Protein and Amino Acids
Leo Galland, M.D., F.A.C.P., F.A.C.N. Foundation for Integrated Medicine
How much protein does a person really need? Does the source of protein matter?
__________________________________ “Few issues in nutritional science have aroused such long-standing and deep-seated controversies as protein and amino acid requirements.” Millward, J Nutr 1997
The Elements of Life
Carbon Oxygen Hydrogen Nitrogen Sulfur Phosphorus
“Minerals”: Ca, Mg, Na, K, Fe, Zn, Cu, Se, Mn, Cr, Mo, Vn, Ni...
Essential Amino Acids
Isoleucine Leucine Lysine Methionine* Phenylalanine* Threonine Tryptophan Valine Arginine* Histidine
Major Non-essential Amino Acids
Alanine Asparagine Aspartate Cysteine Glutamate Glutamine Glycine Proline Serine Tyrosine
The Fate of Dietary Protein
Digestion and absorption (efficiency varies by 25%, depending upon protein source) Maintenance of body protein stores Net protein synthesis (less than 10% of minimum requirements, even in children) Synthesis of non-protein compounds Oxidative deamination
Essential Non-Protein Nitrogen-Requiring Processes
Nucleic acid synthesis, including adenosine for ATP (glutamate, aspartate, glycine, glutamine) Nervous system: Neurotransmitter/neuropeptide synthesis (phenylalanine, tryptophan, glutamate….) Immune system: Cytokine production,Anti-oxidant protection (taurine; glutathione: cysteine, glutamate, glycine) Skeletal muscle: Creatine (methionine, arginine, glycine) Cardiovascular system: Nitric oxide synthesis (arginine) GI tract: Mucin secretion (threonine, cysteine, serine, proline)
How dietary protein is recorded:
body weight [800-1500]
of kcalories consumed [10-20]
Minimum Protein Requirements
Obligatory Nitrogen Loss (metabolic ward) 36 mg/kg/day urinary (85%) 12 mg/kg.day fecal (13%) 8 mg/kg/day sweat, skin, saliva, hair (2%) 54 mg of nitrogen/kg/day total Replacement requires 340 mg protein/kg/day
70 kg person: 24 gm/day
WHO safe minimum: 750 mg/kg/day, of which 84 mg/kg should be essential amino acids
70 kg person = 52 gm/day 60 kg person = 46 gm/day
Minimum Safe Protein Requirements for Children
Newborns 1.85 mg/kg/day Infants: 1.5-1.65 gm/kg/day Toddlers: 1.1-1.2 mg/kg/day School children: 1.0 mg/kg/day Adolescents 0.9-0.95 mg/kg/day N-balance depends upon caloric intake. Fewer calories increase protein needs. Profound interindividual differences
US Adult Protein RDA's
female Calories 1900-2200 2300-2900 Protein
46 gm 71 gm about 10% of calories typical US diet: 15% of calories popular weight loss diets: 30% of calories excess protein is oxidized by deamination
Ketogenic Amino Acids
Exclusively ketogenic: Leucine Lysine Ketogenic and glucogenic: Threonine Isoleucine Phenylalanine Tyrosine Tryptophan
Compared to typical U.S. diet:
high dietary protein (19-35% of calories) relatively low level of dietary carbohydrate (2240% of calories) variable fat intake (28-58% of calories)
The paradoxical nature of hunter-gatherer diets: meat-based, yet non-atherogenic L Cordain, S B Eaton, et al Eur J Clin Nutr 2002; 56,
Suppl 1, S42-S52
13 known quantitative dietary studies of HG demonstrate that animal food provided the dominant (65%) energy source, while gathered plant foods comprised the remainder (35%). Comprehensive review of 229 HG societies: mean subsistence dependence upon gathered plant foods was 32%, whereas it was 68% for animal foods.
Changes in nutritional status and patterns of morbidity among freeliving elderly persons: a 10-year study. Vellas et al, Nutr 1997; 13 :515-9
304 healthy French elderly (median age 72 in 1980): 97 (34.2%) remained healthy;74 (26.5%) became frail or sick; 54 (19.1%) died, 57 (20.1%) dropped out. Median protein intake was 0.8-1.2 g/kg of body weight in 1980-81. Protein intake 1.20-1.76 g/kg associated with fewer health problems over the next 10 years vs protein intakes < 0.8 g/kg
High-protein low fat diets are effective for weight loss and favorably affect biomarkers in healthy adults. Johnson et al. J Nutr 2003; 134: 586-91. 2003;
20 adults, low fat (<30% kcal) diets, consuming either 10% or 30% protein Weight loss (-6% over 6 weeks) and fat loss (-9 to -11%) not affected by protein Cholesterol (-10 to -12%), insulin (-25%), uric acid (-22 to -30%) similar changes Hunger and satiety better with high protein Ca-balance unaffected, N-balance better
A Reduced Ratio of Dietary Carbohydrate to Protein Improves Body Composition and Blood Lipid Profiles during Weight Loss in Adult Women. Layman DK. J.Nutr. 2003; 133:411-417
24 women age 45 to 56, BMI >26 kg/m2 Isocaloric, matched-fat diets, 68 vs 125 g protein/day for 10 weeks. HP loss of fat/lean (6.3 ± 1.2 g/g) vs LP (3.8 ± 0.9). Cholesterol down 10 for both, TGs down only for HP (21%) LP had higher insulin responses to meals and postprandial hypoglycemia HP reported greater satiety. Increasing the proportion of protein to CHO in the diet of adult women has positive effects on body composition, blood lipids, glucose homeostasis and satiety during weight loss.
Randomized trial on protein vs carbohydrate in ad libitum fat reduced diet for the treatment of obesity. Skov et al. Int J Obes 1999; 50:418-30
50 subjects, protein of 12% vs 25% of kcal, mean BMI of 30.8 and 30.0. 27 week weight loss: high protein 8.9 kg, high CHO 5.1 kg 27 week fat loss: high protein 7.6 kg, high CHO 4.3 kg (84-85% of total weight loss) Kcal consumed: 2139 high protein vs 2605 high CHO.
Dietary protein and risk of ischemic heart disease in women. Hu et al, Amer J Clin Nutr, 1999. 70: 221-7
80,082 women aged 34–59 y Median protein 14.7% of kcal to 24.0% of kcal by quintile. Higher protein associated with less tobacco and alcohol use, more exercise and multivitamin and vit E supplements, more fat, saturated fat, cholesterol, folate, meat, dark bread, fruits and vegetables, and less carbohydrate (white bread, potatoes, sweets and desserts.) High protein intakes reduced risk of ischemic heart disease: RR 0.74 (95%). Both animal and vegetable protein contributed to the lower risk, but most of the protein came from animal sources. This inverse association was similar in women with low- or high-fat diets. Conclusion: Increased dietary protein does not increase and may reduce risk of ischemic heart disease.
Short-term effects of substituting protein for carbohydrate in the diets of moderately hypercholesterolemic human subjects. Wolfe BM, Giovannetti PM. Metabolism 1991 Apr;40(4):338-43.
Hypercholesterolemic human subjects (four men, six women) Diets: 23% v 11% of energy as protein, 24% as fat, 53% v 65% as carbohydrate. Isocaloric substitution of protein for CHO during low fat diet High protein: HDL-C higher by 12% (p<.01), total cholesterol (TC) lower by 6.5% (p< .001), LDL-C lower by 6.4% (p<.02), TG lower by 23% (p<.02). LDL-C/HDL-C lower by 17% (p<.001).
Cardiovascular Disease and Diabetes: Inverse relationship between urinary markers of animal protein intake and blood pressure in Chinese: results from the WHO Cardiovascular Diseases and Alimentary Comparison (CARDIAC) Study. Liua L et al, Int J Epidemiology 2002;31:227-233
Urinary 3-methylhistidine (3MH) excretion (a biological marker of animal protein intake) and BP in 11 Chinese population samples 3MH and 3MH/creatinine were inversely associated with BP and hypertension, even after adjustment for age, sex,
Na/K ratio, BMI, calcium and magnesium. “The results provide strong evidence that animal protein intake is associated inversely with BP in Chinese
Impact of diet on blood pressure and age-related changes in blood pressure in the US population. Hajjar et al. Arch Intern Med. 2001;161:589-93.
All individuals >20 yrs old (n = 17,030) surveyed in NHANES III Systolic BP and pulse pressure positively associated with higher Na, alcohol, and protein intakes (P<.05) Age-related increase in systolic BP was attenuated by higher Ca and protein intakes.
An increase in dietary protein improves blood glucose response in persons with type 2 diabetes. Gannon et al. Am J Clin Nutr 78: 734-41.
10 men, 2 women, age 39-72, BMI 22-37 2250 kcal: 55% CHO, 15 % protein, 30% fat vs 40% CHO, 30% protein, 30% fat Glycemic response to high protein diet (AUC) was 40% lower. Glycated Hb decreased 0.8% at 30% protein vs 0.3% (p<.05) over 5 weeks.
Meat and dairy food consumption and breast cancer: a pooled analysis of cohort studies. Missmera et al. Int J Epidemiol 2002;31:78-85
Eight prospective cohort studies: 351 041 women, 7379 diagnosed with invasive breast cancer during 15 years of follow-up. No significant association between intakes of total meat, red meat, white meat, total dairy fluids, or total dairy solids and breast cancer risk. J-shaped association for egg consumption where, compared to women who did not eat eggs, breast cancer risk was slightly decreased among women who consumed <2 eggs per week but slightly increased among women who consumed 1 egg per day.
Dietary factors and the survival of women with breast carcinoma. Holmes MD, et al. Cancer 1999;86:826-35
1,982 female registered nurses with breast cancer diagnosed between 1976-1990 who completed a food frequency questionnaire. The main outcome measure was time to death from any cause. The relative risk (95% confidence interval) of mortality comparing highest with lowest quintile of protein intake was 0.65 (0.47-0.88).
Meat, cancer and dietary advice to the public. Hill, Eur J Clin Nutr 2002;56 Suppl 1:S36-41
Epidemiological data are consistent with a protective role for fruit, vegetables and whole grain cereals in colon cancer with no role for meat consumption as a risk factor. Meat may play a protective role in gastric cancer. Data from Europe are not consistent with those from the US because of the different contexts (meal composition) within which meat is consumed in different countries
Meat consumption and colorectal cancer: a review of epidemiologic evidence. Noral & Riboli, Nutrition Reviews 2001;59: 37-47
Review of 36 studies, most show no significant effect for any kind of meat Relative risk ranged from 0.41-2.87 Studies with significant adverse association: RR 1.33-2.87 for total meat in 5/32 studies RR 1.04-2.35 for red meat in 8/26 studies RR 1.18-2.87 for processed meat in 13/32 studies
Protein consumption and bone mineral density in the elderly : the Rancho Bernardo Study. Promislow et al. Am J Epidemiol 2002;155:636-44
572 women and 388 men aged 55-92 years. Positive association between animal protein consumption, assessed by FFQs in 1988-1992, and BMD measured 4 years later. Negative association between vegetable protein and BMD was observed in both sexes. Increasing protein consumption appearing to be more beneficial for women with lower calcium intakes, but evidence for this interaction was not consistently strong.
Effect of Protein Intake on Bone Mineralization during Weight Loss: A 6-Month Trial. Skov et al. Obesity Research 10:432-8 (2002)
65 overweight adults, 6-month of high protein (HP: 107.8 g/d)vs low protein (LP: 70.4 g/d) matched fat diets. BMC loss, adjusted for differences in fat loss, was greater in the LP group than in the HP group [difference in LP vs. HP, 44.8 g (95% confidence interval, 16 to 73.8 g); p < 0.05]. Independent of change in body weight and composition during the intervention, high protein intake was associated with a diminished loss of BMC (p < 0.01).
Protein supplements increase serum IGF-1 levels and attenuate proximal femur bone loss in patients with recent hip fracture. Schurch et al. Ann Int med 1998; 128: 801-9.
82 patients, mean age 80 years, mean dietary protein 45-51 g/day, recent femoral fracture, vit D3 200,000 IU given Supplement: 250 kcal, 20 g protein/35 gm CHO/3 g fat vs 54 g CHO, Ca/Mg/P/A/K1 Protein improved femoral healing at 1 y, increased IGF-1 and pre-albumen
A high dairy protein, high-calcium diet minimizes bone turnover in overweight adults during weight loss. Bowen et al. J Nutr 2004; 134: 568-573
60 subjects (BMI 27-40) lost mean of 9.7 kg over 12 weeks on diets of 34% protein, 41% CHO, 24% fat Diet 1: dairy-based, 2400 mg Ca/day. Diet 2, meat-based: 500 mg Ca/day Bone resorption markers increased more with meat-based diet and osteocalcin increased only with meat-based diet
Meta-analysis of the effects of soy protein intake on serum lipids. Anderson et al NEJM. 1995;333:276-82
Meta-analysis of 38 controlled clinical trials Soy protein intake averaged 47 g/day. Compared with animal protein, soy effect:
Total-C decreased 23.2 mg/dl (9.3%, p<.05) LDL-C decreased 21.7 mg/dl (12.9 %, p<.05) TG decreased 13.3 mg/dl (10.5 %, p<0.05) HDL-C increased 2.4% (NS). TC and LDL-C Changes directly related to the initial serum cholesterol (P < 0.001)
A Dietary Portfolio Approach to Cholesterol Reduction. Jenkins et al. Metabolism 2002; 51: 1596-1604
7 men, 6 women age 43-84, BMI 21-31, on diets low in saturated fat and cholesterol Per 1000 kcal: Soy protein 22.7 g Viscous fiber 8.2 g (oats, barley, psyllium, okra, eggplant) Plant sterols 1 g (margarine) Raw unblanched almonds 2.9 g LDL-C decreased 29% (p<.001), LDL/HDL decreased 26.5% (p<.001)
Legume consumption and risk of coronary heart disease in US men and women. Bazzano et al. Arch Intern Med. 2001;161:2573-8
9632 men and women who participated in NHANES 1 and were free of CVD Frequency of legume intake was estimated using a 3-month food frequency questionnaire, 19 years of follow-up, 1802 incident cases of CHD and 3680 incident cases of CVD were documented. Legume consumption was significantly and inversely associated with risk of CHD (P =.002 for trend) and CVD (P =.02 for trend) after adjustment for established CVD risk factors. Legume consumption 4 times or more per week compared with less than once a week was associated with a 22% lower risk of CHD (relative risk, 0.78; 95% confidence interval, 0.68-0.90) and an 11% lower risk of CVD (relative risk, 0.89; 95% confidence interval, 0.80-0.98).
The Impact of protein on renal function decline in women with normal renal function or mild renal insufficiency. Knight et al, Ann Int med 2003; 138: 460-7
1624 nurses age 42-68, followed for 11 years, protein intake measured by FFQ (mean 76 g/d) GFR estimated from serum creatinine, age, height, weight by 2 formulas No effect of protein on GFR in women with baseline GFR>80 ml/min/1.73 m-squared. Initial GFR of 55-80 ml/min (S-creatinine .771.1mg/dl, mean .88) showed a decline in GFR of 7.72 ml/min/10 g increase in protein. Meat protein>dairy protein. No effect of vegetable protein.
Purine-Rich foods, Dairy and Protein Intake, and the Risk of Gout in Men. Choi et al, NEJM 2004; 350: 1093-1103
47,150 men followed for 12 years Incidence of gout increased with increasing intake of protein from meat or seafood and decreased with increasing intake of dairy protein. No effect of total protein Relative risk: 1.41 for 2.5 vs 0.5 meat servings/day 1.51 for 0.8 vs 0.04 seafood servings/day 0.56 for 4.2 vs 0.5 dairy servings/day
Protein Consumption May Affect Mineral Bioavailability
High meat diets increase zinc bioavailability in elderly women (Hunt et al, Am J Clin Nutr 1995; 62: 621-32) and iron and zinc utilization in young women, with no effect above 3 oz lean beef/d. (Johnson & Walker, J Am
Diet Assoc 1992; 92: 1474-8).
Replacement of 25% meat protein by soy protein decreased zinc absorption and protein digestibility
(Sandstrom et al, J Nutr 1986; 116: 2209-18)
Large Neutral Amino Acids Share Common Transporters
The ratio of tryptophan to leucine, isoleucine, valine, phenylalanine and tyrosine (5LNAA) influences brain serotonin concentration Exercise and CHO loading raise this ratio High protein diets lower this ratio
Control of brain serotonin by the diet. Wurtman RJ, Fernstrom JD. Adv Neurol 1974;5:19-29
Implications of Competitive Transport of LNAA into Brain
Tryptophan/5LNAA is lower in major depression, correlates with severity of depression and with plasma cortisol level following dexamethasone suppression. Tryptophan/5LNAA is higher after strenuous exercise and in patients with fibromyalgia, correlates with intensity of post-exertional fatigue, reversible with BCAA feeding
References on LNAA Transport
Decreased plasma tryptophan concentration in major depression: relationship to melancholia and weight loss. Anderson IM, et al. J Affect Disord 1990;20:185-91 Relationship between the dexamethasone suppression test and the Ltryptophan/competing amino acids ratio in depression. Maes M, et al. Psychiatry Res 1987;21:323-35 Plasma tryptophan and five other amino acids in depressed and normal subjects. DeMyer MK, et al Arch Gen Psychiatry 1981;38:642-6
Serotonergic markers and lowered plasma branched-chain-amino acid concentrations in fibromyalgia. Maes M, et al Psychiatry Res 2000; 4;97:11-20. Amino acids and central fatigue. Blomstrand E. Amino Acids 2001;20(1):25-34
Glutathione (GSH) Levels Depend Upon Dietary Sulfur Amino Acids
GSH/GSSG is the major human redox pair Malnutrition, fasting and alcoholism deplete hepatic and WBC GSH levels Depletion of GSH impairs immune function and detoxification of substrates like acetaminophen Loading with sulfur AA reverses these effects
High protein intake (up 30% of kcal) is not detrimental and may produce improved health outcomes. Dairy and vegetable protein may have different effects than meat protein. Elderly patients often consume too little protein and should be encouraged to increase intake to >1 gm/kg/day (pulse feeding of 0.8 g/kg at one meal may work best: Arnal et al, Am J Clin Nutr 1999; 69: 1202-8)