by Jim Stoppani, PhD. Bodybuilding.com
In "Mega Growth Factors," Part 1 of our two-part series on insulin-like growth factor-1 (IGF-1), published in the March 2012 issue of FLEX, we covered the difference between circulating IGF-1 and locally produced IGF-1 in the muscle and how to maximize both through different training techniques. Although there is some debate over the benefits of high circulating IGF-1 levels, it is still too early to count out this powerful growth factor.
In Part 2, we discuss how to boost IGF-1 levels both in the bloodstream and in the muscle through diet and supplements. These strategies should be used in conjunction with the training strategies covered in Part 1 for best results.
Growth Factor Feeding
Although the foods we eat are often thought of as just a means to getting the proper macronutrients (protein, carbs, and fat) into our bodies, food has a powerful impact on our body's physiology and biochemistry.
For example, some nutrients, such as omega-3 fats, have been found to turn on and turn off certain genes. So it should come as no surprise that the diet you follow can impact your levels of IGF-1. Use these four feeding strategies to help keep your IGF-1 levels on the high side.
Be A Carnivore ///
HOW IT WORKS: Research confirms that a diet high in protein is associated with higher circulating IGF-1 levels. Particularly, diets higher in animal proteins have been shown to increase circulating IGF-1 levels.
Researchers from the United Kingdom have reported that vegans have IGF-1 levels that are about 15% lower than meat eaters and have IGFBP-1 and IGFBP-2 (two IGF binding proteins that inhibit the anabolic actions of IGF-1) levels that are 20-40% higher than meat eaters. Numerous other studies also support this contention and show that those who consume higher amounts of animal proteins have higher IGF-1 levels.
DO THIS: As FLEX has long recommended, you should be consuming a minimum of 1 gram of protein per pound of body weight each day. The majority of that protein should come from animal meats, such as beef, poultry, and fish.
Consider Quinoa ///
HOW IT WORKS: Although studies suggest that a higher carb intake is associated with lower IGF-1 levels, one carbohydrate that you may want to consider eating more of as a side to your protein is quinoa. This pseudograin is actually a seed and not a grain like rice, oats, or wheat. Because of this, quinoa is a complete protein, containing all essential amino acids.
So it's a great way to boost the protein content, not just the carb content, of your meals. Another great reason to have quinoa as a side dish is that it may help to boost IGF-1 levels. One Swedish study reported that children eating a formula created from cooked quinoa for two weeks had a significant increase in their levels of IGF-1.
DO THIS: Consider replacing those sides of rice or potatoes with quinoa. One cup of cooked quinoa provides about 220 calories, 8 grams of protein, 40 grams of carbs (5 grams of fiber), and 4 grams of healthy fats.
Don't Forgo Fat ///
HOW IT WORKS: FLEX has long recommended that bodybuilders eat about 0.5 grams of fat per pound of body weight, or about 100 grams of fat for a 200-pound bodybuilder. That typically equates to about 30% of the total daily calories. This is a moderate amount of fat and is the amount that has been found to keep testosterone levels highest in hard-training athletes.
But in addition to keeping testosterone levels high, a higher fat diet may also help to keep IGF-1 levels high. Studies show a correlation between higher intake of dietary fat and IGF-1 levels. And low-fat diets are shown to lower IGF-1 levels.
In fact, research from the University of California-Los Angeles has reported that when subjects are placed on a low-fat diet for just 11 days, IGF-1 levels drop by 20% and IGFBP-1 levels increase by 53%. Subjects who were followed for almost two years on the low-fat diet had IGF-1 levels that were 55% higher and IG FBP-1 levels that were 150% higher than baseline.
DO THIS: Aim to eat about a half gram of fat for every pound you weigh. Choose from sources such as salmon, walnuts, mixed nuts, olive oil, and avocado. Also, don't be afraid of saturated fat, which is essential for keeping testosterone levels high and may be essential for keeping IGF-1 levels high. Get it from beef, dairy, poultry, pork, and egg yolks.
Dairy Does You Good ///
HOW IT WORKS: In addition to animal meats, FLEX has always recommended dairy as another animal protein that is very high quality. Mainly this quality stems from the fact that dairy contains two types of proteins: whey and casein, which are both well established as beneficial for muscle growth. Yet another reason why dairy may be beneficial for muscle growth is the fact that it can raise IGF-1 levels.
Several studies have shown that milk consumption significantly increases circulating IGF-1 levels, as well as levels of IGFBP-3 (also an IGF-1 binding protein that boosts the anabolic action of IGF-1). It's not known exactly how milk achieves this, but several possibilities exist. It may be due to the high protein content in milk, as higher overall protein intake is associated with higher IGF-1 levels. The protein in milk is composed of both whey and casein. Both of these proteins have been shown to individually increase IGF-1 levels (read the next section, "Supplement Strategies," for more info).
A third way that milk may increase IGF-1 levels is via its calcium content. Higher calcium intake is associated with higher IGF-1 levels. And yet another reason, and a more direct one, is the fact that milk contains bovine IGF-1, which has the same structure as human IGF-1. (And although raw milk is highest in IGF-1 levels, research shows that pasteurization does not lower the levels of IGF-1 significantly.)
DO THIS: Most of the studies on dairy were done with milk, not dairy products such as cottage cheese or yogurt. So to ensure the biggest IGF-1 boost, you should consider a few glasses of milk per day in addition to dairy products.
Since milk provides 8 grams of protein per cup, with 80% of that being casein protein (about 6 grams of casein per cup), mixing your post-workout whey protein with about 2 cups of milk is a good way to get a mixed protein for better muscle growth. Also consider adding some milk to your between-meal shakes.
In addition to whole foods, using certain supplements can further help you boost both circulating IGF-1 levels and the amount of IGF-1 that your muscles produce. These six supplements are supported by science for their ability to raise IGF-1 levels.
Casein Protein ///
HOW IT WORKS: FLEX has long advocated taking a casein shake before bed as a means of stopping the breakdown of muscle while you fast during sleep. This is due to casein's very slow digestion rate. We now also recommend adding casein to your post-workout whey shake, as research confirms that this can help to further promote muscle growth better than whey alone.
One reason for casein's ability to boost muscle growth may be its ability to increase IGF-1 levels. Research from the University of Copenhagen-Denmark suggests that when you compare just whey to just casein, it's the casein that seems to boost circulating levels of IGF-1, as well as IGFBP-3, better than whey. And truth be told, while researchers in the above study used mainly whey protein in the pre- and post-workout shakes, there were approximately 6 grams of casein protein per shake.
An earlier study from South Dakota State University-Brookings reported that subjects taking a mixed protein (mainly whey and casein) and carbohydrate shake after workouts experienced significantly greater circulating IGF-1 levels than those consuming just carbs.
DO THIS: If you follow FLEX's long-standing suggestion to add casein to your diet, you'll have all your bases covered. Replace about 10-20 grams of your post-workout whey with casein protein and also have 20-40 grams of casein right before bed.
HOW IT WORKS: We bet you know a lot about creatine, like the fact that it boosts muscle strength and size. And you may even know that one of its main effects is to provide the quick energy muscles need during weight workouts. It also pulls more water into the muscle cells. But we bet you didn't know that supplementing with creatine can increase the amount of IGF-1 produced by the muscles.
Belgian researchers at the Catholic University of Louvain (Louvain-la-Neuve) discovered that subjects who loaded creatine for five days had higher expression of IG F-1 levels in their muscle fibers. University of Copenhagen researchers reported that men taking creatine for 16 weeks while following a strengthtraining program had an increase in the number of nuclei in their muscle fibers.
Although they did not measure IGF-1 levels in the muscle fibers, an increase in the variant of IGF-1 known as mechano-growth factor (MGF) could be responsible for the increased nuclei number, which is one way that muscles grow.
DO THIS: Take 2-5 grams of creatine before and after every workout and with a morning protein shake on days you don't train.
HOW IT WORKS: While you likely are familiar with calcium's role in helping you stay lean, you probably don't realize that calcium is critical for muscle contraction. But that's just one way that it can help you get bigger and stronger. Like magnesium, calcium is another mineral that has a positive relationship with IGF-1 levels. That is, the higher the intake of calcium, the higher the levels of IGF-1 in the blood. Calcium has also been shown to boost testosterone levels in men.
DO THIS: Calcium can help you stay lean, as well as boost IGF-1 and testosterone levels. Take 500-600 milligrams twice a day with 1,000 IU of vitamin D to help with absorption.
HOW IT WORKS: Colostrum, like milk, comes from cows. The major difference between regular milk and colostrum is the amount of time that it is produced by the cow.
Cows produce colostrum only shortly before and shortly after giving birth. Colostrum is essentially a form of milk that is much higher in IGF-1 and immune-enhancing compounds.
Research studies on the effect of colostrum in athletes have reported that it can help to increase muscle mass and strength as well as prevent fatigue by buffering levels of acidity that rise during exercise.
Its mass- and strength-producing effects are likely due to its high IGF-1 content, which has been shown to rise during colostrum supplementation.
DO THIS: Take about 5 grams of colostrum with your pre- and post-workout shakes, as well as with your morning and nighttime shakes.
HOW IT WORKS: ZMA is a patented form of zinc and magnesium aspartate, along with vitamin B6 to enhance the absorption and utilization of these two minerals. Although minerals aren't what you typically think of as critical supplements for building serious muscle size and strength, these two have a plethora of research confirming their effectiveness.
A study by researchers at Western Washington University-Bellingham found that NCAA football players taking ZMA nightly during an eight-week spring training program had an increase in both IGF-1 levels and testosterone, while those taking a placebo had a drop in both.
In addition to improvements in anabolic hormone levels, the ZMA-supplemented athletes made significantly greater gains in strength and power. Other research has also shown a positive relationship between magnesium intake and IGF-1 levels.
DO THIS: Take one dose of ZMA (30 milligrams of zinc, 450 milligrams of magnesium, 11 milligrams of vitamin B6) 30-60 minutes before bed without food.
Whey Protein ///
HOW IT WORKS: Of course, whey protein is a popular muscle builder. That's due to its ability to rapidly deliver its amino acids to your muscles. And those amino acids happen to be high in the branched-chain amino acid leucine, which is critical for stimulating muscle protein synthesis, a mechanism for muscle growth.
Yet another reason why whey is so effective for boosting muscle growth may be the fact that whey can also boost IGF-1 levels. Australian scientists recently reported that older women taking a 30-gram whey protein shake every day for two years had significantly higher IGF-1 levels than those taking a placebo. Sure, they were little old ladies and it could have simply been the additional protein intake that helped to raise IGF-1. But other research suggests that whey taken around workouts may increase IGF-1 levels produced in the muscle, which may be the most critical IGF-1 of all for muscle growth.
Baylor University (Waco, TX) researchers gave men either 40 grams of carbs or 40 grams of protein (mainly whey protein) before and after workouts for 10 weeks. They reported that the guys getting the whey protein shake not only had a greater increase in muscle strength and muscle mass than the guys taking just carbs, but their circulating levels of IGF-1 increased by more than twice as much, and their levels of IGF-1 produced in the muscle fibers increased by more than three times as much as the guys taking carbs.
DO THIS: As FLEX has long recommended, be sure to take a minimum of 20 grams of whey protein within 30 minutes of workouts and about 40 grams of whey protein immediately after workouts to maximize IGF-1 levels in both the blood and the muscle fibers.
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