Later On

A blog written for those whose interests more or less match mine.

Oh, no: French-press coffee & cholesterol

with 23 comments

From Science News, 30 November 1996, bad news. OTOH, the news is 10 years old, so maybe new discoveries have vindicated coffee. (Also: I drink French-press coffee, and all my blood signs are excellent.)

UPDATE: A very good point emailed by a friend: “I would advise you not stating your medical experience. Whether or not you don’t experience a change in cholesterol is not the point—that’s why they have large studies. Some smokers live until they are 90. If a smoker bragged about his avoidance experience, it would look foolish.”

Many coffee aficionados eschew the filtered brew, arguing that filters remove some of a bean’s savory flavor. What filtering really does — besides screening out gritty grounds — is eliminate coffee’s oils, rich in alcohols known as diterpenes. Two of these alcohols, cafestol and kahweol, can elicit a number of unhealthy changes in the blood of regular coffee drinkers.

The newest diterpene effect to be identified — an increase in blood levels of an enzyme that is normally associated with damage to liver cells — emerged in a 6-month long Dutch trial with healthy, coffee-loving volunteers.

Rob Urgert and his colleagues at Wageningen Agricultural University in the Netherlands recruited 46 men and women to participate in the experiment. All of the volunteers received a locally popular blend of coffee and strict instructions on how to brew two batches of it each day.

Urgert’s group directed half the men and women to pour boiling water through 33 grams of ground beans sitting in a cone-shaped filter until the dripping brew filled a half-liter jar.

The remaining volunteers were told to pour their boiling water and ground beans together into a French press — also known as cafetière — coffee maker. The top of this type of pot is fitted with a large plunger. The volunteers were told to stir the mix and then to let the grounds steep for 2 to 5 minutes before they pushed the plunger down. (This effectively stops the brewing and traps any floating grounds so that they won’t enter the cup.) The coffee was then decanted into another bottle.

The participants, all healthy and between the ages 19 and 69, were told to drink almost a liter of the coffee daily for 24 weeks. Every 2 to 4 weeks, the scientists brought the volunteers in for blood tests that measured concentrations of cholesterol, triglycerides, and a host of liver enzymes.

A report of the study, published in today’s British Medical Journal, shows that men and women who drank the filtered coffee exhibited no changes over the course of the trial in any of the assayed blood constituents. Previous studies by Urgert’s group had shown that such a filter effectively removes all of the coffee-oil’s diterpenes. Those who drank coffee made by the French press method, however, displayed a host of undesirable changes.

For instance, levels of one liver enzyme (alanine aminotransferase) nearly doubled early in the trial. This enzyme serves as a marker of potential stress to the liver, Urgert explains. “If there is some change in liver cell integrity, the concentration of these enzymes in the blood can rise.”

Fortunately, he notes, the enzyme rise among cafetière coffee drinkers was far less than that in persons with liver disease. Moreover, his data indicate, the rise in these enzymes is transient. Levels were already falling by the end of 24 weeks and continued to fall further during the 12 weeks after the trial ended.

However, Urgert told Science News Online, the enzyme findings remain interesting because “until now there have been very few foods identified as having such an effect on liver cells.”

The Dutch nutrition scientists also observed a sharp, transitory 26 percent rise in serum triglyceride levels among the men and women drinking French-pressed coffee. Like the liver-enzyme changes, however, the triglycerides fell as the study progressed. By the end of 24 weeks, their concentrations had already returned to levels recorded before the start of the study.

Of far greater concern, Urgert believes, were increases of between 9 and 14 percent in the concentrations of low-density-lipoprotein (LDL) cholesterol — the so-called bad cholesterol — in volunteers drinking the pressed brew. An increase this large in LDLs, a risk factor for heart disease, might over a lifetime elevate an individual’s chance of developing coronary disease by up to 20 percent, he notes. Also observed in several shorter studies by this group, this potent elevation in LDL concentrations shows no sign of attenuating with time.

“These [diterpenes] are amazingly predictable,” Urgert observes. “If you knew much you gave to Dutch volunteers, you could almost exactly predict their change in LDL cholesterol.”

This link to persistent LDL increases “should also apply to Turkish coffee, which contains similar amounts of cafestol and kahweol per cup,” the researchers point out. Significant LDL increases might also accompany heavy consumption of Italian espresso, they add. However, owing to the small size of espresso cups, one would have to drink some 25 cups per day.

The good news: Grandma’s old metal percolator basket will filter out the diterpenes almost as effectively as do the new generation of filtering drip coffee makers.

What if you mix your coffee up from instants? No problem. Analyses of 19 different instant coffees marketed in Europe, the United States, and North Africa — including 6 decaffeinated brands — turned up only “minimal” quantities of the diterpenes in the brewed drinks.

That doesn’t mean that some forms of coffee are completely innocuous. A study conducted in California, a few years back, showed that drinking at least two cups a day throughout life can increase the risk that an individual will suffer from osteoporosis in old age.

Tea drinkers, by contrast, can take heart in their habit. [The Younger Daughter will love this. - LG] The diterpenes that caused LDL and other changes in the new study are not found in other hot beverages. Most regular (not herbal) teas also are rich in a class of compounds known as flavonoids. These can largely halt oxidative changes in the blood — changes that can transform dietary fats into artery-clogging plaque.

References:

Barrett-Connor, E., J.C. Chang, and S.L. Edelstein. 1994. Coffee-associated osteoporosis offset by daily milk consumption. Journal of the American Medical Association 271(Jan. 26):280.

Urgert, R., et al. 1996. Comparison of effect of cafetière and filtered coffee on serum concentrations of liver aminotransferases and lipids: Six month randomized controlled trial. British Medical Journal 313(Nov. 30):8.

Urgert, R., et al. 1995. Levels of the cholesterol-elevating diterpenes cafestol and kahweol in various coffee brews. Journal of Agricultural and Food Chemistry 43(August):2167.

Written by LeisureGuy

29 October 2006 at 2:36 pm

23 Responses

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  1. Ah but …

    “…latest research has not only confirmed that moderate coffee consumption doesn’t cause harm, it’s also uncovered possible benefits. Studies show that the risk for type 2 diabetes is lower among regular coffee drinkers than among those who don’t drink it…”

    From a 2006 Harvard press release.

    Steven

    29 October 2006 at 6:38 pm

  2. Do you have any information regarding baking with coffee grounds? I have a recipe that calls for 1/4 cup of finely ground coffee.
    This sound like it could be very harmful. I could substitute margarine for butter and that would reduce the amount of cholesterol over all. Would some of the cholesterol bake out? Do you have a breakdown on how much cholesterol is in a gram of coffee
    grounds?

    John Perry

    30 March 2007 at 9:25 pm

  3. I know nothing of baking with coffee grounds, but unless you eat whatever you’re making in a large quantity every day for months, I don’t think it would have any measurable effect at all on your cholesterol level.

    Note that the coffee itself (a plant product) contains no cholesterol, but rather some oils that apparently influence cholesterol production in those consuming it.

    LeisureGuy

    31 March 2007 at 5:46 am

  4. Have there been any studies done regarding paper filters and gold metal filters? I’m concerned about continued use of the “gold filters”.

    Bob Carmody

    17 April 2007 at 5:03 am

  5. I know of no formal studies, though the common wisdom is that coffee tastes better with the gold filters since paper filters absorb some of the oils responsible for rich taste. FWIW, I don’t know whether the above study has held up under replication.

    LeisureGuy

    17 April 2007 at 7:11 am

  6. “Ah but …latest research has not only confirmed that moderate coffee consumption doesn’t cause harm, it’s also uncovered possible benefits. Studies show that the risk for type 2 diabetes is lower among regular coffee drinkers than among those who don’t drink it…” From a 2006 Harvard press release.”

    The Harvard study isn’t relevant to those drinking metal screened or french-press, or boiled unfiltered coffee. The Harvard study is a study of U.S. coffeedrinkers, the overwhelming majority of which use PAPER-FILTERED coffee, which reduces cafestol levels (which play a key role in raising cholesterol levels) by a LARGE margin over either french-press or metal-screen filtered coffee.

    Bottom line, if you’re concerned about raised cholesterol levels, drink paper-filtered coffee or reduce FP or metal-screen coffee drinking to occasional use only. It also wouldn’t hurt to change your diet and increase your exercise regime.

    Anonymous

    28 February 2008 at 8:47 am

  7. I just started drinking French Press last week, and it’s so much better than paper or metal filters. I do have a concern for a cholesterol spike, it doesn’t seem clear on what a “safe” amount would be, I typically drink 2 regular sized cups in the morning – should I be concerned? I actually just pulled up a search on FP for basic research, and I find a lot of concerning information about cholesterol – not good. I always though Coffee in moderation is a heart healthy food.

    Beejo

    4 January 2010 at 1:19 pm

  8. The French press does make delicious coffee. Use your judgment. If your lifestyle is healthy in all other respects, I don’t see that two cups of French press coffee a day are going to make any great difference.

    LeisureGuy

    4 January 2010 at 1:27 pm

  9. I have been drinking 6 to 8 cups of french press for years and I love it. Now I understand why my LDL kept creeping up even with excercise. This is sad news to me as I do not care much for filtered coffee at Starbucks which is in my opinion has the best coffee… Filtered coffee tastes tasetless but I may have to change to it.

  10. I finally gave up coffee altogether in favor of white tea.

    LeisureGuy

    7 May 2010 at 6:46 pm

  11. I have extensively used a french preess and several coffee machines (filtering). There is an obvious difference in the amount of ground coffee needed for the same strength of cup. The machine takes almost double the amount for a similar product. Could it be these “scientists” have failed to notice this obvious fact? This would result in the french press users effectively getting a DOUBLE dose which is not really a comparative study.

    Marcus

    13 May 2010 at 7:07 am

  12. Scientists are smarter than most people think and put quite a bit of thought into their experimental design, which is also subject to peer review. You can pretty much bet that any idle thought that crossed your mind as you read the report was taken account of. But the obvious answer is to read the actual report (prior to questioning the value and validity of the study).

    LeisureGuy

    13 May 2010 at 8:26 am

  13. My main concern would be if you are living a healthy lifestyle or not. If you are getting enough exercise and have a nutritious diet i don’t think a cup of coffee is going to have a major effect on cholesterol levels.

    nutritionsupplementsreviews

    23 August 2010 at 11:36 am

  14. To clarify any questions about this study, here’s a larger view or metastudy of 50 such studies on coffee’s effects on serum cholesterol:
    http://aje.oxfordjournals.org/content/153/4/353.full

    “Coffee Consumption and Serum Lipids: A Meta-Analysis of Randomized Controlled Clinical Trials”

    The Dutch study is typical of results of these other studies done in various countries by various scientists.

    Jim Redman

    10 November 2010 at 2:52 pm

  15. As I keep reading more and more about health and eating certain foods, I feel like I’m piecing together a huge puzzle. It seems that I can’t have my peanut butter, my dairy, and now my COFFEE???!!!!!! I’ll just start using paper filters =). I think the conclusion I’m coming to is that just the act of being alive is what’s going to cause our demise ;)

    Beth

    13 May 2011 at 7:33 am

  16. Eating right does amount to figuring out a huge puzzle—mainly, I suppose, because we now have lots of choices. But don’t focus solely on foods to avoid: there are also foods that should be eaten. My own list of regularly eaten foods:

    1/2 tsp turmeric daily (in hot cereal)
    Ample fiber, beginning with oat-bran cereal with chia seed
    Sources of omega-3 (chia seed, lots of fish, including sardines and wild salmon)
    White tea daily, with a squeeze of lime
    Lots of vegetables, including dark greens
    1/2 c pomegranate juice daily (arterial health)
    2 pieces of fruit a day

    LeisureGuy

    13 May 2011 at 8:00 am

  17. my dad survived a year’s ‘tour’ of WW2 in a bomber, ate nothing but bbq steaks and spuds, drank scotch and perk coffee like water, didn’t excersice at all, smoked for 30 years and almost made it to 90. i eat almost vegetarian style, lots of fruit, excercice daily, spend lots of time outside, only drink booze occasionally, only drink filtered coffee a couple of times per day, don’t smoke, was never shot at by enemy forces, and i have probs at 56 with heart and cholesterol. i think the air was cleaner in the 20th century, there was more oxygen, the sun didn’t strip off your skin in a half hour like now, food had more vitamins as we didn’t ship everything across the world and it wasn’t processed so much, and despite a depression and 2 wars, people back then just didn’t worry to a frenzy like we do about whether we should wear green or red and why we need to buy so many useless things that keeps us broke, so those with lard & whiskey diets that smoked plain end ciggies and put money IN the bank and saved, lived far longer than they should have…?? mindset, my fine freckled friend…mindset. so boil up a big pail of swedish coffee, cast yer inhibitions into a west wind and watch the sunrise.

    Anonymous

    23 June 2011 at 9:24 am

  18. I’m making (reluctantly) the switch from pressed coffee to filtered-with-paper coffee. After moving to NYC seven years ago and living with a mini-sized kitchen that was part of the living room and had no counter space — I switched to pressed coffee. Seven years later, my LDL levels have nearly doubled. I’m thinking I prefer filtered coffee — or even black tea — to a daily dose of Lipitor.

    B.A.

    1 March 2012 at 4:39 am

  19. But what I want to know is, is a gold filter as good as filtering out the oils as a paper filter?

    B.A.

    1 March 2012 at 4:40 am

  20. @B.A.: From my reading, the idea of the gold filter is that it does not filter out the oils, which is why some people prefer it. I know of no studies on the relative cholesterol effects of gold filters vs. paper filters, though. In the meantime you might try a fish-oil supplement and turning your diet toward increasing its omega-3 content. Here’s more information.

    LeisureGuy

    1 March 2012 at 5:23 am

  21. @ Anonymous
    23 June 2011 at 9:24

    LOL!!
    You are so right.

    Iris

    14 April 2012 at 4:06 pm

  22. B.A., how many cups a day were you drinking? Do you think that other factors (diet, exercise) have stayed constant?

    Halli

    21 August 2012 at 4:37 pm


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