Straight Talk on Controversies
In May 2015, Dr. David Klurfeld, National Program Leader, USDA Agricultural Services, investigated the gaps in understanding the relationship between meat and health. In his published review he states:
Meat is one of the most nutrient dense foods, providing high-quality protein, heme -iron, zinc, and vitamins B6 and B12. Despite these advantages, epidemiological studies have linked consumption of red and processed meat with obesity, type 2 diabetes, cardiovascular diseases, and cancers. Most observational studies report small, increased relative risk. However, there are many limitations of such studies including inability to accurately estimate intake, lack of pre-specified hypotheses, multiple comparisons, and confounding from many factors including body weight, fruit and vegetable intake, physical activity, smoking, and alcohol. All these can limit the reliability of conclusions from these studies. This observational research is heterogeneous and does not meet the standards to infer cause and effect.
In 2014, a team of researchers also noted several limitations of using observational research to establish diet-health relationships. Perhaps the best advice given is having a moderate intake of a variety of foods is the best dietary advice!
The section below highlights research worth noting related to cancer, heart disease and diabetes.
Meat and Cancer: The findings on red meat and cancer are inconsistent. People consume diets, not single foods, so determining cause and effect between foods and health outcomes is very challenging. Further, cancer is a complex disease and no one single food causes cancer.
While red meat has most often been linked to colon cancer, In 2010 a comprehensive review of the science concluded that “the currently available epidemiologic evidence is not sufficient to support an independent positive association between red meat consumption and colorectal cancer.” A second look at the subject concluded that the link was non-existent for women and extremely weak for men. These findings echoed findings of one of the largest studies ever done at Harvard University using “pooled data,” an approach considered to be one of the most precise. That study concluded “Greater intake of either red meat (excluding processed meat) or processed meat was not related to colorectal cancer risk.”
Saturated fat and Heart Health: In 2015, researchers published a systematic review of randomized control trials (RCTs) that looks at dietary fat, cholesterol and the development of coronary heart disease. They focused upon the science that could have supported the United States’ and United Kingdom’s shift to recommending low-fat diets to prevent heart disease. They concluded that the evidence showed no differences in all-cause mortality and non-significant differences in heart disease mortality, resulting from the dietary interventions leading them to conclude, “Government dietary fat recommendations were untested in any trial prior to being introduced. Dietary recommendations were introduced for 220 million US and 56 million UK citizens by 1983, in the absence of supporting evidence from Randomized Control Trials (RCTs).”
In August 2015, researchers at McMasters University published a study in the British Medical Journal where they reported no clear association between higher intake of saturated fats and death for any reason, coronary heart disease (CHD), cardiovascular disease (CVD) or ischemic stroke. The Institute of Medicine recommends limiting saturated fat as much as possible, while still maintaining a nutritionally adequate diet.
Diabetes: Headlines have suggested that red meat could potentially cause Type 2 diabetes. Most recent stories have been based upon a 2013 study from the Harvard School of Public Health. The study concluded that red meat increased inflammation in the body and this limited the body’s ability to process glucose, a condition known more commonly as diabetes. But just months later, a clinical study found that regular red meat consumption reduced inflammation and helped improve muscle strength when combined with resistance training. While many dietary factors for managing diabetes have been suggested, a 2004 review indicates that achieving a healthy BMI and exercising are the best ways to prevent diabetes.
And, on August 2015, McMasters researchers wrote in the British Medical Journal indicated that their team found no clear association between higher intake of saturated fats and type 2 diabetes.
In August 2015, researchers at McMasters University published a study in the British Medical Journal where they wrote, “The team found no clear association between higher intake of saturated fats and death for any reason, coronary heart disease (CHD), cardiovascular disease (CVD), ischemic stroke or type 2 diabetes.”
In terms of managing diabetes, it is important to limit sugar intake given the body’s impaired ability to produce or use insulin and process sugar. Foods with low “glycemic index” are beneficial. Fresh meats and poultry do not have a glycemic index because they do not raise blood glucose. If breaded or marinated, they can contain carbohydrates that can raise blood glucose. Information can be found on the nutrition label to help people with diabetes select the best meat or poultry product for their unique needs.
The short answer: Fresh meat and poultry are naturally low in sodium, typically having 100 mg or less per serving. For example, a broiled, 3.5 ounce hamburger contains 77 mg of sodium. Sodium may be added during cooking or at the table. Prepared and cured meat and poultry have sodium added when they are made at a plant or in a meat department and levels are declared on the packages. All these choices can be part of balanced eating. As well, food companies are offering many lower sodium options to make sure consumer have choice.
Salt is added when meat products are prepared into lunch meats, franks, bacon, and other products. Salt is part of the product’s “identity” just as it is part of the taste associated with a pretzel or smoked salmon. However, the processed meat category is extremely varied and meat processors produce an array of reduced-sodium products, such as:
- Hot dogs with 250 mg of sodium or less per serving;
- Low sodium deli meats, bacon, ham and breakfast sausage with 140 mg of sodium or less per serving; and
- Very low sodium deli meats with 35 mg of sodium or less per serving.
Now the longer answer:
In 2010, the U.S. Dietary Guidelines for Americans recommended that Americans reduce daily sodium intake to less than 2,300 milligrams (mg) per day and further reduce intake to 1,500 mg per day among persons who are 51 years and older and those of any age who are African American or have hypertension, diabetes, or chronic kidney disease. The 1,500 mg applies to about half of the U.S. population, including children, and the majority of adults.
While efforts are underway to reduce sodium in foods, it is important to highlight that sodium is essential for human health and development. In particular it:
- Regulates the body's electrolyte balance
- Helps to prevents dehydration
- Maintains many of the body's cellular functions.
Salt has also been a vehicle to prevent nutrient deficiencies such as its fortification with iodine to help prevent goiter and iodine deficiency disorders in children.
Meat and poultry processors respond to federal, state and local sodium reduction efforts by offering a variety of new and reformulated prepared products that contain lower levels of sodium. At the same time, it is important to highlight: sodium does many important things in food such as add unique flavor, texture, food safety and shelf life.
Foods at the grocery store can be found with sodium claims such as :
|Salt/Sodium-Free||Less than 5 mg of sodium per serving|
|Very Low Sodium||35 mg of sodium or less per serving|
|Low Sodium||140 mg of sodium or less per serving|
|Reduced Sodium||At least 25% less sodium than in the original product|
|Light in Sodium or Lightly Salted||At least 50% less sodium than the regular product|
|No-Salt-Added or Unsalted||No salt is added during processing, but not necessarily sodium-free. Check the nutrition label.|
Sodium Intake: How Low Should it Be?
While some science has raised concerns about sodium and its impact on heart health, other less reported science has found different results.
Researchers publishing in the Journal of the American Medical Association studied more than 3,600 patients for eight years. “Low sodium excretion did not translate into less morbidity or improved survival. On the contrary, low sodium excretion predicted higher cardiovascular mortality.” They concluded, “Taken together, our current findings refute the estimates of computer models of lives saved and health care costs reduced with lower salt intake. They do also not support the current recommendations of a generalized and indiscriminate reduction of salt intake at the population level. However, they do not negate the blood pressure−lowering effects of a dietary salt reduction in hypertensive patients.
The study’s bottom line: people with diagnosed hypertension should reduce salt intake, but salt restriction is not necessary or appropriate for the bulk of the population.
More recently, researcher at McMasters University studied the sodium levels in the urine of 100,000 people. Higher sodium in the urine indicates higher sodium in the diet. The researchers noted in their New England Journal of Medicine paper that most of the global population consumes between 3.0 and 6.0 g of sodium per day (that equals 7.5 to 15.0 g of salt per day) and said that guidelines on cardiovascular disease prevention recommend a maximum sodium intake of 1.5 to 2.4 g per day. They then compared sodium in the urine with cardiovascular outcomes and concluded, “An estimated sodium intake between 3 g per day and 6 g per day was associated with a lower risk of death and cardiovascular events than was either a higher or lower estimated level of intake.”
Given the conflicting evidence, the Centers for Disease Control and Prevention asked the Institute of Medicine to review the science. In 2013, IOM published a full report and concluded:
- The available evidence on associations between sodium intake and direct health outcomes is consistent with population-based efforts to lower excessive dietary sodium intakes.
- The evidence on health outcomes is not consistent with efforts that encourage lowering of dietary sodium in the general population to 1,500 mg/day.
- There is no evidence on health outcomes to support treating population subgroups differently from the general U.S. population.
The Institute of Medicine recommends that total fat make up 20-35% of your daily energy needs. Fats are essential nutrients that give the body energy, and help the body absorb fat soluble vitamins like A, D, E and K. Fats are classified as saturated or unsaturated, but most foods have both types.
Saturated fat is solid at room temperature, which is why it is called a "solid fat." It is mostly in animal foods, such as milk, cheese, and meat, poultry and fish. Saturated fat is also found in tropical oils, such as coconut oil, palm oil, and cocoa butter. The Institute of Medicine suggests keeping saturated fat intake as low as possible, while still maintaining a nutritionally adequate diet.
Trans fats has been linked to an increased risk of heart disease. For this reason, the Institute of Medicine recommends having a trans fat intake as low as possible. Trans fats are unsaturated fats that are naturally occurring in animal foods. Naturally occurring trans fats are considered safe. These are sometimes confused with artificial trans fats that are created by adding hydrogen to liquid vegetable oils to make them more solid, often called “artificial trans fat.” In June 2015, the U.S. Food and Drug Administration (FDA) made a determination that partially hydrogenated oils are no longer Generally Recognized as Safe (GRAS) in human food, and need to be removed from processed foods in three years.
Monounsaturated fat is found in avocado, nuts, and vegetable oils, such as canola, olive, and peanut oils.
Polyunsaturated fat is found in vegetable oils such as safflower, sunflower, sesame, soybean, and corn oils and is the main fat found in seafood. The two types of polyunsaturated fats are omega-3 and omega-6 fatty acids.
Omega-3 fatty acids are found in soybean oil, canola oil, walnuts, and flaxseed. They are also found in fatty fish and shellfish as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Meat and poultry also contain Omega-3 fatty acids, but at lower levels than fish.
Omega-6 fatty acids are found mostly in liquid vegetable oils like soybean oil, corn oil, and safflower oil. Meat and poultry are rich sources of Omega-6 fatty acid. Pork, chicken and beef are among the top ten sources of Omega 6-fatty acids.
Evolution in Thinking: Diet and Health
Emerging science in nutrition impacts our understanding of the complex relationship between diet and health. As examples, let’s take a look at saturated fat and cholesterol.
For decades, Americans were told to reduce their saturated fat consumption to prevent heart disease. Americans responded by reducing red meat consumption and increasing their carbohydrate consumption. Coinciding with the shift in eating patterns was a sustained increase in obesity rates.
As researchers continued to pursue their hypothesis, more evidence emerged that saturated fat is not clearly linked to heart disease. In 2010, a meta-analysis of 21 studies concluded, “There is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD or CVD.” Four years later, a 2014 meta-analysis of 32 separate studies prompted researchers to write, “Current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats.”
The view of cholesterol also has evolved. Cholesterol is a substance that the body makes naturally. It is also found in meat, poultry and eggs. For a long time, it was thought that too much cholesterol, either produced by the body or found in foods, could cause high blood cholesterol and increase risk of heart disease. Initially, the public health community waged a war on all dietary cholesterol. Later, it became clear that this was too simplistic an approach.
More recently, in 2014, British researchers concluded that when carbohydrates are substituted for fat, the shift can raise levels of a dangerous type of fat in the blood called triglycerides, and lower the “good type” of cholesterol. Another paper published by the Annals of Internal Medicine, reported that “Current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats.”
Experts agree that vegetarian diets can be healthy, but they require vigilance to ensure that essential vitamins and minerals that are either plentiful in or unique to animal products are not missed. The Academy of Nutrition and Dietetics indicates that vegetarians are at risk for the following deficiencies: iron, vitamin B12, calcium, vitamin D, zinc, and omega-3 fatty acids. Research shows that vegetarians have lower levels of vitamin B12 in the blood, some studies even report this may increase the risk of heart disease. The more foods that are eliminated from the diet, the trickier adequate nutrition becomes. That’s why vegan diets require extreme vigilance, especially for children.
Expert groups such as the American Academy of Pediatrics, the Canadian Pediatric Society, and the Academy of Nutrition and Dietetics agree that vegetarian and vegan diets can be healthy for children, if careful attention is given to the key nutrients listed above. According to the Canadian Pediatric Society, “significant medical consequences could result from inattention to nutrient needs.”
University of Massachusetts researchers in 2014 examined vegetarian diets and bone health and wrote, “Vegetarian diets have been shown to contain lower amounts of calcium, vitamin D, vitamin B-12, protein, and n–3 (ω-3) fatty acids, all of which have important roles in maintaining bone health. Although zinc intakes are not necessarily lower quantitatively, they are considerably less bioavailable in vegetarian diets, which suggests the need for even higher intakes to maintain adequate status… On balance, there is evidence that vegetarians, and particularly vegans, may be at greater risk of lower BMD (bone mass density) and fracture.”
By contrast, balanced diets that include lean meat, poultry and fish, plenty of fruits and vegetables, and whole grains increase the chance that all essential nutrients will be consumed. Balance, however, is the operative word. Overconsuming meat and under-consuming vegetables or whole grains could also result in nutrient deficiencies. Federal data show that Americans, in average, consume meat and poultry within recommended levels. Unfortunately, fruits vegetables and whole grains are under-consumed and may be replaced by discretionary fats and sugars.
Sticking With Vegetarianism
Recent research by the Humane Research Council reveals that adherence to a vegetarian diet is often poor. In fact, recent polls showed that 84 percent of self-identified vegetarians return to eating meat. The study also revealed that two percent of American adults are current vegetarians or vegans, 10 percent are former vegetarians/vegans, and 88 percent have never been vegetarian or vegan. More than half of the ex-vegetarians and vegans gave up on their vegetarian diets within their first year; a third went back to meat within three months.
Likewise, according to a 2005 survey by CBS News, three times as many American adults admit to being "ex-vegetarians" than describe themselves as current vegetarians. This means that three out of four people who give up meat change their minds and return to a diet that includes meat. “It seems that for most people, vegetarianism is a phase rather than a permanent change in lifestyle,” Psychology Today wrote in a piece about the subject.
Why I Am Not a Vegetarian, by William Jarvis, Ph.D., former head of Loma Linda University School of Public Health
Cured meats very safe choices. Meat curing is a term referring to any process that helps preserve meat. It can mean salting, brining, aging, drying or canning. The goal of all of these processes is to slow spoilage and prevent the growth of microorganisms. The key ingredient in cured meats is a curing agent. In the U.S. and Canada, typically that ingredient is sodium nitrite, and more recently indirect addition of nitrite from natural sources.
Nitrite is generally recognized as safe by the U.S. Food and Drug Administration. While nitrite is typically added to cured meats, 93 percent of human nitrite intake comes from vegetables, particularly leafy and root vegetables like spinach, celery and beets, and from human saliva. Vegetables contain nitrate and when they come in contact with saliva, nitrate is converted to nitrite. In fact, the body makes nitrite as part of its normal, healthy nitrogen cycle. To reduce nitrite consumption, one must reduce vegetable consumption. While consumers get very little nitrite from cured meats, it performs an important role in preventing bacteria growth and preventing foodborne illness like listeriosis and botulism.
Researchers at the National Institutes of Health (NIH) have studied nitrite extensively and concluded that it is actually an inexpensive and simple medical treatment for a number of conditions like preeclampsia in pregnancy, cardiovascular disease, promoting wound healing, treating diabetes, treating sickle cell anemia, treating heart attack and stroke and helping ensure successful organ transplantation.
Because concerns were raised in the late 1970s about nitrite safety, the U.S. National Toxicology Program, which maintains the U.S. list of identified carcinogens, conducted a rat and mouse feeding study and concluded in 2000 that nitrite is not a carcinogen.
Interestingly, the Mediterranean diet is widely hailed by nutrition experts as one of the healthiest dietary patterns. While olive oil is most often associated with the diet, the 2015 U.S. Dietary Guidelines Advisory Committee recently reviewed what typically comprises a Mediterranean diet and concluded, “Red and processed meats are higher in the Mediterranean-style diets but lower in the DASH-style diet than is recommended by the USDA Food Patterns.”
Grilling is an excellent way to prepare meat and poultry products because it reduces fat and adds flavor. While the evidence is still not conclusive, some studies suggest there may be a slightly increased cancer risk related to eating food cooked by high-heat cooking techniques like grilling, frying, and broiling because extremely high heat can create something called heterocyclic amines or HCAs. According to USDA’s Food Safety and Inspection Service, based on present research findings, eating moderate amounts of grilled meats like fish, meat, and poultry cooked — without charring — to a safe temperature does not pose a problem.
To prevent charring, remove visible fat that can cause a flare-up. Precook meat in the microwave immediately before placing it on the grill to release some of the juices that can drop on coals. Cook food in the center of the grill and move coals to the side to prevent fat and juices from dripping on them. Cut charred portions off the meat.
Some research has shown that marinating meat can prevent the formation of HCAs.
Antibiotics are used in livestock and poultry production to treat disease in animals that have become ill, to prevent the spread of a disease to other animals in a herd or flock and to control disease once they have occurred in herds and flocks. Some producers have pledged to raise their livestock and poultry without the use of antibiotics.
While this approach can be preferred by some consumers because it reflects their values or their perspectives about how animals should be raised, according to Dr. Mike Lacy of the University of Georgia, the nutrition of meat and poultry derived from animals that have been given antibiotics or that have never been given antibiotics are equal.
Keep in mind that strict withdrawl periods must be followed before the animals may be processed for food. Canadian Food Inspection Agency and the USDA monitors for residuesand federal data shows that antibiotic residues are not an issue in the U.S. or Canada.
The North American meat and poultry case is abundant with products produced in many different ways, including organically. Some people find that organic meat and poultry comes from systems that reflect their values, and that’s a valid reason to choose a product. Some people prefer organic products because they believe certain organic products taste better. While it’s common to hear people claim that organic foods offer a nutrition advantage, the science simply doesn’t support that claim.
Researchers at the London School of Hygiene looked at all the evidence available and concluded in 2009, ”There is no evidence of a difference in nutrient quality between organically and conventionally produced foodstuffs.”
The journal Scientific American in 2011 also reviewed the evidence and wrote, “It appears that organic foods do not offer superior nutrient content as compared to conventionally produced ones.” And in 2012, Stanford University Researchers published in the Annals of Internal Medicine and wrote, “The published literature lacks strong evidence that organic foods are significantly more nutritious than conventional foods.”
Many recent films and web sites claim that grass-fed beef is significantly more nutritious than grain fed beef, but the facts show that the two are quite similar in their nutrition profiles.
Keep in mind that all cattle are grass-fed for the majority of their lives. Some cattle are fed a mixture of corn and other grains for the last few months of their lives, which causes the cattle to gain weight and develop the intermuscular fat that improves meat tenderness and juiciness. Grass-fed cattle, by contrast, eat grass only for their entire lives.
Meat from grain finished cattle tends to have a slightly higher saturated fatty acid profiles than grass fed beef but it also contains higher levels of the healthful monounsaturated fatty acid, oleic acid. Grass-fed beef has slightly higher Omega 3 profiles than corn fed beef. But the nutrition similarities are far more significant than the differences and both are excellent, nutrient dense foods.
Texas A & M University has done some of the most important work comparing the nutrition similarities and differences and concluded that there is no difference in healthfulness.