As deadly as smoking

Christiane Fux studied journalism and psychology in Hamburg. The experienced medical editor has been writing magazine articles, news and factual texts on all conceivable health topics since 2001. In addition to her work for, Christiane Fux is also active in prose. Her first crime novel was published in 2012, and she also writes, designs and publishes her own crime plays.

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Protein has a previously unknown, dark side: even moderate consumption can increase the risk of cancer. However, this does not apply to everyone.

Yogurt for breakfast, a salmon fillet for lunch, a portion of mozzarella in the evening - that sounds pretty healthy. In fact, such a diet could be fatal in the long run. Because consuming animal protein in abundance is obviously frighteningly risky: Anyone who consumes a lot of meat, fish, cheese, etc., quadruples their risk of dying of cancer. That is true at least for middle-aged people. A high-protein diet would be just as dangerous as tobacco consumption.

This finding is based on a large long-term study: More than 6300 participants over 50 years of age were asked about their eating habits and monitored over a period of almost 20 years. "We were not interested in whether a certain diet is good for you in the next three days, but rather whether it helps you live a hundred years," said Valter Longo, head of the study from the University of Southern California, in an interview with

Targeting protein consumption

For their study, Longo and his colleagues divided the diet of the participants into three categories: If the diet consisted of more than 20 percent proteins, this was classified as high protein consumption. A proportion of 10 to 19 percent of protein was considered moderate. They rated a protein consumption of less than 10 percent as low. In addition, the researchers divided the participants into two age groups: one group comprised the 50 to 65 year olds, the second the age group over 66 years.

Fourfold risk of death from cancer

The evaluation showed that high protein consumption increased the risk of death from cancer among middle-aged participants more than fourfold. Even those who only consumed moderate amounts of protein were not on the safe side: the risk of dying from cancer in this group was still three times higher than among the protein-savers. However, this did not apply to vegans: If the protein came mainly from plant sources such as legumes, the negative effect was hardly present.

Other causes of death also increased with protein consumption, such as dying from the effects of diabetes. Overall, the risk of premature death in the group of high consumers increased by 74 percent.

Risky protein hunger

This finding is frightening, as many people consume far more than the maximum recommended 0.8 grams of protein per kilo of body weight per day. The reasons for this vary - for some, a decent piece of meat is simply part of a meal. Others want to feed their muscles with a protein-rich diet and even resort to protein bars and shakes. And then there is the army of those who want to lose weight with what are known as low-carb diets. In return, fewer carbohydrates often mean more protein. "Such diets could actually be very risky in the long term," says Longo.

Eat more protein as you get older

Interestingly, in the group of participants over 65 years of age, the researchers could not find an increased risk of death associated with high protein consumption. On the contrary: in the elderly, the advantages of a protein-rich diet apparently predominated - their risk of death decreased with moderate or copious protein consumption.

Double-edged growth factor

The reason for the age-dependent different effects of protein consumption is probably the growth factor IGF-1, which increases with higher protein consumption. IGF-1 is important for child growth and muscle building, but it also promotes cancerous growth. "Everyone develops cancer cells in the course of their life," says Longo. “The question is: does a tumor grow from it?” It has now been shown that personal protein consumption has a considerable influence on this. In tests with mice, the scientists were able to show that the IGF-1 level actually increased in animals with a high protein consumption - and with it the risk of cancer.

This also explains why protein does not harm seniors: Since the IGF-1 level naturally falls with age, a protein-rich diet no longer has a negative impact, but strengthens the dwindling muscles.

Eat a low protein diet

The researchers cannot yet say whether a protein-heavy diet increases the risk of death from cancer in adults under 50 in the long term. "In order to be able to prove this, we would need a much higher number of participants," explains the scientist - because naturally far fewer people die in the younger age groups than among the older ones. "Nevertheless, we believe that the effects on cancer risk are also present in younger adults."

Source: Morgan E. Levine. Low Protein Intake Is Associated with a Major Reduction in IGF-1, Cancer, and Overall Mortality in the 65 and Younger but Not Older Population, Cell Metabolism, Volume 19, Issue 3, 407-417, 4 March 2014

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