As many as 37 percent of breast cancer cases may be attributable to exposure to bovine leukemia virus.
Bovine Leukemia Virus as a Cause of Breast Cancer
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Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
Intro: As many as 37 percent of breast cancer cases may be attributable to exposure to bovine leukemia virus, which I first did a series about years ago. In this two-part series, I review the science behind this phenomenon and update it with the more recent data. To see the original series, check out the doctor’s note for this video.
The incidence of breast cancer is continuously increasing worldwide. In the U.S., this amounted to a 40 percent increase in the incidence by the turn of this century. Currently, the main approach is early detection and treatment. That’s important, but why not pay more attention to primary prevention; in other words, protecting people from being exposed to risk factors for breast cancer so that they never develop breast cancer in the first place?
“Overall, it is estimated that 20 percent of all human cancers have an infectious origin.” Viruses can trigger cancer by turning on cancer genes or turning off cancer suppressing genes, but they can also contribute to tumor formation just by causing chronic inflammation. Currently, cancer-causing viruses are considered the major plausible hypothesis for a direct cause of human breast cancer. How did we get here?
It all started about 40 years ago when a professor of virology at UC Berkeley learned how mouse mammary tumor virus was discovered. Scientists swapped baby mouse pups from mice with a high incidence of mammary cancer with pups from mouse strains with a low incidence, and found that the cancer incidence matched the foster mothers, showing it wasn’t genetic. “It occurred to me,” the professor thought, “that humans are foster-nursed on the cow.”
Bovine leukemia virus (BLV) had just been identified as a cancer-causing cow virus. At the time only about 1 in 10 U.S. dairy cows were infected, but now it’s closer to half. We started out with 2/3s of herds affected. Then, it was more like 80 percent, based on their milk testing positive for the virus, and 100 percent of the herds in the larger industrial farms. And now, more than 9 out of 10 U.S. herds are affected, a continuation of the historical trend of the persistent proliferation of BLV within U.S. dairy herds.
We’ve long known that countries with the highest milk consumption also had the highest breast cancer incidence. And it’s not just a matchup between dairy consumption and breast cancer incidence on the country level. Individual women who are lactose intolerant and consume less dairy also seem to have decreased risk of breast cancer. Oh, but come on, there’s lots of stuff in milk that could be contributing to the cancer risk, like saturated fat and the presence of cancer-promoting growth hormones, like IGF-1.
Yes, we know bovine leukemia virus is present in marketed beef and dairy products. About half of milk and meat samples turn up positive for the virus. In fact, you can sample the virus straight out of the air on dairy farms, on surfaces, and in the milk itself. Most milk is pasteurized, but many dairy products, like raw aged cheeses are not. And who hasn’t eaten a pink-in-the-middle hamburger at some point in their life?
Yes, we have evidence that people are exposed to the virus. Yes, we have evidence that people are actively infected with the virus. But it wasn’t until 2015 that we learned infection rates were highest in cancerous breast tissue, so much so that as many as 37 percent of breast cancer cases may be attributable to exposure to the bovine leukemia virus. That was enough for me to trigger a whole series of videos on the role the virus plays in breast cancer, and how the meat and dairy industries responded to the news. Okay, now that we’re all back up to speed, what’s the latest update? That’s what I’ll cover next.
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- Martinez Cuesta L, Lendez PA, Nieto Farias MV, Dolcini GL, Ceriani MC. Can Bovine Leukemia Virus Be Related to Human Breast Cancer? A Review of the Evidence. J Mammary Gland Biol Neoplasia. 2018;23(3):101-7.
- Gannon OM, Antonsson A, Bennett IC, Saunders NA. Viral infections and breast cancer - A current perspective. Cancer Lett. 2018;420:182-9.
- Buehring GC, Sans HM. Breast Cancer Gone Viral? Review of Possible Role of Bovine Leukemia Virus in Breast Cancer, and Related Opportunities for Cancer Prevention. Int J Environ Res Public Health. 2019;17(1):209.
- Labyed M, Hassou N, Bennani B, Ennaji MM. Chapter 23 Viral etiology involved in the emergence of the breast cancer. Emerging and reemerging viral pathogens. Academic Press. 2020:507-37.
- Lawson JS, Salmons B, Glenn WK. Oncogenic Viruses and Breast Cancer: Mouse Mammary Tumor Virus (MMTV), Bovine Leukemia Virus (BLV), Human Papilloma Virus (HPV), and Epstein-Barr Virus (EBV). Front Oncol. 2018;8:1.
- Sinha G. Bovine Leukemia Virus Possibly Linked to Breast Cancer. J Natl Cancer Inst. 2016;108(2):djw020.
- LaDronka RM, Ainsworth S, Wilkins MJ, Norby B, Byrem TM, Bartlett PC. Prevalence of Bovine Leukemia Virus Antibodies in US Dairy Cattle. Vet Med Int. 2018;2018:5831278.
- USDA. Bovine leukosis virus (BLV) on U.S. Dairy Operations, 2007. APHIS.USDA.gov. October 2008.
- Baltzell KA, Shen HM, Krishnamurthy S, Sison JD, Nuovo GJ, Buehring GC. Bovine leukemia virus linked to breast cancer but not coinfection with human papillomavirus: Case-control study of women in Texas. Cancer. 2018;124(7):1342-9.
- Ji J, Sundquist J, Sundquist K. Lactose intolerance and risk of lung, breast and ovarian cancers: aetiological clues from a population-based study in Sweden. Br J Cancer. 2015;112(1):149-52.
- Buehring GC, DeLaney A, Shen H, et al. Bovine leukemia virus discovered in human blood. BMC Infect Dis. 2019;19(1):297.
- Olaya-Galán NN, Corredor-Figueroa AP, Guzmán-Garzón TC, et al. Bovine leukaemia virus DNA in fresh milk and raw beef for human consumption. Epidemiol Infect. 2017;145(15):3125-30.
- Stobnicka-Kupiec A, Gołofit-Szymczak M, Górny RL, Cyprowski M. Prevalence of Bovine Leukemia Virus (BLV) and Bovine Adenovirus (BAdV) genomes among air and surface samples in dairy production. J Occup Environ Hyg. 2020;17(6):312-23.
- Buehring GC, Shen HM, Jensen HM, Jin DL, Hudes M, Block G. Exposure to Bovine Leukemia Virus Is Associated with Breast Cancer: A Case-Control Study. PLoS One. 2015;10(9):e0134304.
- Buehring GC, Philpott SM, Choi KY. Humans have antibodies reactive with Bovine leukemia virus. AIDS Res Hum Retroviruses. 2003;19(12):1105-13.
- Buehring GC, Shen HM, Jensen HM, Choi KY, Sun D, Nuovo G. Bovine leukemia virus DNA in human breast tissue. Emerg Infect Dis. 2014;20(5):772-82.
Motion graphics by Avo Media
Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
Intro: As many as 37 percent of breast cancer cases may be attributable to exposure to bovine leukemia virus, which I first did a series about years ago. In this two-part series, I review the science behind this phenomenon and update it with the more recent data. To see the original series, check out the doctor’s note for this video.
The incidence of breast cancer is continuously increasing worldwide. In the U.S., this amounted to a 40 percent increase in the incidence by the turn of this century. Currently, the main approach is early detection and treatment. That’s important, but why not pay more attention to primary prevention; in other words, protecting people from being exposed to risk factors for breast cancer so that they never develop breast cancer in the first place?
“Overall, it is estimated that 20 percent of all human cancers have an infectious origin.” Viruses can trigger cancer by turning on cancer genes or turning off cancer suppressing genes, but they can also contribute to tumor formation just by causing chronic inflammation. Currently, cancer-causing viruses are considered the major plausible hypothesis for a direct cause of human breast cancer. How did we get here?
It all started about 40 years ago when a professor of virology at UC Berkeley learned how mouse mammary tumor virus was discovered. Scientists swapped baby mouse pups from mice with a high incidence of mammary cancer with pups from mouse strains with a low incidence, and found that the cancer incidence matched the foster mothers, showing it wasn’t genetic. “It occurred to me,” the professor thought, “that humans are foster-nursed on the cow.”
Bovine leukemia virus (BLV) had just been identified as a cancer-causing cow virus. At the time only about 1 in 10 U.S. dairy cows were infected, but now it’s closer to half. We started out with 2/3s of herds affected. Then, it was more like 80 percent, based on their milk testing positive for the virus, and 100 percent of the herds in the larger industrial farms. And now, more than 9 out of 10 U.S. herds are affected, a continuation of the historical trend of the persistent proliferation of BLV within U.S. dairy herds.
We’ve long known that countries with the highest milk consumption also had the highest breast cancer incidence. And it’s not just a matchup between dairy consumption and breast cancer incidence on the country level. Individual women who are lactose intolerant and consume less dairy also seem to have decreased risk of breast cancer. Oh, but come on, there’s lots of stuff in milk that could be contributing to the cancer risk, like saturated fat and the presence of cancer-promoting growth hormones, like IGF-1.
Yes, we know bovine leukemia virus is present in marketed beef and dairy products. About half of milk and meat samples turn up positive for the virus. In fact, you can sample the virus straight out of the air on dairy farms, on surfaces, and in the milk itself. Most milk is pasteurized, but many dairy products, like raw aged cheeses are not. And who hasn’t eaten a pink-in-the-middle hamburger at some point in their life?
Yes, we have evidence that people are exposed to the virus. Yes, we have evidence that people are actively infected with the virus. But it wasn’t until 2015 that we learned infection rates were highest in cancerous breast tissue, so much so that as many as 37 percent of breast cancer cases may be attributable to exposure to the bovine leukemia virus. That was enough for me to trigger a whole series of videos on the role the virus plays in breast cancer, and how the meat and dairy industries responded to the news. Okay, now that we’re all back up to speed, what’s the latest update? That’s what I’ll cover next.
Please consider volunteering to help out on the site.
- Martinez Cuesta L, Lendez PA, Nieto Farias MV, Dolcini GL, Ceriani MC. Can Bovine Leukemia Virus Be Related to Human Breast Cancer? A Review of the Evidence. J Mammary Gland Biol Neoplasia. 2018;23(3):101-7.
- Gannon OM, Antonsson A, Bennett IC, Saunders NA. Viral infections and breast cancer - A current perspective. Cancer Lett. 2018;420:182-9.
- Buehring GC, Sans HM. Breast Cancer Gone Viral? Review of Possible Role of Bovine Leukemia Virus in Breast Cancer, and Related Opportunities for Cancer Prevention. Int J Environ Res Public Health. 2019;17(1):209.
- Labyed M, Hassou N, Bennani B, Ennaji MM. Chapter 23 Viral etiology involved in the emergence of the breast cancer. Emerging and reemerging viral pathogens. Academic Press. 2020:507-37.
- Lawson JS, Salmons B, Glenn WK. Oncogenic Viruses and Breast Cancer: Mouse Mammary Tumor Virus (MMTV), Bovine Leukemia Virus (BLV), Human Papilloma Virus (HPV), and Epstein-Barr Virus (EBV). Front Oncol. 2018;8:1.
- Sinha G. Bovine Leukemia Virus Possibly Linked to Breast Cancer. J Natl Cancer Inst. 2016;108(2):djw020.
- LaDronka RM, Ainsworth S, Wilkins MJ, Norby B, Byrem TM, Bartlett PC. Prevalence of Bovine Leukemia Virus Antibodies in US Dairy Cattle. Vet Med Int. 2018;2018:5831278.
- USDA. Bovine leukosis virus (BLV) on U.S. Dairy Operations, 2007. APHIS.USDA.gov. October 2008.
- Baltzell KA, Shen HM, Krishnamurthy S, Sison JD, Nuovo GJ, Buehring GC. Bovine leukemia virus linked to breast cancer but not coinfection with human papillomavirus: Case-control study of women in Texas. Cancer. 2018;124(7):1342-9.
- Ji J, Sundquist J, Sundquist K. Lactose intolerance and risk of lung, breast and ovarian cancers: aetiological clues from a population-based study in Sweden. Br J Cancer. 2015;112(1):149-52.
- Buehring GC, DeLaney A, Shen H, et al. Bovine leukemia virus discovered in human blood. BMC Infect Dis. 2019;19(1):297.
- Olaya-Galán NN, Corredor-Figueroa AP, Guzmán-Garzón TC, et al. Bovine leukaemia virus DNA in fresh milk and raw beef for human consumption. Epidemiol Infect. 2017;145(15):3125-30.
- Stobnicka-Kupiec A, Gołofit-Szymczak M, Górny RL, Cyprowski M. Prevalence of Bovine Leukemia Virus (BLV) and Bovine Adenovirus (BAdV) genomes among air and surface samples in dairy production. J Occup Environ Hyg. 2020;17(6):312-23.
- Buehring GC, Shen HM, Jensen HM, Jin DL, Hudes M, Block G. Exposure to Bovine Leukemia Virus Is Associated with Breast Cancer: A Case-Control Study. PLoS One. 2015;10(9):e0134304.
- Buehring GC, Philpott SM, Choi KY. Humans have antibodies reactive with Bovine leukemia virus. AIDS Res Hum Retroviruses. 2003;19(12):1105-13.
- Buehring GC, Shen HM, Jensen HM, Choi KY, Sun D, Nuovo G. Bovine leukemia virus DNA in human breast tissue. Emerg Infect Dis. 2014;20(5):772-82.
Motion graphics by Avo Media
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Title
Bovine Leukemia Virus as a Cause of Breast Cancer
LicenseCreative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
Content URLDoctor's Note
You may remember that I’ve previously discussed The Role of Bovine Leukemia in Breast Cancer and the Industry Response to Bovine Leukemia Virus in Breast Cancer.
Stay tuned for the next video: Breast Cancer and the Bovine Leukemia Virus in Meat and Dairy.
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