Archive for July, 2009

Protein Needs for Training . . .

nutrition | Posted by admin July 26th, 2009

Protein has been considered a key nutrient for sporting success by athletes of all eras and in all sports. Whereas ancient Olympians were reported to eat unusually large amounts of meat, today’s athletes are provided with a vast array of protein and amino acid supplements to increase their protein intakes.

Protein plays an important role in the response to exercise. Amino acids from proteins form building blocks for the manufacture of new tissue including muscle, and the repair of old tissue. They are also the building blocks for hormones and enzymes that regulate metabolism and other body functions. Protein provides a small source of fuel for the exercising muscle.

Some scientists have suggested that endurance and resistance-trained athletes in heavy training may have increased daily protein needs – up to a maximum of 1.2-1.7 g per kg body weight (BW), compared to the recommended intake of 0.8 g/kg BW for a sedentary person. However, the evidence for this increase in protein needs is not clear or universal. Part of the confusion is caused by problems involved in scientific techniques used to measure protein requirements. The debate over the precise protein needs of athletes is largely unnecessary.

Dietary surveys show that most athletes already consume diets providing protein intakes above the maximum recommended level, even without the use of protein supplements. Therefore, most athletes do not need to be encouraged or educated to increase their protein intakes. These surveys, however, relate mostly to athletes eating typical Western-style diets, and more information is urgently needed on athletes eating different food types.

Athletes most at risk of failing to meet their protein needs are those who severely restrict their energy intake or dietary variety. An adequate energy intake is important in promoting protein balance or increasing protein retention.

Although some resistance-trained athletes and body builders consume more than 2-3 g/kg BW, there is no evidence that these high daily protein intakes enhance the response to training or increase the gains in muscle mass and strength. Such diets are not necessarily harmful, but they are expensive and can fail to meet other nutritional goals, such as providing the fuel needed to optimize training and performance.

Recent studies have focused on the acute response to workouts of both endurance and resistance training. Enhanced protein balance is a desirable goal of the recovery phase – to overturn the increased rates of protein breakdown that occur during exercise, and to promote muscle growth, repair and adaptation following the exercise stimulus. These studies have found that eating a small amount of high-quality protein, combined with carbohydrate, enhances protein synthesis during the recovery period.

There is some evidence that the response is enhanced when these nutrients are provided soon after exercise, or in the case of a resistance workout, perhaps before training. Further work is required to fine-tune guidelines for the optimal amount, type and timing of intake of these nutrients, and to confirm that these eating strategies lead to an enhancement of the goals of training. In the light of this information, it appears sensible to focus on the total balance of the diet and the timing of protein-carbohydrate meals and snacks in relation to training, rather than on high protein intakes per se.

Special sports foods such as sports bars and liquid meal supplements can provide a compact and convenient way to consume carbohydrate and protein when everyday foods are unavailable or are too bulky and impractical to consume. However, the additional cost of these products, and the fact that they contain only a limited range of nutrients, must be taken into account. There is little justification for using very expensive protein-only powders or amino acid supplements. Everyday foods are likely to be just as effective.

Proper Intake of Macronutrients & Micronutrients – Young Athletes

nutrition, performance | Posted by admin July 12th, 2009

Critical Micronutrients:
Current research and trends point to deficiencies in calcium, iron, folate, vitamin B6, and zinc for young athletes. The functions, risks of deficiency, and recommendations for each vital micronutrient follow.

Proper intake of calcium is needed to support bone growth, increase bone mass, and aid in nerve impulses and muscle contraction. Poor calcium intake can lead to decreased bone mass and consequential increased risk for stress fractures and other bone-related injuries. Because a young athlete’s growing bones cannot handle as much stress as an adult’s mature bones, optimum bone health is critical; overuse and overtraining injuries are more apt to occur in a pediatric or adolescent athlete. To ensure proper bone health, keep in mind that the adequate intake of calcium for children aged 9 to 18 is 1,300 milligrams per day.

While iron is noted for its oxygen-carrying capacity, it is also a major player in the energy metabolism of carbohydrate, protein, and fats. For this reason, young athletes with iron-deficiency anemia may experience performance inhibition ranging from decreased work capacity to extreme fatigue, impaired immune function, and impaired cognitive reasoning. Because iron deficiency is one of the most common nutrient deficiencies in the world, it is imperative that professionals working with young athletes are aware of the athlete’s iron intake. On the other hand, it is important to note that iron toxicity is the most common cause of poisoning death in young children. If you want to avoid recommending a supplement, you can recommend food items that are high in iron, such as red meat and enriched cereals and grains, coupled with fruits and vegetables that are high in vitamin C, which aids in iron absorption.

B Vitamins
Both vitamin B6 (pyridoxine) and folate are members of the B-complex of vitamins and are critical components of energy metabolism and blood health. Both are critical for amino acid metabolism and good sources of each are enriched grain products and assorted animal products. Research differs on whether there are changes in folate and vitamin B6 levels during periods of heavy training. However, the conclusion is usually that exercise does not increase the requirements for these nutrients and the dietary reference intake should be followed. In general, a B-complex deficiency can lead to fatigue, muscle soreness, apathy, and loss of cognitive function.

While an extreme zinc deficiency is uncommon in the United States, athletes are at risk due to poor consumption of foods rich in this mineral. Zinc plays a role in more than 300 enzymatic reactions in the body and is critical for wound healing, tissue growth and maintenance, and immune function. Various studies have shown that zinc status directly affects basal metabolic rate, thyroid hormone levels, and protein utilization; thus, zinc is critical to athletes. Dietary protein enhances zinc absorption, and athletes who are most at risk of a deficiency may be vegetarians or those who primarily eat a grain-based diet. With the myriad critical functions to which zinc is linked, consumption of adequate levels of zinc should be stressed.

Critical Macronutrients:
With an increase in energy expenditure comes a subsequent need for an increase in the intake of carbohydrate, protein, and fat. Current research and trends point to deficiencies in overall total energy and carbohydrate intake. Also of concern is deficient fluid intake and consequent altered hydration status of young athletes. The functions, risks of deficiency, and recommendations for each vital macronutrient follows.

In athletes, poor carbohydrate intake results in inadequate glycogen stores and premature fatigue, which not only compromises performance but also forces the body to rely on another source for fuel: protein. Glucose from carbohydrate sources is essential to most body functions during exercise. If glucose is not available for use as fuel during physical activity, the body will take from its protein stores for energy via gluconeogenesis. Because carbohydrate is the preferred fuel for athletic performance, approximately 55% of total daily calories should come from carbohydrate. The young athlete has the capacity to store carbohydrate in the form of glycogen, but this capacity is limited, so carbohydrate must be consumed daily. Carbohydrate needs are based on body weight and intensity of activity. The American Dietetic Association (ADA) has set the following recommendations for the young athlete:
• 3 to 5 grams of carbohydrate per kilogram for very light intensity training;
• 5 to 8 grams of carbohydrate per kilogram for moderate or heavy training;
• 8 to 9 grams of carbohydrate per kilogram for preevent loading (24 to 48 hours prior); and
• 1.7 grams of carbohydrate per kilogram for postevent refueling (within two to three hours).

Protein is an essential part of the young athlete’s diet, and the role of protein for youth includes building, maintaining, and repairing muscle and other body tissues. It should be noted that an adequate protein intake with inadequate caloric intake prohibits protein balance, even when the recommended daily allowance for protein is consumed. Therefore, it is critical that young athletes consume enough calories to maintain body weight. While adult endurance and strength athletes may need more protein per pound of body weight, additional protein needs for young athletes have not been specifically evaluated. However, the ADA has set the following recommendations:
• Athletes who have just begun a training program require 1 to 1.5 grams per kilogram per day of protein.
• Athletes participating in endurance sports require 1.2 to 1.4 grams per kilogram per day of protein.
• Athletes who restrict calories must be certain to consume adequate protein for muscle building and repair. A minimum of 1.4 grams per kilogram per day is recommended.
• Vegetarian and vegan athletes should be counseled to ensure that adequate intake of protein is consumed from plant sources.
• Consuming an overabundance of protein can lead to dehydration, weight gain, and increased calcium loss. This is critical to monitor as research shows that the population of young athletes is already at risk for calcium deficiency.

While carbohydrate is often spotlighted as the preferred fuel for sports, there are some bodies of research suggesting that lipid or fat may be the preferred fuel for children. This may be due to the higher rate of fat oxidation in children. As a major energy source, fat is essential for light- to moderate-intensity exercise and for endurance exercise. Below are some easy-to-follow guidelines for consumption of fats:
• While a low-fat diet can be followed, it is important that young athletes consume an average of 20% to 30% of calories from fat.
• Like adults, young athletes should aim to significantly lower the amount of saturated and trans fat in their diet. The focus should be on an intake of healthy fat from plant oils and soft margarines made with vegetable oils and on limiting the amounts of fried and processed foods.

Maintaining fluid balance is critical for the young athlete. As rates of youth participation in endurance events climb, legitimate concerns about fluid status have arisen. Aside from the risk of heat-related illness, dehydration is strongly associated with fatigue during exercise. This risk is increased in certain environmental conditions such as high heat and humidity. Compared with adults, young athletes may be at a higher risk for altered fluid status for several reasons: Children experience greater heat stress and heat accumulation, and they have a greater ratio of surface area to body mass and absorb heat more readily. Signs of dehydration in children include dark urine, small urine volume, muscle cramps, reduced sweating, increased heart rate, headaches, and nausea. Specific recommendations for fluid consumption are as follows:
• Child and adolescent athletes should aim to replenish lost hydration stores during and after an event. This can be done by weighing the athlete before and after an event and replacing fluids lost (16 to 24 ounces for every pound lost).
• For activities lasting less than 60 minutes, select water for hydration.
• For activities lasting more than 60 minutes, select sports beverages for hydration, electrolytes, and energy from carbohydrate. Select a beverage that provides 6% to 8% carbohydrate.
• Lastly, be aware that children do not instinctively drink enough fluids to replace lost stores and thirst does not always indicate when the body is in need of more fluids.

Leptin: How Diabetes & Obesity Are Linked –

Fitness, nutrition | Posted by admin July 5th, 2009

Like two peas in a pod, the obesity and type 2 diabetes epidemics have joined forces in an attempt to ravage America’s health … and it’s working, as hundreds of millions of people have been significantly affected by this deadly pair.

But how are these two epidemics intertwined? Popular belief is that if one eats too much sugar, they’ll get fat and develop diabetes; and, if they don’t get diabetes it’s merely because their body is producing enough insulin to keep up with the sugar. However, researchers have discovered evidence that there’s more to the obesity-diabetes connection than this classic way of thinking: The missing link? Leptin.

Leptin is the way that your fat stores speak to your brain to let your brain know how much energy is available and, very importantly, what to do with it. Studies have shown that leptin plays significant if not primary roles in heart disease, obesity, diabetes, osteoporosis, autoimmune diseases, reproductive disorders, and perhaps the rate of aging itself. Many chronic diseases are now linked to excess inflammation such as heart disease and diabetes. High leptin levels are very pro-inflammatory, and leptin also helps to mediate the manufacture of other very potent inflammatory chemicals from fat cells that also play a significant role in the progression of heart disease and diabetes.

Leptin: A Key Player in Your Health

Leptin plays a far more important role in your health than, for instance, cholesterol, however few doctors are taught to pay attention to it, or even know much about it. Leptin’s critical importance is largely unknown to the medical community because there are no known drugs that regulate its activities and therefore there is no incentive to spend money to educate doctors about leptin’s crucial role in health and disease. The only known way to reestablish proper leptin (and insulin) signaling is via diet and, as such, these can have a more profound effect on your health than any other
known modality of medical treatment. New studies support prior studies that have shown the brain and liver to be of paramount importance in regulating your blood sugar levels especially in type 2 or insulin resistant diabetes. It had been previously believed that the insulin sensitivity of muscle and fat tissues were the most important factor in determining whether one would become diabetic or not. It should be noted that leptin plays a vital role in regulating your brain’s hypothalamic activity which in turn regulates much of our “autonomic” functions; those functions that you don’t necessarily think about but which determines much of your life (and health) such as:

•Body temperature
•Heart rate
•Stress response
•Fat burning or storage
•Reproductive behavior and
•Newly discovered roles in bone growth and blood sugar levels

These studies also illustrate the complexity of hormonal orchestration. Especially with very important hormones like insulin and leptin with far ranging effects, a particular cell can be resistant to one effect while the other stays intact. For instance, it had been shown previously that cells may become resistant to the effects of insulin on glucose influx (which may be protective in limiting the amount of glucose entering cells and thus intracellular glycation), while that same cell may not become resistant to the effects of insulin on cellular proliferation that tell cells to multiply, as these are mediated by two separate pathways. Thus a person with high insulin levels, being insulin resistant in regards to glucose, would still be at a much higher risk of cancer, and this indeed is what happens; high insulin levels are associated with many common forms of cancer. Also, different organ systems become resistant at different rates. Therefore, just taking or artificially raising (by drugs) insulin, and/or leptin, will not correct the problems in the orchestration of the signals, any more than playing the tuba louder will fix mistakes in the written music. However a strategic diet that emphasizes good fats and avoids blood sugar spikes coupled with targeted supplements to enhance insulin and leptin sensitivity by resensitizing your cell’s ability to hear hormonal messages correctly, will allow your life to be the symphony it was meant to be.

REf: Dr.Ron Rosedale

Cell Metabolism March 2005; Vol 1, 169-178 (Free Full-Text Article)