Ultimate Nutrition

By Robbie Durand, MA, CSCS

Maximizing Testosterone Levels Through

Dietary Manipulation

Men looking to enhance muscle mass and strength and reduce body fat need to have optimal testosterone (T) production. Testosterone helps to achieve these goals and improve well-being in men. It's well documented that men using Lupron (i.e., a drug that suppresses natural testosterone) lose muscle mass and gain fat. However, the changes are reversed upon testosterone replacement.³²

The loss of natural endogenous testosterone is one of the primary reasons for the loss of lean muscle mass that occurs with aging. Most men know testosterone is the primary male hormone responsible for giving them the fitness gains they want. Consequently, the big question every man is asking is this: How can you naturally increase it?

Testosterone (T) production is influenced by a variety of factors including age,⁷ training status,¹⁸ amount of body fat stores^7,30 and diet.^2,10,11 

Many people know that as you age, testosterone levels decrease; high-intensity training can increase testosterone levels (i.e., high volume with shortened rest periods¹⁸), but did you know that excess body fat is associated with decreased circulating testosterone levels?^7,30 All the more reason to get in shape and lose those love handles. There's been debate among researchers about which diet (i.e., low-fat or low-carb) is best for men looking to lose weight. For those of you looking to get ripped, consuming an extremely low-fat diet might not be the way to go.

    Yes, that's right. Diet, too, can influence testosterone production based on the latest research. A recent study in the Journal of Clinical Endocrinology and Metabolism reported that when subjects were switched from a high-fat diet (greater than 30 percent calories from fat and less than 20 grams of fiber per day) to a low-fat diet (less than 15 percent calories as fat and 25-30 grams of fiber per day) it significantly reduced total and free testosterone levels and adrenal androgens (androstendione and DHEA-S).³⁵

Before we get into how diet can influence testosterone production we have to learn a little about male endocrinology. Besides a place for thinking dirty thoughts about women all day long, your brain contains intricate networks of endocrine glands that regulate testosterone production. For those of you who slept through human physiology, here's a primer: The natural order for stimulating testosterone production is that the hypothalamus sends a signal to your pituitary gland via the gonadotrophin-releasing hormone (GnRH). GnRH then travels to the pituitary gland and releases leutinizing hormone (LH). LH circulates in the blood, where it binds to Leydig receptors located on the testicular membrane, which stimulates testosterone production. (See Fig. 1)

            Total Calories and Testosterone Production 

  Based on the research, total calories, as well as the types of dietary fats, can influence testosterone production. Insufficient calorie intake has been shown to cause marked reductions in testosterone levels via reductions in LH pulsatility.^3,4 Basically, the signal for testosterone production has been shut down when you go on a calorie-restricted diet. It's no coincidence that weight trainers trying to get ripped tend to lose muscle mass while following a severely calorie-restricted diet. Periods of under-nutrition (i.e., skipping a single meal) have been shown to suppress GnRH release from the pituitary.⁴

When conducting dietary studies, compliance (i.e., strictly following the diet) is a huge issue, since dietary studies are known to be flawed because many participants lie about being on the diet. So, researchers like to use apes because they have similar reproductive physiology to human subjects and the scientists can control the amount of food they're getting and keep a close eye on them to make sure they're following the exact diet. In male apes, for example, fasting results in suppression of LH pulsatility, which in turn results in a suppression of testosterone production, unless the apes are overfed the day before the fast.²⁸ Fasting for five days can lower LH, T and free testosterone by 30-50 percent,²⁷ so if you're planning on going on a Buddhist fast while training hard, don't be surprised if your strength and muscle mass begin to plummet!

Interestingly, during periods of fasting, the reductions in testosterone- mediated changes can be reversed by injections of GnRH, which preserves LH pulsatility patterns.¹ During caloric insufficiency, the amount of calories supplied during re-feeding is linearly related to the increases in mean LH concentration, LH pulse frequency and mean testosterone concentrations during the re-feeding phase.²²

So why do testosterone levels decrease during calorie restriction?  Scientists don't know exactly, but look at it from an evolutionary perspective.  How many lions on the Discovery Channel do you see mating during a famine? None. Reproduction takes place in all animals when food is readily available.  During calorie restriction, your body shuts down all functions not necessary for survival, which unfortunately is the male reproductive axis along with testosterone- something we want for building muscle mass. If you are going to start dieting, it's advisable to slowly begin cutting back your calories rather than jumping into a low-calorie diet.   

What Do Low-Fat Diets Do to Testosterone Production?

In addition to energy-restricted diets, decreases in circulating testosterone levels can occur following diets restricted in fat. As early as 1979, Hill and Wynder¹³ reported that when men consumed isocaloric (containing the same amount of calories) low-fat diets from vegetarian sources (about 25 percent of calories from fat), it resulted in significant decreases in plasma testosterone and the nocturnal release of testosterone, compared to men receiving moderate-fat diets (about 40 percent calories from fat). 

Additionally, Hamalainen et al.,¹⁰ reported that middle-aged men fed a low-fat (less than 25 percent), high-fiber diet for six weeks during a crossover intervention, experienced a significant decrease in testosterone and free testosterone. The free (unbound) testosterone in circulation is generally believed to be the "biologically active" hormone because testosterone is bound to proteins in the blood.¹⁷ These participants experienced a return of testosterone and free testosterone levels to baseline when the subjects were reassigned to the moderate-fat diet (37 percent fat).

 Dorgan et al.,⁶ reported that mean plasma concentrations of total testosterone levels were 13 percent higher when subjects were placed on a high-fat (about 40 percent of energy from fat), low-fiber diet compared to a low-fat (less than 20 percent of energy from fat), high-fiber diet. It's also been reported that low-fat diets such as those consumed by vegetarians may lead to reductions in circulating testosterone levels.^14,15

What Types of Fat Should I Eat? 

In addition to the amount of fat consumed, the types of fats consumed may regulate steroidal hormones in men. Dietary fatty acids are essential for reproduction. Fatty acids influence reproductive function more than just by promoting a supply of energy; they're major components of the cellular membranes. Hamalainen et al.,¹¹ reported there was a 15 percent reduction in serum T concentrations accompanied by a significant decrease in 4-andostendione levels when subjects were switched from a diet rich in animal fats to a diet low in saturated fats and high in polyunsaturated fats. Total dietary fat, saturated fatty acids and monounsaturated fats have been found to be positively correlated with resting T concentrations in men,³⁴ whereas diets high in polyunsaturated fats have been shown to be inversely correlated with T levels.^9,19  

Additionally, rats fed diets rich in monounsaturated fats had greater 17b-dehydrogenase activity (a key enzyme in the testosterone synthesis pathway in the male rat) and plasma androgen concentrations compared to rats fed diets rich in saturated and polyunsaturated fats.²⁹ It's been shown that when isocaloric meals containing different proteins and different quantities and types of fat are administered to subjects, meals with a high polyunsaturated to saturated fats ratio result in significant reductions in testosterone levels.^5,9  

Other Factors Affecting Testosterone Levels

            In circulation, testosterone is bound to sex hormone binding globulin (SHBG, 60 percent), albumin (38 percent) and a small amount is free testosterone (two percent). Free testosterone is what is binding to the receptor sites and activating the receptors. SHBG is a circulating glycoprotein that's produced by the liver and binds testosterone and other steroids with high affinity and is thereby an important predictor of total testosterone in men.  

So, to break it down in layman's terms, you want to minimize the amount of SHBG in your bloodstream so more testosterone and free testosterone is available. SHBG levels are inhibited by insulin, IGF-1, glucocorticoids and testosterone, while they're stimulated by estrogen and thyroxine production.¹² This may be a good reason to limit your consumption of soy products, as they contain significant amounts of phytoestrogens, which ultimately increase SHBG and limit the amount of testosterone binding to the receptor. 

SHBG is also positively correlated with increased fiber intake and negatively associated with protein and animal fat.² SHBG was found to be significantly decreased after a two-week high-fat diet (100 grams of fat per day) compared to a low-fat diet (less than 20 grams of fat per day).¹⁶

            Insulin as a Regulator of Sex-Hormone Binding Globulin

Insulin's role in the regulation of SHBG may explain why low-fat, high- fiber diets result in reduced androgens, as these diets may delay the rate at which glucose is absorbed through the small intestines, resulting in fewer fluctuations in blood glucose and insulin. Both fasting and glucose-stimulated insulin levels have been found to be inversely related to serum SHBG,² and fasting insulin levels have been found to be inversely related to the testosterone/SHBG ratio.

Acute hyperinsulinemia has been documented to increase testosterone concentrations by decreasing SHBG.²⁰ Pasquali et al.,²⁴ reported that when subjects took Diazoxide, (a drug that abolishes the glucose-induced release of insulin) it led to a reduction in T and an increase in SHBG. This may be why it's important to have small, frequent meals throughout the day as opposed to three large meals, as these small bursts of insulin throughout the day may lower SHBG making more free testosterone available.

Hold the Metamucil...

Research addressing the effect of dietary fat on testosterone production is problematic since designing diets that are isocaloric results in low-fat diets higher in carbohydrates and frequently higher in fiber. In addition to diets with insufficient fats, which may have deleterious effects on androgen production, diets high in fiber also seem to play a role. Howie and Shultz¹⁴ reported that there was an inverse relationship between dietary fiber intake and T production.

            Other researchers have hypothesized that high intakes of dietary fiber may influence circulation of steroid hormones by altering the absorption of androgen precursors such as cholesterol from the intestines.²⁶ Natural fibers (e.g., brans or oat hulls), as well as purified fibers (e.g., cellulose and lignin), have the ability to bind natural steroid hormones. In vitro studies have suggested lignin has the greatest impact on binding steroid hormones. Each natural fiber bound the following percentage of hormones:  lignin (87 percent), followed by wheat and oat bran (45 percent each), corn bran (44 percent) and oat hulls (32 percent).⁴³ A combination of a low-fat diet, flaxseed (rich source of lignan) and omega-3 fatty acids over a 34-day period resulted in a significant decrease in cholesterol, testosterone and free testosterone.⁵ Vegetarians consuming about 50 grams of fiber a day excrete in stool samples approximately twice as much estrone, estradiol-17 b and testosterone compared to omnivores consuming 20 grams of fiber a day.²⁵   

            In conclusion, total caloric intake, as well as the types of dietary fats (i.e., saturated, polyunsaturated and monounsaturated), have the ability to regulate reproductive hormones in man. Many diets being advocated to the public, such as the Ornish diet, are extremely low in fat²¹ to reduce cardiovascular disease. Yet these diets may be detrimental to building muscle due to significant reductions in circulating androgens. Based on the literature, low-calorie diets and diets low in fat and high in fiber may result in reductions in testosterone in man, possibly by increasing SHBG or by decreasing steroid precursors. In addition, a diet with high saturated to polyunsaturated fat ratios seems to be positively associated with testosterone levels.

Does this mean you should go out and consume whole cream, beef and steak every day? No! It should be mentioned that epidemiological studies have shown a link between high saturated fat diets and prostate cancer.^8,26,33  The intention of this article is to point out that those who consume low-fat diets year- round may be missing out on strength and size gains due to sub-optimal testosterone production. Incorporating some olive oil and red meat into your diet in moderation may lead to more anabolic hormone production for optimal muscle gains. Listed below are sources of dietary fats and the foods that commonly contain the highest amounts of them. 

GRAPH  SHOULD  BE  IN  FITNESS  RX FOR MEN  CREATIVE  FOLDER  PER ALAN

Dietary Fats

Sources of Monounsaturated Fats

olive oil

rapeseed oil 

hazelnuts 

almonds

Brazil nuts 

cashews

avocado

sesame seeds

pumpkin seeds

Sources of Saturated Fats*      

butter

cheese

whole milk

cream

fatty meats (ground beef, steak, pork, etc.)

*They are also found in some vegetable oils, including coconut, palm and palm kernel oils.

Sources of Polyunsaturated Fats

safflower

sesame

soy

corn and sunflower-seed oils

nuts and seeds

References

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