For May 24, 2013
- Choosing The Best Fuel For Endurance
Choosing The Best Fuel For Endurance
By DENNIS R. SPARKMAN, PH.D.Most endurance athletes choose to consume a low fat, high carbohydrate diet, and some practice a strict vegetarian lifestyle. From a health standpoint, such dietary practices will both reduce the risk of cardiovascular disease and diminish the number of deaths from chronic disease. From a sports perspective, this diet will optimize the storage of muscle and liver glycogen, which can be used as a source of energy during training. Recently, some individuals have advocated the use of dietary fat supplements, or "fat loading," to spare glycogen stores and improve performance. The reasoning behind this is that fat appears to be such a perfect energy molecule. When fat and carbohydrates are compared, fat has several characteristics that would make it a great energy molecule. First, there is more than twice as much energy stored in a gram of fat (9 kcal) as a gram of carbohydrate (4 kcal). Since glycogen is highly hydrated, an equal amount of energy stored as fat weighs only 6-8% of what an equivalent amount of glycogen would weigh. Fat can also be stored as tiny droplets in close proximity to the muscle mitochondria where it is easily accessible for oxidation into energy. This oxidized fat also provides 1.3 times more energy per carbon molecule. Finally, after 15-20 minutes of endurance training, hormonal stimulation causes the body to burn more fat as an energy source. In this case, it could be reasoned that if fat is such an efficient energy substrate, eating more fat might cause the body to burn fat and spare muscle glycogen, thus increasing endurance. Some studies in rats have even supported this theory. In a perfect world, this might be the case, however, don't start eating potato chips for breakfast just yet. Nearly all human studies have shown that high fat diets can actually reduce glycogen stores and decrease performance. In one case, individuals were fed a diet consisting of 76% fat for four days. When they were asked to run until exhaustion, those who fat loaded reached exhaustion 40% sooner than those who didn't. The reason for this is that the body can't oxidize fat as well as it can glycogen during intense exercise. During exercise, only about 30% of our energy is derived from fats. Also, the oxidation of fat may produce more energy, but it requires 75% more oxygen. This puts greater stress on the cardiorespiratory system. Exhaustion during exercise is directly linked to glycogen depletion. When the muscle shifts over to fat burning when glycogen levels are exhausted, the ability to maintain intensity drops off 65%. Therefore, the only recommended supplementation for endurance runners is carbohydrate loading to increase muscle glycogen stores. For athletes training at high intensity, about eight-ten grams of carbohydrate per kilogram body weight should be eaten daily. Most studies have shown that athletes fail to get this amount of carbohydrates in their daily meals. Therefore, athletes should make up the difference by using a carbohydrate supplement before, during and after training to load, sustain, and replenish glycogen stores, respectively. Fat may be a perfect energy molecule in theory, but in the real world of exercise it can't live up to its potential. Besides, eating a high fat diet would certainly be disastrous to both your health and physique. Nieman DC. Carbohydrates or fats: which is best for endurance exercise? Veg Nutr 1997; 1: 17-21.CARNITINE BOOSTS POWER Carnitine has an integral role in muscle metabolism. It is responsible for the transport of fatty acids for oxidation and energy production within the mitochondria of muscle cells. When muscles are used, this can result in a deficit of carnitine and limit the amount of energy produced. A study has shown that supplementation with L-carnitine can prevent this deficit. When seven long-distance runners were given two grams L- carnitine per day, they found that their peak running speed increased by 5.68%, their heart rate slowed, oxygen consumption decreased, respiratory exchange ratios were lower and blood carnitine levels increased. These findings show that supplementation with L-carnitine positively affects aerobic capacity. Swart I, Rossouw J, Loots J, et al. The effects of L-carnitine supplementation in plasma carnitine levels and various performance parameters of male marathon athletes. Nutr Rev 1997; 17: 405-414. ANTIOXIDANTS PROTECT ACTIVE MUSCLES Supplementation with antioxidants is associated with a reduction in the number of oxygen free radical damage. One good example is the vitamin E-induced reduction in the oxidation of LDL, which greatly reduces the risk of coronary artery disease. It has now been shown that supplementation with 294 mg vitamin C, 1,000 IU vitamin E and 60 mg ubiquinone can protect muscles against acute exercise-induced lipid damage. The antioxidant potential of eight endurance athletes was measured after a 31 km run both with and without antioxidant supplementation. The supplementation increased the athletes' antioxidant potential of LDL and serum, and reduced lipid oxidation. The generation of oxygen-free radicals is increased during long periods of intense exercise; and, if left unchecked, can damage the lipid portion of the muscle cell's membrane. The daily supplementation with a cocktail of antioxidants will not only reduce this exercise-induced damage, it will also reduce the risk of cardiovascular disease. Vasankari T, Kujala U, Vasankari T, et al. Increased serum and low-density-lipoprotein antioxidant potential after antioxidant supplementation in endurance athletes. Am J Clin Nutri 1997; 65: 1052-1056.
- The Role Of Pyruvate In Weight Loss
The Role Of Pyruvate In Weight Loss
By DENNIS R. SPARKMAN, PH.D.
Pyruvate is the last metabolite in the breakdown of glucose (glycolysis). In the past several years it has become available as a dietary supplement and nine well-controlled human studies have not only demonstrated that it is a safe dietary supplement, but that it has a host of functions that are beneficial to the human body. Among these are enhanced weight loss and fat loss, reduced weight and fat regain following a calorie restricted diet, increased exercise endurance, decreased perceived exertion. The problem with these studies was that they used pyruvate in amounts that ranged from 31 to 100 grams per day, which are impractical outside of a research setting. Now a study has looked at what the minimum amount of pyruvate that is necessary to achieve these results.
Fifty-three individuals took part in a study where one group took 6 grams of pyruvate per day for six weeks and two other groups took either a placebo or nothing, respectively. Each group exercised for 30 minutes five times per week. Although there was no change in their absolute bodyweight, those who supplemented with pyruvate had a 12% decrease in percent bodyfat, lost 4.8 pounds of fat, gained 3.4 pounds of muscle, and had a 2.2% increase in basal metabolic rates. Additionally, they reported a 17.7% increase in vigor and 71% decrease in fatigue.
According to previous studies in animals, scientists have been able to estimate that the minimum effective daily dose of pyruvate in humans is between three and six grams. Although the six grams per day used in this study is far less that the amounts used in previous studies, it is effective in helping to reduce bodyfat, increase lean muscle mass, as well as increasing vigor and decreasing fatigue during exercise.
Colker C, Stark R, Kaiman D, et al. The effects of a pyruvate based dietary supplement on weight loss, body composition, and perceived vigor and fatigue levels in mildly overfat individuals. Am J Clin Nutr. 1997 (in press).
Bone is a dynamic tissue. It breaks down and re-builds itself constantly. As we age, the re-building process falls behind the breaking down process, resulting in weak, porous bones that are more prone to breaking.
Osteoporosis is a condition, not a disease, in which the calcium content of the bone has depleted sufficiently enough over time that the bones become brittle, porous and are likely to fracture from even minimal trauma. There are no symptoms of osteoporosis until a fracture occurs, indicating the condition is in the advanced stages with little likelihood of successful treatment.
More than 20 million Americans are affected by osteoporosis--a condition most of us believe is "for women only." In fact, twenty percent of the people who fall victim to this often debilitating condition are men. Their bone loss typically begins in their mid to late 40's and increases to a 10% loss by the age of 75. If it continues, this bone loss is classified as osteoporosis.
Many health specialists believe about half of bone loss is determined by lifestyle factors. Whether you are a man or woman there are useful steps you can take to prevent osteoporosis. This includes drinking 2 to 3 servings of calcium containing milk products or supplementing the diet with 800 to 1000 milligrams of calcium, drinking alcohol in moderation, abstaining from tobacco use, and participating in weight-bearing exercise on a regular basis.
- Dieticians look at health effects of coffee
Dieticians look at health effects of coffeeFrom Medical Correspondent Linda Ciampa
(CNN) -- Millions of Americans jump start their day with a cup of coffee, but what are the health effects of this morning ritual? That is the question being discussed at this week's American Dietetic Association's (ADA) meeting in Atlanta.
"The research shows us that moderation which is about three cups of coffee a day is fine. It does not cause disease," said ADA's Edith Howard Hogan.
While it is unlikely that coffee will cause cancer, heart disease or osteoporosis, there are a few reasons some people should cut back on their intake.
For instance, studies have shown drinking more than three cups of coffee a day may affect a woman's fertility and increase pregnant women's risk of early delivery. And while the evidence in humans is inconclusive, caffeine has been shown to cause birth defects in rats.
Also to be considered is caffeine's impact on mood and sleep. Dr. John Hughes of the University of Vermont and others say the substance is addictive and for some people, as little as a cup of coffee a day is too much.
"If you have anxiety or insomnia, it's very important to look at your caffeine intake and cut down on your caffeine and see if that makes it better, because this is an easy fix," said Hughes.
But stopping cold turkey is not always easy, some people experience withdrawal symptoms including headaches and cramps.
Experts say caffeine is something that should be given up slowly. The best way to quit is by reducing the number of cups of coffee you drink each day, or diluting the full strength coffee with a decaffeinated version. As you slowly reduce intake the caffeine craving with disappear.
- 5 Tasty Lunches to Take to Work
5 Tasty Lunches to Take to Work
5 Great Lunch Ideas for Both Kids and Adults
(MSNBC Health, September 1999) � Some kids love PB&J � peanut butter and jelly, of course � but as a school lunch day after day, it can be a bore. So spare your child the lunchtime blues by packing some fresh and innovative meals. No time for meal-making during the morning rush? Then pack them the night before. Audrey Cross, a professor of nutrition at Columbia University, offers some simple recipes for fun and nutritious lunches, as shown on NBC�s �Weekend Today.�
PACKING SCHOOL LUNCHES can be a frustrating chore for parents who want to make something creative and nutritious that their kids will want to eat. A recent survey from Quaker found that 60 percent of parents disagree with their children over what to pack in their lunch boxes, and 70 percent of parents are concerned that kids are eating unhealthy snacks. According to the survey, the snacks kids want most often are chips (72 percent), cookies (72 percent) and candy bars (55 percent). And according to a 1998 study in Consumer Reports, Americans spend more than $5 billion a year on nearly 2 billion pounds of luncheon meats. The most popular choice is ham; balogna and turkey tied for second. These three meats account for more than 2/3 of the lunch meat market.
This inevitable pattern results in the same old thing: sandwiches, or sending kids off to school with money to buy their lunch. Sandwiches can quickly become boring and predictable, and letting kids decide on their own nutritional intake can be dangerous. So below are five meals sure to shake up the made-at-home menu. They�ll also give your kids great nutritional value.
But first, let�s do away with one common complaint: It takes too long to make lunches in the morning. Actually, this is a myth. A recent study showed that it actually took the same or less time to make these meals than it did to make the �fast-cooking� meals that have become so popular.
Five fun lunches
THREE LITTLE PIGS
Make pigs-in-a-blanket using low-fat wieners wrapped in a low-fat crescent roll with mustard dip. Pack with cucumber spears, cherry tomatoes, watermelon cubes and bottled water.
Serve whole-wheat bow-tie pasta with a primavera topping of saut�ed eggplant, tomato, squash, basil, garlic, pepper and mushrooms (these veggies are full of flavor, fiber and vitamins and minerals). Pack with a slice of semolina Italian bread (a complex carbohydrate � energy source), honeydew melon (rich in fluids), and cranberry juice (fortified with vitamin C)
Burrito means �little burro� and it�s a perfect name because these rolled-up tortillas carry an entire meal inside. Fill your burrito with:
- Mashed beans (excellent source of fiber, iron, B vitamins)
- Chopped lettuce (fiber)
- Diced tomatoes (lycopene & vitamin A)
- Shredded cheese (calcium & protein)
Pack with baked tortilla chips, mango or papaya cubes tossed with lime juice (to keep them from discoloring) and orange juice (vitamin C).
ROASTED VEGGIE POCKETS
Roast squash, eggplant, mushrooms or your choice of veggies over a grill, then stuff into a whole-wheat pita. Add a small container of plain yogurt for topping. Pack with cantaloupe cubes, a cereal bar (for energy and calcium), and chocolate milk.
On 4-inch-long kebob sticks, alternate precooked chicken cubes, halved small red potatoes, red pepper and broccoli. Add a small container of dip such as nonfat plain yogurt with dill. Pack with some colorful fruit � a kiwi and peach compote is a good choice � and orange juice.
More great lunch ideas
- Leftovers make great lunches, too. Older kids often have access to a microwave in their school cafeteria so they can heat up home-cooked meals. Just pack the leftovers in a microwaveable container and they can nuke it at lunchtime.
- To keep lunches safe till eating time, refrigerate them overnight. Then pack them in thermal containers or use a frozen fruit juice box to keep them cold until meal time.
- For smaller children, make all ingredients bite-size � no cutting should be required. Finger foods are also favorites of kids: cutting vegetables and fruits into finger-size pieces makes them more fun and easier to eat. Dips are also a favorite for children. Use herb dips for veggies or spiced dips (nonfat yogurt with cinnamon) for apple slices.
- And remember, adults may want to pack their lunches, too. Homemade lunches are much healthier than most quick-foods, and they actually save time in the long run. Just compare the time it takes to make these tasty lunches (not much) with the time it takes to go out and �grab� lunch.
- Weight training benefits children
Weight training benefits children
NEW YORK (Reuters Health)--Weightlifting programs can improve the muscle tone and endurance in children - and help them to feel good about their athletic performance, researchers conclude.
They recommend that resistance training programs for children include a high number of repetitions lifting moderate weights rather than few lifts of heavy weights, noting that high-repetition, moderate-weight training "resulted in more favorable changes in upper body strength."
In their study, Dr. Avery Faigenbaum and colleagues at the University of Massachusetts, in Boston the Boston researchers assigned 11 girls and 32 boys between five and 12 years of age to eight weeks of weight training. Half of the children engaged in workouts consisting of six to eight repetitions of each exercise, using relatively heavy weights. The other half of participants completed an average 13 to 15 "reps," but with lighter loads.
In their report, published this month in the electronic version of the journal Pediatrics (www.pediatrics.org), the authors conclude that weight-training programs "can enhance the muscular strength and muscular endurance of children."
They also note that there were differences in outcome depending on the training regimen used. While leg muscle endurance improved in both exercise groups, children using high-rep, moderate weights experienced "significantly greater" gains in muscle endurance compared with children in the low-rep, high-weight group.
And while leg muscle strength increased by 31 percent in children engaged in low-rep, high-weight workouts, the benefit was even greater-- nearly 41 percent - in children involved in high-rep, moderate-weight workouts.
Most of the children appeared to show the greatest improvements in strength during the first four weeks of the program, with lower body muscles tending to be more responsive to weight training than muscles in the upper body.
The Boston team conclude that children should begin weight-training using moderate weights and a single set of 13 to 15 repetitions per exercise. This type of program "not only allows for positive changes in muscular performance," they explain, "but provides an opportunity for each child to experience success and feel good about his/her performance."
The researchers note that three major organizations - the American Academy of Pediatrics, the American College of Sports Medicine, and the National Strength and Conditioning Association - support children's participation in "appropriately designed and competently supervised" weight training programs.
Source: Pediatrics 1999;104/1/e5.
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