Media coverage of a study published Tuesday in the journal Cell Metabolism makes some startling claims, warning that a diet high in protein and low in carbohydrates decreases longevity in middle-aged people as much as smoking cigarettes and drastically increases their cancer risk. However, here are several reasons to take these reports with a grain of salt.
Researchers used self-reported data over a short (24-hour) time period. Plus, the researchers presumed that, over the 18-year follow-up period, people ate mostly the same as they did during the one day they originally documented. These limitations disturb some dietitians, who who may dispute the study's assertion that people don't change their diets very often.
The study didn't differentiate among different animal proteins. Therefore, participants who loaded up on bacon and sausage were lumped together with those who ate mainly lean beef, poultry and seafood.
Work, stress and lifestyle choices besides food may have caused the mortality findings. The authors don't allow for exercise, family, stress levels, BMI, type of work performed or access to quality preventive medical care.
The study used mice to validate some of their findings. Research in mice often produces outcomes that don't pan out when tested on humans. According to the FDA, "Nine out of ten experimental drugs fail in clinical studies because we cannot accurately predict how they will behave in people based on laboratory and animal studies." In addition, research from 2011 performed in mice showed that a high protein diet actually decreased cancer risk, in direct conflict with this study.
The high carb, low protein diet which the study endorses has been shown to increase the risk of developing Alzheimer's disease and other forms of dementia later in life. There is no cure for Alzheimer's, and the disease eventually kills everyone who develops it. In his book, "Grain Brain," neurologist Dr. David Perlmutter insists that diets high in grains and sugars are bad for brain health at any age.
Low carb diets, according to some studies, can help or even reverse type 2 diabetes. Uncontrolled blood sugar levels in a person with diabetes can lead to amputations, kidney failure and other serious health problems, as well as early death. Fruits, grains and other high carbohydrate foods raise blood sugar levels, making blood sugar control even more challenging in someone with diabetes.
Numerous studies, such as those referenced by the Harvard School of Public Health and the British Journal of Nutrition, have shown that high protein, low carb diets help people lose weight and maintain weight loss. The country of Sweden has even taken the dramatic step of recommending against a diet high in carbohydrates for its citizens to combat obesity. The problem of too many people carrying around too much weight alarms the medical community due to its association with myriad health problems and premature death.
High carb diets may even harm children, setting up babies for weight problems later in life.
The study makes no comparison between a high protein diet and smoking. Some reporter apparently came up with this analogy, and others copied it. The CDC considers smoking the leading cause of preventable death and says that smoking takes approximately 10 years from a person's life expectancy. Studies show that one in two smokers will die from smoking related illnesses.