DEBUNKED: 2/3rds of Cancer "Just Bad Luck"

Dr. Mona Patrick here. Today we're going to discuss good news. You don't actually have to live a healthy lifestyle. Apparently cancer is mostly due to bad luck. In fact, it's not preventable at all. So pack it up, guys, go home. Just kidding. But if you've been following recent headlines, that's precisely what the media has been conveying to us, that 2/3 of all cancer cases are just due to bad luck. In fact, the majority of cancer cases are due to bad luck. But why? Today we're going to discuss what this recent cancer paper actually says and how the media got it wrong. But before we get started, I just want to state that the way this study was presented by both the authors and the media really blew my mind.

I probably don't have to tell you guys this, and I may be beating a dead horse, but I'm firmly in the camp that you can prevent cancer to a very, very large degree. That's not to say that there isn't a bad luck component to cancer, but the way this headline was presented was very misleading. There are 2 important points that Science magazine tried to drive home in their follow-up press release. One is that the study did not include all cancers. In fact, it omitted 2 of the most prevalent cancer types: breast cancer and prostate cancer. 2, remember that 2/3 number? Well, here's what it does not mean. It does not mean that 2/3 of all cancers are just due to bad luck. Here's what it does mean.

2/3 of variation in cancer rates between different tissues, such as the prostate or the breast or the brain, can be explained by the fact that cells in these tissues divide at a different rate and therefore can lead to replication errors. Replication errors can lead to random mutations, much like DNA damage can. While the media is to blame for the way the study's findings were conveyed to the public, The authors also share some of that blame. Vogelstein, an author on the paper, stated he thinks more research funding should be put towards early diagnostics because these cancers are going to keep on coming.

While no one argues with the fact that research funding shouldn't be put towards early diagnostics, the reality is this paper did not show that diet and lifestyle do not influence cancer incidence, and it did not show that these cancers are going to keep on coming regardless of lifestyle interventions. The International Agency for Research on Cancer published a statement that it disagrees with the message that's associated with the study's findings because it is in conflict with over 5 decades of international research, which has shown that cancer rates vary in different tissues between different populations over time. For example, esophageal cancer is common in West Africa and rare in East Africa. Colorectal cancer, once rare in Japan, is increased fourfold over the last 2 decades.

This is indicative that environmental factors can influence cancer rates in different tissues. I've been a little critical up until this point. The reality is I think the study's findings are quite interesting, particularly when they're dissociated from the toxic message that's been attached to it. The study looked at stem cell divisions in different organs over a lifetime and plotted it against a lifetime risk of cancer for 31 different types of cancer. But what are stem cell divisions and why are they relevant to cancer? Well, every organ in the body consists of cells, and some of those cells are stem cells. The non-stem cells have a limited lifespan and they have to be replaced in order for the organ to keep functioning.

Stem cells can replace damaged old cells, but in order for them to do that, they have to replicate the entire genome of the cell, which consists of around 3 billion nucleotides, which are structural units that make up DNA. The enzymes that replicate the DNA are called DNA polymerases. Considering there are around 3 billion nucleotides that need to be replicated, you can imagine this leaves a lot of room for error. In fact, these DNA polymerases are imperfect. On average, around 120,000 sequence errors are made per cell division. Did you get that? 120,000 sequence errors are made every time a cell replicates its genome. Fortunately, 99% of those errors are corrected by the proofreading component of DNA polymerases.

Stem cell replication rates do vary between different organs, and this can be correlated to a higher incidence of cancer for that particular organ. For example, in humans, colon cancer is much more common than cancer of the duodenum, the first part of the small intestine. Stem cells in the colon divide 10 to the 12 times, whereas stem cells in the duodenum divide 10^10 times. So stem cells are dividing much more rapidly over a lifetime in the colon versus the duodenum. Not mentioned in this study is that while different tissues have different stem cell replication rates and thus can lead to mutations in stem cells, the way in which these mutations arise from replication error, as I mentioned, can be influenced by the environment.

These same DNA polymerases that replicate the entire genome in the stem cells Require magnesium to do just that. It's one of the many reasons I'm a magnesium junkie and why I eat a ton of chlorophyll-containing leafy greens, because magnesium's right at the center of that chlorophyll molecule. These polymerase enzymes require magnesium to work efficiently. Without magnesium, they're more prone to making sequence errors, and in addition, their ability to fix those sequence errors is also compromised, Regardless of what tissue we're talking about. Magnesium is intimately linked to the stability of the genome, whether we're talking about the ability to prevent DNA sequence errors during cellular replication or the ability to repair damaged DNA.

In general, magnesium is a very important dietary micronutrient that is critically linked to being able to prevent potential cancer-causing mutations. For those of you that have heard me speak before, you know that I talk a lot about magnesium because it's so important. And yet 45% of the US population, almost half the country, does not meet the daily requirement for magnesium, suggesting people aren't eating their greens. To highlight the importance of magnesium in cancer incidence, a study involving 47,000 men that were followed for 18 years found that those men with the highest magnesium levels had the— had 40% decreased in all-cause mortality and a 50% decrease in cancer mortality compared to men with the lowest magnesium levels.

The bottom line is, while there is a bad luck component to cancer, there are many different ways in which cancer incidence can be lowered by certain dietary and lifestyle factors. Magnesium is just one that happens to influence the, the DNA replication error rate amongst different tissues across the board, whether we're talking about stem cells and tissues that proliferate more often or less often. So for now, make sure you dose up on that magnesium by getting your dark green leafy vegetables. I'm Dr. Rhonda Patrick, and I'll catch you next time.