Sugar and Cancer: Friend or Foe?

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In this episode, Dr. Diane Reidy-Lagunes talks to medical oncologist Santosha Vardhana about sugar and cancer. What is our favorite food’s metabolic role in cancer and in treatment?

Cancer Straight Talk from MSK is a podcast that brings together patients and experts, to have straightforward evidence-based conversations. Memorial Sloan Kettering’s Dr. Diane Reidy-Lagunes hosts, with a mission to educate and empower patients and their family members.

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Show transcript


Dr. Diane Reidy-Lagunes: It's been called cancer’s favorite food and cancer's best friend. Does the stuff in the white bulb [Phonetic] [00:00:05] cause cancer cells to grow and is there a link between eating sugar and the development of cancers? Let’s get into it.

Hello, I’m Dr. Diane Reidy-Lagunes from Memorial Sloan Kettering Cancer Center and welcome to Cancer Straight Talk. We’re bringing together national experts and patients fighting these diseases to have straightforward, evidence-based conversations. Our mission is to educate and empower you and your family members to make the right decisions and live happier, healthier lives. For more information about the topics discussed here or to send your questions, please visit us at

Today, I’m thrilled to have Dr. Santosh Vardhana to address the link between sugar and cancer. Dr. Vardhana is a Physician Scientist here at MSK. In the clinic, he cares for patients with lymphoma, but his research focuses on metabolism or how sugar or glucose is taken up by ourselves and what happens when those cells are cancer. Santosh, welcome to the show.


Dr. Santosh Vardhana: Thanks for having me.


Dr. Diane: It’s really great. I’m very excited to have you here. I think before we get into the concept of diet and sugar as it relates to what we eat, can you just walk us through this or metabolism of a cancer cell, meaning what do cancer cells actually need to survive and how do they actually get those nutrients.


Dr. Santosh: I think that’s a great way to start and maybe we can even take a step back from there and ask what is metabolism and why should we even care about it. So metabolism refers to the process by which any cell or organ or organism like a person takes up nutrients and what purposes they use it for by breaking it down and turning it into other things. The reason that cancer cells do metabolism differently is that their goals are different. So if you think about all of our body's normal cells they’re mostly just trying to make energy to stay alive because you're a fully formed adult, you don’t really need to make that many more cells, you have all the cells you need. So you just need to make energy to power your daily processes. But a cancer cell is trying to do something fundamentally different.

The real goal of a cancer cell is not to just keep up, it's to make more of itself specifically to double the total amount of stuff that makes up a cell so it can turn into two cells. One way that you can make more stuff is to just take up more stuff. So one of the primary transitions that a cancer cell makes when it decides to turn from a non-cancerous cell to a cancerous cell is to say, you know what, “I'm going to take up as much sugar as I can and I'm going to turn it into all the stuff I need to make new cells.” And that explains a lot of things that we see in cancer for anybody who has ever had a PET scan that's just an imaging study, a CAT scan except you are injected with a labeled version of sugar and the cancerous parts of your body light up because they're sucking up all that radioactive sugar. And it also tells us molecularly what's happening with cancer.


Dr. Diane: So when you're talking about at this cancer level, which is fascinating, we know based from Biology 101 that glucose breakdown can come from lots of things. It can come from a patient’s muscle, it can come from lots of different things not only the simple sugar. So the body can meticulously break down lots of different things through gluconeogenesis and other things to get that glucose. Is that correct?


Dr. Santosh: So that is correct. One way to think of it is like a cancer has got its foot on the gas and doesn't have a break. What that means is that it's going to do anything to grow and it's going to take up anything, it's going to use anything. So if there is sugar around, great. If there isn't sugar around, you’ll take up fat or protein. We actually study this in the lab a lot. We deprive cancer cells of all different kinds of nutrients and no matter what we deprive eventually cancer cells will eat something else. Cancer cells will eat other dead cancer cells and turn it into fuel for themselves. They’ll eat free protein.

Whereas your immune system is like any other normal cell in your body. It's responding to like all the normal cues that your body has. So if you're starving, your immune system like all your normal cells are going to say, “This is not a good time to make more of myself.” So one of our fundamental challenges when we’re trying to improve the immune system is how do we help our immune system fight a metabolic fight when the deck is stacked against us.


Dr. Diane: Let’s talk about diet.


Dr. Santosh: Let’s do it.


Dr. Diane: So the stuff in the white bulb got a bad rap and we talked a little bit about that before, but we’ll get down to it. Can it contribute to the development of cancer and is it actually the sugar or is it just something else going on there?


Dr. Santosh: The problem is that people who eat a lot more sugar --.


Dr. Diane: Lots of other things going on.


Dr. Santosh: Yeah, they do a lot of other stuff that’s not so great. That being said here are few things that we know. Cancer incidence tracks very closely with increases in body mass index and obesity as a surrogate for caloric intake. And if you drill down a little bit deeper and you look at the glycemic index, which is basically a measure of how easily the food that you eat can get turned into sugar. So the simpler we call it more processed food is the higher a glycemic index it has, that is also associated with not only cancer, but these tend to be very specific types of cancer, so breast cancers, GI cancers, gastrointestinal cancers are definitely associated with that process.

And the inverse is also somewhat true, which is that a high-fiber diet, a diet that is high in complex carbohydrates, a kind of higher protein diet is associated with a relatively lower incidence of cancer. And so from the 30,000 foot view those associations are there and that makes sense like if you are a cell that happened to have acquired a mutation that tells it to gobble up a bunch of sugar well, that one cell is going to turn way more easily into 10 cells if there is a lot of free sugar hanging around and it's going to be a bit of a tougher barrier to get over if there is less sugar hanging around. So it’s an observation that matches with a prediction, I guess.


Dr. Diane: Right, so the suggestion is refined sugars, soft drinks with your Coke, your Sprite.


Dr. Santosh: Yes.


Dr. Diane: The stuff in the white bulb, pure fructose that type of sugar could easily get into the blushing potentially to these cells in a way again observational, we see could potentially be worse than for example an apple so that not all sugar is the same in terms of what’s in a name.


Dr. Santosh: That's exactly right. And I think that the way that you stated it is also exactly right. So we would never refer to like taking in more sugar as the driver because you're never going to turn something into a cancer without the mutation or the change in its genetics that makes it want to grow faster. But if the pantry is full it's a little bit easier. And one thing that we don't understand quite as well is why the more complex carbohydrates or high-fiber diets are associated with a lower incidence of cancer. But I think it's most likely has to do with the fact that since your body has to work harder to convert that to the nutrients you need that's why people who eat more complex foods get full with fewer calories and this is a calorie thing basically.


Dr. Diane: And so certainly the association as you said with simple sugars being more correlated to obesity we know that many cancers unfortunately are associated to that. So that cause and effect remain to be seen. All right, and so then the next step would be the treatment of cancer. So this is one that repeatedly comes up in clinic all the time. We have a patient actively on treatment and now like everything we want to be empowered to have whatever control is possible and diet is one that could be potentially used. So could the restriction of sugar either somehow improve treatment options and/or hasten the sort of growth if you will.


Dr. Santosh: Right, so this is the most complicated and therefore the most important question to ask because the more straightforward portion of this which is to tell people to eat a kind of conventionally healthier diet to reduce the risk of developing cancer, but that's already good advice just for life. And it's a more complicated question when a patient has cancer and is receiving treatment. And the primary reason that it's so complicated is because the desire to slow the cancer growth runs smack up against the problem of the person who has the cancer and their ability to recover from these toxic processes. So as you well know as we both know from seeing patients both in the clinic, in the hospital any intervention to treat cancer is a toxic process that requires healing after. If you get surgery, your body needs to physically heal and itself back together and same thing if you get like radiation therapy.

If you get chemotherapy, well chemotherapy is nothing more than a drug that kills any cell in your body that's dividing. Well, you kill the cancer cells that's great, but you have some normal cells in your body that need to divide like the lining of your gut or your hair follicles or your blood products, your red blood cells, white blood cells and platelets and they need to recover. Well, for them to grow they also need sugar. And as intriguing as the association between diet and cancer is, one of the first things that we learn as oncology fellows is that the greatest predictor and I am fairly certain still the greatest predictor of how patients do with chemotherapy or even surgical therapy is what we call their performance status. So how well can they do their daily tasks. And so any dietary modification that would interfere with your ability to be strong enough to tolerate treatment is not going to be a viable strategy.

So that's the first and most important thing to get on the table for everybody to understand. The second question is well, could we move the needle in a smaller way, in a more tolerable way during therapy. And the answer is maybe, but there is no hard data to prove anything beyond the recommendations that we would have already had. So we would say, it's very reasonable to eat a healthy Mediterranean style complex carbohydrate diet. But we also usually combine that with a companion recommendation, which I have personally heard you tell patients also, which is chemo makes you not want to eat very much and it's more important for you to get calories than anything else. So if you hate a Mediterranean diet and the only thing that you can get down is like a McDonald's milkshake, you got to do it.


Dr. Diane: And that's absolutely, right. Yeah, I had a patient, just a quick anecdote, a very dear patient who had gone onto YouTube and on YouTube there was this starve your cancer away video. And so the premise was apparently that it was going to be more beneficial to fast for two days before you got your chemo. And unfortunately, her chemo is high-dose Cisplatin, which she hadn’t told anybody what she had done. So Cisplatin, as you know can really hurt your kidneys and other things and she has been almost a week in the hospital because like you said, her normal cells got damaged. And so that is not one that we would advocate and I think you hit it, which is often we have to listen to our body and what we need because we need to keep that fight going and to keep that performance that as strong.


Dr. Santosh: Right, and it helps to or if it does help to remember like as we said before like these cancer cells will do anything and live on anything to survive. So one way to think about is like well, do you think you can outlast your cancer with the two days starve that they probably know what to do and can get by scavenging other things including their dead partner cells right by them. And so harsh starvation diets are more likely to interfere with your ability to tolerate the drugs that we know work or the treatments that we know work than they are to have a toxic effect specifically on your cancer cells. And so I think what I would say to any patient considering anything like this is first and always first talk to your doctor before you make any decisions about how to modify your diet. But a good rule of thumb is to proceed with a diet that you would otherwise consider to be healthy and something that is tolerable if you weren't getting this treatment and to listen to your body as you say.


Dr. Diane: Talk to me lastly about the ketogenic diet because that's another one that’s yeah, you got to talk about, it always comes out.


Dr. Santosh: So just for people who haven't heard about it that the ketogenic diet has mostly been studied as a weight loss mechanism. So essentially the way the ketogenic diet works is this. We have this organ in our bodies called the liver and the liver among its many, many jobs, one of them is maintaining a normal sugar level in our blood and figuring out what to do with the extra sugar. And if you have extra sugar, it gives you a kind of a 24 hour backup called your glycogen stores. And then if you have anything in excess of that it turns it into fat essentially. And so what the ketogenic diet is, is a diet where you take in very little free sugar and instead you replace that with either fat or protein.

And so protein as we mentioned before can be converted to sugar, but it's very expensive for the body to do it and fats cannot be converted to sugar. And so what happens is that your body burns the fat that you consume for energy and then it actually burns your body's normal fat stores to supply something called ketone bodies because your brain is a unique organ that really can only live on a couple of different nutrients. One is glucose or sugar and the other is this specialized nutrient called the ketone body. And so it turns out that if you restrict the amount of glucose in your diet, you can get your body to burn your fat stores and so it's an effective way of getting people to lose weight. But because it's a good way to kind of keep excess sugar-free of your body, it was a reasonable hypothesis to suggest that it might be an effective cancer therapy.

The sustainability of the ketogenic diet is a real problem and the long-term consequences are something that we really don't understand. I know that there are actually some clinical trials ongoing and I think it's really valuable work to be done. But at the same time would not advise it at all as a strategy to pursue outside because I would say it's as or far more likely to put you in a tough physical position as it is to provide you a benefit that were not sure even exists.


Dr. Diane: And you said before if I were an organism or not just those cancer cells, so all those other cells that need those healthy nutrients will be starving too. So lastly, when you take it back to the clinic in your lymphoma specialties, what do you tell your patients overall in terms of keeping well and overall health to get through these treatments as it relates not only to nutrition but overall.


Dr. Santosh: I kind of proceed according to what we had talked about before. I say to the extent that you can tolerate it a diet that is rich and complex carbohydrates, proteins, sort of mixed balanced diet, the Mediterranean diet is just one that I happen to like. In lymphoma world, of course, we’re also a little bit concerned about anything that might be infectious because so many of our patients have extremely low blood counts that put them at risk of infections. So we typically tell them, but I think this has been my advice for anybody getting cancer therapy don't go to an open buffet.


Dr. Diane: Right, that’s probably a good advice for most of us.


Dr. Santosh: Yeah, honestly, it really is avoid deli meats and stuff like that. But we always, always complex it with that. If you're having a hard time with chemo and there are only certain things that you can eat getting enough calories into your body that you can get yourself up each day and lead as close to what you would consider to be like a high quality of life is more important. It's not just for the physical benefits, but as again we both know the process of going through treatment for cancer whatever setting it's in, whether it's on a specific timeline or its indefinite is a mental emotional physical –.


Dr. Diane: Marathon.


Dr. Santosh: Marathon. And so maintaining what you consider to be a quality of life is should be a really important priority, so we always encourage that too.


Dr. Diane: Absolutely. Thanks so much. It was super informative.


Dr. Santosh: Oh, it’s my pleasure. Thanks for having me.


Dr. Diane: Dr. Santosh Vardhana, Medical Oncologist and Scientist. Thank you for listening to Cancer Straight Talk from Memorial Sloan Kettering Cancer Center. For more information or to send us any questions you may have, please visit Help other people find this helpful resource by reading and reviewing this podcast at Apple podcasts or wherever you listen to your podcasts. These episodes are for you, but are not intended to be a medical substitute. Please remember to consult your doctor with any questions you have regarding medical conditions. I am Dr. Diane Reidy-Lagunes, onward and upward.