exposed to smoke. For example, if a child can't hear a teacher's questions or instructions, they could act in ways that would cause them to be diagnosed with ADHD or ADD. "We need to alter our public policies to protect the innocent bystanders who would otherwise be exposed to smoke," said Lalwani.

The Return of the 8x8 Myth

Hooray! One of my favorite pet peeves is in the news again. It's the infamous — and endlessly debunked — 8x8 rule, namely that adults should be sure to drink at least 8 glasses of water per day. 

I got interested in this several years ago because I'm a human camel: I don't drink anywhere near that much water and I feel fine. So I wondered where this myth came from. 

Answer: after undoubtedly prodigious research, Heinz Valtin of Dartmouth concluded a decade ago that it most likely came from a single paragraph in an obscure government report in 1945. Here it is:

A suitable allowance of water for adults is 2.5 liters daily in most instances. An ordinary standard for diverse persons is 1 milliliter for each calorie of food. Most of this quantity is contained in prepared foods.

Note two things: 

First, this is based on no actual research at all. It's just a casual guess. 

Second, even if it's true, it was misinterpreted. 

Everyone read the first sentence, which suggests that a 2000-calorie diet requires 2000 ml of water, or roughly 64 ounces. But they sailed right by the second sentence, which says that you get a lot of this automatically in the food you eat. So even if this was good advice, it really meant something like five or six glasses of water per day, not eight or more.

So how much water should you drink? Answer: as much as you want. If you're thirsty, drink some water. If you're not, don't bother. And "water" includes coffee, tea, soft drinks, and pretty much any other water-based beverage. Water with caffeine in it is just as good as water without it.

So why am I writing about this yet again? Because I'm amused by the fact that every couple of years someone rediscovers this myth, looks into it, and publishes a journal article debunking it. Valtin wrote about water requirements in 2002, the Institute of Medicine tackled the subject in 2004, and in 2008 Dan Negoianu and Stanley Goldfarb published a comprehensive piece in the Journal of the American Society of Nephrology concluding that for normal, healthy people there's no evidence one way or the other that drinking lots of water has any health benefits. It doesn't clear your kidneys of toxins, it doesn't improve organ function, it doesn't help you lose weight, it doesn't prevent headaches, and it doesn't improve your skin tone. (On the other hand, it doesn't do any harm, either. If you're thirsty, feel free to drink some water.)

But that was three years ago, so it's time for another go-around. Jen Quraishi has the latest debunking today, reporting on a piece by Margaret McCartney in the current issue of the British Medical Journal. 

While McCartney didn't see evidence backing up the 2-liter-a-day rule, she did see bottled water companies pushing the "water = health" idea to sell more of their products.

This time, though, there's a brand new source of dubious hydration nonsense to be debunked: the bottled water industry.

 As McCartney wrote on her blog: "The bottled water industry is pushing the idea that we should drink more than we normally would with the promise of health benefits, and I don’t think there are any. 

That's all. 

And I would recommend tap rather than bottled water: cheaper, and far better for environment." 

The bottled water companies were not happy with McCartney's attitude. In response, the European Federation of Bottled Waters wrote a letter to BMJ about McCartney's article and cited a recommendation that "at least two liters of water should be consumed per day."

McCartney, in fact, goes even further than other researchers I've read: according to Jen, "she found evidence that mental performance suffers when people drink more water than they're thirsty for." So take it easy on the Big Gulps, OK?

sitting Is Killing You: part 8/8

sitting Is Killing You: part 7

sitting Is Killing You: part 6

sitting Is Killing You: part 5

sitting Is Killing You: part 4

Sitting Is Killing You: part 3

Sitting Is Killing You: part 2

Sitting Is Killing You: part 1

Sitting really is the cause of much of people's aches and pains.  For the next more than a few days I'm going to be putting out these nice cartoons explaining just how it's hurting you.