The Journal of the American Medical Association reported last year that a seven-year study of 3,107 women who had had breast cancer (all of them under the age of 70, all of them having had tumors larger than 1 cm) found no cancer-protective benefit of increasing consumption of fruits and vegetables beyond 5 servings a day.
Very nearly half of the women in the Women's Healthy Eating and Living trial who had had breast cancer were just encouraged to eat 5 servings of fruits and vegetables a day. The rest of the women who had had breast cancer were coached to eat twelve servings of fruits and veggies every day, and to reduce their consumption of saturated fat.
The coaching worked. At the end of four years, the women who had received nutritional counseling were found to be consuming:
- 65 per cent more vegetables
- 25 per cent more fruit
- 30 per cent more fiber and
- 13 per cent less saturated fat.
But what was the effect on health?
- Women who ate more fruits and vegetables consumed an average of 1538 calories a day and weighed an average of 163 pounds.
- Women who ate fewer fruits and vegetables consumed an average of 1559 calories a day and weighed an average of 162 pounds.
- 256 out of 1537 women on the high fruit-and-vegetable diet had a recurrence of breast cancer.
- 262 out of 1551 on the Five-A-Day plan had a recurrence of breast cancer.
All other things held equal, women who got the very most servings of fruits and vegetables (more than 9 a day) and the very most fiber (more than 25 g a day) had measurably but not significantly lower rates of breast cancer return.
The lowest levels of saturated fat consumption were, as you might expect, linked to lower rates of breast cancer. However, it was impossible to determine whether additional fat really increased risk of cancer or not (a little more than the minimum fat seemed to, a little more seemed to reduce risk although not as low as the lowest-fat group, and still more raised risk again).
And among women who consumed the most calories, more than 1980 calories a day, eating more fruits and vegetables actually was associated with higher rates of recurrent cancer, although the differences were not statistically significant (there was a measurable probability that there was no real relationship between eating fruits and veggies and staying cancer-free in women who ate the most fruits and vegetables and the most calories).
So does this mean that fruits, vegetables, fiber, and lower fat aren't beneficial for women who have been diagnosed with breast cancer?
Not at all. This study just finds that Five-A-Day may be enough, and more will not necessarily help.
Pierce JP, Natarajan L, Caan BJ, Parker BA, Greenberg ER, Flatt SW, Rock CL, Kealey S, Al-Delaimy WK, Bardwell WA, Carlson RW, Emond JA, Faerber S, Gold EB, Hajek RA, Hollenbach K, Jones LA, Karanja N, Mad lensky L, Marshall J, Newman VA, Ritenbaugh C, Thomson CA, Wasserman L, Stefanick ML. Influence of a diet very high in vegetables, fruit, and fiber and low in fat on prognosis following treatment for breast cancer: the Women's Healthy Eating and Living (WHEL) randomized trial. 1: JAMA. 2007 Jul 18;298(3):289-98.