Risks incurred by consuming meat
Source: www.fleisch-macht-krank.de
In industrial countries, life-style diseases such as obesity, diabetes, high cholesterol, high blood pressure, heart disease, and cancers are widespread. There is an abundance of epidemiologic data showing that a vegetarian diet is associated with a lower risk for these diseases.
Nevertheless, meat, sausages and fish are still considered to be a part of the normal diet. The myth that these are especially healthy and valuable foodstuffs is still widespread. Many members of the medical profession also still believe that meat is a vital force in your diet.
In modern epidemiological models, the public health risk of different diets is classified differently to those of a few centuries ago. A low intake of vegetable foodstuffs is now considered a risk factor for phytochemical deficiency diseases, including many tumor diseases, cardiovascular disease and degenerative diseases.
The following presents factual data demonstrating that meat consumption is connected with considerable health risks. This information is based on scientific publications available in the Medline database, either as abstracts or original works.
Bone diseases
Meat products contain on average more phosphorus than calcium, as opposed to vegetable food. A raised dietary phosphorus/calcium ratio leads to secondary hyperparathyroidism. (1)
Parathormone from the parathyroid gland leads to a mobilisation of calcium from the bones. Adolescents are at particular risk for this, as insufficient bone mass in puberty is a risk factor for osteoporosis in later life. A study of young women showed a negative correlation between protein and phosphorus intake and radial bone thickness. (2)
Animal proteins contain more sulfurous amino acids than vegetable proteins. Protons resulting from the degradation of sulfurous amino acids are a major source of acid. A continuous excess of acid promotes the demineralization of the bones, since H+ ions bind to phosphate ions during formation of hydrogen phosphate.
In 2001 several studies were published on “acid-base metabolism” and bone metabolism (3, 4, 5).
A Swiss research group at the University of Lausanne showed that an acid forming diet increased the excretion of calcium by 74 %, compared with an alkaline forming diet.
In a study of osteoporotic fractures, a research group from the University of California published results showing that the risk of a hip fracture in post-menopausal women essentially depends on the composition of their diet. Older women with a high intake of animal, rather than vegetable, proteins ran a significantly higher risk for hip fractures than people in a control group. The incidence of hip fractures in individual countries correlates with the ratio of animal to vegetable protein in the daily diet. These researchers concluded that a low-grade metabolic alkalose is probably the optimum acid-base status.
The Framingham Osteoporosis Study also showed that a high consumption of fruit and vegetable had a protective effect on bone structure (6).
Rheumatic diseases
All animal products, especially meat, sausages and fish, contain abundant arachidonic acid. Prostaglandins and leukotriens belong to the metabolites of arachidonic acid. An increase in prostaglandin E can be detected in the synovial fluid of people who suffer from rheumatism. It also contributes to the development of cartilage erosion (7).
The more arachidonic acid is ingested in the diet, the more inflammatory substances can be produced. There are several publications on the anti-inflammatory and analgetic effect of a vegetarian diet on rheumatism (8, 9).
A vegan diet is evidently particularly effective here since no arachidonic acid is ingested.
Tumor diseases
Frying, boiling and grilling of meat and fish produces heterocyclic amines. These substances result from a chemical reaction between the amino acids and the creatine of the muscular substance. Several studies have shown that heterocyclic amines have considerable genotoxic and mutagenic potential (10, 11).
Heterocyclic amines are a risk factor for several tumor types, in particular for colon carcinoma. Cancers of the stomach, esophagus, prostate, pancreas, kidney and breast have also been associated with heterocyclic amines within the medical literature (12).
Uruguay and Argentine belong to the countries with the highest consumption of beef and suffer also from the highest rates of cancer of the breast and of the colon. Some studies also report a cardio toxic effect of heterocyclic amines (13, 14, 15).
In addition to heterocyclic amines other carcinogenic substance are produced in the intestine during the digestion of meat. A study by the University of Hohenheim found that a diet high in fat and meat increases the toxicity of fecal water to the intestinal epithelia (16).
Protein degradation by flora within the colon also produces potentially toxic substances, including ammonia, phenols, indols, and amines, as well as N nitroso compounds and sulfide (17).
A study at the University of Cambridge demonstrated a close correlation between the formation of N nitroso compounds and the amount of red meat consumed (18).
Epidemiological studies have demonstrated a correlation between the consumption of red meat and the incidence of colorectal carcinoma. Meat protein also constitutes a significant substrate for bacterial production of sulfide in the intestines. Sulfide compounds also contribute to the development of colitis (19).
Increased concentrations of the insulin-like growth factor I (IGF-1) promote the development of tumor diseases. In 2002 a study of the University of Oxford was published on the IGF concentrations in different diet types. Vegans had significantly lower IGF-1 concentrations than meat-eaters and lacto-ovo vegetarians. In addition, the concentrations of IGF binding proteins (IGFBP-1 and IGFBP-2) were increased in this group. (20).
Hypercholesterinemia
Since vegetable foodstuffs are nearly cholesterol free, the intake of cholesterol via nutrition results from the consumption of animal foodstuffs.
Endogenous cholesterol production is regulated via the insulin/glucagon ratio. Test persons with increased cholesterol concentrations were also shown to have a higher insulin/glucagon ratio than test persons with normal cholesterol values (21).
The composition of dietary proteins influences the release of the metabolism hormones insulin and glucagon. Animal proteins stimulate the release of insulin and activate HMG-CoA reductase, the limiting enzyme for cholesterol synthesis.
Vegetable proteins usually contain more arginine than lysine. Animal proteins on the other hand contain more lysine and leucine than vegetable proteins. A cholesterol-lowering effect, especially of soy protein, was demonstrated in several studies, which was mainly attributed to the high arginine concentration of this vegetable protein (22, 23, 24).
A high intake of lysine in form of animal proteins increases the incorporation of arginine into atherogenic apoproteins, such Apo E. These proteins are transport molecules for fats such as cholesterol. Some studies report a report a more favorable HDL/LDL ratio in vegetarians (25, 26, 27).
The LDL cholesterol of vegetarians has proved less susceptible to oxidization than that of non-vegetarians. This is attributed to the high intake of antioxidant substances by vegetarians.
Diabetes mellitus
The fatty acid pattern of cell membranes, which is essentially influenced by the dietary intake of fatty acids, exerts a considerable effect on the sensitivity of insulin receptors.
Meat and sausages contain a relatively high number of saturated fatty acids. Several studies have shown that a high intake of saturated fatty acids reduces insulin sensitivity and promotes insulin resistance (29-32).
The Western diet with its high intake of fat and saturated fatty acids is a considerable risk factor for insulin resistance and type 2 diabetes. It is well-known that insulin resistance leads to hyperinsulinism. Chronically raised insulin levels are a risk factor for cardiovascular disease and for various kinds of tumors.
The adherents of the Atkins diet (plenty of meat and fat) claim that the advantages of this diet are due to a diminished insulin response which facilitates weight reduction. In fact, food rich in protein leads to an above-average insulin response surpassing its glycemic index (33).
Iron and oxidative stress
Iron is one of the essential trace elements. About 70% is contained in the blood pigment hemoglobin and in the muscle pigment myoglobin. Many significant metabolism enzymes are iron dependent, which is why a lack of iron should be prevented.
In 1992 a connection between increased iron reserves and a 2.2 fold increased risk for cardiac infarction was first described. This finding has been confirmed by other studies (34, 35).
Heme iron from red meat is resorbed ten times as well as iron of vegetable origin. There is a positive connection between the risk for cardiac infarction and the intake of heme iron. Excess iron forms free radicals and damages LDL via oxidative stress. Oxidative damage to LDL, on the other hand, is the most important pathogenetic principle for the formation of foam cells and atherosclerotic plaques.
A well-balanced vegetarian diet does not lead to a lack of iron. Vegetarians, as a rule, have lower iron reserves, which according to a recent study results in a higher insulin sensitivity (36).
Psyche and cortisol level
A diet rich in protein leads to a rise in cortisol in the saliva and in the blood serum. A diet rich in carbohydrates does not have this effect (37, 38, 39).
Hypercortisolism not only has an immune suppressive effect but can also over time damage hippocampal cells which are important for memory formation and for learning behavior (40).
A diet with a greater emphasis on carbohydrates has a favorable effect on the formation of serotonin in the brain. A sufficient supply of serotonin improves mental health.
BSE and immune reactions
Just two years ago the »BSE« issue caused considerable agitation among the public. BSE has disappeared from the headlines since so-called risk material now has to be removed during slaughtering and BSE tests are compulsory by law. To date, the meat (i.e. muscle) of slaughtered cattle has been classified as not harmful to health.
This supposition must be questioned since the finding of the Nobel Prize winner Stanley Prusiner that considerable amounts of prions are present in the muscular system of infected mice. In March 2002 there was a startling publication on this issue in one of the most renowned scientific journals, the »Proceedings of the National Academy of Sciences« (41).
At the 7th Congress on Infectious Diseases and Tropical Medicine, the Berlin Robert Koch Institute presented a study on golden hamsters. The prion agent causing scrapie added to the hamster’s food was found in concentrated amounts in all muscle tissues examined (42).
In January 23, 2003, the news programme »Monitor« broadcast an interview with the Munich neuropathologist Prof. Hans Kretschmar who had repeated the tests of the Californian scientists on mice and also found prions in muscle meat. Prof. Kretschmar called these findings quite worrying, since an infection via muscle meat could not be excluded (43).
As a consequence of the first known case of BSE in the USA several scientific articles were published on December 23, 2003 questioning what we know of this disease. United Press International (UPI) published a long article on Creutzfeld-Jakob disease (CJD) on December 29, 2003. Up until then, the classical form of CJD had been assumed to be unconnected with BSE. Only the so-called variant form of this disease affecting younger people had been connected with infected beef consumption.
New research at the University of London has found that an infection with BSE prions can cause the variant, as well as the classical, form of CJD. In Switzerland numerous cattle have been BSE-infected in the past. The incidence rate of CJD cases has doubled in the last three years. CJD, like Alzheimer’s disease, is among the neurodegenerative diseases which often cannot be clearly distinguished on the basis of the clinical picture. Neuropathologists at several universities in the USA conducted autopsy studies on people who had been diagnosed by specialists during life as having Alzheimer’s disease. What makes these results so alarming is that 3 to 13% of these cases were found to have not Alzheimer’s disease, but Creutzfeld-Jacob disease.
In the USA the number of people dying of Alzheimer’s disease increased 50-fold from 1979 to 2000. In 2000, these amounted to no less than 50,000 people. At present the number of people suffering from Alzheimer’s disease in the USA is estimated at approximately 4 million. Realistically one has to assume that the number of unknown cases of CJD is high (44).
On October 1, 2003 an interesting study by scientists of the University of California was published in PNAS-online. The American scientists had found out that after red meat consumption the human metabolism incorporates certain sugar compounds denominated as N-glycolylneuraminic acid (Neu5Gc) into various tissues. Neu5Gc antibodies were identified in various subjects. This provided the first proof that molecules from the ingestion of meat can generate an immune response in the human metabolism. Regular ingestion of meat promotes detrimental immune responses and can make the body more susceptible to inflammation, with all the secondary diseases that ensue (45).
Environmental toxins
About 90 % of all dioxins and furans are ingested via the consumption of animal foodstuffs. Approximately half of them come from milk and milk products. The concentration of persistent pollutants increases as they move up the food chain. The final consumer may then ingest toxic amounts of the pollutant.
In almost every food scandal the fact is emphasized that no toxicologically relevant concentrations were measured and therefore there is no danger to the public.
Many environmental toxins are substances that have a hormonal or anti-hormonal effect on organisms (endocrine disruptors). In 2002 two studies of the University of London were published showing that several xenooestrogens combined had a considerable hormonal effect. Each of these substances alone had a concentration below NOEC (No-observed-effect concentration) (46, 47).
References:
(1) Calvo MS et al: Persistently elevated parathyroid hormone secretion and action in young women after four weeks of ingesting high phosphorus, low calcium diets; J Clin Endocrinol Metab 1990 May; 70(5): 1334-40
(2) Metz JA et al: Intakes of calcium, phosphorus, and protein, and physical-activity level are related to radial bone mass in young adult women; Am J Clin Nutr 1993 Oct; 58(4): 537-42
(3) Buclin T et al: Diet acids and alkalis influence calcium retention in bone; Osteoporos Int 2001; 12(6): 493-9
(4) Sellmeyer DE et al: A high ratio of dietary animal to vegetable protein increases the rate of bone loss and the risk of fracture in postmenopausal women. Study of Osteoporotic Fractures Research Group; Am J Clin Nutr 2001 Jan; 73(1): 118-22
(5) Frassetto L et al: Diet, evolution and aging – the pathophysiologic effects of the post-agricultural inversion of the potassium-to-sodium and base-to-chloride ratios in the human diet; Eur J Nutr 2001 Oct; 40(5): 200-13
(6) Tucker KL et al: Bone mineral density and dietary patterns in older adults: the Framingham Osteoporosis Study; Am J Clin Nutr 2002 Jul; 76(1): 245-252
(7) Stanczyk J et al: The role of cyclooxygenase and prostaglandins in the pathogenesis of rheumatoid arthritis; Pol Merkuriusz Lek 2001 Nov; 11(65): 438-43
(8) Muller H et al: Fasting followed by vegetarian diet in patients with rheumatoid arthritis: a systematic review; Scand J Rheumatol 2001; 30(1): 1-10
(9) Huber R et al: Clinical remission of an HLA B27-positive sacroiliitis on vegan diet; Forsch Komplementarmed Klass Naturheilkd 2001 Aug; 8(4): 228-31
(10) Sinha R et al: Dietary intake of heterocyclic amines, meat-derived mutagenic activity, and risk of colorectal adenomas; Cancer Epidemiol Biomarkers Prev 2001 May; 10(5): 559-62
(11) Anderson K et al: Meat intake and cooking techniques: associations with pancreatic cancer; Mutat Res 2002 Sep 30; 506-507(C): 225
(12) Matos E et al: Review on meat consumption and cancer in South America; Mutat Res 2002 Sep 30; 506-507(C): 243
(13) Adamson RH et al: Studies on the carcinogenic and myocardial effects of 2-amino-3methylimidazo (4,5-f) quinoline (IQ) in nonhuman primates; Princess Takamatsu Symp 1995; 23: 260-7
(14) Adamson RH et al: Carcinogens in foods: heterocyclic amines and cancer and heart disease; Adv Exp Med Biol 1995; 369: 211-20
(15) Davis CD et al: Protective effect of N-acetylcysteine against heterocyclic amine-induced cardiotoxicity in cultured myocytes and in rats; Food Chem Toxicol 1995 Aug; 33(8): 641-51
(16) Rieger MA et al: A diet high in fat and meat but low in dietary fibre increases the genotoxic potential of „faecal water“; Carcinogenesis 1999 Dec; 20(12): 2311-6
(17) Hughes R et al: Protein degradation in the large intestine: relevance to colorectal cancer; Curr Issues Intest Microbiol 2000 Sept; 1(2): 51-8
(18) Bingham SA et al: Effect of white versus red meat on endogenous N-nitrosation in the human colon and further evidence of a dose response; J Nutr 2002 Nov; 132(11 Suppl): 3522S-3525S
(19) Magee EA et al: Contribution of dietary protein to sulfide production in the large intestine: an in vitro and a controlled feeding study in humans; Am J Clin Nutr 2000 Dec; 72(6): 1488-94
(20) Allen NE et al: The Associations of Diet with Serum Insulin-like Growth Factor and Ist Main Binding Proteins in 292 Woman Meat-Eaters, Vegetarians, and Vegans; Cancer Epidemiol Biomarkers Prev 2002 Nov; 11(11): 1441-8
(21 Hubbard R et al: Effect of dietary protein on serum insulin and glucagon levels in hyper- and normocholesterolemic men; Atherosclerosis 1989 Mar; 76(1): 55-61
(22) Sanchez A et al: Plasma amino acids and the insulin/ glucagon ratio as an explanation for the dietary protein modulation of atherosclerosis; Med Hypotheses 1991 Aug; 36(4): 324-9
(23) Carroll KK et al: Soy consumption and cholesterol reduction: review of animal and human studies; J Nutr 1995 Mar; 125(3 Suppl): 594S-597S
(24) Wong WW et al: Cholesterol-lowering effect of soy protein in normocholesterolemic and hypercholesterolemic men, Am J Clin Nutr 1998 Dec; 68(6 Suppl): 1385S-1389S
(25) Robinson F et al: Changing from a mixed to self-selcted vegetarian diet-influence on blood lipids; J Hum Nutr Diet 2002 Oct; 15(5): 323-9
(26) Hoffmann I et al: Giessen Wholesome Nutrtion Stuudy: relation between a health-conscious diet and blood lipids; Eur J Clin Nutr 2001 Oct; 55(10): 887-95
(27) Bederova A et al: Comparison of nutrient intake and corresponding biochemica parameters in adolescent vegetarians and non-vegetarians; Cas Lek Cesk 2000 Jul 5; 139(13): 396-400
(28) Nagyova A et al: LDL and HDL oxidation and fatty acid composition in vegetarians; Ann Nutr Metab 2001; 45(4): 148-51
(29) Vessby B: Diatary fat and insulin action in humans; Br J Nutr 2000 mar; 83 Suppl 1:S91-6
(30) Vessby B et al: Substituting dietary saturated for monounsaturated fat impairs insulin sensitivity in healthy men and women: The KANWU Study; Diabetologia 2001 Mar; 44(3): 312-9
(31) Van Dam RM et al: Dietary fat and meat intake in relation to risk of type 2 diabetes in men; Diabetes Care 2002 Mar; 25(3): 417-24
(32) Mann JI: Diet and risk of coronary heart disease and type 2 diabetes; Lancet 2002 Sep 7; 360(9335): 783-9
(33) Holt SH et al: An insulin index of foods: the insulin dmand generated by 1000-kJ portions of common foods; Am J Clin Nutr 1997 Nov; 66(5): 1264-76
(34) Tanaka T et al: Vegetarian diet ameliorates symptoms of atopic dermatits through reduction of the number of peripheral eosinophils and PGE2 synthesis by monocytes; J Physiol Anthropol Appl Human Sci 2001 Oct; 20(6): 353-61
(35) Klipstein-Grobusch K et al: Dietary iron and risk of myocardial infarction in the Rotterdam Sudy; Am J Epidemiol 1999 Mar 1; 149(5): 421-8
(36) Hua NW et al: Low iron status and enhanced insulin sensitivity in lacto-ovo vegetarians; Br J Nutr 2001 Oct; 86(4): 515-9
(37) Slag MF et al: Meal stimulation of cortisol secretion: a protein induced effect; Metabolism 1981 Nov; 30(11): 1104-8
(38) Ishizuka B et al: Pituitary hormone release in response to food ingestion: evidence for neuroendocrine signals from gut to brain; J Clin Endocrinol Metab 1983 Dec; 57(5): 1111-6
(39) Anderson KE et al: Diet-hormone interactions: protein/ carbohydrate ratio alters reciprocally the plasma levels of testosterone and cortisol and their respective binding globulins in man; Live sci 1987 May 4; 40(18): 1761-8
(40) Kirschbaum C et al: Stress and treatment-induces elevations of cortisol levels associated with impaired declarative memory in healthy adults; Live Sci 1996; 58(17): 1475-83
(41) Bosque Patrick J et al: Prions in skeletal muscle; Proc Natl Acad Sci USA, 2002 Mar 19, Vol 99, Issue 6, 3812-3817
(42) FAZ.NET, 8. April 2003
(43) WDR Monitor, 23.01.2003
(44) Mad Cow: Linked to thousands of CJD cases? By Steve Mitchell, United Press International, Published 12/29/2003
(45) Proc.Natl. Acad. Sci. USA, 10.1073/pnas.2131556100
(46) Silva E et al: Something from „nothing“—eigtht weak estrogenic chemicals combined at concentrations below NOECs produce significant micture effects; Environ Sce Technol 2002 Apr 15; 36(8): 1751-6
(47) Rajapakse N et al: Combining xenoestrogens at levels below individual no-observed-effect concentrations dramatically enhances steroid hormone action; Environ Health Perspect 2002 sep; 110(9): 917-21
