Exposure to bovine leukemia virus from meat or dairy products (or blood transfusions from people who eat meat or dairy products) is a risk factor for cancer.
In 2015, researchers in California found bovine leukemia virus (BLV) sewn into the DNA of breast cancer tumors in humans who had undergone mastectomies. The virus was detected at a much higher rate than in normal breast tissue obtained from breast reduction surgery. Based on this difference, they calculated that 37% of breast cancer cases could be attributable to exposure to BLV, possibly through consumption of milk or meat from infected animals.
In contrast, the milk and meat industry appears to be more concerned about consumer confidence than about consumer cancer. Scientifically, however, research priorities have shifted to the question: “Can we replicate the California results?” As it turned out, the answer was yes. They were reproduced among Iranian women. Reproduced in Brazil. In Australia, the connection was even stronger. We found the same thing in Texas. They found that women diagnosed with breast cancer were significantly more likely to have bovine leukemia virus DNA present in their breast tissue than women without cancer, with an attributable risk of 51.82%, indicating that this meat and dairy virus may be responsible for at least half of the breast cancer cases in the Texas women studied.
Overall, six of the eight studies conducted to date have detected the virus in human breast tissue, “strongly suggesting that BLV can indeed infect humans and that the breast may be a potential target for infection.” Four of the five studies that compared infection rates in cancerous and normal breast tissue found that the virus was, on average, four times more likely to be detected within the tumor. How is it different from other breast cancer risk factors? Five years of hormone replacement therapy can increase your risk of breast cancer by 30%. If you have been taking oral contraceptives for more than 10 years, your risk may increase by 40%. Becoming obese later in life can increase your risk by 60%. Having a first-degree relative with breast cancer can double your risk. However, if the udder becomes infected with bovine leukemia virus, the risk can be quadrupled, as shown below and at 2:16 in my video Breast Cancer and Bovine Leukemia Virus in Meat and Dairy.The only risk factors stronger than BLV infection were having a BRCA gene mutation, like Angelina Jolie, or having been exposed to high doses of ionizing radiation, clearly in the wrong place at the wrong time, like in Hiroshima and Nagasaki during World War II.
Beyond corroboration, one study suggested that older patients were more likely to test positive for bovine leukemia virus. That makes sense if the BLV is due to exposure to dairy or meat. As you get older, you eat more often, which increases your chances of getting infected over time. Researchers also found that the virus occurs before cancer is diagnosed. They found that the cancer was present in some breast tissue three to 10 years before the cancer was discovered. “This refutes the idea that the virus invades cells that are already malignant,” he says, dispelling the theory that the virus is somehow attracted to the cancer after the fact. Could this explain the consistent finding that breast cancer tissue is more susceptible to harboring infection? Again, the data showed no. It appears that the virus came first. Although this review does not provide absolute evidence that BLV causes breast cancer, based on the best available evidence, BLV infection does appear to be a risk factor for breast cancer.
The latest fact is that BLV has also been detected in human blood. This has many potential implications. For example, blood banks don’t test it. Therefore, it is possible to become infected by consuming meat or dairy products or from the blood of someone who has consumed meat or dairy products. This could also mean that BLV can cause leukemia in people. The same goes for chimpanzees. Two infant chimpanzees were fed milk from cows naturally infected with BLV, but both died of leukemia. I didn’t even know that chimpanzees could get leukemia. This certainly suggests that leukemia could be transmitted or induced through consumption of milk from BLV-infected cows, or that the virus could be carried to other organs by blood-borne spread. The virus causes blood cancer in cows, but this may be because cows are slaughtered and made into hamburgers while they are still young, so tumors don’t have time to grow in other organs.
How worried should we be about bovine leukemia virus? “It’s not clear whether this is good news or bad news.” If future studies show that BLV causes breast cancer in humans, there will be significant implications for the dairy and livestock industries. But that means there is something we can do. Perhaps we need to act now to eradicate the infection from cattle, rather than wait for a final verdict. Twenty-one countries have already eradicated BLV from dairy cattle. In contrast, the prevalence of BLV in the United States continues to increase. If industry isn’t actively working to eradicate the disease, the least they can do is eliminate some of the practices that spread the disease between animals.
BLV is spread through blood via contaminated needles, saws or gouge dehorners, ear taggers, hoof knives, tattoo pliers, nose clippers, and other tools of the agribusiness trade. However, “Given the emerging information about BLV in human breast cancer, it is prudent to encourage its elimination in cattle, especially in the dairy industry.” In any case, the hope is that it may help alleviate the scourge of breast cancer.
doctor’s note
If you missed the previous video, see “Bovine Leukemia Virus as a Cause of Breast Cancer.”
Avoiding the risk of infections such as BLV is also an advantage of producing meat without using animals. Watch my video “The Human Health Effects of Cultivated Meat: Food Safety.”
