Image 1: If Chris, "the Techician", Aceto's usually well-informed sources are right and the former Mr Olympia Jay Cutler is currently trying to lose muscle (I heard him say that on Heavy Muscle Radio), Cutler would be ill advised if he ingested ~20g of non-essential amino acids during and / or in-between extended fasts and hours of arduous low-intensity cardio sessions (img MuscleTech)
Those of you who followed the "Amino Acids for Super Humans" series I did earlier this year on Carl Lanore's Super Human Radio may remember the arginine < > citrulline < > ornitine cycle and how I tried to explain that, from a physiological perspective, arginine's role in ammonia detox is probably as, if not more important than its role in the production of nitric oxide. What most of you will probably have overheard, or, in the respective shownotes, over-read, was my reference to a 2006 study from the University of Paris, which was - at least to my knowledge - the first study to show that citrulline (much like leucine) increases protein synthesis and thusly reduces the loss of muscle protein in old malnourished rats (Osowska. 2006). As it is often the case with isolated study results like that, these observations have not gotten much attention within the research community, so that it is not very surprising that the latest information on citrulline's putative role in whole body protein homeostasis come from the same laboratory at the Sorbonne, as the previously cited ones.
Citrulline vs. Leucine, and non-essential aminos as a control!?
What is particularly interesting about these results, the scientists from the Département Biologie Expérimentale, Métabolique et Clinique at the Pharmaceutical Faculty of the venerable Université Paris Descartes published in the (btw. highly recommendable) Journal Amino Acids, is that they allow for a direct comparison of the magnitude and the mechanismthe ingestion of citrulline, leucine or a mix of other non-essential amino acids has on the fractional protein synthesis in skeletal muscle tissue (Tibialis anterior) in a fasted state (18h food deprivation).
Figure 1: Fractional protein synthesis (in %/h) in tibialis anterior muscle of fasted rats 50 minutes after administration of leucine, l-citrulline or isonitrogenous (to leucine) non-essential amino acids (data adapted from Plenier. 2011)
To my own surprise the winner of the battle of the "protein anabolic amino acids" is neither the usual (leucine), nor the unusual suspect (citrulline), but rather the non-essential amino acid combo which consisted of 1.35g/kg of alanine, glycine, proline, histidine, asparagine and serine.
Alanine, glycine, proline, histidine, asparagine, serine - Non-essential high potentials?
Let's briefly put this surprising result into (a human) perspective: If we assume that you are on an extended intermittent fast, traveling or had - for whatever other reason - no access to food for 18h, then the ingestion of 0.22g/kg of a non-essential amino acid mixture (if you weigh 80kg that would be 17.5g), would induce a 9.37% greater increase in muscle protein synthesis than the same amount of leucine and a 16.67% greater increase than 23g of l-citrulline.
Figure 1: Phosphorylation of Akt, s6K, 4EBP1 (left) and AMPK (right) 60min after administration of leucine, l-citrulline or isonitrogenous (to leucine) non-essential amino acids (data adapted from Plenier. 2011)
If we combine the previous calculations with the data from the Western blot analyses of the PI3K/Akt, mTORC1, ERK1/2/MAPK pathways and AMP kinase component, it becomes even more obvious that this study provides further evidence against the current over-emphasis of l-leucine which is so prevalaent especially among the bodybuilding-oriented physical culturists. As I have pointed out in previous posts, here at the SuppVersity, pushing the "protein-anabolic gas-pedal" through the floor (=ingesting huge amounts of leucine on its own) makes no sense if your car has long run out of fuel (=there are no amino acids to synthesize).
Against that background it is actually not very surprising that the protein synthesis in the fasted leucine group was reduced, although the phosphorylation of p70S6K was identical and the one of 4EBP1 even greater (both indicate that the protein synthetic machinery was set into gear) than in the fed control. What is surprising, though, is the fact that the actual protein synthetic response in the leucine group fell 10% short of the one that was observed in the tibialis muscle of the rodents which receive an isonutrogenous amount of non-essential amino acids. After all, previous studies have suggested that the induction of measurable increases in protein synthesis was an exclusive property only branched chain (BCAA) or essential (EAA) amino acid mixtures would posses. Methodological differences in the design of respective studies aside, Servane Lé Plenier and his colleagues suggest the following two possible explanations for the surprising effects the alanine, glycine, proline, histidin, asparagine and serine combo exhibited on skeletal muscle protein synthesis in the fasted state:
[firstly,] in the fasted state, NEAA homeostasis is maintained by catabolism of essential amino acids (EAA) - alanine, for example, is produced in muscle from LEU and pyruvate - and limited EAA availability affects MPS since it is well known that a deficiency in one amino acids may be a limiting step for protein synthesis. Hence, in the fasted state, NEAA administration could spare EAA utilization and thereby preserve MPS.
[secondly,] one or more amino acids in the NEAA mixture could display specific anabolic properties. For example, alanine has been shown to stimulate liver protein synthesis in starved rats (Perez-Sala. 1987), but to the best of our knowledge this effect has not been shown in muscle. Similarly, proline and glycine may possess pharmacological properties that could indirectly modulate protein synthesis.
Personally, I don't believe that any of the non-essential amino acids (NE-AA) in the NE-AA formula actually had an individual effect on protein synthesis beyond its ability to spare essential amino acids and its availability as a substrate for inter-organ amino acid transfer (especially for alanine and asparagine, which are transaminated in the liver, this could be an important factor). So that the practical implications of this study should be clear: if you want to minimize muscle loss during a(n) (intermittent) fast, you better have some non-essential amino acids with your leucine!
One question answered, 999 new ones raised
Image 2: If you have read all Intermittent Thoughts articles which dealt with the AMPK/mTOR Metabolic Seesaw and the respective follow-ups, you will probably already have noticed that the ingestion of non-essential amino acids had the least impact on the fasting-induced increase in AMPK-phosphorylation of all three treatments. And I guess I don't have to tell you that this is good news for all intermittent fasters out there - spare the muscle, improve your health and burn the fat, what more can you as for?
Unfortunately, this study leaves us with way more questions than answers. I personally, for example would venture the guess that theingestion of a complete EAA product would result in an even more profound amelioration of the fasting induced reduction in fractional protein synthesis. That being said, the latter could also compromise another advantage of the non-essential amino acids, I have not even mentioned, yet: their almost non-existent effect on intra-muscular AMPK-expression (cf. figure 2, right). If you read all Intermittent Thoughts articles which dealt with the AMPK/mTOR Metabolic Seesaw and the respective follow-ups, you will be familiar with notion that the fasting-induced phosphorylation of intra-muscular AMPK is responsible for the majority of the health, as well as the closely related fat-burning effects of (intermittent) fasting. Now, if the ingestion of a ~20g bolus of alanine, glycine, proline, histidine, asparagine and serine could increase your skeletal muscle protein synthesis back to almost normal levels (NE-AA -12.5% vs. leucine-only -20%), while keeping the AMPK-alpha levels maxed out (cf. figure 2, right), it would at least warrant an experiment before we totally discard the possibility that, under certain circumstances, such as the fasting window of an intermittent fast, the oftentimes disregarded "non-essential amino acids" could perhaps be more than just a band-aid when you have run out of essential ones.
Whether there will be a place for citrulline in particular is questionable, though. With the least effect on protein synthesis and the greatest impact on AMPK, it would de facto be a "band-aid" solution, for everyone who fasts, deliberately. In other contexts, however, l-citrulline supplementation could well have its merits. In cancer patients it could for example be used to ameliorate muscle loss without triggering the pro-carcinogenic (Garcia-Maceira. 2009), but I guess this would be the topic of another study and another blogpost, here at the SuppVersity ;-)
Image 1: Despite its presence in meat, fish and dairy, it is near impossible to achieve supra-physiological and thus ergogenic carnosine levels without supplemental beta alanine.
Beta alanine, unlike l-alanine is one of the "beta-amino acids", indicating that it is neither essential nor proteinogenic, i.e. it is not built into proteins or used in the synthesis of major enzymes. Nevertheless, beta alanine plays a major role with regard to health in general and brain health and muscular performance, particular.
Taken orally, as a supplement, beta alanine (BA) has a slight sweet taste to it (the artificial sweetener suosan is derived from BA). It is highly water soluble and the funny tingles, which can be avoided by either taking it with food or by taking smaller servings (e.g. 5x 800mg for a total of 4g, which would be a reasonable amount for carnosine "loading") multiple times a day, aside, it is virtually side effects free (some people also develop benign allergic skin or mucosal reactions and/or diarrhea). According to Jeffrey R. Stout from the University of Oklahoma, who is one of the scientists behind many of the the commonly cited studies on beta-alanine and exercise performance, humans, in contrast to other mammals, cannot synthesize beta alanine (PerfNut. June, 2006). Humans get their beta-alanine directly from BA-containing dipeptides in our food:
Carnosine (beta-Alanyl-L-histidine),
Anserine (beta-Alanyl-N(pi)-methyl-L-histidine) and
Balenine (beta-alanyl-N tau-methyl histidine)
are dietary sources of beta alanine. All three are particularly high in meat, eggs, dairy, which is why vegetarians tend to have significantly lower beta alanine intakes. With beta alanine being a non-essential amino acid, low intakes of beta alanine would not be a problem, if it were not the rate limiting substrate in muscular (and cerebral) carnosine synthesis.
Note: This is the detailed transcript of my show notes to "Amino Acids for Super Humans Part IV" click here to download the podcast if you want to listen before / during / after you read the rest of the notes
Beta alanine, the rate-limiting substrate in carnosine synthesis
Carnosine, i.e. beta-Alanyl-L-histidine (C9H14N4O3), is a dipeptide which was first isolated by Gulewitsch and Amiradzhibi at the dawn of the 20th century. Yet, science begins only recently to grasp all the remarkable health and performance benefits, its presence in muscle, nerve and other tissues may provide. In the following I will summarize the most relevant facts and findings:
carnosine levels are particularly high in brain tissue and fast-twitch muscle fibers (Harris. 1998)
mean concentrations are 17.5 ± 4.8 mmol kg−1 dm in females and 21.3 ± 4.2 mmol kg−1 dm in males (Mannion. 1992),
interestingly muscle carnosine levels of sprinters and other sports with short bursts of high intensity work are elevated compared to non-athletes and athletes from endurance-oriented sports such as marathon runners
carnosine & the brain
carnosinemia (a rare condition of low carnosine levels) effects almost exclusively the brain, which indicates that it is of utmost importance to brain health
carnosine levels (in all tissues) decline with age; scientists speculate about the role of low carnosine levels in dementia and other age-related neurological diseases
carnosine's antiglycation effect makes it a promising therapeutic agent in the treatment of AGE-related (AGE = advanced-glycation-end-products) pathologies such as Alzheimer's (Reddy. 2006)
carnosine & athletic performance
Figure 1: In one of the most recent studies beta alanine supplementation @ 4g/day significantly improved performance and body composition in trained football players and wrestlers (Jun 13, 2011)
carnosine appears to have general anti-oxidant capacity and could thus protect athletes from exercise induced oxidative stress
carnosine has a PH of 6.9-7.0, which is identical with the normal intracellular PH level of 7.0 (cf. blood PH is higher: 7.4); similar to bicarbonate (PH ~8.0) which is an excellent extra-cellular buffer, carnosine can act as a buffer on the cellular level
by buffering H+ ions which are produced in the course of strenuous exercise sessions, it reduces the buildup of lactic acid, which other than its base, lactate cannot be readily "recycled" as fuel (Catham. 2002), but contributes to exercise induced and acidosis and consecutive performance decrements (Böning. 2008)
Increasing carnosine levels by beta alanine supplementation
I has been shown, that oral beta alanine supplementation can elevate carnosine levels (in muscle) by up to 80% (Derawe. 2010). The beneficial effects of the practice of what I would like to call carnosine loading (via BA supplementation) have been confirmed by numerous studies in the course of the last decade. In a 2010 review of the literature Sale et al. conclude:
β-Alanine supplementation has consistently been shown to augment muscle carnosine concentrations in man [...] There is now a growing body of evidence to show that β-alanine supplementation of 4 weeks or longer evokes significant improvements to exercise capacity, especially when that performance is likely to be limited by the accumulation of H+ ions in the skeletal muscle (i.e. in high-intensity exercise tests lasting between 1.5 and 4 min)
In that, it is important to note that the immediate effects, many fitness enthusiasts report on the health and body building boards on the Internet, are probably placebo and/or psychological effects related to the tingling sensation, most people get from beta alanine intakes in the range of 1g+.
Muscle carnosine levels rise gradually, a sensible supplementation regimen would thus span 4-6 weeks with a daily intake of 3-5g of beta alanine per day - preferably in divided doses to avoid the tingling and ensure proper absorption.
Studies show that after a certain time-frame, which varies according to interpersonal differences and training modalities, carnosine levels saturate. Whether or to which extent continuous supplementation makes sense in these circumstances has not yet been elucidated and would certainly depend on the individual athletic demands.
Tingles, flushing and myocardial suffocation
Regardless of whether they enjoy or hate the tingling sensation that comes with higher doses of beta alanine, neither the "lovers" nor the "haters" can provide a 100% scientifically proven explanation for their occurrence.A common theory relates to the process of carnosine synthesis, of which you have already learned that it involves two amino acids: beta alanine and l-histidine. The latter is abundant in muscle tissue and the generally accepted hypothesis is that it is released in the presence of beta alanine in order to form carnosine. If a sudden spike in serum beta alanine levels occurs, the amount of histidine that is released from the muscle tissue could either surpass the amount of beta alanine that is actually there to recombine to carnosine, which would subsequently be stored within the muscle (or other tissue), or there is simply not enough carnosine synthetase (the enzyme which catalyzes the reaction of beta alanine + l-histidine to carnosine) available. In both instances there would be a net increase in "free floating" l-histidine in the blood stream, which in turn could undergo decarboxylase by the respective enzyme, L-histidine decarboxylase. The histamine produced in this reaction could then activate histamine receptors at the tissue level and provoke an "allergic" reaction that feels like a tingling sensation. Both, the non-occurrence of the tingling as well as the few reported instances, where the latter are accompanied by a rash on the tingling body parts, would support the histamine-hypothesis.
In Joe Antonio's Performance Nutrition Podcast,back in 2006, however, Jeffrey R. Stout suggested another possible mechanism (PerfNut. June, 2006). According to Stout, a direct interaction of the beta-alanine molecules with neurons in the respective tissue would be responsible for the (un-?)comfortable sensation.
And, to make things even more complicated, I would like to suggest a third hypothesis: Those of you who have had thequestionable experience of (over-)consuming GABA orally, may have noticed that, the shortness of breath aside, the activation of peripheral GABA receptors can provoke a feeling which is not all too different from the BA-tingles. With beta alanine being a GABA-A & GABA-C agonist, this would be another, yet possibly the least likely, explanation.
Beta Alanine & Taurine - archenemies or synergists?
Figure 3: The structural difference in their molecular structure is the outward sign of the very different biological functions of alanine (left) and beta-alanine (right); one part of the energy supply chain, the other a potent H+ buffer
Whatever the reasons for the tingles are, they are just as benign as oral beta alanine supplementation in general. In this respect, any possible concerns, my report on the hypoxic consequences of beta alanine induced taurine depletion in isolated cardiomyocytes might have brought up, would be inappropriate. Other than cells in a petri dish, your heart, or rather your whole body can very well take counter-measures against overtly high beta alanine levels and consequent cellular taurine depletion. The latter could at worst become an issue, if you decided do lace all your foods, drinking water and whatever else you consume with tons of beta alanine for weeks to deliberately deplete your taurine stores.
In the aforementioned study the scientists found that "buffering" (remember these experiments were done in a petri dish) the beta alanine with equal amounts of taurine, i.e. one taurine molecule for each beta-alanine molecule. If you wanted to mimic this equilibrium state in your supplemental regimen, the higher molecular weight of taurine (125.15 g mol−1), as opposed to beta alanine (89.09 g mol−1), would dictate a ratio of about 3:5. A reasonable way of achieving this could be 1.5g of beta alanine upon waking, 1.5g before workout, 2.5g taurine post-workout and another 2.5g before bed.
Personally, I do not think that supplementary taurine intake would be necessary (assuming you keep your beta alanine intake in the suggested range of 3-6g per day), but since both amino acids appear to have ergogenic potential (and taurine is also involved in many other metabolic processes) it may make sense to supplement both, anyway. Whether would be necessary or even beneficial to take them one at a time in order to avoid competitive absorption is yet questionable. Under the assumption that the ratio is not totally off - like 15g of bet alanine and 500mg of taurine - I assume that you will absorb reasonable amounts of both, even when you take them together.
Beta alanine, does it have endocrine effects as well?
Aside from the neurological effects of beta alanine (Tiedje. 2010) there is yet another hitherto hardly recognized effect of 3-Aminopropanoic acid (BA) in mammals: Beta alanine appears to modulate estrogen metabolism. A 2010 study by Yang et al. (Yang. 2010) found that beta alanine significantly (-18%) decreased estradiol levels in adult rats. This is an interesting observation, especially if one takes into account the results of Walter et al. (Walter. 2010) who recorded a significant weight gain in 44 women supplemented with 1.5g of beta alanine for 8 weeks. In contrast to other studies on male subjects, the weight gain was not due to superior increases in lean mass (measured, unfortunately, by air displacement instead of DEXA), as the latter increased similarly in the control group.
Note: The study by Yang et al. does not conflict with existing human data from Hoffman 2006 and Hoffman. 2008, who found no increase in testosterone, growth hormone or cortisol response to exercise in football players and experienced resistance trainers after 10, respectively 4 weeks of beta alanine supplementation. Those endocrine parameters remained unchanged in the Yang study, as well.
It is common knowledge that the reduced estrogen production at the onset of menopause is partly responsible for the weight gain women experience at that age. That the opposite, i.e. weight loss, and more specifically, fat loss, is a consequence of lower estradiol levels in men is yet less well known. And despite the fact that this hypothesis warrants experimental verification, it may be possible that small, yet statistically significant endocrine modulations due to beta alanine supplementation may in part explain both, the weight gain the women in the Walter study experienced (Walter. 2010), as well as the improvements in fat loss and retention of lean mass in dieting wrestlers in the recently published study by Kern et al. (Kern. 2011).
Bottom line: Although beta alanine is the next "big thing" since protein and creatine supplements, it probably is a way smaller "big thing". If you got to chose and are no athlete competing in weight classes, creatine will probably provide greater benefits in view of performance increases and body recomposition or muscle building. If you can afford taking both, however, do not hesitate! Studies like Hoffman 2006 make it quite clear that the combination of creatine and beta alanine, which work via distinct mechanisms of action, is the way to go for the non-drug taking athlete who is looking for the slight edge which so often decides on victory or defeat.
Histidine as a fat loss adjuvant? Laughable? Not for the obese! For lean folks like her? We'll see...
If I had to guesstimate the number of fitness enthusiasts who have ever heard of histidine at all, I would say that 50% probably don't even know what it is, while the majority of the lightened ones will re-iterate what the supplement business has been preaching them "You get more than enough histidine, anyway. So don't worry our superior beta-alanine supplement will work even if you don't take additional histidine."
Short term studies confirm this notion. It looks as if we usually have more than enough histidine to have it recombine with beta alanine and form carnosine, but long-term studies are missing and let's be honest: How likely is it that an essential amino acid is nothing but a servant to a non-essential amino acid from the 2nd row?
Early results: Histidine modulates feed efficiency
Actually we could have known that histidine could have some merit as a standalone supplement for more than 50 years now, so I am not sure if the recent publications of two studies by Feng et al. in Diabetolgy and Kumi Kimura et al. in Diabetes, the journal of the American Diabetes Association are going to change that over night. What is certain, though, is that they clearly support findings that date way back into early mid 20th century, when Ellison & King found that the provision of a low histidine diet to rodents increased the feed efficiency (=weight gain per energy unit) by 75%, while the addition of 0.75% histidine (per kg chow) to an already histidine sufficient diet (Ellison. 1968) led to a 30% decrease in food efficiency.
About 45 years later, the previously mentioned studies on the effects of histidine on hepatic gluconeogenesis (Kimura. 2013) and insulin resistance (Feng. 2013) in rodents and human volunteers, respectively, could bring the hitherto often depreciated histamine precursor back to the center of scientific attention.
4g/day histidine improve insulin restiance, reduce fat mass and suppress inflammation
In that, the study by Feng et al., which investigated the effect of 4g/day supplemental histidine on the degree of insulin resistance, inflammation, oxidative stress and metabolic disorders in 100 obese women with the metabolic syndrome (aged 33–51 years; BMI≥28 kg/m²), is probably of greater significance for the average physical culturist that the nevertheless enlightening rodent trial by Kimura et al. we are going to address later.
Figure 1: Changes in amino acid levels, glucose & lipid metabolism, body composition and markers of inflammation after 12 weeks on placebo or 4g/histidine per day (Feng. 2013)
The effects the 4g/day of histidine had especially on the markers of inflammation are quire impressive for an amino acid of which you probably thought as either the "abundant" essential amino acid that's only an adjutant to 100% non-essential and on it's own just about as useless carnosine precursor beta alanine or - even worse - as the nasty precursor to the "allergy inducing", "inflammatory" organic nitrogen compound histamine.
"Hold on, but histidine is an allergy causing nasty bitch, isn't it?"
While the former perspective on histidine is laughable anyway, the fact that there were no increases in histamine levels and none of the participants experienced side effects such as headaches, which have been observed in previous trials with whopping amounts of 64g(!) of histidine per day (Geliebter. 1994) as they have been used, when scientists still believed that the main mechanism of histidine on body weight modulation was mediated by appetite reduction, are probably relevant. After all, histamine does play a role in the inflammatory response system of your body that the latter is not negatively, but positively affected by the consumption of pretty high amounts of histidine, is thus an important and in a way counterintuitive observation. On the other hand,
First the glucose repartitioning effects of isoleucine (learn more), now the benefits of histidine - what other secrets are still out there in the world of amino acids?
[h]istidine is a free radical scavenger and can chelate divalent metal ions (Babizhayev. 1994; Lee. 1999). Its effects against oxidative stress have been well investigated in animals and cells. Histidine has beneficial effects on liver and lung injury in rats and has been reported to protect against diabetic complications in a mouse model of diabetes through its actions against oxidative stress (Lee. 2005; Cuzzocrea. 2007; Yan. 2009). It can restrict accumulation of free radicals and delay activation of extracellular signal-regulated kinase and c-jun N terminal kinase in neuronal cells (Kulebyakin. 2012).
Against that background it is actually not surprising that the levels of TNF-α, IL-6 and c-reactive protein (CRP) dropped by 33%, 35% and 33% in the course of the 12 week study period.
Health and weight loss, two independent pairs of shoes?
If histidine is a metal chelator, do I have to be afraid of losing zinc? That's easy to answer and the answer is no and not just because I believe that the importance of zinc is way overrated (cf. "15mg of Zinc are plenty"). Schechter & Prakesh have shown in 1979, already that the ingestion of 4g of histidine on a daily basis influences the excretion of zinc only in the very short run. After 2 weeks the body achieves a new steady state and the zinc excretion returns to normal. What? No you did not pee out all the zinc before. In fact histidine increases the absorption of dietary zinc as well (cf. Freeman. 1977).
Moreover the changes in serum histidine were correlated with the changes in HOMA-IR, NEFA, TNF-α, SOD, GSH-Px, WC, FM and BMI even after further adjustment for age and serum histidine, protein intake, physical activity, alcohol use, current smoking and menopause at baseline.
"Thus, improved insulin sensitivity and alleviation of inflammation and oxidative stress could be due to the increased serum histidine." (Feng. 2013)
What's questionable, though, is how interrelated the modest, but statistically significant weight, or rather fat loss (-6% total fat mass) and the improvements in inflammation are. If we take a peek at the aformentioned rodent study by Kimura et al. who observed that the effects of histidine are mediated mainly centrally via histamine action on the H1 receptors in the brain, which will - independently of insulin (!) - downregulate the hepatic glucose production, it becomes more and more evident that non-obese / insulin-resistant individuals for whom an abundant hepatic glucose production hardly ever is a problem are less likely to benefit than the patients with type 2 diabetes, Kimura et al. implicate as the group that would be most likely to benefit from high histidine diets.
What else do we know about l-histidine?
In the end, we are thus back to square one. But maybe we can find other arguments in favor or against keeping an eye on adequate histidine intake that would be significant for the non-diabetic majority(!?) of the SuppVersity readers, as well. Let's see, what about
Ok, put up or shut up - where is the relation between histidine, histamine and obesity? As so often I have to say in advance that the intricacies of the role the histamine receptors in the brain play in the regulation of food intake and metabolism are not yet fully understood. What we do know is that histidine is the dietary precursor for histamine and that the latter can interact with the same receptors (H1-H3) which participate in the regulation of dopamine, serotonin, and norepinephrine release and exert direct modulatory effects on food intake, meal frequency, adiposity and thermogenesis (Masaki. 2003; Masaki. 2004; Yoshimoto. 2006; Yoshimatsu. 2008).
improved absorption of vitamin B12 and increased liver folate levels (Williams. 1976)
low histidine intake increases carnosine breakdown, so that the ant-inflammatory intra-cellular buffer carnosine you are trying to increase by taking BA would decrease to be used as a histidine source if you actually got too little histidine in your diet (Tamaki. 1984)
increased absorption and excretion of zinc, with a primer on the former, when intakes are low, so that the overall result is an improved management of zinc (Sandström. 1985; Van Wouwe. 1989)
potential anti-Alzheimer's effects; if we simply assume that an increased amount of dietary histidine could ameliorate the histidine and histamine reductions in the brains of Alzheimer patients (Mazurkiewicz-Kwilecki. 1989), it would be logical to assume that the presence of this metal-chelator could prevent the accumulation of toxic levels of copper in the brain
significant increases in UCP-1 activity (+57%) in brown adipose tissue and thus higher energy expenditure, reduced appetite, significantly lower feed efficiency (-30%), reduced insulin levels (-48%) and significantly lowered visceral fat pad weights; allegedly in rodents w/ additional 5% histidine in the diet (Kasaoka. 2004)
Now you could certainly argue that the studies which support the weight loss effects Feng et al. observed in their obese subjects were almost exclusively conducted on rodents... what am I supposed to say? You're right and you know that I am very skeptical that UCP-1 and brown adipose tissue activity play a significant role in human weight / body fat control. Still, the high correlations between the histidine / total protein ratio Okubo et al. observed in a cohort of non-obese 18y-old female Japanese students does clearly suggest that at least part of the effects are not species specific (Okubo. 2005).
Additional health effects
Milk thistle is unquestionably the more prominent liver protectant (learn more)
Furthermore, histidine also prevented colitis by reducing gastric inflammation (Andou. 2009) and exerted ameliorative effects on
LDL oxidation and glycation (Lee. 2005),
alcohol induced liver failure (Liu. 2008),
acetaminophen induced liver injury (Yan. 2009),
diet induced hepatic steatosis (Mong. 2011)
when it was co-administered with carnosine. Unfortunately, none of the studies tested, whether the same results would have been observed if only one of the compounds had been used in the respective rodent trials.
So, no strings attached? Well, not exactly...
As usually the dose-response curve is yet non-linear and an exuberantly high intake of histidine (8% of the diet in rodents → far more than 70g per day for humans) can lead to copper depletion and corresponding lipid disturbances in cholesterol metabolism (Harvey. 1981). Needless to say that for people with a messed up histamine metabolism far lower doses could potentially exert negative effects. It should be mentioned though that the equation"more histidine = more histamine" does not necessary hold - just take a look at the data from the Feng study: More histamine? Yes! Beneficial effects? Yes! Increased circulating histamine? No!
Bottom line: Wile it appears likely that the provision of supplemental histidine in amounts of up to 4g/day could provide a highly beneficial adjunct to exercise and diet intervention in obese and/or diabetic individuals, it remains to be seen, whether or not lean, healthy and insulin sensitive fitness enthusiasts benefit to a similar degree.
Histidine content of various foods; w/ a focus on high histidine food items
While I would exclude that the profound anti-inflammatory effects Feng et al. observed could hamper your performance / gains, I would not exclude that the non-vegetarian majority of the SuppVersity readers is not exactly at risk of running out of histidine anytime soon (see table on the right for good dietary sources). Against that background, you may have to revise your perspective on this rarely talked about amino acid. What you probably don't have to do, though, is to go and buy a pouch of l-histidine to up your histidine intake to exorbitantly high levels... well, at least not until research on human beings confirms the beneficial effects on UCP-1, insulin and the body fat levels Ksaoka et al. observed in non-obese rodents.
References:
Andou A, Hisamatsu T, Okamoto S, Chinen H, Kamada N, Kobayashi T, Hashimoto M, Okutsu T, Shimbo K, Takeda T, Matsumoto H, Sato A, Ohtsu H, Suzuki M, Hibi T. Dietary histidine ameliorates murine colitis by inhibition of proinflammatory cytokine production from macrophages. Gastroenterology. 2009 Feb;136(2):564-74.e2.
Babizhayev MA, Seguin MC, Gueyne J, Evstigneeva RP, Ageyeva EA, Zheltukhina GA. L-carnosine (beta-alanyl-L-histidine) and carcinine (beta-alanylhistamine) act as natural antioxidants with hydroxyl-radical-scavenging and lipid-peroxidase activities. Biochem J. 1994; 304(Pt 2):509–516.
Cuzzocrea S, Genovese T, Failla M et al. Protective effect of orally administered carnosine on bleomycin-induced lung injury. Am J Physiol Lung Cell Mol Physiol. 2007; 292:L1095–L1104
Ellison JS, King KW. Mechanism of appetite control in rats consuming imbalanced amino acid mixtures. J Nutr. 1968 Apr;94(4):543-54.
Feng RN, Niu YC, Sun XW, Li Q, Zhao C, Wang C, Guo FC, Sun CH, Li Y. Histidine supplementation improves insulin resistance through suppressed inflammation in obese women with the metabolic syndrome: a randomised controlled trial. Diabetologia. 2013 Jan 30.
Freeman RM, Taylor PR. Influence of histidine administration on zinc metabolism in the rat. Am J Clin Nutr. 1977 Apr;30(4):523-7.
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