Is Red Meat Harmful? Benefits, Risks and New Scientific Research

Dietitians, health professionals and scientists have spent years examining benefits and risks of red meat to decide whether it is good or bad for health.

Researchers say red meat contains important nutrients including protein, vitamin B-12 and iron. However, evidence suggests excessive intake may increase certain cancers, heart disease and other problems. We examine research, official dietary advice and potentially healthy quantities.

Introduction – How Does Red Meat Affect Health?

Red meat is generally classified as muscle meat from cattle, lambs, goats or other land mammals.

On one hand, red meat is a good source of nutrients, particularly vitamin B-12 and iron is a good source of nutrients such as these. The human body needs these nutrients to produce new erythrocytes (red blood cells).

It also supplies proteins needed for muscles, bones, other tissues and enzymes.

However, research links regular consumption with cardiovascular disease, certain cancers, kidney and digestive problems and death.

To avoid oversimplifying, some studies suggest the type and quantity consumed have the greatest effect.

Lean, unprocessed cuts such as sirloin, steak and tenderloin may be healthier because they lack processing and excessive salt, fat and preservatives.

Including bacon, hot dogs, sausages, ham, salami and similar meats, processed red meatsappear to pose the highest health risk.

Is Red Meat Nutritious?

It contains beneficial nutrients including iron, vitamin B-12 and zinc.

Animal foods such as meat and dairy are main sources of B-12. Vegetarian or vegan diets may therefore require extra B-12 to prevent B-12 deficiency anemia.

According to the US Department of Agriculture, 100 grams (g) of raw ground beef contains:

• 247 calories
• 19.07 g fat
• 17.44 g protein
• 1,97 milligrams (mg) iron
• 274 mg potassium
• 4.23 mg zinc
• 2.15 micrograms vitamin B-12

Many factors can affect the nutritional value of meat. For example, the calorie and fat content of meat cut from different parts of an animal varies. In addition, the way the farmer raises the animal, the animal's diet, and even the animal's age and sex can affect the nutritional value of the meat.

The US National Institutes of Health (NIH) lists heme iron as well supplied by red meat. Heme iron occurs only in red meat, poultry and seafood. Nonheme iron occurs in plants and fortified foods such as cereals and plant milk.

Meat iron has higher bioavailability, meaning easier bodily use. Although many obtain enough, NIH says some groups risk iron deficiency anemia :

• Infants 
• Young children 
• People with heavy periods 
• Pregnant women

Cardiovascular Disease and Saturated Fat

Many studies show increased cardiovascular risk with regular red meat intake. Experts have long attributed the association to saturated fat.

The American Heart Association (AHA) says red meat generally has more saturated fat than chicken, fish or legumes. High saturated fat and any trans fat may raise cholesterol and heart disease risk. It recommends limiting intake and choosing lean cuts.

- Related topic: Can Saturated Fats Be Healthy? (Detailed)

Contrary to assumptions, red meat is not the main trans fat source in an unhealthy Western diet. Packaged, processed and fried foodstend to contain much more.

Also, legumes are alternative heart-healthy protein sources, including: 

• Borlotti beans
• Beans
• Chickpeas
• Soybeans 
• Lentils
• Peas
• Black-eyed peas

A meta-analysis of 36 studies concluded:

Replacing red meat with high-quality plant protein led to "better" blood fat concentrations, but not when replaced with low-quality carbohydrates.

The meta-analysis also found no significant blood pressure difference between red meat and animal protein diet groups when separately examining total cholesterol, LDL (bad cholesterol) and HDL (good cholesterol).

The research questioned the connection between saturated fat and heart disease . Review authors said researchers overstated saturated fat’s role in heart disease development.

A cardiology team also wrote that saturated fat does not clog arteries or increase heart disease risk. Another article says numerous analyses and reviews do not support the association.

Taken together, evidence exists both for and against saturated fat’s role. Research continues.

Heart Disease and Trimethylamine N-Oxide

Beyond saturated fat, some studies suggest other potential heart risks from red meat.

A recent study found higher blood trimethylamine N-oxide (TMAO) in regular red meat consumers. Intestinal bacteria produce TMAO during digestion. Researchers link this toxin to increased heart disease and mortality.

The study found TMAO levels in red meat consumers were three times higher than in white meat or plant protein consumers. Levels returned to normal approximately 4 weeks after stopping red meat.

Red Meat, Cancer and Mortality

Some recent studies suggest increased cancer or death risk, although findings vary.

The International Agency for Research on Cancer (IARC), part of WHO, classified red meat in its 2015 report as Group-2A (probably) carcinogenic; processed meat was Group-1 (definitely) carcinogenic.

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Based on large studies, the article says higher red meat intake increases the likelihood of colorectal cancer . Both red and processed meat pose risk, but processed meat appears to increase it more.

Research also found higher risks among red meat consumers for pancreatic and prostate cancer. Higher processed meat intake also increased stomach cancer risk.

Authors say processing may increase cancer-causing chemicals, explaining greater risks associated with processed meat.

Other studies examining red meat and cancer:

One study followed women for 7 years, numbering over 42.000, and linked greater intake with breast cancer. Women replacing it with poultry had lower risk.

Another followed 53.000 women and 27.000 men for 8 years, finding higher mortality particularly with processed meat. Participants initially had no heart disease or cancer. An extra half portion daily was linked to a 10% greater mortality risk.

A large study following people for 10 years, over 120.000 men and women, linked processed but not unprocessed red meat to higher mortality.

Cooking Methods and Cancer

Frying or grilling meat over open flame at high heat creates heterocyclic amines and polycyclic aromatic hydrocarbons, which may cause cancer-related DNA changes (see the relationship between barbecued meat and cancer).

The US National Cancer Institute lists ways to reduce exposure: 

• Avoid cooking meat, including white meat, over open flames or very hot metal surfaces
• To reduce high-heat cooking time, first partially heat meat in a microwave beforehand
• Turn meat regularly during cooking 
• Do not eat charred pieces
• Eating dark leafy vegetables with cooked meat is another good way to support the body.

How Much Red Meat Is Too Much?

Guidelines vary.

IARC says limit intake to 3 portions weekly, equivalent to 340-510 grams. Limit processed meat as much as possible if eaten. Meat is valuable but not necessary for health; legume and grain mixtures can supply sufficient protein.

AHA recommends lean portions no larger than 170 gr "occasionally."

Not everyone agrees red meat must be avoided or limited. Another article states that excessive focus on restricting red meatmay lead people to less nutritious foods such as processed junk food.

Summary

Linking one food or group with health problems is difficult because genetics, environment, health history, stress, sleep, lifestyle and other dietary factors affect disease development.

Nevertheless, evidence grows that high red meat intake, particularly processed meat, may cause health problems.

Major organizations such as IACR and AHA recommend more plants and less meat to fight disease.

People may therefore reduce red and processed meat and focus on fruit and vegetables. Remember that replacing red meat with processed low-quality carbohydrates may worsen insulin sensitivity, triglycerides and overall health.