by Sudha Bhat on  January 20, 2015 at 3:42 PM Health In Focus
Too Much Protein is 'As Bad as Smoking' In Middle Age - Study
Your diet is like a bank account. Good food choices are good investments. You should make sure that you eat smart in order to keep fit. A well-planned balanced meal, which includes plenty of fruits, vegetables, protein, carbohydrates and so on that provides your body the nutrition it needs to function properly.

Why is protein important?

Protein is the major component of all human cells such as bone and muscle. It is composed of 'building blocks' known as amino acids. 8 out of the total 22 amino acids are considered as essential amino acids since our body cannot produce them and we have to get them from the food we eat. It is important to eat the right kind and amount of protein daily for proper growth, to keep your bones healthy, for production of hormones and brain development.

Proteins are classified into animal and plant proteins. Meat, cheese and eggs are examples of animal proteins which are also known as primary proteins since they contain all eight essential amino acids and are thought to be important for growth. Plant protein sources are pulses, legumes, lentils, tofu and other soya products. They are called as incomplete proteins because they don't contain all of the essential amino acids. However, it is believed that when eaten in the right combination it is possible to get all the essential amino acids, for example beans and grains complement each other in their amino acid profiles when eaten together.

High protein diets such as Atkins diet, South Beach diet, liquid protein diet and others, have been extremely popular in the past for their quick weight-loss results. These diets allow consumption of unlimited amounts of all meat, poultry, fish, eggs and most cheeses and cut down on amount of carbohydrates ingestion.

Study links high protein intake to cancer and other diseases

According to the latest study, which analyses the impact of protein consumption on longevity, having a diet rich in meat, eggs, milk and cheese could be as harmful to health as smoking. The risk is equivalent to the danger of developing cancer by smoking about 20 cigarettes each day. Research conducted in the past have shown a link between cancer and red meat, but this is the first time research was done to show the risk of death caused by regularly eating too much protein.

Researchers from the University of Southern California conducted a study and found that people who ate a high protein diet were 74 percent more likely to die of any cause within the study period as compared to people on low-protein diet. The study also showed that they were many times more likely to die of diabetes. This was found to be true for people below 65 years of age; however, this trend appeared to be reverse for those above 65 years of age. The results of the study was published in the journal Cell: Metabolism.

The researchers took pre-existing data from one of the largest national surveys of health and nutrition done in the United States known as NHANES III. They studied about 6,300 people over the age of 50 and followed them for 18 years, which included analyzing their death rates and cause of death.

The three study groups were formed according to their protein intake:
  • High - 20% or more of calories from protein (1,146 people)
  • Moderate - 10 to 19% of calories from protein (4,798 people)
  • Low - less than 10% of calories from protein (437 people)
The study results were as follows:
  • The study group who ate a high-protein diet were found to be four times more likely to die from cancer, and twice as likely to die from any cause.
  • The group which consumed moderate amounts of protein had a three-fold higher chance of dying of cancer.
  • These effects were either reduced or were not there at all in subjects whose high-protein diet was mainly plant-based such as beans. The probable reason for this is because proteins in plants have a different composition, and don't stimulate growth hormones as efficiently as meat proteins.
  • In subjects who were aged 65 and over, an opposite effect was seen. High protein intake in this age group was linked to a 60% reduced risk of dying from cancer and a 28% reduced risk of dying from any cause. Similar effects were observed in subjects with moderate protein intake.
The researchers felt that chicken, fish, pulses, vegetables, nuts and grains were healthier sources of protein, however, a chicken breast or salmon fillet would account for about 40 percent of recommended daily protein intake.

The researchers thought that the higher-protein intake and higher risk of death from cancer was associated with higher insulin-like growth factor-I (IGF-I) levels in the subjects. Protein controls the growth hormone IGF-I, which helps bodies grow but has been linked to cancer susceptibility.

It was also stipulated that the amino acids that proteins are made of could reduce cellular protection and increase damage to DNA, both of which is a possible explanation as to why high-protein intake is linked to cancer.

One of the lead researchers, Dr. Valter Longo said "We provide convincing evidence that a high-protein diet - particularly if the proteins are derived from animals - is nearly as bad as smoking for your health."

Dr. Longo also stated that the results of the study suggest that the Mediterranean diet, which is low in animal protein and high in carbohydrates could be best for extending life span.

Dr. Eileen Crimmins, a co-author of the study commented "The research shows that a low-protein diet in middle age is useful for preventing cancer and overall mortality. However, we also propose that at older ages, it may be important to avoid a low-protein diet to allow the maintenance of healthy weight and protection from frailty."

Dr. Gunter Kuhnle, who is a food nutrition scientist at the University of Reading thought that it was potentially dangerous to compare effects of smoking to effect of high intake of protein. He thought that this could be misinterpreted by the public, especially the smokers who would not think of quitting smoking if their protein loaded sandwich was equally unhealthy.

One of the experts in metabolic medicine from Glasgow University, Prof Naveed Saattar, thought that the low-protein effect in older people could be due to "survival bias", where those who reportedly lived longer are already generally healthier.

Prof Tim Key, a Cancer Research UK epidemiologist, said: "Further research is needed to establish whether there is any link between eating a high protein diet and an increased risk of middle aged people dying from cancer."

All said and done, a balanced diet was still the best option. There is no diet that will do what eating healthy does. So eat right and take care of your body, after all it is the only place you have to live.

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