Sugar, carbs and cancer links

November 2, 2017 by Sam Apple, Los Angeles Times
Credit: CC0 Public Domain

In August of 2016, the New England Journal of Medicine published a striking report on cancer and body fat: Thirteen separate cancers can now be linked to being overweight or obese, among them a number of the most common and deadly cancers of all - colon, thyroid, ovarian, uterine, pancreatic and (in postmenopausal women) breast cancer.

Earlier this month, a report from the Centers for Disease Control and Prevention added more detail: Approximately 631,000 Americans were diagnosed with a body fat-related in 2014, accounting for 40 percent of all cancers diagnosed that year.

Increasingly, it seems not only that we are losing the war on cancer, but that we are losing it to what we eat and drink.

These new findings, while important, only tell us so much. The studies reflect whether someone is overweight upon being diagnosed with cancer, but they don't show that the excess weight is responsible for the cancer. They are best understood as a warning sign that something about what or how much we eat is intimately linked to cancer. But what?

The possibility that much of our cancer burden can be traced to diet isn't a new idea. In 1937, Frederick Hoffman, an actuary for the Prudential Life Insurance Co., devoted more than 700 pages to a review of all the medical thinking on the topic at the time. But with little in the way of evidence, Hoffman could only guess at which of the many theories might be correct. If we've made little progress since then in pinpointing specific foods that cause cancer, it's in large part because nutrition studies aren't well-suited to cracking the problem.

A cancer typically arises over years, or decades, making the type of study that might definitively establish cause and effect - an experiment in which people are randomly assigned to different diets - nearly impossible to carry out. The next-best option - observational studies that track what a specific group of individuals eats and which members of the group are later diagnosed with cancer - tends to generate as much confusion as knowledge. One day we read that a study has linked eating meat to cancer; a month later, a new headline declares the exact opposite.

And yet researchers have made progress in understanding the diet-cancer connection. The advances have emerged in the somewhat esoteric field of cancer metabolism, which investigates how cancer cells turn the nutrients we consume into fuel and building blocks for new cancer cells.

Largely ignored in the last decades of the 20th century, cancer metabolism has undergone a revival as researchers have come to appreciate that some of the most well-known cancer-causing genes, long feared for their role in allowing cancer cells to proliferate without restraint, have another, arguably even more fundamental role: allowing to "eat" without restraint. This research may yield a blockbuster cancer treatment, but in the meantime it can provide us with something just as crucial - knowledge about how to prevent the disease in the first place.

Lewis Cantley, the director of the Cancer Center at Weill Cornell Medicine, has been at the forefront of the cancer metabolism revival. Cantley's best explanation for the obesity-cancer connection is that both conditions are also linked to elevated levels of the hormone insulin. His research has revealed how insulin drives cells to grow and take up glucose (blood sugar) by activating a series of genes, a pathway that has been implicated in most human cancers.

The problem isn't the presence of insulin in our blood. We all need insulin to live. But when insulin rises to abnormally high levels and remains elevated (a condition known as insulin resistance, common in obesity), it can promote the growth of tumors directly and indirectly. Too much insulin and many of our tissues are bombarded with more growth signals and more fuel than they would ever see under normal metabolic conditions. And because elevated insulin directs our bodies to store fat, it can also be linked to the various ways the fat tissue itself is thought to contribute to cancer.

Having recognized the risks of excess insulin-signaling, Cantley and other metabolism researchers are following the science to its logical conclusion: The danger may not be simply eating too much, as is commonly thought, but rather eating too much of the specific foods most likely to lead to elevated insulin levels - easily digestible carbohydrates in general, and sugar in particular.

This is not to say that all cancers are caused by too much or that we should never eat sugar again. Michael Pollak, a metabolism researcher and director of cancer prevention at McGill University in Canada, says that the best approach to sugar is to think of it like a spice - something to occasionally sprinkle on foods, as opposed to an ingredient in nearly every meal and too many drinks.

Nutrition is an inherently messy science. But recent advances in research are sending us an increasingly clear message about our diet. Winning the war on cancer may depend upon whether we're ready to hear it.

Explore further: Obesity linked to 13 types of cancer (Update)

Related Stories

Obesity linked to 13 types of cancer (Update)

October 3, 2017
There's a link between obesity and 40 percent of all the cancers diagnosed in the United States, health officials reported Tuesday.

Weight-loss surgery may curb risk for certain cancers

October 17, 2017
(HealthDay)—Weight-loss surgery could help some severely obese people reduce their risk for cancer by at least 33 percent, a new study suggests.

Obesity behind surge in kidney cancers

April 24, 2017
An estimated 20,000 kidney cancer cases have been caused by obesity over the last decade in England, according to new figures from Cancer Research UK.

High blood sugar levels in older women linked to colorectal cancer

November 30, 2011
Elevated blood sugar levels are associated with an increased risk of colorectal cancer, according to a study led by researchers at Albert Einstein College of Medicine of Yeshiva University. The findings, observed in nearly ...

Where body fat is carried can predict cancer risk

May 23, 2017
Scientists have found that carrying fat around your middle could be as good an indicator of cancer risk as body mass index (BMI), according to research published in the British Journal of Cancer today.

Unhealthy insulin levels may boost breast cancer risk

January 15, 2015
(HealthDay)—After menopause, unhealthy insulin levels may predict breast cancer risk even more than excess weight, new research suggests.

Recommended for you

Researchers discover specific tumor environment that triggers cells to metastasize

November 21, 2017
A team of bioengineers and bioinformaticians at the University of California San Diego have discovered how the environment surrounding a tumor can trigger metastatic behavior in cancer cells. Specifically, when tumor cells ...

New study points the way to therapy for rare cancer that targets the young

November 21, 2017
After years of rigorous research, a team of scientists has identified the genetic engine that drives a rare form of liver cancer. The findings offer prime targets for drugs to treat the usually lethal disease, fibrolamellar ...

Clinical trial suggests new cell therapy for relapsed leukemia patients

November 20, 2017
A significant proportion of children and young adults with treatment-resistant B-cell leukemia who participated in a small study achieved remission with the help of a new form of gene therapy, according to researchers at ...

Cell-weighing method could help doctors choose cancer drugs

November 20, 2017
Doctors have many drugs available to treat multiple myeloma, a type of blood cancer. However, there is no way to predict, by genetic markers or other means, how a patient will respond to a particular drug. This can lead to ...

Researchers discover a new target for 'triple-negative' breast cancer

November 20, 2017
So-called "triple-negative" breast cancer is a particularly aggressive and difficult-to-treat form. It accounts for only about 10 percent of breast cancer cases, but is responsible for about 25 percent of breast cancer fatalities.

Study reveals new mechanism used by cancer cells to disarm attacking immune cells

November 20, 2017
A new study by researchers at The Ohio State University Comprehensive Cancer Center - James Cancer Hospital and Solove Research Institute (OSUCCC - James) identifies a substance released by pancreatic cancer cells that protects ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.