9 augustus 2013: Bronnen: Cancer Prevention Research, J Nutr. 2007 Oct;137(10):2264-9

Rauwe knoflook eten zou de de kans op longkanker (44%) sterk verminderen. Zelfs na correctie voor roken bleek het verschil 30%. Dat waren de resultaten van een Chinees epidemologisch onderzoek bij 1424 longkankerpatiënten en
4500 gezonde volwassenen over een periode van 2003 tot 2010.

Al eerder onderzochten Australische onderzoekers de effecten van knoflook eten bij het voorkomen van darmkanker.
Zij stelden in de conclusies van een meta analyse van epidemiologische studies in 2007 dat regelmatig knoflook eten de kans op darmkanker met ca. 30% kan verminderen.  Echter uit de grote Cancer Prevention Study II Nutrition Cohort blijkt dat mocht er bewijs zijn dit alleen geldt voor vrouwen en is volgens de onderzoekers van die studie erg zwak en zeker niet significant.

We moeten er wel bij opmerken dat er een verschil zit in hoe er onderzocht is. De Chinese onderzoekers hebben specifiek en ook via persoonlijk contact het onderzoek uitgevoerd. In de andere studies is heel algemeen gevraagd naar leefstijl en voedingsgewoonten en dit vertaalt in analyses in deelstudies. Bij die laatste methode is het onderzoek dus minder specifiek en daardoor ook minder betrouwbaar naar mijn mening. En wellicht speelt het eten van rauwe knoflook i.p.v. bereidde knoflook (in eten enz.) ook nog een rol, maar daarover lees ik niets in deze onderzoeken.

Studieresultaten:

Uit het Chinese onderzoek kwam naar voren dat de kans op longkanker in zijn algemeenheid met 44% verminderde door regelmatig rauwe knoflook te eten (minimaal 2x per week). Zelfs nadat de gegevens waren gecorrigeerd voor de effecten van roken, de grote boosdoener van longkanker, bleek het verschil nog altijd 30% te zijn.

Voor de Chinese studie werden alle deelnemende volwassenen persoonlijk gevraagd naar hun leefstijlgewoonten en vooral naar of zij rookten of gerookt hadden en of en hoe vaak zij rauwe knoflook aten.

Uit de analyse van de antwoorden, vastgelegd in vragenlijsten, bleek dat de mensen die minstens twee keer per week rauwe knoflook aten een significant lagere kans hadden op het ontwikkelen van longkanker. Zelfs na correctie naar roken bleek het verschil nog altijd ca. 30% procent te zijn in het voordeel van rauwe knoflook consumptie.

De resultaten van het Chinese onderzoek: Raw Garlic Consumption as a Protective Factor for Lung Cancer, a Population-Based Case–Control Study in a Chinese Population zijn online gepubliceerd in het tijdschrift Cancer Prevention Research. Voor het volledige studierapport moet u betalen. Het abstract staat hieronder

Het volledige studierapport van de Australische onderzoekers: Does Garlic Reduce Risk of Colorectal Cancer? A Systematic Review1–3  is gratis in te zien.

Hier het abstract van die studie met daaronder het abstract van de Chinese studie.

On balance, there is consistent scientific evidence derived from RCT of animal studies reporting protective effects of garlic on Colorectal Cancer despite great heterogeneity of measures of intakes among human epidemiological studies.

Source: J. Nutr.vol. 137 no. 10 2264-2269

Does Garlic Reduce Risk of Colorectal Cancer? A Systematic Review1–3

  1. Richard J. Head6

+ Author Affiliations

  1. 4Sansom Institute, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, 5000 Australia; 5Department of Nutrition and Dietetics, Flinders University, Adelaide, 5001 Australia; 6Preventative Health National Research Flagship CSIRO, Adelaide, 5000 Australia; and 7School of Science and Primary Industries, Charles Darwin University, Casuarina Campus, Darwin, 0909 Australia
  1. *To whom correspondence should be addressed. E-mail: suong.ngo@.cdu.edu.au.

Colorectal cancer (CRC) is the 3rd leading cause of cancer death in the United States and the 2nd leading cause of cancer death in Australia. Environmental factors play important roles in the multiple-stage process of CRC and nutritional intervention has been identified as playing a major role in its prevention. The aim of this study was to review systematically the scientific evidence from all studies conducted over the last decade that examined effects of garlic on CRC. Levels of evidence were ranked from level I to level V according to study designs and the quality of each study was assessed against a set of quality criteria based on those used by the National Health and Medical Research Council in Australia. One randomized controlled trial (RCT, level II) reported a statistically significant 29% reduction in both size and number of colon adenomas in CRC patients taking aged garlic extract. Five of 8 case control/cohort studies (level III) suggested a protective effect of high intake of raw/cooked garlic and 2 of 8 of these studies suggested a protective effect for distal colon. A published meta-analysis (level III) of 7 of these studies confirmed this inverse association, with a 30% reduction in relative risk. Eleven animal studies (level V) demonstrated a significant anticarcinogenic effect of garlic and/or its active constituents. On balance, there is consistent scientific evidence derived from RCT of animal studies reporting protective effects of garlic on CRC despite great heterogeneity of measures of intakes among human epidemiological studies.

Protective association between intake of raw garlic and lung cancer has been observed with a dose–response pattern, suggesting that garlic may potentially serve as a chemopreventive agent for lung cancer.

Source: Cancer Prev Res6; 711

Raw Garlic Consumption as a Protective Factor for Lung Cancer, a Population-Based Case–Control Study in a Chinese Population

  1. Jin-Kou Zhao1,2

+ Author Affiliations

  1. Authors' Affiliations: 1Department of Non-communicable Chronic Disease Control, Jiangsu Provincial Center for Disease Control and Prevention; 2Department of Epidemiology and Statistic, School of Public Health, Nanjing Medical University, Nanjing; 3Ganyu County Center for Disease Control and Prevention, Ganyu; 4Dafeng County Center for Disease Control and Prevention, Dafeng, Jiangsu, China; 5Center for Human Nutrition, David Geffen School of Medicine; and 6Department of Epidemiology, Fielding School of Public Health, University of California, Los Angeles, Los Angeles, California
  1. Corresponding Author:
    Jin-Kou Zhao, Jiangsu Provincial Center for Disease Control and Prevention, No. 172 Jiangsu Road, Nanjing 210009, China. Phone: 86-25-8375-9411; Fax: 86-25-8375-9411; E-mail: jinkouzhao@hotmail.com
  1. Z.-Y. Jin and M. Wu contributed equally as first authors.

  2. Z.-F. Zhang and J.-K. Zhao contributed equally as senior authors.

Abstract

Protective effect of garlic on the development of cancer has been reported in the in vitro and in vivo experimental studies; however, few human epidemiologic studies have evaluated the relationship. A population-based case–control study has been conducted in a Chinese population from 2003 to 2010, with the aim to explore the association between raw garlic consumption and lung cancer. Epidemiologic data were collected by face-to-face interviews using a standard questionnaire among 1,424 lung cancer cases and 4,543 healthy controls. Unconditional logistic regression was used to estimate adjusted ORs and their 95% confidence intervals (CI), and to evaluate ratio of ORs (ROR) for multiplicative interactions between raw garlic consumption and other risk factors. After adjusting for potential confounding factors, raw garlic consumption of 2 times or more per week is inversely associated with lung cancer (OR = 0.56; 95% CI, 0.44–0.72) with a monotonic dose–response relationship (Ptrend < 0.001). Furthermore, strong interactions at either additive and/or multiplicative scales were observed between raw garlic consumption and tobacco smoking [synergy index (SI) = 0.70; 95% CI, 0.57–0.85; and ROR = 0.78; 95% CI, 0.67–0.90], as well as high-temperature cooking oil fume (ROR = 0.77; 95% CI, 0.59–1.00). In conclusion, protective association between intake of raw garlic and lung cancer has been observed with a dose–response pattern, suggesting that garlic may potentially serve as a chemopreventive agent for lung cancer. Effective components in garlic in lung cancer chemoprevention warrant further in-depth investigation. Cancer Prev Res; 6(7); 711–8. ©2013 AACR.


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