According to the latest research, a low-protein diet may protect against some kinds of cancers, whilst a high-protein diet may intensify the risk for malignancies.
The findings of this preliminary research prove that slim people on a long-term, low-protein, low-calorie diet or who take part in regular stamina exercise training have lower levels of plasma growth factors and certain hormones like insulin-like growth factor 1 (IGF-1), for example. These substances have been connected with a greater risk of developing cancer, particularly pre-menopausal breast cancer, prostate cancer and some forms of colon cancer.
"We are aware that there is a connection between nutrition and cancer," stated lead author Dr Luigi Fontana, an assistant professor of medicine at Washington University in St. Louis. "There are some types of cancer that are connected with levels of IGF-1, which is a relevant growth factor stimulating the proliferation of cells."
If levels of IGF-1 are high, there is a greater probability that mutated cells will become cancerous, explained Fontana, who is also a scientist at Istituto Superiore di Sanita, in Rome, Italy. "We discovered that people who follow a low-calorie, low-protein diet have lower IGF-1 than slim athletes eating a Western diet. This indicates that low protein intake may decrease IGF-1, independent of body weight," he explained.
The research was published in the December issue of the American Journal of Clinical Nutrition.
How the research was carried out
For the research, Fontana’s team observed and inspected 3 groups of people. The first included twenty one slim men and women, consumed a low-protein, low-calorie, raw food, vegetarian diet. The second group, made up of twenty one people did regular endurance running, averaging about 48 miles during a week. These runners consumed a typical Western diet that included more calories and protein than the first group. The third group included twenty one inactive people who also ate a typical Western diet, higher in sugars, processed refined grains and animal products.
Participants of the first group averaged a daily consumption of 0.73 grams of protein per kilogram of body weight. The runners consumed 1.6 grams, and inactive people consumed 1.23 grams of protein per day. According to Fontana, the suggested daily allowance for protein consumption is 0.8 grams.
The scientists discovered that participants of the first group had considerably lower blood levels of IGF-1 in comparison to the runners or the inactive people. High levels of IGF-1 have been associated with pre-menopausal breast cancer, prostate cancer and certain types of colon cancer.
Additionally, lower IGF-1 levels are linked to increased life duration in animals, Fontana observed.
Reduce the intake of animal products
Fontana believes that if people consumed more whole grains, beans, fruits and vegetables and far fewer animal products, they would be healthier. He suggests eating fish, low-fat dairy products and, sometimes, some red meat. This kind of diet decreases total calories and the amount of protein consumed, and it may also lead to lower levels of IGF-1.
"A lot of the citizens of the United States and Italy are eating fifty percent more protein than what is suggested," Fontana claimed. "If we eat fifty percent more calories than recommended, we become overweight or even obese. What happens if you consume fifty percent more protein than required - we still do not know."
Fontana speculated that consuming too much protein increases the risk for cancer and also speeds up the process of ageing, "but further research is essential to find out if my hypothesis is true or false."
One specialist also believes that a high-protein diet escalates the risk for certain types of cancer.
"Lately, we have published a paper that also demonstrates that a high-protein diet is bad for you. It decreases the rate of survival; it increases the risk of cancer," said Dr Dimitrios Trichopoulos, the Vincent L. Gregory Professor of Cancer Prevention at the Harvard School of Public Health’s Department of Epidemiology.
Protein diet may up mortality
This research was published online in the November 29 issue of the European Journal of Clinical Nutrition. The scientists collected data concerning the diets of 22 944 healthy adult citizens and discovered that eating low-carbohydrates and high-protein diets was connected with increased mortality.
Trichopoulos believes that levels of IGF-1 may be the reason for the greater risk of cancer isk. Nonetheless, other factors may also be at work, he added.
Regardless of his and Fontana’s findings, Trichopoulos is not ready to recommend a low-protein diet in order to decrease the risk of cancer or to live longer. Another latest study contradicted this finding, Trichopoulos said. "At this stage, we ought to wait for explanation," he said.
