Tuesday, March 06, 2007

Garlic Fails to Live up to its Cholesterol-lowering Claim

This isn't going to bode well for garlic fiends. It might bode well for people who find themselves in the vicinity of garlic fiends, assuming garlic fiends give up their garlic habits. Though, if they're thinking about it, let it not be because of this one study.

Researchers from Stanford reported in the February 26th issue of the Archives of Internal Medicine, a sister publication to JAMA, that neither raw garlic nor garlic supplements improved cholesterol levels (LDL, HDL, triglycerides, total cholesterol) in participants during a 6-month trial.

Here's the abstract:
Effect of Raw Garlic vs Commercial Garlic Supplements on Plasma Lipid Concentrations in Adults With Moderate Hypercholesterolemia

WebMD has a nice synopsis:
Garlic May Not Lower Cholesterol: Study Shows No Improvement in Cholesterol Levels From Raw Garlic or Garlic Supplements

The authors investigated three garlic formulations, a dried garlic product (Garlicin), an aged garlic extract (Kyolic), and raw garlic. The study used wonderful research protocol, which won't forecast continued healthy sales for those supplements. But I have reservations about that raw garlic arm of the study.

Follow the Bouncing Clove

The raw garlic was provided as part of a condiment, to be added to a sandwich, which was also provided. Sandwiches were consumed daily, and along with their garlic condiments, were picked up twice a week. "Participants were instructed to heat the sandwich bread or filling as desired, but not the condiment because it contained the raw garlic and heat causes allicin loss." Allicin is the supposed active ingredient in garlic.

The garlic that was provided in the condiment that was provided in the sandwich that was provided to participants twice a week, and which, hopefully (because we can't follow these sandwiches after we release them to sandwich eaters) was always kept at a temperature no higher than 39.2ºF, did not come from a freshly squashed garlic clove. It came from an individually packaged 4 gram amount of previously crushed garlic that had been kept frozen at -80ºC (-112ºF) for some period of time. The authors don't say what that period of time was, but the following sentence provides a clue, "Allyl thiosulfinate content in raw garlic stored at -80ºC ... was unchanged after 2 years." While it may be fair to claim that the garlic consumed in the study was raw, it's a stretch to call it fresh.

Here are my reservations:
  1. Allicin, a component of crushed garlic which was measured to be present in "stable amounts" throughout the trial, may not be the only active ingredient in garlic:

    "Garlic is important as a whole food or herb because [it supplies] many sulfur-containing and other phytochemicals which can have antioxidant and bioactivity."
    - Recent Advances on the Nutritional Effects Associated with the Use of Garlic as a Supplement

  2. What other possibly active ingredients may have been depleted in the course of garlic being crushed, measured, packaged, super-frozen, held for some period of time (up to 2 years), thawed from -112ºF (without heat?), unpackaged and mixed into a condiment, packaged again, distributed to study participants, held for some period of time (up to 4 days), at temperatures sometimes above 39.2ºF, and possibly warmed (microwaved?) before consumption?

  3. Garlic may provide cardiovascular (and other) benefit by means other than cholesterol lowering, e.g. through anti-clotting action, decreased atherosclerosis, or what the lead author himself describes:

    "It's still possible that garlic has an anti-inflammatory effect, or a blood-pressure-lowering effect, or an anticancer effect - all of which should be studied rigorously."
    - Christopher Gardner PhD, Stanford University

As with all studies, these results are only applicable to a population with similar characteristics as the study group - in this case a group that is primarily non-Hispanic white, post baccalaureate degree educated, and residents of one of the wealthiest areas in the country.

I'm sorry FRE, I'm sticking to my clove-a-day habit :)

Photo: Homegrown.

No comments: