Protein Basics • Proteins are molecules have many enzymatic and structural functions related to the growth, maintenance and repair. • The goal of dietary protein intake is to contribute the amino acids necessary to assimilate proteins for skeletal structures and hormones, function as cell membrane receptors and maintain fluid balance.
H O H2N - C - C OH Amine R carboxyl • Protein needs are estimated by measuring nitrogen balance... • Nitrogen balance= • in (protein intake) – out (sweat, urine and feces) Protein Turnover 200g-400g daily Protein Degradation: catabolism Protein Synthesis: anabolism These two mechanisms employ different pathways. Both pathways are always “on”. Nitrogen balance reflects the net protein degradation or synthesis at the whole body level.
Protein Synthesis • For athletes in training their goal is to maintain or increase lean body mass (FFM) • An increase in muscle size and thus mass is caused by an increase in protein synthesis. • Increased protein synthesis is reflected by an positive nitrogen balance... Anabolic environment. • Muscle mass maintenance (endurance athletes) is sustained by discouraging protein degradation. • Protein degradation is reflected in a negative nitrogen balance... Catabolic environment.
Dietary Protein Requirements • The RDA for protein in normal sedentary individuals is 0.8g/kgBW (1kg=2.2lbs) • For a 130lbs person=(130/2.2)*0.8 = 47g • For a 180lbs person=(180/2.2)*0.8 = 65g • Athletes have increased protein needs compared to sedentary people but there is some debate about how much protein athletes really need...
Protein and Athletes • General belief: • Endurance performance = CHO intake • Strength/Power performance = protein intake • But this is not true. All athletes have an increased need over sedentary people for dietary protein. • Goal of endurance athletes: provide amino acids for energy , maintain FFM • Goal of resistance athletes: gain/maintain FFM
Protein Needs in Athletes • Endurance Athletes: • Protein oxidation occurs as an energy source • After prolonged or high intensity exercise a negative net protein balance is seen • Training seems to have a protein sparing effect, protein oxidation during exercise decreases with training • Recommendations, agreed upon by most researchers: • 1.2-1.8g/kgBW • For 130lbs person (1.5g/kgBW)= 88g • For 180lbs person (1.5g/kgBW)= 122g
Meeting dietary protein needs in Athletes... • Endurance: • Ex: Tour de France. Athletes have difficulty maintaining energy balance but are in nitrogen balance. Research has shown a linear relationship between energy intake and protein intake. When they consumed 12% protein of 6500kcal, easily met requirements. When energy intake matches output in endurance exercise athletes don’t need to supplement with extra protein.
Protein Needs in Athletes • Resistance Training/Strength Athletes: numerous research studies but no clarity about how much “extra” protein a strength athlete needs. • The goal of the resistance trained athlete is to increase FFM (must be in positive protein balance after exercise, promote muscle synthesis) • The general consensus is that a general increase in dietary protein intake will promote muscle growth
Strength Athletes • Research has shown: • Tarnopolsky et al. recommended that athletes involved in high intensity sports & resistance training consume 1.76g/kg/BW of protein to maintain a positive nitrogen balance. • 130lb person = 104g • 180lb person = 144g • They also showed that 1.0g/kgBW maintained nitrogen balance while 2.77g/kgBW attained a positive balance that was twice that of the lower group.
Also evidence that body-builders require only 0.82g/kgBW to maintain balance... • Surprisingly one study found that athletes couldn’t maintain nitrogen balance with an intake of 2.0g/kgBW. Conflicting results in dietary protein recommendations are due to problems with methods used and intensity of the training.
Lemon et al. adds to the body of literature suggesting that strength and power athletes need between 1.5-2.0g/kgBW Evidence has shown: • protein needs in strength athletes increase with changes in intensity and volume to their training • This need for “extra” protein is negated after 12 days of training. (temporary in response to a training stimulus) • With further increases in training loads, protein requirements are also increasing to promote synthesis.
Meeting dietary protein needs in Athletes... • If athletes consume 15% of their calories as protein are they getting enough to promote an increase in FFM? • Let’s do the math for a male involved in a moderate intensity resistance training program (160lbs=72.7kg): PROTEIN CONSUMED: TDEE = 3000kcal 15% of 3000kcal= 450kcal/4kcal/gPRO = 112g PRO = 112/72.7 = 1.45 g/kg BW/day
Meeting dietary protein needs in Athletes... • What about 20%? 3000kcal *20%= 569kcal/4kcal/gPRO=140g PRO = 1.9 g/kg/day Is simply increasing dietary protein intake sufficient to maintain or increase FFM?
After exercise the environment of the body is catabolic (favors protein breakdown). • Feeding promotes protein synthesis: • Increases amino acid pool • Elevated plasma insulin reduces protein breakdown What should I eat? A mixed meal is recommended with at least 1g of CHO/kg BW and 0.5g PRO/kg BW after an intense training session. 180lbs (81.8kg) = 82g CHO and 41g PRO
Protein Intake and Protein Synthesis Rasmussen et al. (2000) • After a bout of resistance exercise subjects were fed 6g of a.a. plus 35g sucrose • Plasma a.a. increased 3-fold, insulin increased 10-fold • Muscle protein synthesis was increased 3.5 fold. There was no increase in breakdown. • Control condition saw a net protein breakdown.
The effect of timing... • If feeding is delayed by 24hours net protein balance is negative and no muscle hypertrophy occurs. • Order of CHO and protein in post-exercise meal...should CHO precede protein? • Shifting environment to the “fed” state by ingesting CHO first may limit the oxidation of absorbed amino acids • Trade-off is that the stimulatory effect of amino acids on protein synthesis is delayed with this tactic. • CHO/PRO consumption during exercise... • Insulin levels are very low at the end of exercise, consuming carbohydrate would maintain them and decrease protein oxidation. • If athlete is using a muscle group and then moves on to another muscle group, significant time would pass until the post-exercise meal.
Muscle growth, fat loss • In order to promote muscle growth we need an anabolic environment and to be in both energy surplus and positive nitrogen balance. • To minimize fat gain during an anabolic state of training, choose lean proteins (chicken/fish) vs. fatty ones (beef/lamb) • Fat loss requires an energy deficit, but that’s a catabolic state. • To minimize muscle loss during an energy deficit, increasing protein intake >20% would be suitable to maintain nitrogen balance. Successfully increasing FFM is a delicate balance between energy intake and expenditure that must be carefully planned and closely monitored.
Protein Sources • 9 essential amino acids that must be obtained in the diet • Protein Quality: • Complete protein • have all amino acids, including the essential ones Ex: meat, fish and dairy products • Incomplete protein • Have some of the amino acids, not all Ex: nuts, grains, legumes (vegetarian athletes may need to supplement with synthesized pure amino acids)
Beef (3oz) 28g Pork (30z) 28g Milk (1 cup) 8g Egg (1) 6g PB (1tbsp) 8g Apple (1) 2g Choose lean protein sources. Chicken has subcutaneous fat that can be peeled away but beef cuts have fat marbled throughout the skeletal muscle. Protein Sources
Whey is derived from cow’s milk. As the schematic on the right shows, whole milk is 13% “stuff”. That stuff is ~27% protein The protein is ~20% whey
What is whey anyway? According to the Whey Protein Institute, whey is: a pure, natural, high quality protein...it is a rich source of the essential amino acids needed on a daily basis by the body. In its purest form, as whey protein isolate, it contains little to no fat, lactose or cholesterol… whey provides a number of benefits in areas including sports nutrition, weight management, immune support, bone health, and general wellness. A less biased description is: cow’s milk protein
Why could whey be better than other protein sources? Whey protein also has a relatively high proportion of branched chain amino acids (BCAA) BCAA – amino acids (leucine, isoleucine, valine) are not synthesized and therefore must come from the diet Leucine is an initiator of protein synthesis Whey protein is rapidly absorbed; data are mixed on whether this affects protein synthesis Whey protein is a dairy protein and recent research suggests that calcium and other minerals in dairy may aid in weight loss