Eating a low-carbohydrate, high-protein diet may reduce the risk of cancer and slow the growth of tumors already present, according to a study published by the American Association for Cancer Research.
The study was conducted in mice, but the scientists involved and independent observers say the findings are definitive enough that similar effects in humans, though unproven, seem plausible.
Most human population studies link traditional diets high in fruits and vegetables but low in sugars and starches – such as age-old, fast-disappearing “Mediterranean” diets – to lower cancer risks overall (Key TJ et al. 2004).
As the authors of a 2005 review wrote, “We recommend the adoption of dietary patterns emphasizing regular physical activity, fruits and vegetables, whole grains, legumes, nuts, seeds, and low-fat dairy products to all people at risk for cancer … These recommendations may be incorporated into enjoyable cultural food patterns as exemplified by Mediterranean-type diets.” (Williams MT, Hord NG 2005)
The authors of the new mouse study put it pointedly, saying, “This shows that something as simple as a change in diet can have an impact on cancer risk,” said lead researcher Gerald Krystal, Ph.D., of the British Columbia Cancer Research Centre (AACR 2011).
Mouse study links cancer to standard, high-carb American diet
Dr. Krystal and his colleagues implanted various strains of mice with human tumor cells or with mouse tumor cells and assigned them to one of two diets, proving the three essential “macronutrients” in specific proportions (Krystal G et al. 2011):
Western-Style Diet – about 55 percent carbohydrates, 23 percent protein, and 22 percent fat.
Low-Carb/High-Protein Diet – about 15 percent carbohydrates, 58 percent protein, and 26 percent fat.
The researchers characterized the Low-Carb/High-Protein Diet as resembling the ones advised in the bestselling Perricone Prescription and South Beach Diet books.
This comparison holds in terms of the proportions of the three macronutrients, if not with regard to the primary protein source that both diets' authors recommend … seafood and its accompanying omega-3 fats, rather than poultry and red meats.
The results were consistent and showed that the tumor cells grew slower in mice placed on the Low-Carb/High-Protein Diet.
Second study links low-carbohydrate, high-protein diet to reduced breast risk
In a separate study by Krystal's team, mice genetically predisposed to breast cancer were put on these two diets.
Almost half of the mice on the Western diet developed breast cancer within their first year of life, while none on the Low-Carb/High-Protein Diet did.
Interestingly, only one mouse eating the Western diet reached a normal life span (approximately 2 years), with 70 percent of them dying from cancer.
In contrast, more than half the mice in the Low-Carb/High-Protein Diet group reached or exceeded a normal life span, and only 30 percent developed cancer.
Why would a high-protein, low-carb diet deter cancer?
When asked to speculate on the biological mechanism behind the beneficial effect of the Low-Carb/High-Protein Diet, Krystal said that tumor cells, unlike normal cells, need significantly more glucose (blood sugar) to grow and thrive.
As a consequence of limiting blood levels of glucose, restricting carbohydrate intake limits release of insulin … the sugar-uptake-stimulating hormone, which has been shown to promote tumor growth in both humans and mice.
Furthermore, he noted, low-carbohydrate, high-protein diets are known to boost the ability of the immune system to kill cancer cells and help prevent obesity, which leads to the chronic, “silent” inflammation that promotes cancer.
Anti-inflammatory drug potentized low-carb diet's protective power
Dr. Krystal's team also tested the effect on tumor development of two drugs: an mTOR inhibitor drug – which inhibits cell growth – and the prescription pain drug Celebrex, which inhibits a key pro-inflammatory enzyme called COX-2.
Both of these drugs further protected the mice fed the Low-Carb/High-Protein Diet, but the added protection afforded by Celebrex was substantially greater.
Given the known risks of Celebrex and other synthetic COX-2 inhibitors – such as now-banned Vioxx – it seems far wiser to use natural inflammation modulators.
These include fish-derived omega-3s and many plant foods ... especially culinary herbs and spices, berries, grapes, cocoa and dark chocolate, green tea, turmeric (curcumin), ginger, olives, extra virgin olive oil, beans, and whole grains.
All of these foods are rich in polyphenol-type “antioxidants” … whose health benefits do not flow from direct antioxidant effects inside our bodies, which, unlike the potent antioxidant powers they exhibit in test tube experiments, are quite weak.
Instead, food-borne polyphenols exert generally anti-inflammatory, anti-tumor “nutrigenomic” influences on gene expression.
American Association for Cancer Research (AACR). Low-Carbohydrate, High-Protein Diets May Reduce Both Tumor Growth Rates and Cancer Risk. June 14, 2011. Accessed at http://www.aacr.org/home/public--media/aacr-in-the-news.aspx?d=2396
Kontou N, Psaltopoulou T, Panagiotakos D, Dimopoulos MA, Linos A. The Mediterranean Diet in Cancer Prevention: A Review. J Med Food. 2011 Jun 11. [Epub ahead of print]
Krystal G et al. A Low Carbohydrate, High Protein Diet Slows Tumor Growth and Prevents Cancer Initiation. Cancer Res. June 14, 2011; Published Online First June 14, 2011; doi:10.1158/0008-5472.CAN-10-3973. Accessed at http://cancerres.aacrjournals.org/content/early/2011/06/10/0008-5472.CAN-10-3973.abstract