Lettuce and lung cancer.

Lung cancer risk: Data about lung cancer risk was provided by a pooled analysis of 6 cohorts and 2 additional studies including a total of 9,130 cases. Nonsignificant protective effects were found in the pooled analysis (24) and the male part of a cohort of very large size (29) including 6,860 cases. No significant association was found in the remaining cohort (2).

Inclusion of intermediate levels of consumption:
No significant effect of any level of consumption was found in any cohort. Results suggest that any possible protective effect may allready be found at the level of 1.26 servings/week.

RRs for lettuce in servings/week.

Lung cancer mortality: No data was found.

Conclusion: Nonsignificant protective effects of lettuce against lung cancer risk were found in a pooled analysis of 6 cohorts and the male part of another cohort including 75% of all cases. No other associations were found. Since all associations were nonsignificant evidence was judged suggestive for an association between lettuce and lung cancer risk. This protective effect was found at the level of consumption of ≥ 1.26 servings/week.

Author

Cohort name

Subjects

Years of follow-up

Cases

End point

Consumption of

Relative Risk (RR)

Adjustments

29) Wright ME (2008)

The NIH-AARP Diet and Health Study

472,081 subjects (281,288 men and 190,793 women) aged 50-71.
(USA)

8
(1995-2003)

See variables

Lung cancer risk

Compositae (lettuce)

All men (3,834 cases):
RR = 0.92 (0.83-1.02; P = 0.09) for the highest vs lowest quintile of consumption.

Amount specific data (servings per 1000 kcal per day):
0.01: RR = 1.
0.06: RR = 0.98 (0.90-1.08).
0.14: RR = 0.96 (0.87-1.05).
0.26: RR = 0.95 (0.86-1.05).
0.63: RR = 0.92 (0.83-1.02).

In analyses stratified by histological type, higher consumption of the compositae group was most protective against squamous cell carcinomas among men (RR = 0.74; 95% CI = 0.58-0.93; P = 0.02).

**Men. Stratified by smoking status:**
Never smokers (141? cases)	Former smokers (2,110? cases)	Current smokers (1,583? cases)
RR = 0.78 (0.44-1.37; P = 0.17) for the highest vs lowest quintile of consumption.	RR = 0.87 (0.76-1.00; P = 0.06) for the highest vs lowest quintile of consumption.	RR = 0.99 (0.84-1.18; P = 0.91) for the highest vs lowest quintile of consumption.

All women (2,201 cases):
RR = 1.02 (0.89-1.16; P = 0.29) for the highest vs lowest quintile of consumption.

Amount specific data (servings per 1000 kcal per day):
0.02: RR = 1.
0.09: RR = 0.89 (0.78-1.01).
0.21: RR = 0.94 (0.83-1.07).
0.39: RR = 0.93 (0.81-1.06).
0.91: RR = 1.02 (0.89-1.16).

**Women. Stratified by smoking status:**
Never smokers (170? cases)	Former smokers (835? cases)	Current smokers (1,196? cases)
RR = 1.16 (0.71-1.89; P = 0.45) for the highest vs lowest quintile of consumption.	RR = 1.15 (0.93-1.42; P = 0.05) for the highest vs lowest quintile of consumption.	RR = 0.91 (0.76-1.10; P = 0.44) for the highest vs lowest quintile of consumption.

One serving of vegetables = 1 cup of raw, leafy vegetables, 1/2 cup of other vegetables, or 6 ounces of juice.

Age, energy intake, race, education, BMI, smoking status, smoking dose, time since quitting, alcohol intake, physical activity, and family history of any cancer.

24) Smith-Warner SA (2003)

Pooled analysis of 6 prospective studies.

330,784

6-13

3,026

Lung cancer risk

Lettuce

INCLUSION CRITERIA:

At least 50 incident lung cancer cases.
Assessment of usual diet.
Conduct of a validation of the diet assessment method or a closely related instrument.
Assessment of smoking habits.

INCLUDED STUDIES (Follow-up years/No. of lung cancer cases):

The Alpha-tocopherol, Beta-carotene Cancer Prevention Study (Only the placebo group is included in this analysis). (1985-1996/298 men)
Albanes D, Heinonen OP, Taylor PR, Virtamo J, Edwards BK, Rautalahti. Alpha-Tocopherol and beta-carotene supplements and lung cancer incidence in the alpha-tocopherol, beta-carotene cancer prevention study: effects of base-line characteristics and study compliance. J Natl Cancer Inst. 1996 Nov 6;88(21):1560-70. Full text
The Canadian National Breast Screening Study. (1980-1993/149 women)
Rohan TE, Jain M, Howe GR, Miller AB. A cohort study of dietary carotenoids and lung cancer risk in women (Canada). Cancer Causes Control. 2002 Apr;13(3):231-7. Abstract
The Health Professionals' Follow-up Study. (1986-1996/244 men)
Feskanich D, Ziegler RG, Michaud DS, Giovannucci EL, Speizer FE, Willet WC. Prospective study of fruit and vegetable consumption and risk of lung cancer among men and women. J Natl Cancer Intst. 2000 Nov 15;92(22):1812-23. Full text
The Iowa Women's Health Study. (1986-1996/433 women)
Steinmetz KA, Potter JD, Folsom AR. Vegetables, fruit, and lung cancer in the Iowa Women's Health Study. Cancer Res. 1993 Feb 1;53(3):536-43. Full text
The Netherlands Cohort Study. (1986-1992/843 men, 131 women)
Voorrips LE, Goldbohm RA, Verhoeven DT, van Poppel GA, Sturmans F, Hermus RJ. Vegetable and fruit consumption and lung cancer risk in the Netherlands Cohort Study on diet and cancer. Cancer Causes Control. 2000 Feb;11(2):101-15. Abstract
The Nurses' Health Study B. (1986-1996/379 women)
Feskanich D, Ziegler RG, Michaud DS, Giovannucci EL, Speizer FE, Willet WC. Prospective study of fruit and vegetable consumption and risk of lung cancer among men and women. J Natl Cancer Intst. 2000 Nov 15;92(22):1812-23. Full text

RELATIVE RISK:

RR = 0.90 (0.74-1.10; P = 0.07) for the highest vs lowest quartile of consumption.

Amount specific data (servings):
0: RR = 1.
> 0 to < 1/week: RR = 0.93 (0.77-1.12).
> 1/week to 1/2/day: RR = 0.83 (0.67-1.02).
≥ 1/2/day: RR = 0.90 (0.74-1.10).

One serving = 1 cup.

P for between-study heterogeneity: 0.79.
P for between-study heterogeneity due to sex: 0.63.

Adjusted for education, BMI, alcohol intake, calories, smoking status, smoking duration for past/current smokers, amount smoked for current smokers.

14) Feskanich D (2000)

The Nurses' Health Study

&

The Health Professionals' Follow-up Study

77,283 US women (38-63 years) and 47,778 men (40-75 years)

Women: 1984-1996.

Men: 1986-1996.

516? women, and
258? men

Total lung cancer risk

Iceberg lettuce, romaine lettuce

No significant association with risk (no data shown).

Not defined, but probably: age, follow-up cycle, smoking status,years since quitting among past smokers, cigarettes smoked/day among current smokers, age at start of smoking, total energy intake, and availability of diet data after baseline measure.

11) Voorrips LE (2000)

The Netherlands Cohort Study

62,573 women and 58,279 men aged 55-69.

6.3
(1986-1992)

910?

lung cancer risk

lettuce

RR = 0.7 (0.5-1.0; No P value) per 25 g/day increment.

age, sex, current smoker, years of smoking cigarettes, habitual number of cigarettes per day, highest educational level, family history of lung cancer and the other vegetables of the raw vegetable group.

2) Kvale G (1983)

No cohort name.

10,602 men.
(Norway)

11.5
(1967-1978)

All: 69.
Squamous and small cell: 41.

Lung cancer risk

Lettuce


Primary tumours:	Squamous and small-cell carcinomas:
Relative odds = 0.96 (P = 0.87) for the highest vs lowest quartile of consumption (> 6 vs < 1 times/month).	Relative odds = 0.37 (P = 0.15) for the highest vs lowest quartile of consumption (> 6 vs < 1 times/month).

Age, cigarette smoking, region and urban/rural place of residence.