Functional Formularies’ objective is to educate about the important link between nutrition and health. Our recent webinar, The Crucial Role of Nutrition in Cancer Treatment, received many questions regarding the role of dietary intervention in improving cancer outcomes. These questions primarily centered around the subject of protein and the amino acid glutamine. This particular webinar was to encourage care providers and patients to look specifically at carbohydrate and sugar restriction as beneficial tools to slow cancer growth (see recent blog on Sugar and Cancer, posted on July 27th, 2017) In addition, the topic of protein and glutamine restriction was discussed as they relate to supporting a ketogenic diet and to limiting cancer metabolism, respectively.
In efforts, to collectively answer these questions I have expounded more thoroughly on the subject of cancer metabolism in this blog post. There were very few questions regarding the scientific evidence supporting the relevance of the Warburg Effect to cancer treatment. However, some questions posed by participants inquired about the benefits of a dietary intervention that limits whole grains (presumably because of their fiber content), fruit (because of their antioxidants), and legumes (they contain both fiber and phytonutrients). I emphasize the importance of both fiber and plants in supporting overall health, especially when it comes to cancer. Fortunately, patients do not have to consume sugar and extremely carbohydrate-dense foods in order to acquire that essential plant fiber. Other than berries and some citrus fruits (lemons and limes), most fruit contains too much sugar for the metabolically carbohydrate-demanding cancer. On the other hand, green leafy vegetables and non-starchy vegetables provide everything that fruit does without the sugar and fructose content.
Grains offer the patient little other than satiety and eating their traditional diet. All grains are largely carbohydrate sources and can contribute large amounts of glucose quickly. Legumes, although higher in fiber and often more moderate in their carbohydrate content, are also not as effective as vegetables in offering micronutrients and phytonutrients without the glucose. Neither grains or legumes, nor fruit for that matter, are essential components or sole sources of critical nutrients. Rather most have become convenient ways for acquiring some nutrients with a high degree of consumption satisfaction and/or satiety.
We must become clear on the amount of carbohydrates found in certain foods. Kale, for instance, by some may be thought to be a food that would require limited consumption based upon its carb content. Clarification in understanding that fiber is included under the total carb value, but that it does not actually contribute any glucose to the bloodstream. This may be information that is relatively new to some; therefore, continued independent study concerning “net carbs” is recommended.
The important take home message here is that green leafy vegetables and non-starchy vegetables can be eaten freely. They do not contain significant amounts of carbohydrates and are the richest sources of micronutrients in the plant world.
To further expound on the topic of protein consumption, it is important that care providers understand the limitations of research supporting increased protein consumption, and calories for that matter. This research and the frequent advice patients receive “just get plenty of calories, it doesn’t matter from where or how” is focused solely on avoiding cachexia (a loss of a patient’s critical organ reserve). Weight maintenance or weight gain is not the outcome we should be fixated on. Sure, cachexia is a condition that is associated with poor outcomes, but it is also closely tied to advanced cases and aggressive, metastasized cancer. If we center our efforts around preventing weight loss while simultaneously feeding cancer cells and advance tumor growth; then there is no efficacy in the treatment. Furthermore, people regularly die of cancer without cachexia.
The ketogenic diet can accommodate protein levels as high as 20% of total caloric intake, but it is highly individualized. Some patients can handle 20% protein but most will be able to stay in ketogenesis with levels around 10-15%. Either way, these are not levels of protein restriction that will result in muscle wasting. They are simply levels that will allow the body to maintain nutritional ketosis.
Additionally, glutamine restriction is a concept worthy of expounding on. The misconceptions about glutamine restriction could possibly stem from the fact that some institutions still administer glutamine post colon cancer surgery or for those with head and neck cancer? Or maybe this is because people have heard so many good things about various L-glutamine protocols? While glutamine is certainly the most abundant amino acid in circulation, research is not suggesting that dietary levels can be zero but rather that it is best to not add supplemental amounts where large rises in circulating glutamine can feed otherwise dependent cancer cells or tumors. Again, the favorable research with respect to cancer treatment and supplemental glutamine is not examining the effect on the cancer but rather the influence on issues such as an individual’s tolerance for chemotherapy or their weight.
Although, the concept of glutamine restriction was not the most important learning objective for last week’s talk but rather an adjunct dietary strategy that can apply additional pressure to cancer cells with limited metabolic pathways at their disposal, I have attached three recent papers that should serve as excellent resources on this particular topic. In the end, these methods should be discussed as synergistic approaches where their combined effect is greater than the sum of their parts. I hope that this has been helpful.
Please see resources below for further research and independent study on this subject.
~ John Bagnulo MPH, PhD. - Director of Nutrition
Glutamine and Cancer Metabolism
Altman B et al. From Krebs to clinic: glutamine metabolism to cancer therapy. Nature Reviews Cancer 2016;16:619–634.
Chen L, Cui H. Targeting Glutamine Induces Apoptosis: A Cancer Therapy Approach. Lemarié A, ed. International Journal of Molecular Sciences. 2015;16(9):22830-22855.
Krzysztof PM et al. Key Roles of Glutamine Pathways in Reprogramming the Cancer Metabolism. Oxidative Medicine and Cellular Longevity Volume 2015 (2015), Article ID 964321, 14 pages