Protein Breakdown

Protein degradation is the process of breaking down proteins into their constituent amino acids. These amino acids contribute to the intracellular free amino acid pool, which may be exported into the plasma, directly oxidized, or reincorporated back into tissue protein (synthesis). Although most athletes think only of maximizing protein synthesis, it is equally logical to try to attenuate degradation, for net protein balance is a function of synthesis minus degradation. A bodybuilder, for...

Summary

The role of carnitine in metabolism is very critical it is a key component of the enzymes responsible for transporting long-chain FAs across the mitochondrial matrix where they can be used to produce energy. Carnitine is endogenously produced from the essential amino acids lysine and methionine in amounts that are sufficient to maintain homeostasis, when an individual's dietary intake includes a low to moderate amount of meat products. If there is a deficiency of carnitine, it is typically a...

Estimated Protein Requirements for Athletes

Sedentary men and women Elite male endurance athletes Moderate-intensity endurance athletes1 Recreational endurance athletesb Football, power sports Resistance athletes (early training) Resistance athletes (steady state) Female athletes a Exercising approximately four to five times per week for 45 to 60 min. b Exercising four to five times per week for 30 min at < 55 VO2peak. Partially adapted from Tarnopolsky, M., Nutrition, 20, 662, 2004. 1.2 g kg day. Similar results were found in young...

Casual Athlete and Fitness Enthusiast

A second group that would benefit from HMB supplementation is the fitness enthusiast or casual athlete who frequently changes his training routine through periods of low to moderate to high activity and often participates in strenuous single bouts of competitive activity, such as road races, softball games, golf tournaments, etc. Supplementation of 3 g of HMB day should improve the gains experienced from either resistance or endurance training as well as help minimize the muscle damage that...

Metabolic Actions of Carnitine

The most widely investigated aspect of carnitine is the carnitine-dependent transport of fats to the intermitochondrial membrane however, some other established roles include the preservation of membrane integrity, stabilization of a physiologic coenzyme A acetyl-CoA ratio in the mitochondria, and the reduction of lactate production.78 Carnitine serves as a cofactor for several enzymes, including carnitine translo-case and acylcarnitine transferases I and II, which are essential for the...

Lipid metabolism Digestion and Transport

The lipid component of the typical Western diet consists of triglycerides, phospholipids, and cholesterol. Triglycerides constitute the majority of dietary lipid intake, reaching approximately 150 g day. Digestion of triglycerides is initiated by lingual lipase, which is secreted by glands in the mouth, contributing to limited digestion in the stomach. In order for lingual lipase to exert its effect on triglycerides, emul-sification must take place by a combination of stomach contraction and...

Chondroitin Sulfate

There are no known or reported contraindications to chondroitin sulfate supplementation. Concerns have been expressed for the theoretical possibility that chondroitin sulfate may have antithrombotic activity and should be avoided by those with hemophilia and those taking anticoagulants, such as warfarin. It may also be immunosuppressive.49 Since the most common form sold is a salt, those on salt-restricted diets should use a salt-free supplement. Because there are no data, children and pregnant...

Chemical structures and synthesis

Fatty acids are hydrocarbon chains with a carboxyl group (-COOH) at one end and a methyl group (CH3) at the other. Fatty acids vary in chain length, degree of unsaturation,1 and location of double bonds2 and can be classified as saturated (no double bonds), monounsaturated (single double bond), and polyunsaturated (several double bonds). Unsaturated fatty acids can be classified in two different ways the delta (A) and the omega (ro) numbering system.1,3 In the delta system, the carboxyl carbon...

Dynamic State of Body Protein

Proteins and other molecules derived from AAs in cells are catabolized sooner or later and must be replaced as needed to maintain cell function. Maintaining this balance requires a relatively constant supply of AAs, often referred to as the AA pool of free AAs available for synthesis of proteins or other nitrogenous compounds. The total AA pool in the human body includes AAs circulating in blood plasma and AAs found within cells. Under most conditions, the average person's AA pool contains...

Mechanism of action

While only small amounts of octacosanol are ingested in the diet, many health benefits have surfaced, in part due to researchers developing octacosanol in a supplement form. Most studies to date have used a wheat germ oil extract or policosanol, a natural mixture of primary alcohols isolated from sugar cane wax, of which octacosanol is the primary component. Octacosanol has the potential to benefit human health in many areas, in particular exercise performance, platelet aggregation, and plasma...

The Effects of Carnitine Supplementation on Performance

V02, VC02, RER, BLa-, plasma glucose FFA, V02 RER, V02, HR, BLa-, plasma glucose V02 max, BLa- RER, RPE, BLa-, HR, fat oxidation V02, VC02, substrate oxidation Swim performance, BLa-RER, FFA, V02 f V02 max, no change, BLa-, RER No change No effect of carnitine No effect of carnitine J, RER, no other changes t V02 max, I BLa-No effect of carnitine No change during exercise No effect of carnitine No effect of carnitine however, is another issue. L-carnitine is very well tolerated, and there seems...

MCTGs and Health

Health concerns are an important issue with high-fat diets and diets high in MCTGs. Considering that it has been claimed that MCFAs do not increase plasma cholesterol, Tholstrup et al. compared the effects of a diet rich in either MCFAs or oleic acid on fasting blood lipids, lipoproteins, glucose, insulin, and lipid transfer protein activities in healthy men. The trial employed a double-blind, randomized, crossover design, with 17 healthy young men. The treatments consisted of replacing part of...

Nonendurance Activities

Antonio and Street42 propose that the ergogenic benefits of glutamine observed in certain groups of athletes and not in others may be due to its protective role against protein degradation, potentially enhancing recovery following resistance training sessions however, this is yet to be determined among athletes participating in such sports. Since strength and resistance training result in glycogen depletion and increased protein turnover, Antonio and Street42 have suggested that glutamine...

Interactions with other nutrients and drugs

The synergistic effects of ro-3 and ro-6 fatty acids and drugs used in the treatment of Crohn's disease have been reported.6566 Amino-salicylic acid (5-ASA) therapy with ro-3 fatty acids supplementation in the treatment of pediatric patients with Crohn's disease delayed the relapse of episodes. The synergistic effect of the drug and supplement were observed by 5-ASA inhibition of factors of the inflammatory cascade cyclooxygenase, thromboxane-synthetase, and platelet activating factor (PAF)...

As and PS

Many studies to date have demonstrated an acute increase in MPS following AA supplementation in association with exercise.159,297,328 Consequently, the studies reviewed below are those that may address some of the open issues discussed in the introduction to this section (Section 15.7.3). The main question is whether the regular practice of ingesting appropriately formulated mixtures of AAs at proper times in relation to an exercise bout in healthy, normally fed (balanced diet and eating...

Overview of metabolism Chemical and Physical Properties

Fatty acids (FAs) consist of a carbon chain of varying lengths with a hydrocarbon tail and a carboxyl group for a head. Upon ionization of the carboxyl group, a negative charge is created. By means of an ester bond, an FA is attached to a molecule of glycerol forming a molecule of water and a monoglyceride. A triglyceride (TG) consists of three FAs attached to a molecule of glycerol by means of ester bonding. FAs can be classified according to the number of carbons they contain (chain length),...

Dietary and Supplemental Sources

Most foods contain trace amounts of HMB. Fruits and vegetables have relatively low HMB concentrations ranging from 1 to 5 nmol g, while most meats have higher concentrations ranging from 15 to 25 nmol g.34 However, some foods of plant origin have concentrations of HMB comparable to those seen in products of animal origin. For example, an herbal tea was found to contain 26 nmol HMB g, while asparagus and squash have 22 nmol HMB g.35 Although diet is a source of HMB, endogenous production of HMB...

References

Leucine as a regulator of whole body and skeletal muscle protein metabolism in humans. Am J Physiol 1992 263 E928-E934. 2. Frexes-Steed M, Lacy DB, Collins J, Abumrad NN. Role of leucine and other amino acids in regulating protein metabolism in vivo. Am J Physiol Endocrinol Metab 1992 262 E925-E935. 3. Nissen S, Sharp R, Ray M, Rathmacher JA, Rice J, Fuller JC, Jr., Connelly AS, Abumrad N. The effect of the leucine metabolite -hydroxy- -methylbutyrate on muscle...