What’s new? (What does this article add?)
Actually the relationship between dietary SAAs intake and severity and frequency of pain is unknown. Consumption too excessive SAAs or lack of intake may can effect on MPs. The relationship between dietary SAAs pattern on inflammation and pain was not statistically significant in this study. More than 98% of participants consume higher amount of RDA of methionine and cysteine. It means no deficiency of SAAs is found.
Introduction
Musculoskeletal pain (MPs) is a widespread public problem and there is a need to control effectively and manage severity and frequency of pain in patients. MPs are multifaceted and affect 13.5% to 47% of total population(1,2). In the U.S. MPs alone can impose great financial pressure(3). Aging is a strong risk factor for many chronic diseases and pain is the common point between them (4). However, the impact of population aging on the prevalence of pain is not known. MPs especially in lower back, neck, shoulders and knees are major cause of disability throughout life(5–7). Evidences show that most treatments (pharmacological and non- pharmacological intervention) do just a little short-term cure not long-term efficacy for MPs (7,8) . Recently, lifestyle changes, poor sleeping, smoking, stress, unhealthy diet and obesity have paid our attention to further managing chronic pain(6). Dietary changes have strong effects (positive and negative) on a person’s health(9). Among macronutrients, the role of dietary protein can be examined from several aspect like producing the protective layers of bones and joints (10,11) and improving joint/skeletal health(12). Sulfur amino acids (SAAs), as a part of protein structure, (13) can be one of the precursors of neurotransmitters, antioxidative metabolic intermediates such as glutathione and play a role in inflammation, severity and frequency of MPs finally (10). Among SAAs methionine and cysteine are sold as variety of sulfur-containing supplements (Glucosamine sulphate, chondroitin sulfate and methylsulfonylmethane (MSM)) in the markets to reduce chronic inflammatory pain today (14,15) . Methionine which is an indispensable amino acid, is resistant to oxidation by reactive oxygen species (ROS) (16) and it is needed for proper growth (17).
It seems that the amount of SAAs received from daily diet is inappropriate with individual needs. So many number of researches report that SAAs consumption have an alleviating action on a large number of chronic diseases and degenerative changes which is associated with normal aging by inhibiting oxidative stress(18). One of the main role of SAAs that is proved in articles is providing sulfates for synthesizing essential metabolic mediators like GAG (glycosaminoglycans),CoA (coenzyme A), SAM (S-Adenosyl-L-Methionine), GSH (glutathione) and etc. in the body. Furthermore Sulfating is necessary for detoxification of many drugs such as acetaminophen which is used widely for relieving of pain by the liver (13). Unfortunately no studies have been performed to address this very important question.