NUTRIENT TIMING

Introduction
Exercise enthusiasts in aquatic exercise and other modes of exercise regularly seek to improve their strength, stamina, muscle power and body composition through consistent exercise and proper nutrition. It has shown that proper nutritional intake and a regular exercise regimen will bolster the body in achieving optimal physiological function (Volek et al., 2006). The science behind nutrient timing suggests that knowing what to eat and when to eat is a critical key to successfully achieving these health, fitness and performance goals. This article will synthesize the current understanding of how nutrient timing helps to repair tissue damage, restore physiological function, replenish glycogen stores, and promote muscle growth.

What Is Nutrient Timing?
Nutrient timing is the application of knowing when to eat and what to eat before, during and after exercise.It is designed to help athletes, recreational competitors, and exercise enthusiasts achieve their most advantageous exercise performance and recovery. There are three distinct phases in the nutrient timing system that are based on muscle, its nutritional requirements, and its recovery demands for best strength and endurance results. But first, a basic review of the hormones of exercise is warranted.

The Hormonal Responses To Exercise
Within the body are numerous catabolic (breaking down) and anabolic (building up) hormones that are stimulated by exercise.Catabolic hormones aid in the disassembly of nutrients for energy production or cells needs. The main catabolic hormones of exercise are epinephrine, norepinephrine, cortisol and glucagon. Anabolic hormones support muscle hypertrophy (growth), tissue repair, inflammation control, and facilitate the regulation of carbohydrate, fat and protein metabolism. The anabolic hormones of interest during exercise are insulin, testosterone, IGF-I and growth hormone. 

The Catabolic Hormones
During aerobic exercise, levels of epinephrine and norepinephrine are elevated to prepare (or mobilize) the cells for the breakdown of glycogen (converting it to glucose for fuel) in the liver and muscle. These hormones also increase the heart rate, blood pressure, heart contractility, blood redistribution to muscle, and respiration rate to meet the physiological needs of the continuous dynamic exercise.

Cortisol is largely responsible for the breakdown of carbohydrate and fat for energy during exercise. It is a very important catabolic hormone that is activated when low blood glucose levels are present, such as during exhaustive exercise. If the body is low in glucose and glycogen, cortisol will send amino acids to the liver to make new glucose, referred to as gluconeogeneses. Thus, in exercise, when carbohydrate sources are dwindling, cortisol takes the building blocks of proteins (amino acids) and uses them for new glucose synthesis. Glucagon stimulates fat breakdown and also helps to raise blood glucose levels by increasing the release of glucose and the rate of gluconeogeneses (Ivy & Portman, 2004).

The Anabolic Hormones
One widely known anabolic hormone is insulin. Insulin sensitivity is increased during aerobic and resistance exercise, which literally means there is an enhanced glucose uptake for muscle contraction. It also accelerates the transport of amino acids into muscle and stimulates protein synthesis in muscles (Levenhagen et al., 2001). However, during sustained aerobic exercise insulin levels in the blood decrease slightly because epinephrine and norepinephrine inhibit the release of insulin from the pancreas.

Another important anabolic hormone is testosterone. Testosterone is a powerful hormone for protein synthesis and muscle hypertrophy. The amount of testosterone within the body increases with exercise (Ivy & Portman, 2004). Growth hormone is an anabolic hormone that promotes bone and cartilage growth. It is also responsible for stimulating IGF-I, a hormone responsible for the development of muscle cells from myoblasts (immature muscle cells) into myotubes (growing muscles cells) and then into mature muscle fibers. High levels of IGF-I are needed in order to promote muscle hypertrophy. Growth hormone also increases protein synthesis (Volek, 2004). 

The Three Nutrient Timing Phases
The nutrient timing system is split into three distinct phases: 
1) Energy Phase (just before and during workout)
2) Anabolic Phase (post 45 minutes of workout)
3) Growth Phase (remainder of the day)

The Energy Phase
Muscle glycogen is the primary fuel (followed by fat) used by the body during exercise. Low muscle glycogen stores result in muscle fatigue and the body's inability to complete high intensity exercise (Levenhagen et al., 2001). The depletion of muscle glycogen is also a major contributing factor in acute muscle weakness and reduced force production (Haff et al., 2000). Both aerobic and anaerobic exercise decrease glycogen stores, so the need for carbohydrates is high for all types of exercise during this energy phase.
Several hormonal and physiological responses occur during the energy phase. Cortisol levels are increasing, insulin levels are slightly decreasing, and muscle glycogen levels are becoming depleted, making the energy phase catabolic (Ivy & Portman, 2004). Therefore, the goals with the energy phase are to increase nutrient (primarily carbohydrate and some protein) delivery to muscles, spare glycogen and protein loss, limit immune system suppression, minimize muscle damage and prepare nutritionally for a faster recovery (Ivy & Portman, 2004). 
Prior to aerobic exercise, protein intake with carbohydrate supplementation has been shown to stimulate protein synthesis post-exercise (Volek et al., 2006). The combined intake of carbohydrate and protein (pre-exercise) also aids in the rate of muscle recovery after exercise (Ivy & Portman, 2004).
Carbohydrate supplementation prior to resistance training can increase the body's capacity to perform more sets, repetitions and prolong a resistance training workout (Haff et al., 2000). It will help to maintain blood glucose levels, sustain immune function, and aid in the suppressing of cortisol (Ivy & Portman, 2004). 

The Anabolic Phase: The 45-Minute Optimal Window
The anabolic phase is a critical phase occurring within 45 minutes post-exercise. It is during this time that muscle cells are particularly sensitive to insulin, making it necessary to ingest the proper nutrients in order to make gains in muscle endurance and strength. If the proper nutrients are ingested 2 - 4 hours post-exercise they will not have the same effect. It is also during this time in which the anabolic hormones begin working to repair the muscle and decrease its inflammation.
Immediate ingestion of carbohydrate is important because insulin sensitivity causes the muscle cell membranes to be more permeable to glucose within 45 minutes post-exercise. This results in faster rates of glycogen storage and provides the body with enough glucose to initiate the recovery process (Burke et al., 2003). Muscle glycogen stores are replenished the fastest within the first hour after exercise. Consuming carbohydrate within an hour after exercise also helps to increase protein synthesis (Gibala, 2000). 

The Growth Phase
The growth phase consists of the 18 - 20 hours post-exercise when muscle repair, growth and strength occur. According to authors Ivy and Portman, the goals of this phase are to maintain insulin sensitivity in order to continue to replenish glycogen stores and to maintain the anabolic state. Consuming a protein and carbohydrate meal within 1 - 3 hours after resistance training has a positive stimulating effect on protein synthesis (Volek, 2004).
Carbohydrate meals with moderate to high glycemic indexes are more favorable to enhance post-exercise fueling. Higher levels of glycogen storage (post-exercise) are found in individuals who have eaten high glycemic foods when compared to those that have eaten low glycemic foods (Burke et al., 2003). 

Nutrient Timing Supplement Guidelines: Putting it Together for Yourself and Your Clients
Aquatic instructors expend a lot of energy in teaching and motivating students during multi-level fitness classes. Clearly, nutrient timing may be a direction the aquatic profession may choose to pursue to determine if it provides more energy and faster recovery from a challenging teaching load. As well, some students and clients may seek similar results. From the existing research, here are some recommended guidelines of nutrient timing.

Energy Phase
During the energy phase a drink consisting of high-glycemic carbohydrate and protein should be consumed. This drink should contain a 4:1 ratio of carbohydrate to protein and should include approximately 6 grams of protein and 24 grams of carbohydrate. Additional drink composition substances should include leucine (for protein synthesis), Vitamin C and E (because they reduce free-radical levels-which are a contributing cause to muscle damage), and sodium, potassium and magnesium (which are important electrolytes lost in sweat).

Anabolic Phase
During the anabolic phase a supplement made up of high-glycemic carbohydrate and protein should be consumed. This should be a 3:1 ratio of carbohydrate to protein and should contain approximately 15 g of protein and 45 grams of carbohydrate. Other important drink substances include leucine (for protein synthesis), glutamine (for immune system function), and antioxidant Vitamins C and E.

Growth Phase
There are two segments of the growth phase. The first is a rapid segment of muscle repair and growth that lasts for up to 4 hours. The second segment is the remainder of the day where proper nutrition guidelines are being met (complex carbohydrates, less saturated fats--substituting with more monounsatureated and polyunsaturated fats, and healthy protein sources such as chicken, seafood, eggs, nuts, lean beef and beans).
During the rapid growth phase a drink filled with high-glycemic carbohydrates and protein may be consumed. In this phase the ratio of carbohydrates to protein should be 1:5 with 4 grams of carbohydrate to 20 grams of protein. Jenna Bell-Wilson also encourages some protein/carbohydrate snacks during this phase such as:
a) Energy bar and sports drink
b) 2 slices whole-grain toast with 2 tbs peanut butter
c) 1 cup cooked oatmeal with 1/4 cup raisins
d) 1/2 cup sunflower seeds and 1 glass orange juice
e) 1/2 cup of nuts and an apple
The 'Word' on Nutrient Timing
It is not the purpose of this article to 'endorse' any nutrient products currently available on the market. However, the information and discussion in this article better prepares the aquatic fitness professional to guide and educate students about the metabolic and nutrient needs of exercising muscles. 
In the areas of nutrition and exercise physiology, nutrient timing is 'buzzing' with scientific interest. Ingestion of appropriate amounts of carbohydrate and protein at the right times will enhance glycogen synthesis, replenish glycogen stores, decrease muscle inflammation, increase protein synthesis, maintain continued muscle cell insulin sensitivity, enhance muscle development, encourage faster muscle recovery and boost energy levels…that says it all.
References:

Bell-Wilson, J.A. (2005). The Buzz About Nutrient Timing. IDEA Fitness Journal, 41-45.

Burke, L.M., Kiens, B., & Ivy, J.L. (2004). Carbohydrates and fat for training and recovery. Journal of Sports Sciences, 22, 15-30.

Gibala, M.J. (2000). Nutritional supplementation and resistance exercise: what is the evidence for enhanced skeletal muscle hypertrophy. Canadian Journal of Applied Physiology, 25(6), 524-535.

Haff, G.G., Kock, A.J., Potteiger, J.A., Kuphal, K.E., Magee, L.M., Green, S.B., & Jakicic, J.J. (2000). International Journal of Sport Nutrition and Exercise Metabolism, 10, 326-339.

Ivy, J. & Portman, R. (2004). Nutrient timing: The future of sports nutrition. California: Basic Health Publications, Inc. 

Levenhagen, D.K., Gresham, J.D., Carlson, M.G., Maron, D.J., Borel, M.J., & Flakoll, P.J. (2001). Postexercise nutrient intake timing in humans is critical to recovery of leg glucose and protein homeostasis. American Journal Physiology - Endocrinology and Metabolism, 280, 982-993. 

Volek, J.S. (2004). Influence of Nutrition on Response to Resistance Training. Medicine and Science in Sports and Exercise, 36(4), 689-696.

Volek, J.S., Forsythe C.C., & Kraemer, W.J. (2006). Nutritional aspects of women strength athletes. British Journal of Sports Medicine, 40, 742-748

HOW MUCH PROTEIN, REALLY?

 
 

It’s an age-old debate: how much protein should we be eating in a single meal?

For years, popular magazine (and internet) folklore suggested that anything over 20-30g in a meal was a “waste.” That number was arbitrary. No science ever supported the idea that there was a useful within-meal limit for protein intake.

However, a few years back, two particular studies were designed to answer this very question. Well, sort of.

What Does the Research Say?

The first study showed that when college-aged weight-trainers drink 0g, 5g, 10g, 20g, or 40g of protein after a weight training session, muscle protein synthesis is stimulated maximally at the 20g dose. Interestingly, there were no further increases in muscle protein synthesis at the 40g dose.

The second study showed that when young and elderly volunteers were given 30 or 90g of dietary protein in a single meal, the 30g dose maximally stimulated muscle protein synthesis. Again, there were no further increases in muscle protein synthesis at the 90g dose.

Case Closed? Or Is It?

Oddly, since the publication of those two studies, most fitness pros have closed the book on this topic of per meal protein needs. Articles have been written, minds have been made up. Indeed, some authors have even suggested that we’re ignorant wastrels if we dare eat more than 20-30g of protein in a single sitting.

But wait just a second. What did those two studies actually show?

They showed that at 20-30g in a single meal, protein synthesis is maximally stimulated. Which raises an important question: Is muscle protein synthesis the only reason we eat protein? Actually, no.

Protein Synthesis and Breakdown

In a more recent review, Dr. Robert Wolfe, one of the top protein researchers in the world, argues that, while the muscle protein synthesis information above is interesting, it’s essentially useless when planning lunch.

You see, 20-30g of protein at a single meal does max out protein synthesis. The studies are clear on that one. However, what this information misses is that protein anabolism is a function of protein synthesis and breakdown. And, according to the research, protein breakdown is slowed with ever-increasing amounts of protein in a single meal. In other words, “there doesn’t appear to be a practical upper limit to the anabolic response to protein in a single meal.” (Quoted from Dr. Wolfe).

So, if you eat a big protein meal, that extra protein isn't "wasted." Instead, it creates a scalable anabolic response in proportion to the intake. It does this by suppressing protein breakdown. By extension, whether you eat small protein meals spread throughout the day, or you eat just a few big protein meals a day, assuming intake is the same, you may benefit from the same anabolic response.

And yes, this claim is backed up by research too.

Check out this study for more. In it, when 80% of the daily protein intake was eaten in a single meal – as much as 100g of protein eaten at once - it was more anabolic than spreading the same amount of protein throughout the day. In essence, large, infrequent protein meals were more anabolic in this study vs. small, frequent protein meals. Of course, as with all research, the data are mixed. Some studies show this effect. Others do not. However, the take-home message is the same: if you actually look at the full body of research, it becomes clear that there’s not really a practical upper limit of protein intake for optimizing muscle protein. So much for the 20-30g myth.

Remember, Muscle Isn’t Everything

Beyond this very narrow view of protein intake (muscle protein synthesis vs. breakdown), there’s a much more important question at stake: why else do we eat protein?

You see, there are other benefits to eating protein beyond muscle building. There’s satiety, the thermogenic effects, the impact on the immune system, and more (see below). Plus, there are probably a few benefits science can’t measure yet. I say the last part because there’s so much experiential evidence suggesting that when you’re training hard and you up your protein intake, you do better. So maybe we just haven’t looked in the right places to notice the real benefits.

Other Protein Benefits

We shouldn’t look at the world through a straw (i.e. see one protein study on one isolated topic and make broad generalizations). So, to help us remember that, let’s review a list of benefits we get from eating extra protein.

Increased thermic effect of feeding – While all macronutrients require metabolic processing for digestion, absorption, and storage or oxidation, the thermic effect of protein is roughly double that of carbohydrates and fat. Therefore, eating protein is actually thermogenic and can lead to a higher metabolic rate. This means greater fat loss when dieting and less fat gain during overfeeding/muscle building.

Increased glucagon – Protein consumption increases plasma concentrations of the hormone glucagon. Glucagon is responsible for antagonizing the effects of insulin in adipose tissue, leading to greater fat mobilization. In addition, glucagon also decreases the amounts and activities of the enzymes responsible for making and storing fat in adipose and liver cells. Again, this leads to greater fat loss during dieting and less fat gain during overfeeding.

Metabolic pathway adjustment –When a higher protein (20-50% of intake) is followed, a host of metabolic adjustments occur. These include: a down-regulation of glycolysis, a reduction in fatty acid synthesis enzymes, and an increase in gluconeogenesis - a carbohydrate “draining” effect where carbons necessary for ridding the body of amino nitrogen is drawn from glucose.

Increased IGF-1 – Protein and amino-acid supplementation has been shown to increase the IGF-1 response to both exercise and feeding. Since IGF-1 is an anabolic hormone that’s related to muscle growth, another advantage associated with consuming more protein is more muscle growth when overfeeding and/or muscle sparing when dieting.

Reduction in cardiovascular risk – Several studies have shown that increasing the percentage of protein in the diet (from 11% to 23%) while decreasing the percentage of carbohydrate (from 63% to 48%) lowers LDL cholesterol and triglyceride concentrations with concomitant increases in HDL cholesterol concentrations.

Improved weight loss profile – Research by Layman and colleagues has demonstrated that reducing the carbohydrate ratio from 3.5 – 1 to 1.4 – 1 increases body fat loss, spares muscle mass, reduces triglyceride concentrations, improves satiety, and improves blood glucose management

Increased protein turnover — All tissues of the body, including muscle, go through a regular program of turnover. Since the balance between protein breakdown and protein synthesis governs muscle protein turnover, you need to increase your protein turnover rates in order to best improve your muscle quality. A high protein diet does just this. By increasing both protein synthesis and protein breakdown, a high protein diet helps you get rid of the old muscle more quickly and build up new, more functional muscle to take its place.

Increased nitrogen status — A positive nitrogen status means that more protein is entering the body than is leaving the body. High protein diets cause a strong positive protein status and when this increased protein availability is coupled with an exercise program that increases the body’s anabolic efficiency, the growth process may be accelerated.

Increased provision of auxiliary nutrients — Although the benefits mentioned above have related specifically to protein and amino acids, it’s important to recognize that we don’t just eat protein and amino acids — we eat food. Therefore, high protein diets often provide auxiliary nutrients that could enhance performance and/or muscle growth. These nutrients include creatine, branched chain amino acids, conjugated linoleic acids, and/or additional nutrients that are important but remain to be discovered. And don’t forget the vitamins and minerals we get from protein rich foods.

(And lest anyone think I’m a shill for the protein powder industry, this last point clearly illustrates the need to get most of your protein from food, rather than supplements.)

Looking over this list of benefits, it’s hard to ignore the fact that we don’t just eat protein for its muscle synthetic effect. We eat protein for a bunch of other reasons too. Since a higher protein diet can lead to a better health profile, an increased metabolism, improved body composition, and an improved training response, why would anyone ever try to limit their protein intake to the bare minimum?

Take-home Message

It seems to me that whether someone’s on a hypoenergetic diet (low calorie) or a hyperenergetic diet (high calorie), the one macronutrient they would want to be sure to “overeat” (relatively speaking) would be protein.

But that’s not what people do, is it?

Instead, they look for the bare minimum of protein (whether it’s 20-30g/meal or 0.8g/kg/day), and then overeat carbohydrates and fats instead. That could prove to be a performance – and body composition – mistake.

So here’s my recommendation for men and women interested in losing fat, gaining lean muscle, and improving their health and performance:

Women – Eat 1 palm-sized portion of lean, complete protein (about 20-30g) with each meal, every few hours. If you eat less frequently, eat a bit more protein with each meal. If you eat more frequently, eat a bit less protein with each meal.

Men – Eat 2 palm-sized portions of lean, complete protein (about 40-60g) with each meal, every few hours. If you eat less frequently, eat a bit more protein with each meal. If you eat more frequently, eat a bit less protein with each meal.

This pattern of intake will make sure you’re getting enough protein to reap all the benefits that this amazing macronutrient has to offer.

Dr. John Berardi is the co-founder of Precision Nutrition and the co-creator of the Precision Nutrition Certification program. For more from Dr. Berardi, check out this free 5-day course exclusively for fitness professionals “The Essentials of Exercise and Fitness Nutrition”.

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