Most people know that fruits and vegetables are essential staples of a healthy diet, and consuming plenty of them have been found to cut the risk of various cancers. However, most of those studies have focused on how fruit and vegetable consumption benefit the health of adults, but we know that a healthy start in life can protect people from diseases later on.
Recently, Maryam Farvid a research associate at Massachusetts General Hospital and a visiting scientist at the Harvard T. H. Chan School of Public Health, and her colleagues launched a study that looked at how diet during adolescence might impact cancer risk. The team culled data from the Nurses’ Health Study, in which 90,000 nurses answered questionnaires concerning their diet and were then followed for various health outcomes, including cancer. 
Farvid and her fellow researchers saw a decreased risk of cancer among women who ate fruits and vegetables during adolescence, and were able to break down that decreased risk depending on the type of produce they ate. Check out some of the team’s findings:
- Women who ate at least 3 daily servings of apples, bananas, and grapes during adolescence had a 25% lower risk of developing breast cancer by middle-age compared with women who ate a half-serving of fruit.
- Women who consumed oranges and/or kale as teenagers had a minor decreased risk of breast cancer.
- Drinking fruit juice did not appear to lower the risk of breast cancer. Fruit juice can’t be considered “fruit” because it contains no fiber, which is one of the most beneficial aspects of fruit, and because it contains mostly sugar. 
- Consumption of fruits and vegetables rich in beta-carotene (carrots, squash, pumpkin, and sweet potatoes) was also linked to a decreased risk.
Not a Concrete ‘Cause and Effect’ Link
“This is the first study that specifically shows that high fruit intake during adolescence may be linked with reduced breast cancer risk.”
She cautioned that “due to the observational nature of the study, we could not provide evidence of cause and effect,” merely a link between fruit and vegetable consumption during adolescence and a decreased risk of breast cancer.
But Guess What – Everyone Should Still Eat Fruit and Veggies
Yet, even without proving cause-and-effect, the results provide insight into how teens ought to be eating. Farvid summed it up to Time this way:
“This study underscores the importance of what a young girl eats for her future health. This study also has an important message for schools and the need to provide students with the opportunity to consume more fruits and vegetables as part of the school meal program.”
And even though the study doesn’t prove cause-and-effect, that doesn’t mean we don’t know how fruits and vegetables prevent cancer. For example, researchers know that vibrantly colored fruits and dark leafy greens contain lots of polyphenols. These antioxidants are known to promote good gut health, and the microbiome of our gut can both prevent disease and treat it, including cancer. 
Lona Sandon, program director in the department of clinical nutrition at the UT Southwestern Medical Center at Dallas, offered even more insight into how fruits and vegetables prevent cancer when speaking to HealthDay:
“Fruit has vitamins, minerals, and all sorts of plant compounds that appear to be healthy for us. And it’s also worth noting if teens are consuming more fruit, what are they not consuming instead? Are they eating less candy, cookies, cakes, and soda? That may play a role as well.”
The connection between sugar and cancer is well documented. One study published a few years ago found that high sugar levels cause the body to increase production of a protein which has been shown to impact cancer risk.
It’s important to point out, though, that the “enemy” is added sugar – the stuff you find in sodas, baked goods, and packaged foods.
Research has also suggested that yeast, specifically Candida albicans, which is often present in vaginal yeast infections, can promote cancer by producing the carcinogens nitrosamines and acetaldehyde, both of which cause inflammation. An overload of sugar in the body can yeast to proliferate.