Heat destroys cholesterol

Garlic does not work as a cholesterol lowering agent

The positive properties of garlic were already known in antiquity, and in America garlic preparations that advertise a cholesterol-lowering effect of their product on their packaging are now among the best-selling herbal supplements. The ingredient in garlic that is supposed to have this effect is allicin. It is produced when the garlic is cut through the release of the enzyme alliinase, which converts the precursor alliin into the active form allicin. The cholesterol-lowering effect of allicin has been proven several times in vitro. In these experiments, allicin inhibited cholesterol synthesis. A positive effect of garlic on blood lipid levels has also been reported in more than 110 animal studies. One of the biggest points of criticism when carrying out the previous studies was the difference in the bioavailability of the sulfur-containing components, especially of course allicin, in the products used. With this objection in mind, the Stanford study used both raw garlic and two of the most popular garlic supplements in California - garlicin® and Kyolic 100® - and examined its effect on the blood lipid levels measurable in the plasma.

Raw garlic has so far been expected to have the greatest effect, as it is said to have the least loss of natural activity compared to the processed products. The powdered garlicin® was selected because bioavailability studies showed it released similar allicin to raw garlic, and the content and potential of allyl thiosulfates are almost identical. Kyolic® , which is stored for months to convert irritants and fragrances into antioxidants, has both qualitative and quantitative substance differences compared to raw garlic and garlicin® on.

Garlic six times a week

The study comprised four groups, one group received raw garlic, one garlicin each® or Kyolic® and another group received placebo. Each product was taken six times a week for a period of six months. The raw garlic was given in portions of four grams, which is the weight of an average toe. Garlicin® was given four pills each and Kyolic® Six pills, the placebo pills four or six each. The allicin concentration of raw garlic and garlicin® was almost identical, but both contained a little less garlic dry matter than Kyolic®• The composition of the supplements was checked at regular intervals to ensure constant test conditions.

Hidden in the sandwich

In order to administer the preparations in a tasty form, sandwiches were prepared and the garlic products were added as a condiment. The test persons were not allowed to heat the condiments because heat destroys the allicin. To add a little variety to the menu, there were 12 different sandwiches, each containing about 375 kcal. Blinding was impossible due to the characteristic strong smell of garlic, but the aim of giving the same sandwiches was to create similar diet conditions for all patients.

Inclusion criterion: moderately increased blood lipid levels

The 169 participants between the ages of 30 and 65 all had moderately elevated blood lipid levels at the start of the study. On average, the LDL concentration was between 130 and 190 mg / dl, the triglyceride concentration was below 250 mg / dl and the body mass index was between 19 and 30. Subjects who were pregnant, breastfeeding, smoked, and patients with a previous one were excluded Heart disease, cancer, kidney dysfunction, diabetes mellitus or those taking medicines for high blood pressure or high blood lipids.

Participants were instructed to avoid adding garlic to their diet, as well as other foods containing onions or leeks, as these also contain sulfur compounds such as allicin. Blood was drawn monthly from the subjects after they had fasted for 12 hours each. The blood was checked enzymatically for LDL levels, HDL levels, triglyerides and the ratio between total cholesterol and HDL. Calorie intake, physical activity and weight were recorded at the time of randomization and in the middle and at the end of the study, and gender was also recorded. 96 to 97 percent of the four study groups ate their sandwiches regularly, and all participants ate at least 80 percent of the sandwiches. Only a few test subjects did not recognize whether they ate a sandwich with raw garlic or not, around 55 percent correctly identified their sandwich as containing garlic or not, 35 percent expressed no assumption. There were differences between the individual groups in terms of physical activity, weight, or calorie intake in the form of saturated fat or fiber. From this point of view, it was therefore not possible to falsify the individual study results.

Garlic does not lower LDL

At the end of the study, there was no significant difference in the plasma blood lipid values ​​between the individual groups. The result is meaningful because the study has three advantages: First of all, the products used were checked before, during and after the study, thereby ensuring the constancy of the main ingredients of garlic, above all those of allicin. Furthermore, compared to processed products, raw garlic would show no change in bioavailability and therefore develop the best overall effect. The third benefit of the study was the six-month duration, during which monthly blood tests were carried out to ensure that a moderate, transient lowering of cholesterol was noticed. In summary, it can be said that the scope and quantity of the preparations used were much larger than previous studies; and it was designed to detect even the slightest deviation in plasma blood fat levels, but it did not. No serious side effects whatsoever were reported; only three of 169 test subjects had heart problems and stenoses in the mouth area. Although 57 percent of the raw garlic group reported bad breath and body odor, only a few test subjects reported gas or other symptoms.

The study results should not, however, be generalized, which could result in other health effects such as B. atherosclerosis prevention or anti-carcinogenic properties. The study also does not allow any statement to be made as to whether higher-dose garlic preparations reduce cholesterol. It is also quite conceivable that the use of garlic (preparations) could be of benefit to patients with a greatly increased cholesterol level. Based on the study results, however, it can be said that the use of garlic or garlic products cannot be recommended if the cholesterol level is moderately high.


Gardener C. et al .: "Effect of Raw Garlic vs. Commercial Garlic Supplements on Plasma Lipid Concentrations in Adults with Moderate Hypercholeserolemia"; Arch. Intern. Med. 167 (4), 346-353 (2007).

Christine Zilinski