most of our health burden from diet in terms of excess mortality and disability is due to:
high salt intake
low wholegrain intake
low fruit intake
the red meat conundrum
intake of unprocessed red meat or processed red meat has been associated with increased cardiovascular and cancer mortality, although studies give different results, especially for different ethnicities and for gender and causality has not be proven 1), 2)
proposed mechanisms of causality include:
red meat is rich in saturated fatty acids, which have been associated with dyslipidemia, particularly elevated low-density lipoprotein (LDL)
red meat intake has been associated with increased levels of inflammatory and oxidative stress markers such as C-reactive protein (CRP) and gamma-glutamyl transferase (GGT) and chronic inflammation may be a causal agent in atherosclerosis and colorectal cancers (perhaps 6% risk instead of 5%) - this may be due to low grade tick-induced mammalian red meat allergy (MMA)
Heme iron in red and processed red meats has been associated with higher risk of type 2 diabetes and cardiovascular diseases
red meat is rich in L-carnitine, and recent research found that L-carnitine metabolism by intestinal microbiota elevates the level of a metabolite known as trimethylamine-N-oxide (TMAO), which was linked with a higher risk of cardiovascular diseases, particularly atherosclerosis
large amounts of sodium are used in some meat processing; high intakes of sodium are associated with elevated blood pressure
processed meats are often high in nitrates which are converted to potentially carcinogenic nitrosamines in the stomach
there is also the environmental sustainability argument against eating red meat3)
beef cattle contribute to high levels of greenhouse gas production (perhaps around 2-3% of emissions) however, lettuce has 3x the GHG emissions of bacon, and fruit has the largest water and energy footprint per calorie.
red meat is not a sustainable diet for the increasingly economically rich and highly populated developing world, although cattle may be able to create a protein source from farming lands not suitable for cropping and they can graze cropping residues, whiled insecticides and herbicides used in cropping may be causing far more harm than good to our environment and ecologic systems
there are also arguments against a vegetarian diet such as:
the studies of vegetarians vs meat eaters often do not allow for the general non-dietary healthy life choices of many vegetarians such as exercise, yoga, etc.
vegetarian diets are associated with poorer protein intake (hence poorer muscle bulk and higher risk of frailty), iron deficiency and B12 deficiency anaemia, poorer health (higher incidences of cancer, allergies, and mental health disorders), a higher need for health care, and poorer quality of life.
if one also cannot have dairy, then there is a major risk of calcium and vitamin D deficiencies and oesteoporosis unless supplements are taken
in evolutionary terms, we are omnivores, our bodies were meant to digest animal fats and proteins, and we naturally produce acids and bile to break down protein quite easily. Protein provides the building blocks of our bodies, and animal sources are the most complete protein sources because they contain all of the amino acids we need for optimal health.
heme iron in steak is the best, most bioavailable source of iron, and a small 4oz serving of beef contains 95% of the DRI for B12, something you can’t get from plants
B12 deficiency can cause permanent neurologic damage to developing infants and is most common in vegetarians and vegans.
To get the same amount of protein in a 4oz steak (181 calories, 0 carbs, 4.5g fat) you’d need to eat 12 oz of kidney beans plus a cup of rice, which equals 638 calories, and 122g of carbs and 0.6g fat. To get the 30g of protein from almonds, you would need to consume a little over 1 cup of chopped almonds, which is over 850 calories and 75g of fat - perhaps not an ideal solution in an increasingly bariatric world - protein and fat intake are probably the main dietary components that cause satiation.
most of the increase in caloric intake from 1970 to 2014 has been due to intake of over-processed grains, caloric sweeteners, salads and cooking oils, and poultry while that from red meat has fallen 30%