Healthy diet is one that is based exclusively or primarily on a variety of unrefined foods of plant origin. Interestingly, although our principles of a healthy diet are based on an increasing number of studies, dietary habits often do not follow prudent dietary recommendations. In western societies, mainly Europe and North America, meat intake has been relatively high for decades. As economic conditions in countries around the world improve, adoption of western dietary principles follow.
Meat consumption has been steadily increasing around the world. Between 1961 and 2007, the world’s meat supply has increased four-fold, from 71 million to 284 million tons. The largest increase has been observed in the case of poultry, from 15 to 87 tons (480 percent) and the lowest in the case of beef and veal, from 38 to 65 million tons. Part of this increase is accounted for by the increase in the world’s population. Still, the supply of meat for every inhabitant of the world during this period has more than doubled. It is estimated that global meat production will grow more than two fold by 2050 compared with production in 1999, from 229 million to 465 million tons.
Pork is the most consumed meat in the world, while the intake of poultry, especially chicken, is growing faster than any other kind of meat. Meat products are divided into red meat, white meat, processed meat, fish and seafood. Red meat includes pork, beef (including veal), lamb, horse meat and goat meat. White meat is mainly chicken and turkey. The Food and Agriculture Organization defines processed meat as meat mixes composed of comminuted muscle meat with varying quantities of animal fat. They include burgers, patties, sausages, nuggets and others. The increase in meat intake observed in the last few decades has been primarily due to higher consumption of meat in developing countries such as China, India, Brazil, Argentina and other countries mainly in Asia and South America.
A number of studies conducted in different countries with people from many ethnic backgrounds documented the detrimental impact of meat intake in terms of a risk of developing chronic health conditions. Meat products contain ingredients, such as saturated fat, cholesterol, and some amino acids, which promote the development of chronic health conditions that are the main cause of death and disability. Scientists in Greece conducted a study with people living on islands in the Mediterranean Sea. The results showed that increased intake of meat fat by 5 percent of calories increased the risk of developing risk factors for cardiovascular disease, such as obesity, diabetes, high blood pressure or high cholesterol, by 21 percent. According to a meta-analysis based on 20 studies (a meta-analysis is an assessment of the impact of one factor on another factor based on many studies) that assessed the impact of meat and meat products on coronary heart disease, each 50 grams of meat consumed per day increases the risk of developing coronary heart disease by 42 percent. According to the same meta-analysis, each 100 grams of meat consumed per day increases the risk of stroke by 24 percent. A study known as the CORA Study, further illustrates the effect of meat on the formation of coronary artery disease. According to results of this study, an increase in meat consumption by 100 grams per day is associated with a 100 percent higher risk of developing coronary heart disease.
Meat is a factor in the development of diabetes. At least two factors contained in meat detrimentally impact risk of this disease: saturated fat and heme iron (iron from meat, especially red meat). According to a study conducted in Melbourne, Australia, known as the Melbourne Collaborative Cohort Study, which involved more than 41,000 individuals between 40 and 69 years of age, those with the highest levels of saturated fat had almost 300 percent higher risk of developing diabetes compared with those consuming it least. Meat is a major source of saturated fat in the diet in most countries. For example, it is estimated that meats, including poultry account for about 40% of saturated fat intake in the United States, which is more than the saturated fat intake from any other food group.
A study with 8,401 members of the Seventh-day Adventist Church has shown that people who ate meat once or more per week had a 29 percent higher risk of developing type 2 diabetes compared to vegetarians. The risk of diabetes among individuals eating sausage was about 38 percent higher. Individuals who have been vegetarians for at least 17 years, had a 74 percent lower risk of type 2 diabetes compared to those who ate meat at least once a week. These results are consistent with those reported in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study, with nearly 25,000 people. Those with the highest consumption of meat had a 50 percent higher risk of developing type 2 diabetes compared to those who consumed it the least. In the case of processed meat the risk was 37 percent higher.
The results of the Women’s Health Study, which included more than 37,000 women over 45 years of age, found that those consuming the highest amount of red meat had a 28 percent higher risk of developing type 2 diabetes. Similarly, individuals with the highest intake of processed meats had a 23 percent higher risk of this disease. Researchers who conducted this study also estimated the risk for type 2 diabetes for specific type of meat consumed. Consumption of hot dogs, two or more times a week resulted in a 28 percent increased risk of developing type 2 diabetes. In the case of bacon, the increase was 21 percent and for hamburgers, the risk increased by 18 percent. Consumption of these products even once a week was associated with a higher risk of developing the disease.
A meta-analysis of 20 different studies conducted on a group of 1,218,380 people, showed a 16 percent higher risk of type 2 diabetes among people who consume the largest quantities of meat and 19 percent when it comes to processed meat, compared to individuals with the lowest intake. In another meta-analysis, that took into account 12 studies, people who consumed the greatest amount of meat had a 17 percent higher risk of developing type 2 diabetes compared to people who ate the smallest amount of meat. When participants with the highest intake were compared to those with the lowest intake, processed meat increased the risk of type 2 diabetes by 41 percent and red meat by 21 percent.
In addition to the detrimental impact of meat intake on the risk of cardiovascular disease and diabetes, meat, especially red and processed meats, increase the risk of cancer of some organs. This effect is well-illustrated by a study conducted in Italy. The researchers compared the risk of death due to cancers of various organs among individuals who ate red meat at least 7 times a week with people consuming it 3 or fewer times a week. Those with intake of 7 or more times per week had over 60 percent higher risk of death in the case of gastric cancer, more than 90 percent in the case of colon cancer, more than 70 percent in the case of rectal cancer, more than 60 percent in the case of pancreatic cancer, more than 60 percent in the case of bladder cancer, more than 20 percent for breast cancer and more than 50 percent higher in the case of endometrial cancer.
A study conducted in the United Kingdom constitutes another example. Its goal was to estimate the impact of meat intake on the occurrence of breast cancer in over 35,000 women aged 35 to 69 years. Those consuming the highest amount of meat (> 103 g per day or about 3.5 oz.) had a 34 percent higher risk of getting a breast cancer compared with vegetarians. Similarly, those with the highest intake of red meat consumption had a 41 percent higher risk, in the case of processed meat a 39 percent higher, and in the case of poultry, a 22 percent higher risk compared to those women who were vegetarians. In case of postmenopausal women, those with the highest amounts of consumed meat had a 64 percent higher risk of breast cancer and in the case of red meat 54 percent higher risk compared with women who did not eat meats. Consumption of poultry increased the risk by 30 percent.
Epidemiological data from Japan and Korea indicate that starting from 1950 the prevalence of colorectal cancer in these two countries increased steadily to the same extent as the increase in the consumption of meat. The figure below illustrates the relationship between intake of meat and cancer rates in these two countries. In another study, known as the Nambour Skin Cancer Study, people who consumed the highest amount of meat had more than 100 to more than 300 percent higher risk of skin cancer.
Meat and meat products contain relatively large amounts of carcinogenic compounds, such as heterocyclic amines, polycyclic aromatic hydrocarbons, nitrates, pesticides (despite the fact that pesticides are used to spray crops and other plants, meats contain significantly greater pesticides residues than the plant products due to their accumulation in animal tissues, a process known as bio-accumulation), and hormones. Some of these compounds are the result of feeding methods, and other due to preparation of meat and meat products for consumption. Consumption of meat and sausages on the grill results in a particularly high risk of developing cancer. Similarly, smoked and fried meats contain higher content of carcinogenic compounds.
Due to the fact that meat consumption is associated with a higher incidence of cancers of various organs, organizations dealing with cancer prevention recommend limiting their intake. A good example of such recommendations are guidelines issued by the World Cancer Research Fund and American Institute for Cancer Research in their monumental document entitled Food, nutrition, physical activity and the prevention of cancer: a global perspective. In it we read: “limit intake of red meat and avoid processed meat.” Further, we read: “population average consumption of red meat to be no more than 300g (11oz) per week, very little if any of which should be processed.”
Eating meat is associated with the occurrence of arthritis. One study, which assessed the impact of meat consumption on the risk of arthritis, was performed at Loma Linda University in California. Among those who ate meat at least once a week, the risk of gout was 49 percent higher in women and 43 percent higher in men compared to individuals who abstained from meat intake. A similar effect was observed in another study conducted in the United Kingdom, known as the EPIC-Norfolk Study. This study included 25,630 people between 45 and 75 years of age. Among those who consumed the largest amounts of red meat researchers observed a 90 percent higher risk of developing arthritis compared with individuals with the lowest intake. Similarly, the group consuming the highest meat and animal products had a 190 percent higher risk of arthritis compared to those with the lowest intake.
Dementia is another health problem that is impacted by meat intake. According to a study, which included people from 7 countries (China, India, Cuba, the Dominican Republic, Venezuela, Mexico and Peru), individuals who consumed the largest quantities of meat had a 19 percent higher risk of developing dementia compared with those with the lowest intake. Similar effect was shown in a study with members of the Seventh-Day Adventist Church in the United States. Those with the highest intake of meat and fish had almost 3 times as high risk for dementia compared to individuals who abstained from meat.
The above mentioned studies clearly show that the higher the consumption of meat, the higher the risk of various lifestyle diseases including cardiovascular disease, diabetes, some cancers, dementia and arthritis. To reduce the risk of developing these health conditions, diet should be primarily based on unrefined plant products and meat intake should be either drastically reduced or completely eliminated. Unfortunately, meat is relatively cheap and readily available. People can find meat in fast food and full service restaurants and grocery stores. Giving up or even reducing meat intake seems to be a thing that goes against the culture. Considering that meat avoidance is an important factor in chronic disease prevention it would be beneficial for any individual to adopt a plant-based diet.