Drink at your own perceived risk

2 05 2012

by Helen Shen

How dangerous is unpasteurized milk? Many health-conscious consumers want to know. The answer depends on how you look at the numbers.

In March, CDC scientists published a study in the journal Emerging Infectious Diseases that tried to quantify this risk by analyzing milk-related disease outbreaks from 1993 to 2006.

The research was widely covered in the mainstream news media, including in a story I wrote for the San Jose Mercury News. The study also attracted a fair amount of online outrage from many raw milk enthusiasts, who treated it as a piece of biased government propaganda.

The CDC media press release, several news stories, and the research paper itself highlighted two main points: first, that 75 percent of raw milk outbreaks occurred in states where raw milk was legal at the time (in an interview with me, first author Adam Langer called this “the most important result of the study”); and second, that raw milk is 150 times more dangerous than pasteurized milk.

Plenty of aspects of the raw milk debate are unscientific. Food choices are personal, cultural, and political. Twelve states allow retail sales of raw milk. Twenty states ban raw milk sales outright. The remaining states allow only limited raw milk sales, such as on-farm transactions.

Unfortunately, emphasizing those particular research findings may have hindered a truly scientific discussion about raw milk risks.

Photo credit: cyclonebill, Wikimedia Commons

Proving the obvious

Let’s think about the first conclusion. Between 1993 and 2006, raw milk caused more outbreaks in states where the unpasteurized product was legal. Is that like saying car accidents happen more often on roads that permit cars?

Langer told me, “It is not necessarily surprising. We do occasionally have to do scientific studies in order to prove what one would think would be obvious. But it is important evidence to show that laws that restrict the sale of unpasteurized dairy products are very important public health tools to reduce the number of outbreaks that are caused by these products.”

Basically, the study suggests that in states that ban raw milk sales, few people consume and get sick from black market raw milk, says Michele Jay-Russell, a food safety expert at UC Davis and a former scientist with the California Department of Public Health.

Hm. That’s probably good news, but it doesn’t offer any real information about how risky raw milk actually might be. That’s where the second point could help.

Outbreaks versus individuals

The authors concluded that raw milk carries 150 times greater risk than pasteurized milk of causing disease outbreaks. (A disease outbreak is a cluster of illnesses thought to originate from the same source. It could involve 2, 200, or 2,000 people.)

Here’s some of the math: Only about 1 percent of the population is thought to consume raw milk. Assuming they consume milk in roughly the same quantities as other milk drinkers, and assuming the two types of milk were equally safe, you’d expect about 1 percent of outbreaks to be related to raw milk. Instead, the CDC found 60 percent of outbreaks—150 times more than expected—were linked to raw milk.But what happens if, instead of using outbreaks, you look at those individuals involved in milk-related outbreaks? Those numbers tell a slightly different story.

In total, raw milk outbreaks sickened 1571 people. Pasteurized milk sickened 2842. So, while raw milk was implicated in 60 percent of outbreaks, it accounted for only 35 percent of all outbreak-sickened individuals. Thirty-five percent is still 55 times more than you’d expect to see from the small fraction of milk drinkers who consume unpasteurized dairy. That’s cause for concern, but it’s a much smaller effect than if you measure risk by outbreaks.

The average reader doesn’t think in terms of disease clusters, but is interested in individual risk. Health agencies, on the other hand, get concerned and become involved when outbreaks occur, says Jay-Russell.

“If you’re part of an outbreak, or if you’re the only one that got sick, it’s all the same ‘badness’ for you personally. From a public health resource standpoint, having these dozens of outbreaks, every one of those requires stopping work on other public health issues,” she said.

Milking a goat
Photo credit: Teunie from nl, Wikimedia Commons

The authors didn’t communicate the reasons for their choice—non-intuitive for the general public—for calculating outbreak statistics in their paper. Nor did they include the relative risk statistics for individuals. Doing so could have helped their case.

But because the omitted statistics would have produced a weaker result, the authors invited criticisms of manipulating the numbers to their advantage.

In a press release entitled “CDC Cherry Picks Data to Make Case Against Raw Milk,” the pro-milk non-profit Weston A. Price Foundation said, “Perhaps most troubling is the authors’ decision to focus on outbreaks rather than illnesses… In addressing the risk posed for individuals who consume a food, the logical data to examine is the number of illnesses, not the number of outbreaks.”

Distracting from the data

Jay-Russell says she’s more concerned that young people and children are disproportionately sickened by raw milk—a finding that received relatively less attention. The CDC study found that 60 percent of individuals sickened by raw milk outbreaks were younger than 20. That number contrasts with 23 percent for pasteurized milk outbreaks.

Even though a small fraction of the population drinks raw milk, the majority of those sickened in raw milk outbreaks are young. This effect is partly explained by the fact that raw milk is touted by its fans as a health food—not just acceptable for children, but especially beneficial to their growth and well-being.

In my next blog post, I’ll examine some of these health claims.


Part of the Problem

31 10 2011

Sarah Jane Keller

by Sarah Jane Keller

It took me a long time to learn that I have a touch of road rage. The first time my husband watched me come slightly unhinged in gridlock, he only had one thing to say: “If you’re complaining, you’re part of the problem.”

Now that I’m spending a year as a California road warrior, it’s a mantra that slaps me with perspective whenever traffic slows to a crawl.

It’s also something that I’ve been thinking about since I fell for the United Nations’ marketing ploy surrounding today’s demographic holiday.

World population is somewhere around 7 billion: “If you’re complaining, you’re part of the problem.”

When I’m the sole person in a five-passenger car, I’m definitely part of the problem. It doesn’t take long for me to redirect my road rage inward.

My Halloween costume is the 4,796,799,300th billion person on Earth. Go to http://www.bbc.co.uk/news/world-15391515 to get an estimate of your number. (Credit: BBC)

The rectangle of environmental damage

Last week, I interviewed biologist Paul Ehrlich as part of my intern duties at the Stanford News Service. Ehrlich, the author of the controversial 1968 book, The Population Bomb, described a simple way to think about the entangled issues of population growth and consumption:

How do you respond to the statement that we should focus on overconsumption, not population growth?

Ehrlich: Most of humanity’s environmental problems trace to too much total consumption, but that consumption is a product of population size and per-capita consumption. Population and consumption are no more separable in producing environmental damage than the length and width of a rectangle can be separated in producing its area – both are equally important.

The next time I find myself trapped in an argument about which one matters more, I’m going to invoke geometry.

Both population and per-capita consumption are equally important, but our contribution to population is decided for us when we’re born, and we all need food, water and shelter. But I also seem to think that I need an iPhone, a Subaru, coffee and a hot shower. Need, maybe not, but that’s what I’m choosing.

Thank you, California

In addition to all of my consumption, I just became one more body in the most populous U.S. state. Thank you California, for your fresh agricultural products and tap water, I’m enjoying your resources.

In The Population Bomb Ehrlich warned of threats to food security, the availability of and access to enough food to live a productive life free from hunger or starvation. Many of his most dire and specific predictions have not come to pass, but we’ve been innovating ways to increase food production since the book was published; yet people generally agree that the current level of hunger in the world is still unacceptable.

The Dos Amigos Pump Plant, part of the California State Water Project, 10 miles south of Los Banos on I-5. Water is pumped up 114 feet so it can flow downhill to the next station. (Photo by Sarah Jane Keller)

California is an example of how we’ve engineered more food out of the land during the past century. It also supplies the U.S. with half of its fruits, vegetables, and nuts, making it an important part of the food system in our neck of the globe.

I recently stopped along I-5 to take in some of California’s extensive plumbing that makes it all possible. The roadside attraction was the Dos Amigos Pumping Plant, part of the California State Water Project (SWP). The pump lifts water in the California Aqueduct 114 feet, so it can flow by gravity 164 miles to the next pumping plant.

The SWP delivers water to two-thirds of the state’s population, with 70 percent going to urban users and 30 percent going to agriculture, according to the California Department of Food and Agriculture. Coincidentally, many initial phases of the project were completed in the years surrounding publication of The Population Bomb.

Having read Cadillac Desert, Marc Reisner’s 1986 opus on Western U.S. water development and sustainability (or lack thereof), seeing the California Aqueduct was like spotting a celebrity. Nothing drives home how we bend natural resources to our will like watching water flow languidly through a concrete conduit, on a journey hundreds of miles through an arid landscape.

I imagined how the water in the California Aqueduct started in the Sierra Nevada, much of it as snow, and how some of it would eventually reach Southern California. To make the journey, it is pumped nearly 2000 feet over the Tehachapi Mountains that divide the San Joaquin Valley and the Mojave Desert.

California’s water system has been described as a Rube Goldberg apparatus, which is not a cliché in this case. Before he became a cartoonist, Goldberg was a sewer engineer in San Francisco.

Water in the California Aqueduct flowing south. According to Aquafornia, "70 percent of California’s runoff occurs north of Sacramento, 75 percent of California’s urban and agricultural demands are to the south." (Photo by Sarah Jane Keller)

A paper, “Reclaiming freshwater sustainability in the Cadillac Desert”, published last year, found that “Reisner’s incisive journalism led him to the same conclusions as those rendered by copious data, modern scientific tools, and the application of a more genuine scientific method.”

Sustainability, according to the authors is defined as allocation of streamflow “to people farms and ecosystems.” They discuss issues that I have not mentioned here such as salination and impacts on biodiversity and fisheries. They mention, but do not analyze, climate change pressures on freshwater.

What would Reisner say about water in a world with 7 billion people? Sadly, we’ll never know because he was lost to cancer over a decade ago, at age 51. But an interview with Reisner, from 2000, in the now defunct magazine, California Wild, will let me give him the last word:

CW: The state’s population is projected to grow another 30 percent by 2020. If there’s enough water to fill California with people from border to border, is population growth a big problem for California?

MR: For California and the world. People ask me “What is the greatest environmental problem?” Some people think it’s water, and I say, “No. It’s population growth, by far.” It eclipses the next five most significant environmental problems combined, and in California it’s not much different.

This ending doesn’t make thinking about our roles on a planet of 7 billion any easier, but I’ll be considering how I contribute to the area of our resource sustainability rectangle, globally and in California.

If you are wondering about the source of your California tap water check out:  http://www.water-ed.org/watersources/default.asp

Gargantuan Gourds

27 10 2011

Helen Shen

by Helen Shen

Wake up, Linus, the Great Pumpkin is finally coming!

On Oct. 10, Leonardo Ureña of Napa won the Half Moon Bay giant pumpkin weigh-off with a 1704-pound behemoth — a new California record. Ureña is part of a blooming subculture of competitive pumpkin growers that are smashing pumpkin records left and right. The world record, set this year at 1818.5 pounds, has been beaten each year for three straight years.

The sport dates back to 1900, when Canadian grower William Warnock grew a 400-pound specimen, declared a world record at the Paris World’s Fair. Since then, record-breaking pumpkins have more than quadrupled in weight. The pumpkin enthusiast website Pumpkinnook.com’s once-exclusive “Club 1000” for pumpkins exceeding 1,000 pounds was updated in 2004 to become the “1100 Club.”

Giant pumpkins on display at the Stanford Shopping Center in Palo Alto. Can you spot the kid? (Photo by Helen Shen)

Jim Borchard Sr. of Borchard Farms in Salinas believes that much of this explosive growth can be traced to genetics. He’s been growing giant pumpkins for over 30 years and even won the Half Moon Bay contest several times “before the pumpkins started getting really big.”

According to Borchard, about 15 years ago, many growers started making super-giant varieties by cross-pollinating pumpkin plants by hand—using a cotton swab to transfer pollen from the male flower of one giant pumpkin to the female flower of another giant pumpkin.

Normally, each pumpkin plant grows several fruits on the same vine. Most modern competitive growers pinch off all the stems but one so that the nutrients from the roots are funneled to a single pumpkin. That one pumpkin could yield anywhere from a few hundred to a thousand seeds. Borchard belongs to the close-knit community of giant pumpkin growers who connect over the internet and swap their best seeds at seed meetings.

If all these pumpkin growers are tapping the same gene pool, I had to wonder whether winning one of these contests comes down to sheer luck. Borchard says luck certainly plays a part. Pumpkin splitting, which happens in normal pumpkins, too, occurs at devastatingly high rates in the giants. Depending on weather and geography, growers need to feed each plant about 500 gallons of water per week. “In August, these guys are taking on sometimes 40 pounds in one day,” he said, and the skin doesn’t always keep pace with the expansion.

Joel Holland holds the Washington state record with this pumpkin from 2009. (Photo by Mari Lou Holland)

Weather is another unpredictable factor. Joel Holland, a giant pumpkin grower from Sumner, Wash., says pumpkins typically fare better at northerly latitudes, but in the last 10 years, he’s seen the epicenter of winning pumpkins shift farther south. He’s noticed a general cooling trend that has helped produce ideal growing conditions in California, while making his own state a little too cold.

Bad weather and pumpkin explosions aside, serious growers can and do try to control other factors. Holland runs a thriving business that sells supplies, fertilizers, and instructional DVDs to fellow giant pumpkin growers.

One of his most popular products is a mycorrhizal soil treatment, which infects the pumpkin root system with a sort of helper fungus. The fungus lives inside the root and puts out “hyphae,” which are tiny rootlets that scout out valuable phosphorus in the soil and bring it back to the mothership. In exchange, the fungus feeds off sugars in the roots.

The contests are decided by weight, not size — although the two are usually correlated. When Holland trucked his own world record-breaking pumpkin from Washington to the Half Moon Bay festival in 1992, he took precautions to keep the fruit from losing water weight through its surface (a process called transpiration). Soaking the stem in water and filling his pickup truck bed with ice helped keep the pumpkin cool and hydrated on the three-day road trip. That pumpkin kept its weight and took first place at 827 pounds.

Is the sky the limit?

So what does one do with a pumpkin the size of a refrigerator? “You’re probably not going to want to make pie out of it,” said Borchard. Most contest pumpkins are not grown for tastiness, and some can have rinds up to 8 to 10 inches thick. Instead, Borchard saves some seeds for trading and planting, and uses the remaining pumpkin bits to feed his cattle and sheep through the winter. Many giant pumpkins are also purchased by businesses for holiday displays.

If there’s any limit to the size these pumpkins can reach, recent data suggests we may still be a ways off. My own data crunching revealed an approximately linear increase in world record pumpkin weights over the past three decades.

“People used to talk like we wouldn’t ever break 1,000,” said Holland. “I’m sure there will be a 1-ton pumpkin within the next 10 years.”

Got raw milk?

20 10 2011

By Tanya Lewis

You drink it. You put it on your cereal. You dunk cookies in it.


Life's first beverage. (Photo by Tanya Lewis)

This magical substance is the first beverage most of us consume, when our wimpy newborn bodies can’t handle much else. But it’s not just a beverage, it’s a hyper-nutritious, calcium-packed nectar, produced by the mammary glands of female mammals to nourish their young.

Yeah, okay, so what’s the story with milk? Well, when I first arrived in Santa Cruz a little over a month ago, milk seemed to be the talk of the town. After all, it turns out, California is the leading producer of milk in the nation. It produced 38 billion pounds of milk in 2006. In fact, California dairy farms produce over 21% of the nation’s total milk supply.

Apparently, all the fuss had to do with recent crackdowns on producers of raw milk (or rather, owners of the milk producers, who were, in fact, farm animals).

Raw milk is milk that has not been pasteurized or homogenized. What exactly is pasteurization? You always see it on milk cartons, but how often do you stop to wonder what it actually involves?

Pasteurization, named after the Frenchman Louis Pasteur, is essentially heating up a liquid or food to kill pathogenic bacteria that can be threatening to your health. Sounds like a good idea, right? Well, the FDA thought so, and it’s become pretty much standard practice in the retail dairy business. But not everyone’s happy about it… more on this later.

Here in California, milk production is regulated by the California Department of Food and Agriculture (CDFA). On their website, they have a chart showing California’s bacteriological standards for milk:




Grade “A” Raw Milk for Pasteurization Bacterial (Standard Plate Count) Limits Not to exceed 100,000 per ml Not to exceed 50,000 per ml
Somatic Cell Count Not to exceed 750,000 per ml Not to exceed 600,000 per ml
Coliform No Standard Not to exceed 750 per ml
Laboratory Pasteurized Count No Standard Not to exceed 750 per ml
Grade “A” Pasteurized Milk Standard Plate Count Maximum 20,000 per ml Maximum 15,000 per ml
Coliform Maximum 10 per ml Maximum 10 per ml

Clearly, California is more anal than the federal government, at least when it comes to bacterial standards.

Back in 2008, the CDFA passed a bill called “AB 1735” which established new standards for coliform bacteria in raw milk sold in California. As of January 2008, the state’s two raw milk bottlers were required to have a final product with no more than 10 coliform bacteria per milliliter (same as pasteurized milk).

What’s a cauliflower coliform anyway? Colforms are a group of bacteria typically found in the environment: in soil, surface water, vegetation and the intestines of warm-blooded animals.  Well, I guess cauliflower could be found in that last one, too. Anyway, coliforms are used as a gauge of sanitary conditions in things like…(surprise) dairy production. They also produce the characteristic “off” taste in sour milk. While most don’t actually cause disease, a small fraction can make you sick, especially if you’re a young child, old person, or have a weakened immune system.

Kiyoshi Shiga (Tanakadate Aikitu Memorial Science Museum)

For example, a strain of E.coli O157:H7 has been implicated in some pretty sordid cases of foodborne illness. They produce a toxin called “Shiga toxin”, named after the Japanese physician and bacteriologist Kiyoshi Shiga, who first described the bacterial origin of dysentery due to Shigella dysenteriae.

(I can think of better things to have named after you than a toxin, but at least he got his own Wikipedia page.)

Shiga toxins work by inhibiting protein synthesis in cells by cleaving off a nucleobase from the RNA of a ribosome. The dysfunctional ribosome stops being able to produce protein. Clearly this not optimal. Shiga toxin-producing E.coli were behind for the recent outbreak in deadly sprouts from Germany.

Another kind of sprouts, of the nonlethal Trader Joe's variety (photo by Tanya Lewis)

But back to milk…

How do coliform get into milk? The most common way is milking cows with wet, grimy udders or using unclean milking equipment. Their presence, while not inherently harmful (unless they’re the toxic variety), has been used as an indicator of sanitation for years. In dairy farms, coliform count is a measure of the fecal bacteria in milk (eww, right?), but coliforms can also signal environmental contamination of drinking water supply systems.

The good news (some would argue) is that pasteurization of dairy products easily kills coliform. Contamination can occur after pasteurization too, though, which is why it’s important to refrigerate milk. For raw milk, California law mandates it be cooled to 50 deg. F after milking begins and maintained at 45 deg. F within two hours after milking.

According to the CDFA, the new standards for coliform count in raw milk can be achieved without pasteurization, “with utilization of sound cleaning and sanitation practices.” They say that on average, about 25% of milk samples from dairy farm inspections fall within the allowable range for colliform bacteria. ** Agreeing with national data collected by USDA’s National Animal Health Monitoring System, and published in the Journal of Dairy Science in 2004 (J. Dairy Sci. 87:2822).

The CDFA lists a few suggestions for minimizing coliform count in raw milk. Here are two of my favorites:

  • Properly managing manure, bedding, housing and pastures to prevent cows from arriving overly dirty at the milking parlor.
  • Use of an appropriate commercially available pre-milking teat sanitizer to further reduce the amount of bacteria contacting milking equipment

    Penny Ice Creamery Pasteurizer, Santa Cruz (photo by Tanya Lewis)

The raw milk bill specifies maximum bacterial counts for a whole range of dairy products, including ice cream, sherbet, and eggnog! I did a bit of “field research” at the Penny Ice Creamery  here in Santa Cruz, and found out their ice cream is a) delicious and b) pasteurized in-shop (see photo).

Well, not everyone’s on board with the raw milk restrictions. Many people consider it their right to drink and distribute raw milk. This isn’t prohibition, after all. Recently, Santa Cruzans (or whatever the right collective noun is) staged a Milk-In at the Downtown Farmers Market. People are serious about their milk, so don’t even try to move their cheese.

On that note, I leave you with some cow pictures:

“Pauline was the pet of President William Howard Taft and is seen here grazing on the south lawn of the White House. She supplied the Taft family with fresh milk daily.” (DC Public Library Commons)

A Canadian Holstein (image from http://www.dairycowdaily.com)

Gladys the Swiss Dairy Cow, as a schoolbus (image from James Lebinski, Wikimedia Commons) More versions of Gladys at wikipedia.org/wiki/Gladys_the_Swiss_Dairy_Cow.