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science nutrition <strong>blog</strong>

NAC Might Impair Nitric Oxide Metabolism

NAC (N-acetylcysteine) is an amino acid derived from L-cysteine, and found in dietary supplements that fight free radicals. Free radicals are highly reactive chemicals produced naturally during metabolism. Excessive and chronic elevations of free radicals break down cell membranes, destroy DNA, trigger muscle soreness and protein breakdown, impair the capacity of the immune system and lead to cardiovascular disease. Physicians often use NAC to break up mucus accumulation in the lungs in conditions such as emphysema, pneumonia, bronchitis and tuberculosis. However, a German study from Hannover Medical School found that NAC might interfere with absorption of nitrite in the kidneys, which could have a negative effect on nitric oxide metabolism— an important chemical for tissue blood flow. NAC helps buffer the effect of excessive free radical accumulation, but it could interfere with nitric oxide metabolism. Avoid pre-workout antioxidant supplements such as NAC, taurine, vitamin C and vitamin E to assure maximum performance and exercise adaptation.

The Antagonistic Effects of Caffeine and Taurine in Energy Drinks

Energy drinks have become a billion-dollar industry, challenging the eye-popping popularity of Starbucks and the likes. Obviously, the main component of energy drinks is caffeine with some being more potent than others. However, many manufacturers feel the need to add supplemental ingredients to their drinks to “boost” their energizing effects. Whether this is for marketing or real effect is left to be determined. In fact, L-carnitine is a popular ingredient (read above).
One of the most popular additives to energy drinks is the non-essential amino acid taurine. Taurine is thought to modulate cell volume, muscle contraction and aid in antioxidant defenses from stress in muscle.1 Unfortunately for the college student during finals week, the scientific literature does not support using taurine to enhance the vitalizing effects of your caffeinated beverage.
A recent animal study evaluated the muscle ergogenic effects of caffeine alone or in combination with taurine, and found no beneficial effect to adding taurine.2 Two human, placebo-controlled studies evaluated the effects of using caffeine, taurine or a combination of the two on attention/ “energy.”3 One double-blind, placebo-controlled study compared 80 milligrams of caffeine with or without one gram of taurine and found that co-administration of taurine attenuated the facilitative effects of caffeine.4 Another study compared 200 milligrams of caffeine with or without two grams of taurine, and further showed that taurine inhibited feelings of vigor normally resulting from caffeine alone.5
In summary, the makers of Red Bull and Monster energy drinks may not be out for your best interest when trying to boost your vigor. Not only does taurine have little effect on its own, but it may also have a detrimental effect on the function of your precious caffeine! Maybe the makers should read MD to boost their brain potential!


(International Journal Of Cardiology, 177: 30-33, 2014)
1. Spriet LL1, Whitfield J. Taurine and skeletal muscle function. Curr Opin Clin Nutr Metab Care 2015;Jan;18(1):96-101.
2. Tallis J, et al. Does a physiological concentration of taurine increase acute muscle power output, time to fatigue, and recovery in isolated mouse soleus (slow) muscle with or without the presence of caffeine? Can J Physiol Pharmacol 2014;Jan;92(1):42-9.
3. Sorkin BC, et al. Executive summary of NIH workshop on the Use and Biology of Energy Drinks: Current Knowledge and Critical Gaps. Nutr Rev 2014;Oct;72 Suppl 1:1-8.
4. Peacock A, Martin FH and Carr A. Energy drink ingredients. Contribution of caffeine and taurine to performance outcomes. Appetite 2013;May;64:1-4.
5. Giles GE, et al. Differential cognitive effects of energy drink ingredients: caffeine, taurine, and glucose. Pharmacol Biochem Behav 2012;Oct;102(4):569-77.