Methylsulfonylmethane (MSM) is a commonly used dietary supplement for those seeking relief from joint pain and muscle soreness. One brand, OptiMSM®, manufactured by Bergstrom Nutrition, is a Generally Recognized as Safe (GRAS) dietary ingredient and typically consumed orally at a dosage between 1 and 6 grams daily [1-3]. It has documented success in reducing inflammation associated with knee osteoarthritis [2-5] and in improving aspects of exercise recovery [6-8]. Furthermore, MSM is a recognized treatment for interstitial cystitis [9] and is used as a permeability enhancer for a number of dermatologic agents [10-12]. These broad applications may be partly attributed to its antioxidant properties [13-18] and effects [19,20].

Our recent work has noted that a daily dosage of 3 grams of MSM results in a significant increase in blood MSM after just two weeks of treatment, with a continued rise in blood MSM after four weeks of treatment. Specifically, in a sample of 20 men, all baseline MSM samples but one (0.028 mM) were below the limit of quantification for the assay and serum MSM values increased across time to a mean (± SD) of 1.68 ± 0.60 mM at week 2 and 1.91 ± 0.81 mM at week 4 [21].

What is presently unknown is whether or not a longer time course of treatment with MSM will result in continued elevation in serum MSM and/or if a lower dosage of MSM (e.g., 1 or 2 grams daily) could yield a similar blood MSM concentrations if ingested over a longer period of time (2, 3, or 4 months versus only 1 month as in our prior work). Knowing this information will allow for more specific recommendations to be made concerning MSM dosing. Therefore, the primary purpose of this study was to investigate the impact of different dosages of MSM (1, 2, or 3 grams daily) over a four month period in relation to blood MSM concentrations in men and women. A secondary purpose of this work was to determine if gender differences exist with regards to blood MSM concentration following oral administration.

Subjects

Healthy, nonsmokers between the ages 18 and 41 years were recruited by word-of-mouth conversations, formal presentations discussing participation, and recruitment flyers posted on and off campus. A total of 31 men and 16 women initially enrolled in this study. Two subjects (1 male and 1 female) elected to drop out after the first month of supplementation: one due to an unpredictable future work schedule and the other due to a reoccurring illness. All subjects were required to: have a body mass less than 102 kg (225 pounds), not use any sulfur-containing supplement or medication, and not be allergic to sulfur-containing supplements or medications. While our prior work included only males, females were included in the present study due to a lack of previous data related to female absorption of MSM and because sulfur metabolism varies across the menstrual cycle [22]. Female subjects were not pregnant, not using oral contraceptives, and reported regular menstrual cycles (27-33 days) over the prior six months.

Health history, medication and dietary supplement usage, and physical activity questionnaires were completed by all subjects and reviewed in detail by an investigator to determine eligibility. Before participation, each subject was informed of all procedures, potential risks, and benefits associated with the study through both verbal and written form. The study procedures were approved by the University of Memphis Institutional Review Board for Human Subjects Research (# PRO-FY2018-26).

Subjects were randomly assigned into one of three groups with equal numbers per group (n=15) with 10 men and 5 women per group. Specifically, subjects were assigned to ingest either 1 gram, 2 grams, or 3 grams of MSM daily for 16 weeks. The MSM was administered as OptiMSM® and was provided by Bergstrom Nutrition (Vancouver, WA). Capsules were provided to subjects in unlabeled bottles every four weeks and subjects were instructed to ingest the capsules in the morning hours each day. Subjects returned their capsule bottles to investigators at the end of each four week period and the remaining capsules were counted to determine compliance to intake. Compliance was calculated as 91% for the 1 gram and 2 gram groups, and 90% for the 3 gram group.

Subjects reported to the lab following an overnight fast and provided a blood sample for analysis of plasma MSM on five occasions: baseline (prior to beginning supplementation) and following weeks 4, 8, 12, and 16 of supplementation. No MSM was ingested on the morning of each lab visit/blood draw. All subjects were instructed to maintain their normal diet and physical activity patterns throughout the 16 week study period. Subjects were asked to record food and drink consumption five days prior to each test visit and refrain from strenuous exercise 24 hours prior to each test visit. Diet logs were analyzed using nutritional software (Food Processor Pro, Esha Research, Salem, OR).

Prior to obtaining the blood sample, subjects voided and then rested quietly while seated in a chair for a period of 10 minutes. Diet logs and capsule bottles were collected. Duplicate measurements of resting heart rate and blood pressure were measured using an automated unit (HEM- 907XL; Omron Healthcare, Hoofddorp, Netherlands). Venous blood samples were collected from an antecubital vein into a Vacutainer®. Blood samples were processed in a refrigerated centrifuge (4°C) in order to obtain plasma. Samples were removed and stored at -70°C until analyzed using a LC-MS/MS method, as described elsewhere [23].

Data analysis

Values for all variables were calculated using a repeated measures Analysis of Variance. Tukey post-hoc testing was performed as appropriate. Gender was included in the model initially to determine the potential differences between men and women. Gender was subsequently removed from the model for further analysis. Analyses were performed using JMP software (SAS, Cary, NC). Data are presented as mean ± SD. Statistical significance was considered at p<0.05.

A total of 45 subjects completed this 16 week intervention study. Data were obtained from all subjects, with the following missing blood samples (subject number-week number): 2-12, 8-4, 9-12, 11-0, 11-4, 11-8, 15-4, 21-8, 21-12, 23-4, 23-12, 25-4, 28-0, 28-4, 28-8, 29-16, 30-12, 36-12, 37-12. This accounts for 10 male and 9 female samples of which 7, 9, and 3 were ingesting either 1, 2, or 3 grams per day, respectively. Moreover, this includes 2, 6, 3, 7, and 1 samples missing from weeks 0, 4, 8, 12, and 16 weeks, respectively. Subject characteristics are presented in Table 1. No differences of statistical significance were noted between groups for any variable (p>0.05).

Table 1: Subject characteristics of 45 men and women assigned to MSM for 16 weeks.

Diet records indicated several group differences (p<0.05); however, there were no differences across time and no group x time interactions (p>0.05). Table 2 presents dietary data and the respective statistical differences.

Table 2: Dietary data of men and women assigned to MSM for 16 weeks. Data are mean ± SD.
*Group effects: kilocalories: 3 Grams > 1 Gram (p=0.0011); protein: 1 Gram > 2&3 Grams (p=0.0006); carbohydrates: 3 Grams < 1&2 Grams (p=0.035); fiber: 1 Gram > 2&3 Grams (p=0.002); fat: 1 Gram > 2&3 Grams (p=0.0004); vitamin E: 1 Gram > 3 Grams (p=0.0007); vitamin A: 2 Grams > 3 Grams (p=0.029). No other statistically significant differences noted (p>0.05).

A group effect was noted for heart rate (p=0.002), with values higher for the 3 grams/day group as compared to the 1 gram and 2 gram groups (p<0.05). No differences of statistical significance were noted for systolic or diastolic blood pressure (p>0.05). Data for heart rate and blood pressure are presented in Table 3.

Table 3: Heart rate and blood pressure data of men and women assigned to MSM for 16 weeks.
Data are mean ± SD.
*Group effect for heart rate (p=0.002); values higher for the 3 grams/day group as compared to the 1 gram and 2 gram groups (p<0.05); values sharing the same superscript letters are different from one another when compared at the respective time (i.e., week #)
No other statistically significant differences noted (p>0.05).

With regards to plasma MSM, a group (p<0.0001), time (p<0.0001), and group x time (p=0.0005) interaction was noted. Specifically, values were higher for the 2 and 3 grams/day group as compared to the 1 gram/ day group and were also higher for the 3 grams/day group as compared to the 2 grams/day group (p<0.05). Values at weeks 4, 8, 12, and 16 were higher as compared to baseline (p<0.05) but no differences were noted between weeks 4-16 (p>0.05). With regards to the interaction, at weeks 4, 8, 12, and 16, values were higher for the 3 grams/day group as compared to the 1 gram/day group (p<0.05). At week 4, values were also higher for the 3 grams/day group as compared to the 2 grams/day group (p<0.05). Data for plasma MSM for all subjects are presented in Figure 1. Since values for week 4 for the respective dosages were near identical to weeks 8, 12, and 16, data for week 4 are not shown and are included in our methodology paper [23]. It should be noted that the response curve when including week 4 data is essentialy the same as that shown in Figure 1, with the exception of the additional week 4 time prior to week 8.

Figure 1: Plasma MSM concentrations of men and women assigned to MSM for 16 weeks.
Data are mean ± SD.
Group: * - 2 and 3 grams/day > 1 gram/day; † - 3 grams/day > 2 grams/day. Time: ‡ - Weeks 8, 12, and 16 > Week 0. Group x time interaction: a – 3 grams/day > 1 gram/day at weeks 8, 12, and 16.
No other statistically significant differences noted (p>0.05).

When including gender in the model, we noted a gender effect (p=0.01). Specifically, higher overall plasma MSM values were observed in women (1082 ± 1006 μM) as compared to men (845 ± 805 μM). The greatest difference between genders occurred with the 2 gram per day dosage. No gender interactions were noted: gender x group (p=0.32), gender x time (p=0.71), and gender x group x time (p=0.99). Data for plasma MSM, separated by gender, are presented in Figure 2.

Figure 2: Plasma MSM, separated by gender, through 16 weeks of MSM supplementation. * Gender effect (p=0.01); higher plasma MSM in women.

We evaluated plasma MSM concentrations in men and women following 16 weeks of oral MSM supplementation at dosages of 1, 2, or 3 grams daily. Our main findings are as follows: 1) baseline plasma MSM concentrations are in the very low micromolar range as measured via LC-MS/MS; 2) plasma MSM concentrations reach a dosedependent steady-state by week 4 and are maintained through week 16 with continuous supplementation; 3) the steady-state plasma MSM concentrations increased linearly with increasing dosages; 4) women had higher overall plasma MSM concentrations than men but values displayed a very similar pattern across time and dependent upon dose. The results presented here are near identical to previously reported pharmacokinetic data, in that baseline MSM values were in the low micromolar range [21,24,25] and blood MSM concentrations after 4 weeks of daily supplementation with 3 grams/day were approximately 1900 μM [21].

Acute MSM pharmacokinetic data indicate that MSM is rapidly absorbed in the upper gastrointestinal tract and slowly removed from the serum [25]. Previous animal studies have reported similar findings, in that MSM is likely absorbed via passive diffusion into enterocytes of the upper gastrointestinal tract followed by homogenous tissue distribution throughout the body [26]. Considering the unique membrane penetrability properties and homogenous tissue distribution of MSM, it stands to reason that body weight may impact blood MSM concentrations as suggested previously [21,25]. Furthermore, difference in blood volume may also influence blood MSM concentrations, as this can be affected by weight, height, and even gender (i.e., women lower than men). Taken together, these factors may contribute to the higher MSM concentrations we observed in women (Figure 2), as body weight was significantly lower (p<0.0001) in women (65 kg) as compared to men (80 kg). Moreover, these discrepancies may have contributed to the observed greater values in the 3 grams/day group compared to the 2 grams/day, though the body weight of our 3 grams/day group was not significantly lower from a statistical point of view.

In our previous study evaluating oral supplementation at 3 grams/ day, serum MSM concentrations appear to have risen non-linearly over the 4-week period, though only 3 measurements were taken [21]. This may suggest values could reach a steady-state as early as 3-4 weeks. Previous clinical trials have demonstrated MSM to be an effective osteoarthritis treatment at dosages of 6 grams/day for 12 weeks [3], 3.375 grams/day for 12 weeks [2,27], and 6 grams/day for 26 weeks [28]. In fact, aggregated locomotor function which includes three functional movement timed tests was significantly improved after only 6 weeks of supplementation with 3.375 grams/day [2]. Unfortunately, these studies, nor any other clinical trials, have correlated blood MSM concentrations with clinical effectiveness. Future studies should focus on eliciting this information in order to develop best dosing practices for MSM and its variety of uses. Moreover, a better determination of elimination half-life and turnover rates for different steady-state concentrations would greatly aid in the development of suggested dosing. These variables may help better understand how quickly MSM levels return to baseline, as prior acute pharmacokinetic data utilizing a cross-over design and dosing of one, two, and three grams demonstrated a significant “order effect” and “carry-over” of MSM between visits following a seven day washout period [25].

In summary, the response to MSM supplementation at escalating dosages was similar between men and women such that low micromolar baseline values rose to dose-dependent steady-states after only 4 weeks of supplementation. With continued daily supplementation, levels were maintained throughout the 16-week trial. If higher plasma MSM values are desired, longer use of lower dosages do not seem to be effective, as bioaccumulation is minimal.

Funding for this work was provided by Bergstrom Nutrition and The University of Memphis.

RJB and CRY were responsible for the conception and design of the study, as well as manuscript preparation. RJB was responsible for data analysis. MB was responsible for subject recruitment, screening, data collection, and manuscript preparation. LL, DM, and CRY were responsible for assay development and analysis of blood samples. All authors contributed to and approved of the final manuscript.

RJB and CRY have received research funding from Bergstrom Nutrition, including this study. Bergstrom Nutrition was consulted in the design of this study. All other authors have no competing interests.