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SPORTS NUTRITION:

Questions and Answers

Since You Asked...

Here are some of the questions we've received at the nutrition corner, and their answers:

It is recommended that everyone should drink at least two quarts of water a day. But, does the temperature of the water have a effect on the body? I am aware that warm water leaves the body faster and cold water has to be heated and requires more energy in order to leave the body. My question is does cold water at approximately 40F have a negative effect on the organs ?

We do not know of any reason to avoid cool water. There are certainly no dramatic effects on "organs" of water at 40F. In an overheated person there might be problems with acute stomach cramping, but that would probably depend upon the individual. Cool water can obviously absorb more heat and can therefore be a means of reducing core temperature.

 

I am a high school student who is interested in the area of dietetics/exercise physiology. I am currently working on a biology report...which includes information about exercising and a balanced diet. Do you have any information on a balanced diet for an active person?

Glad to hear of your interest in nutrition and physiology! When dealing with athletes the first question you must ask is "what type of exercise do they participate in?" For example, a body builder has very different goals and requirements than a marathon runner. While total calories and protein are key issues to the strength athlete, carbohydrate and hydration aid endurance performance...Gatorade has a very good on-line site, at http://www.gssiweb.com.

 

I recently began working out with weights and I am very happy with the results. However, my friends and I are beginning to train for the upcoming NYC marathon and were wondering if there is a diet that can help us in both areas. Even though we do not run very agressive times, it is usually hard to keep weight on once we start training, and it is very difficult not to get tired out in the gym. In addition, some friends have recommended weight gain powders and other supplements to help; how do you feel about such products?

It is difficult to train for both strength and endurance simultaneously. Your caloric expenditure durng marathon training is great, and weight loss may result. You are essentially in a catabolic state at that point. Obviously hard for muscles to hypertrophy. If the marathon is your primary goal, then understand that you'll probably lose some weight during training and that this is not neccessarily negative. In endurance sports, lighter is usually faster. That loss should probably not exceed 10 or so pounds. In the meantime you'll likely feel depleted in the gym: you are glycogen depleted. You must take care to eat enough total calories to limit weight loss, particularly from carbs and protein. Your need are about 1.5x the RDA for protein or about 1.2 gms/kg body weight. You can consume this by eating: 2 plus servings of dairy daily [casein is the highest quality protein], 2 moderate servings of meat or legumes [beans, peas lentils, chickpeas etc]. Round out the diet by eating about 55-60% carbohydrate. The best time to ingest this carb is immediately post exercise. Glycogen synthetase is most upregulated then and the rate of glycogen resynthesis is greatest. Eat about 50-100 grams of carb in the hour post exercise. This can be in solid form [wash down with water] or liquid [sports drinks, juices, low fat milk, soda if you must]. You want to restore glycogen in order to permit subsequent bouts of hard training.

 

As a marathoner, I ran some of my best marathon times (2:55 at age 55) after carbohydrate loading. I always used a depletion phase, however, and I notice you don't mention one. My regimen was 7 days before, do a long run, carbohydrate deplete for about 3 1/2 days (high protein, low carbohydrate), then high carbohydrate for 3 - 4 days. Although I ran some good marathons with this diet, I never did know whether it was the carbo loading, or just good training that was beneficial.

I don't mention the depletion phase of carbo loading for 2 reasons:

You do get slightly better repletion of glycogen if you deplete the muscles first, but that effect is rather slightly, and in some studies not even statistically, evident;

People can be really miserable while eating a low carb diet.

In addition to being the nutritionist here, I also coach a running club and I find that runners can feel so fatigued during those depletion days that it undermines their confidence just before the race.

If you can manage the depletion phase 5-7 days prior to racing that's fine. I'd expect that your sub 7 minute pace performances are attributable to getting many things right during preparation. You obviously train intelligently and avoid injury, you are naturally talented and you have preloaded the muscle with substrate. Low glycogen levels are definitely associated with premature fatigue, so supercompensating them will help prolong exercise as will drinking carbohydrate beverages during the marathon.

 

I have been an athlete involved in cycle racing for 25 seasons and over the last few years have experimented with liquid carbohydrate feeding, without obtaining either noticable improvement or results. I monitor my own blood glucose levels with an 'Accutrend blood glucose meter' and the results, thus far, are not giving me any difference to the old methods such as bananas,malt loaf and water as race foods. I train around 300 miles weekly and my races are between 60 and 90 miles.

If you'll bear with me, I'd like to review the theory behind the commercial carb beverages. During any endurance event there are 2 nutritional goals: prevent dehydration and provide carbohydrate to spare limited muscle glycogen stores. Since beverages containing more than 8% sugar are absorbed from the small intestine more slowly than water, and because those with less than 5% do not extend performance, most sports drinks are formulated to be approx 6% carbohydrate.

These beverages should also contain some salt or sodium. This is not because you are likely to be sodium deficient but because as sodium is transported across the intestinal wall it "pulls" water with it, speeding fluid absorption. The drinks should also contain more than 1 type of sugar. Each type of carb has a transporter molecule in the intestine which carries the sugar into the blood stream. A large dose of only 1 type of sugar "ties up" the available transporters. By dividing the carbs among a few types of sugars you decrease the load any 1 transporter must carry, thereby speeding sugar absorption and pulling water after it. If you look at the sports drinks they typically have glucose and fructose, or sucrose and corn solids etc for this reason: speeding absorption.

By eating malt breads and fruit with large quantities of water you are likely achieving the same result. Bread contains maltodextrins, glucose perhaps sucrose, some sodium while bananas contain fructose and electrolytes. You are providing the needed energy in a variety of forms. If you are also drinking a large volume of water you are creating a dilute slurry in the stomach which can be emptied relatively quickly into the intestine for absorption. The key here is to drink plenty of water.

Cyclist can often tolerate solids far better than other athletes such as runners and hence their options are less limited. Runners cannot easily drink while bouncing up and down with out choking on the fluid, and its even more difficult to down anything solid, thereby making premixed drinks more sensible for them. In addition, cylists do not have as high a rate of nausea or diarrhea after eating in comparison to those athletes in jostling sports. So, to wind this up, it is very possible that you may see no difference in your performance when comparing the 2 types of replenishment you've described.

 

Hello, I am a Personal Trainer, most of my clients happen to be women, I would really appreciate if you could send me info related to proper dieting and exercise for weight loss. If you have a news letter I would like info on how to subscribe.

Although we don't have a newsletter we have written an article entitled "Exercise is not an effective weight loss modality in women" which was published in the Journal of the American College of Nutrition in 1993. This a controversial topic but in our experience dieting must be added to the exercise regimen in order to achieve weight loss in women.

In general, I recommend that the person attempt weight loss prior to any competitive season, since it is difficult to maintain glycogen stores during periods of negative energy balance. High intensity exercise may be harder, therefore. A recreationally exercising individual can engage in training and lose weight simultaneously.

Although a nonexercising women can often limit calories to 1200 Kcal daily, most women who exercise should probably begin with a caloric intake of 1500 calories, or about 500 Kcal less than what they typically eat. You would expect this to produce a loss of 1-1.5 pounds weekly. Try to keep all advice positive. For example instead of saying "avoid filling up on high fat desserts", say "the minimum number of fruit servings daily is 4, and you must eat at least 3 servings of vegetables". Encourage the women to eat well, but substituting low fat items for high fat, eating at least 3 meals daily. You will have to factor time of exercise into your recommendations. I do not recommend dramatically high carbohydrate diets, I believe 55% carbohydrate is sufficient for most women, 15-20% protein and 25-30% fat.

 

I am doing a project for my sports nutrition class. Is there anything you can tell me about choline as an ergogenic aid? Does it do what it is suppose to do? Can you get the same benefit from eating a variety of healthy foods? Is the cost of the product worth it? Is the convenience worth it?

I will try to give you a synopsis of my understanding of cholines use by athletes. I beg your pardon, in advance, if I confuse you.

It has been hypothesized that acetylcholine, a neurotransmitter, is decreased during exercise and that its depletion leads to fatigue. Choline is a precursor to acetylcholine and as such may have a role in the delay of fatigue. Blood levels of choline vary in proportion to dietary intake of choline from such sources as meat and dairy. Since exhaustive exercise has been shown in marathon runners to result in a decrease in blood levels of choline it is possible that less choline is available to regenerate acetylcholine towards the end of exercise. This might neurologically inhibit muscle contraction.

Whew! Does that make sense to you? Spector et al. published a paper in Med Sci Sports and Exerc, vol, #5, pp 668-673, 1995 which describes a double blind study using choline supplementation in cyclists. They showed no improvements in exercise perfomance with the choline supplement, nor did they find any decrease in blood levels of choline during exercise. Based on these findings choline does not appear to enhance exercise tolerance, at least in cyclists. So, no, there is no clear evidence that choline is ergogenic in nature, therefore the expense cannot be justified. Since it is mainly found in meats, as is creatine which clearly aids in strength training, it would be better to advise athletes to eat a well rounded diet which includes some meat daily.

Other references:

Sandage, BW eta l Choline citrate may enhance athletic performance.

Physiologist 35:236, 1992.

Wecker L. Neurochemical effects of choline supplementation.

Can J Physiol Pharmacol. 64: 329-333, 1986.

Conlay et al. Decreased plasma choline concentration in marathon runners [letter]

N Engl J Med. 17:892, 1986.

 

Where can I find some information on sports anemia?

A good starting point might be to look at Gatorade's Sports Science Exchange, at http://www.gssiweb.com. In their Volume 1, Number 6 publication they cover this topic, "Sports Anemia: poor terminology for a real phenomenon". This article includes references, and offers practical insight into the diagnosis and treatment of this condition.