Nutrition & Cancer
FUEL YOUR BODY WITH THE BEST NATURE HAS TO OFFER
So what's the perfect strategy for using nutrition and nutritional supplementation to improve my overall health, reduce or manage side effects, and maybe even enhance treatment efficacy?
There is no singular strategy that works for everyone. Nutritional recommendations in cancer care are nuanced and must be personalized to maximize benefits and minimize harm. What works for one cancer type, may be cautioned against for another cancer type. It also depends on the treatments you've chosen (e.g. chemo, surgery, radiation, or immunotherapy), your underlying health concerns/conditions/symptoms, age, sex, race, ethnicity, genetics, current nutritional status/deficiencies, medications you take, inflammation level in the body, activity level, etc. What may be beneficial for one cancer patient, may be harmful or ineffective for another. It's tricky. Unfortunately, what worked well for your neighbor's cousin's brother-in-law's boss when he went through cancer is likely not the same thing that will work for you. Take others' suggestions with a grain of salt and try your best not to feel discouraged or pressured by random, albeit passionate, dietary recommendations.
Nutrition Interactions in the Body
There's a complex, interconnected network inside our bodies and everything we consume interacts with our body in some way, and this includes foods, beverages, medications, vitamins, recreational drugs, etc.
Some things we consume may:
- work well with or not interfere with other foods, nutrients, or medications
- compete in the body and interfere with other foods, nutrients, or medications
- have too strong or too weak of an impact
- only work in combinations, and used alone don't really make a difference
- increase or decrease the toxicity of cancer treatments (worse or lesser side effects)
- decrease or increase the effectiveness of cancer treatment
- have off-target effects that do more harm than good
- have mild positive effects on sleep, pain, stress, digestion, immunity, etc.
Don't be dismayed! There are foods, botanicals, herbs, and supplements out there that have shown to provide benefit to some cancer patients, though it can be challenging to figure out what those things are. Randomized, double-blind placebo controlled studies are not feasible for studying most nutrients, foods, and diets, so many of these things (about which we are all very curious and hungry for answers) are neglected in research and get lost, ignored, or discredited due to the lack of significant, comprehensive, and/or quality evidence. Nutrition is more evidence-guided as opposed to evidence-based (like conventional medicine and cancer treatment). We have to do our best to review what is and is not known about something and to use the evidence that currently exists, however limited it may be, to help inform and guide our decision-making. And you don't have to do this alone—seek out a Registered Dietician (who specializes or is board certified in oncology) to join and support you in the development of your nutrition plan.
While we know there is not a magic recipe, food item, or diet plan capable of whisking away cancer and guaranteeing optimal health, there does appear to be some well-established consensus regarding a handful of nutritional principles for cancer patients and survivors.
Some of these recommendations include:
- Increase consumption of fresh fruits and vegetables (6-10 servings per day)
- Avoid/limit red meat (less than 8-16 ounces per week)
- Avoid/limit processed and overprocessed foods including deli meats, sausage, bacon, hotdogs, pre-packaged snacks/meals, etc.
- Choose nutrient-dense, "closer to nature" whole foods. For example, eating an orange (versus drinking a glass of orange juice) provides fiber that helps the body process the natural sugar in the orange.
- Choose more "good" fats (omega-3s from fatty, cold-water fish, olive oil, avocados, nuts, legumes, etc.), and avoid/limit trans fats and saturated fats
- Avoid/limit refined sugar, sugar-added foods, and sweetened beverages
- Choose good sources of fiber (nuts, beans, legumes, fruit, vegetables, etc.)
- Choose lower-sodium options when available
- Drink plenty of water
Your body is going through a hard time. It needs support. You likely don't need a complete overhaul, a pantry clean out, or a super strict diet to best support your body. Not because it wouldn’t be beneficial, but because drastic, restrictive changes of that sort are hard to maintain and usually very expensive. The help you provide for your body needs to be consistent and meaningful. What may work well is making slow, small, impactful changes to better support your body during this time. Trade out sweetened coffee for unsweetened, freshly steeped tea, or add beans to a salad for an added protein-and-fiber punch, for example.
So a bunch of stuff is off limits, right?
No, not necessarily, but think about what your body needs to function, fight, and heal as well as possible. You should not hate what you're eating, and you should not feel starved, deprived, or limited. There's so much out there that's good for us and now is a great time to explore. If you want to transition to a plant-based diet, for example, but you can't stand kale, or tofu, or almond milk, that's okay. There are many other sources of vitamins, phytonutrients, protein, fiber, calcium, and healthy fats. Find and choose foods you enjoy eating to meet your health and nutrition goals.
Aim for balance in your diet. No extreme diets have proven effective (or necessary) for cancer elimination. Pay attention to how foods and drinks make you feel. Our bodies can tell us a lot if we tune in and listen a bit more closely.
Did it make me feel tired, bloated, ill, overly full?
Did it make me feel satisfied, energized, alert?
Did my digestion improve?
What foods seem to help me feel the way I want to feel?
What foods put me in a slump or make me feel "blah"?
"Eat What You Want"
Have you heard any of these when asking your doctor about cancer nutrition?
"Eat whatever you want. milkshakes, ice cream..."
"Just try to eat healthy..."
"It doesn't matter as long as you're eating enough food."
"Eat what you normally eat if it sounds good to you. It doesn't really make a difference."
(It certainly does make a difference, but the difference it makes for you may be different than the difference it makes for me.)
This not because oncologists are inept or uneducated; that’s not the case at all. But nutrition, and more specifically cancer nutrition, is not commonly where their expertise lies or where they’ve had much training. Do you know how much nutrition education the average medical student receives? ELEVEN HOURS. That's it.
"Although nutrition education varies by school, a 2021 survey of medical schools in the U.S. and U.K., published in the Journal of Human Nutrition and Dietetics, found that most students receive an average of 11 hours of nutrition training throughout an entire medical program."
"Conversations with patients are already limited by factors like time restrictions, and adding the type of comprehensive and personalized recommendations necessary for meaningful nutritional changes can rarely be shoehorned into a spare few minutes. Plus, even patients who discuss nutrition with their doctor will often need to meet with an RD [Registered Dietitian] to tap into a wide array of services." (source)
Doctors are also frustrated with the lack of education they've received on this topic and are interested in having more significant, helpful conversations with cancer patients about nutrition. Doctors want to be able to give you more, but with overbooked schedules, staff shortages, and increasing patient loads, many are left with little-to-no extra time to teach themselves a complex, evolving discipline. Therefore, we have to lean on the actual experts in this field and that's where Registered Dieticians enter the scene.
You're not going to visit a cardiologist for a sprained ankle or a psychologist for sun-safe skin care recommendations. They're not the right experts for those concerns. If you need guidance on nutrition, go to a nutrition expert. There may be dieticians you can access easily (and maybe at no cost) who work in your cancer clinic or local hospital, or you can seek out an independent dietician (directories available in Resources below). Check with your health insurance provider to understand what nutrition services and providers are included in your plan and what it may cost you out-of-pocket.
If your insurance does not cover dietician services or if you can't locate a local dietician, please visit the Leukemia and Lymphoma Society to explore their free one-on-one dietician consultations. This service is offered to patients of all cancer types!
Leukemia & Lymphoma Society's Nutrition Education Services Center Our registered dietitians have expertise in oncology nutrition and provide free one-on-one consultations by phone or email. Patients and caregivers of all cancer types can receive free nutrition education and consultations from LLS.
Nutrition Education Services Center | Leukemia & Lymphoma Society (llsnutrition.org)
There are additional resources at the bottom of the page to help you locate dieticians and nutrition programs for cancer patients and their families.
Dietician & Nutritionist Credentials:
RDN: registered dietician nutritionist
RD: registered dietician
LDN: licensed dietician nutritionist
LD: licensed dietician
NDTR: nutrition and dietetics technician, registered
Too Sweet to be True?
SUGAR?! Ahh!
But what about the sugar?
Is my cancer gorging itself on the sugar I eat?
Did that cookie last night make my cancer worse?
Is a little bit of sugar okay?
But I've heard that sugar...
Yes, cancer cells use glucose for energy but so do normal healthy cells, especially those in the brain, muscles, and heart. Cancer cells can metabolize different fuel sources (like fatty acids or amino acids) if they can't get their hands on glucose, plus our liver can make all the glucose we need so eliminating dietary sugars will not "starve" the cancer.
Cancer cells are adaptive parasite-like punks and, unfortunately, killing them is not as simple as eliminating sugar.
Cancer cells use a less efficient metabolic pathway, called aerobic glycolysis, to convert glucose into energy (ATP). The energy output is much lower from this system (2 molecules of ATP) versus a more typical cellular respiration process that produces 36 molecules of ATP per glucose molecule. However, cancer cells metabolize glucose more rapidly than healthy cells to make up for aerobic glycolysis' inefficiency. This unique metabolic characteristic of cancer was discovered by Otto Warburg in the 1920s.
This is how a PET scan with radioactive-tagged glucose molecules can lead us to identify cancer in the body. The cancer cells that "light up" on a PET are gobbling up glucose at a higher rate and the PET scan is able to visualize that cellular metabolic function. Most areas of the body will light up (because cells all over our bodies use glucose), but the final image produced for analysis is processed so only the brightest illuminations are highlighted. Pretty cool stuff.
It makes sense as to why we want to believe that sugar is both the culprit and the key to a cancer cure. It gives us something we can control. It gives us something else to focus on, something we can do on our own—cut out sugar—to try to improve the situation. However, it has yet to be proven that eliminating sugar from your diet will also eliminate cancer.
Let's look at glucose and cancer a bit more on a cellular level.
Glucose can be made in the liver and glucose is also stored in the liver. If there is no room to store additional glucose in the liver, it's turned into fat and stored in the abdomen instead. This is the "dangerous" fat we hear about, called visceral fat, that deposits in our abdomen and surrounds internal organs. There is an essential level of visceral fat in the body that protects our organs, but too much can lead to serious health problems. Visceral fat doesn't sit superficially under the surface of our skin like subcutaneous fat.
How can the liver become saturated with glucose? This is where lifestyle and insulin come into play. Insulin is the key that opens the door so glucose can enter cells, and without enough insulin or proper sensitivity to insulin, glucose is denied entry into cells. If glucose cannot enter cells, it will do one of three things: 1) continue to circulate 2) get stored in the liver or 3) is turned into visceral fat if there is glucose overflow in the liver.
Here are a few scenarios in which our bodies can end up with excess glucose in the liver and bloodstream, or excess insulin in the bloodstream:
- If there is too much glucose circulating in the blood, insulin production may ramp up usher more glucose into cells. More keys (insulin) are produced.
- If there are plenty of keys available to open the lock, but the cells are not sensitive to insulin, those keys won’t work well. Guess what happens? More keys (insulin) are pumped out.
- If the body doesn’t produce enough insulin (not enough keys), then glucose will remain in the bloodstream or get stored in the liver.
- If glucose is consumed in excess and floods the circulation, insulin production increases to try to move glucose into cells as quickly as possible.
Insulin is a growth factor, and if there is too much of this growth factor pumping through the body unused, cancer cells can co-opt it for growth and proliferation. Insulin can also signal the liver to produce insulin-like growth factors (like IGF-1) that can increase the risk of developing several types of cancer (Qian, 2020). We certainly do not want any extra growth factors floating around. Controlling insulin and blood glucose levels with nutrition, exercise, and/or medication (whichever is recommended by your doctor), can reduce how much access cancer cells have to this growth factor and others.
Are you deficient in Vitamin D or magnesium? Here's why it could matter:
- Magnesium deficiency is associated with the development of insulin resistance (Li, 2022; Kostov, 2019)
- Vitamin D deficiency has been shown to be associated with insulin resistance (Szymczak-Pajor, 2019)
In an overly simplified way, yes, cancer can benefit from excess glucose or insulin in our bodies, but not in a special "cancer way." When glucose and insulin levels are out of whack for anyone, with or without cancer, the body's organs and tissues are at a greater risk of damage, some of which can be life threatening. For these "normal, everyday" reasons, it's important to be mindful of sugar intake, strive for moderation to help keep insulin levels in check, and to make choices that reduce the chance of developing insulin resistance or type 2 diabetes.
In most situations, having dessert or a sweet treat is okay. It will not turn your cancer into the Hulk. Enjoy that cookie!
Additional Reading:
Article Sugar, Insulin Resistance and Cancer: What's the Link (MD Anderson Cancer Center)
