Nutrition

Nutrition is sometimes referred to as the “fourth pillar” of triathlon.  Rightfully so, as changes in nutrition can have drastic effects on all aspects of performance in the swim, bike or run.  You might be a monster swimmer or cyclist, or an extremely strong runner, but one miscue in nutrition can negate any strength you have.

Hydration

Likely surprising to some, one of the most important aspects to nutrition doesn’t actually relate to food at all… it’s water.

A statistic thrown around quite often is that losing as little as 2 percent of your body weight through sweat can greatly impair your performance.  Given the subjectivity usually dealt with this information however ("greatly impair performance", where's the hard data?), many people tend to ignore just how important hydration can be.  Performance drops can be in the range of 30% (Page 81, The Complete Guide to Sports Nutrition, Anita Bean), a significant amount considering the time, effort and money most athletes put into their training and gear.

Dehydration can come in many forms.  In fact, many gastrointestinal problems may indicate that an athlete isn’t drinking enough:

"Gastric emptying is delayed when you are dehydrated.  It may appear that you do not tolerate a particular product, when what is actually occurring is that the product is unable to empty from your stomach and subsequent drinking causes distention." (Page 116, Sports Nutrition for Endurance Athletes, Monique Ryan)

Symptoms of Dehydration

(Table taken from Sports Nutrition for Endurance Athletes, Monique Ryan)

Mild Dehydration	Dark Urine Decreased Appetite Fatigue Heat Intolerance Light-headedness Small Amount of Urine Thirst
Severe Dehydration	Delirium Difficulty Swallowing Dry or Shrivelled Skin Muscle Spasms Sunken Eyes

A good rule of thumb for endurance athletes is to take in “one millileter of water per calorie" (Page 5, Sports Nutrition for Endurance Athletes, Monique Ryan); this ensures proper processing and functioning of bodily processes.  An athlete that consumes around 4,000 calories per day should therefore consume around 4 liters of water per day.

Daily Nutrition

So what about food?  According to most practitioners, the “proper” diet for an endurance athlete should be heavily focussed on carbohydrates. Generally, this would mean a diet comprised of “about 60 percent carbohydrates, 15 to 20 percent protein, and 20 to 25 percent fat." (Page 15, Sports Nutrition for Endurance Athletes, Monique Ryan)

Calories are of course important in order to meet the energy needs to sustain a training load; but in order to properly recover, athletes should focus their attention on exactly how much carbohydrate and protein they are taking in relative to their current activity level.

Carbohydrate Requirements

(Table taken from Sports Nutrition for Endurance Athletes, Monique Ryan)

Activity Level	Grams (g) of Carbohydrate per Pound of Body Weight
Sedentary Activity	0.40 g/lb
Moderate Activity (less than 60 minutes of moderate intensity, or several hours of low intensity)	2.24 g/lb to 3.00 g/lb
Prolonged Activity (greater than 90 minutes at moderate to high intensity)	3.00 g/lb to 4.50 g/lb
Extremely Prolonged Activity (greater than 3 to 6 hours at high intensity)	4.50 g/lb to 5.50 g/lb

Protein Requirements
(Table taken from Sports Nutrition for Endurance Athletes, Monique Ryan)

Activity Level	Grams (g) of Carbohydrate per Pound of Body Weight
Moderate Training (endurance)	0.45 g/lb
Heavy Training (endurance)	0.50 g/lb to 0.75 g/lb
Intense Training (endurance)	0.80 g/lb to 0.90 g/lb
Strength Training	0.50 g/lb to 0.70 g/lb

This may sound odd given the marketing efforts of many supplement companies, but it should be noted that there are small risks in consuming too much protein in your diet.  Most of these risks stem from the extra effort your body undergoes to convert protein into glycogen.  This process is more taxing on your liver and kidneys (as compared to converting carbohydrates), and requires more fluids to eliminate its end products.

Glycemic Index

Much has been written about the Glycemic Index (GI) these past few years. A great aid in helping level blood sugar levels and maintain a healthy body weight, the GI is simply a measure of carbohydrate quality; comparing how carbohydrates immediately impact blood glucose levels.

Foods with high GI values contain carbohydrates that break down quickly during digestion. This rapid breakdown creates a fast, high blood glucose response in the body (i.e. blood sugar rises signifantly and rapidly).  Foods with low GI values contain carbohydrates that break down more slowly.  This slower digestion creates a much lower blood glucose response in the body (Page 5, The New Glucose Revolution, Dr. Jennie Brand-Miller et al).

"That's fine", you might be saying, "but why are blood glucose levels even important?"

Blood sugar wreaks havoc on your body.  Researchers believe that "heart attacks, leg amputations, strokes, blindness and kidney failure are more common in people with diabetes. The reason: poor blood glucose control can cause damage to the blood vessels in the heart, legs, brain, eyes and kidneys... Poor blood glucose control can also damage the nerves in the feet, leading to pain and irritation, numbness and loss of sensation." (Pages 97 and 98, The New Glucose Revolution, Dr. Jennie Brand-Miller et al)

In addition, it is believed that high insulin levels "contribute to the damage of the blood vessels in the heart, legs and brain. [They are also] thought to be one of the factors that might stimulate muscle in the wall of blood vessels to thicken." (Page 98, The New Glucose Revolution, Dr. Jennie Brand-Miller et al)  This causes the blood vessles to narrow and blood flow to slow or stop, and potentially makes individuals more prone to blood clots, heart attacks and strokes.

So unless you want a heart attack, an amputated leg, bad kidney and brain function, or even blindness... blood sugar levels really don't matter at all.

Sarcasm aside, from a purely athletic perspective, blood glucose levels may be of interest from a recovery standpoint.  It is believed that fluctuation of blood glucose levels may increase inflammation, as cells are continuously stressed and inflammatory responses are triggered (Page 14, The New Glucose Revolution, Dr. Jennie Brand-Miller et al).  This would imply that eating low GI foods may allow better recovery.

Though the idea may be appealing and logical, it should be noted that there is currently no hardfast evidence suggests that GI can assist in athletic performance during an event (i.e. high GI foods don't necessarily give you a tangible boost in atheletic performance).

That aside, how does one find out more about low GI foods?  You could start by looking at http://www.glycemicindex.com/.  This is THE authoritive and official website for the glycemic index, which provides a large database of foods and their associated GI value.

You can also keep a few factors in mind the next time you are buying food or eating a meal.  The GI of a food is typically influenced by (Page 19, The New Glucose Revolution, Dr. Jennie Brand-Miller et al):

Starch Gelatinization	Cooking foods swells and breaks apart the particles/starches that they are comprised of.  This makes them fast to digest and causes higher GI values.
Physical Entrapment (thinks beans)	Fibrous coatings around some foods slows their digestion (as enzymes have to take longer to break them down).  This creates lower GI values.
Particle Size (think refined foods that are highly milled and processed)	Smaller particles have larger surface ares and are thus digested quicker by your body.  This creates higher GI values.
Fibre	Viscous, soluble fibres are slow to digest (as enzymes have to work longer and harder to break them down).  This leads to lower GI values.
Sugar	Counterintuitively, sugar can lead to lower GI values in some foods.  Compared to starch, sugar creates only half as many glucose molecules in the body (leading to lower blood sugar response).  Sugar also inhibits gelatinization by binding to water during digestion.
Acidity (think lemon juice and sourdough bread)	Acids typically slow stomach emptying.  This slows digestion and the rate that starches are absorbed by the body (creating lower GI values).
Fat	Fats also slow stomach emptying.  This slows digestion and the rate that starches are absorbed by the body (creating lower GI values).

Recovery Nutrition

Some notes on recovery nutrition:
1. ”Consume at least 0.5 grams carbohydrates per pound of weight; consider adding 10 - 15 grams of protein if desired.  Drink 24 ounces of fluid for every pound of weight lost during exercise." (Page 85, Sports Nutrition for Endurance Athletes, Monique Ryan)
2. "Emphasizing higher glycemic carbohydrate foods that elicit a higher insulin response... may enhance glycogen resynthesis" (Page 79, Sports Nutrition for Endurance Athletes, Monique Ryan)

Race Nutrition

Some notes on race day nutrition:
1. To “carbo load” one should eat a normal training program diet the week before the race (assuming there is a taper involved); the last few days a high carbohydrate diet should be followed where 3 grams to 5 grams of carbohydrate per pound of body weight is consumed (caloric needs may decrease but carbohydrate ratio should increase); note that every gram of glycogen stored in your body requires three grams of water, carbo loading thus results in several pounds of weight gain (fluid retention is beneficial in race however).
2. Emphasize low fibre foods that cause less gastrointestinal issues.
3. Ideal time to eat is three to four hours before competition; rule of thumb is: "for every hour you allow yourself to digest, consume just less than half a gram of carbohydrate for every pound that you weight" (Page 96, Sports Nutrition for Endurance Athletes, Monique Ryan).