The short answer; plant protein. Why? Simply because we are more likely to suffer from protein excess than protein deficiency.
And the adverse effects associated with long term high protein diets from animal origin, and not plant origin, may include disorders of bone and calcium balance, disorders of kidney function, increased cancer risk, disorders of the liver, and worsening of coronary arteries. Therefore, there is currently more than enough reasonable scientific basis to believe that plant protein is better than animal protein, and not to recommend protein consumption above the current recommended daily allowance, due to its potential disease risks (1).
See below some nutrient differences between beans and beef;
Yes indeed, they both have the same amount of protein. However, beans bring along the reward of phytonutrients and lots of fibre, both key nutrients for good health. Whereas beef has none of them, and comes with the baggage of cholesterol, saturated fat, trans fats, endotoxins, and if it’s not organic; added growth hormones and antibiotics. Meat, when cooked, especially at high temperatures (barbecued, roasted, grilled, deep fried…) releases Advanced Glycation End Products or AGEs, causing inflammation and oxidative stress in our bodies, which accelerates ageing and promotes illness (2). Muscle meat, when cooked, produces Heterocyclic Amines, which have been linked in numerous studies to cancer promotion, according to the National Cancer Institute (3).
Processed meat was also classified in 2015 by The World Health Organisation as type 1 carcinogen (causes cancer) at the same level of tobacco smoking and plutonium, and read meat as a type 2A (probably causes cancer) (4).
There are several studies that link, not just processed or red meat but also, all type of animal products to cancer. Which we’ll see next…
1-I Delimaris. Adverse Effects Associated with Protein Intake above the Recommended Dietary Allowance for Adults. ISRN Nutr. 2013 Jul 18;2013:126929.
2-Semba RD, Nicklett EJ, Ferrucci L. Does accumulation of advanced glycation end products contribute to the aging phenotype? J Gerontol A Biol Sci Med Sci. 2010 Sep;65(9):963-75. Epub 2010 May 17.