Do you open the blinds for your houseplants so they get sunlight during the day?

A new study of vegetables suggests they might produce more anti-cancer phytochemicals if they receive the same treatment.

Researchers at University of California-Davis and Rice University found that harvested cabbages continue to actively produce anti-cancer phytochemicals if they are exposed to daylight. The study is published in the advance issue of Current Biology.

The researchers hypothesized that after cabbages are picked, glucosinolates, phytochemicals that repel insect attacks, accumulate more during daytime than at night, when predatory insect activity is less. Vegetables with high levels of glucosinolates, especially cabbage and other cruciferous plants, also have high levels of anti-cancer phytochemicals such as sulforaphane.

Each plant food contains its own array of beneficial phytochemicals that have evolved to protect it and create its color, flavor and fragrance. Eating foods containing phytochemicals also appear to protect humans from cancer development – evidence that supports AICR’s advice to eat a mostly plant-based diet for lower cancer risk.

Other Picked Produce May Need Daylight, Too

In this study, researchers compared cabbages that were exposed to light in a systematic way and other cabbages not exposed to the same light-dark cycles. Both groups of cabbages were exposed to a common insect predator. The cabbages that did not have the systematic light exposure had lower levels of glucosinolates and less resistance to the insects.

The researchers concluded: “Cabbage stored under 12-hour light/dark cycles may provide as much as 2- or 3-fold more 4MSO phytochemical [a cabbage glucosinolate] if the cabbage were ingested 4-8 hours after initiation of the light period than if the cabbage were stored under constant light or darkness.”

The authors noted that other vegetables and fruits – cabbage, lettuce, spinach, zucchini, sweet potatoes, carrots and blueberries – may also continue to produce phytochemicals in response to daylight.

The take-home tip: You may be able to maximize cancer protection from fruits and vegetables by putting them near a sunny window for awhile before storing them in the fridge or preparing them for your meals.