58,000 Americans are diagnosed with kidney cancer every year, and 13,000 die. Other Developed countries also probably face similar numbers. And the numbers have been rising. While 4 percent of cases are hereditary, what about the other 96 percent?
Historically, the use of tobacco is the only accepted risk factor, but cigarette smoking is declining. So, what’s going on?
Nitrosamines are one of the most potent carcinogens in cigarette smoke. One hot dog, however, has as many nitrosamines and nitrosamides as five cigarettes. These carcinogens are also found in fresh meat as well, including beef, chicken, and pork. So, even though smoking rates have dropped, how do we account for the rise in Kidney cancer over the last few decades? The problem is the meat, both processed and fresh.
An NIH-AARP study is the largest study on diet and health ever performed—about 500,000 men and women followed for nine years. In addition to examining nitrate and nitrite intake from processed meat, they also looked at intake from other sources such as fresh meat, eggs, and dairy. Nitrite from all animal sources, not just processed meats, was associated with an increased risk of kidney cancer. The researchers found no associations with nitrate or nitrite intake from plant sources.
When meat producers advertise their bacon or lunchmeat as “uncured,” this means no nitrites or nitrates added. But if you look at the small print, you’ll often see something like “except for celery juice.” That’s just a sneaky way to add nitrites. Processed meat producers ferment the nitrates in celery to create nitrites, then add it to the meat: a practice even the industry admits “may be viewed as incorrect at best or deceptive at worst.”
But that same fermentation of nitrates to nitrites can happen thanks to bacteria on our tongue when we eat vegetables. So, why are nitrates and nitrites from vegetables on our tongue harmless, but nitrates and nitrites from vegetables in meat linked to cancer?
The actual carcinogens are not nitrites, but nitrosamines and nitrosamides. In our stomach, to turn nitrites into nitros-amines, and nitros-amides, we need amines and amides, which are concentrated in animal products. And vitamin C and other antioxidants in plant foods block the formation of these carcinogens in our stomach. That’s why we can safely benefit from the nitrates in vegetables without the cancer risk. In fact, some of the highest nitrate vegetables, like arugula, kale, and collards, are associated with decreased risk of kidney cancer. The more plants we eat, it appears, the better protection against kidney cancer we’ll have.
Nature Knows Best!