Prevalence of glucosamine and omega-3 fatty acid use and characteristics of users among mid-age women: Analysis of a nationally representative sample of 10,638 women

Abstract

Background

There has been a dramatic increase in the use of dietary supplements over the last few decades and both omega-3 fatty acids and glucosamine are two of the best-selling dietary supplements in many countries. An understanding of omega-3 fatty acids and glucosamine consumption is of significance to health care providers and for future health promotion activities.

Methods

This research involved analysis of data collected from a nationally-representative sample of Australian women as part of the Australian Longitudinal Study on Women's Health (ALSWH). Participants' use of omega-3 fatty acids (FA), glucosamine, their demographics, health status and health care utilisation were measured. Analysis included logistic regression modelling.

Results

Of the 10,638 women in the study, 26.8% reported use of omega-3 FA and 15.9% glucosamine. Women with osteoarthritis (OR=2.529; 95% CI: 2.190, 2.921), other arthritis (OR= 1.618; 95% CI: 1.375, 1.905), and joint pain (OR= 2.699; 95% CI: 2.305, 3.160) were more likely to use glucosamine (all p<0.001). In contrast, those with diabetes (OR= 0.471; 95% CI: 0.343, 0.646) or depression (OR= 0.764; 95% CI: 0.657, 0.887) were less likely to use glucosamine (both p<0.001). Women with osteoarthritis (OR=1.481; 95% CI: 1.297, 1.691) and joint pain (OR= 1.456; 95% CI: 1.306, 1.622) were more likely to use omega-3 FA (all p<0.001).

Conclusions

Substantial prevalence rates for use of glucosamine and omega-3 FA amongst mid-aged women highlights the need for health practitioners and policymakers to be mindful of the possible significant role of such supplement use as part of patient health-seeking behaviours.

Introduction

There has been a dramatic increase in the use of dietary supplements in Western societies over the past few decades (1., 2., 3.) which has been attributed to population ageing (4) and an increase in the prevalence of chronic diseases, that conventional medicine often fails to adequately treat (5., 6.). Omega-3 fatty acids (FA) and glucosamine are two of the most popular dietary supplements in many countries. Research has identified omega-3 FA (fish oil/omega-3/DHA or docosahexaenoic acid) (37%) and glucosamine (20%) as the first and second most commonly used natural (non-vitamin, non-mineral) products among American adults (7). A UK cohort study of 1,646 older supplement users found fish liver oils constituted 84% of all oils taken by participants and identified glucosamine/chondroitin as used by 11% of men and 18% of women (2). Another study of older New Zealand men reported 13% of participants used fish oils or glucosamine/chondroitin preparations (8). In Australia, glucosamine and omega-3 FA are among the top five complementary medications that GPs (glucosamine 85%, rank 1; omega-3 FA 83%, rank 3) or community pharmacists (glucosamine 95%, rank 1; omega-3 FA 90%, rank 4) recommend to patients (9).

Recent research in Australia has found that glucosamine (9) and omega-3 FA (10) use are high among women, non-smokers, those having higher income and private health insurance. The use of these two supplements was also found to be associated with geographical region (glucosamine higher in rural and omega-3 FA higher in urban setting) (10, 11). The findings of these two studies also suggested that the two supplements may be used for the management of osteoarthritis (glucosamine) or osteoarthritis, osteoporosis, high cholesterol, anxiety and/or depression (omega-3 FA) (10, 11).

Glucosamine is commonly used as a preventive measure and treatment for joint problems and osteoarthritis (12., 13., 14.). However, the evidence base for the effectiveness of it as a treatment for osteoarthritis remains inconclusive (15., 16., 17., 18., 19., 20., 21., 22.). It has been suggested that the heterogeneity of research findings could be exacerbated by factors such as varying formulations (e.g. glucosamine sulfate vs. hydrochloride), variations in quality, industry bias, and/or methodological variability (23, 24).

The clinical evidence base for omega-3 FA is varied depending on the specific condition. There is ample evidence in the literature that omega-3 FA help in preventing or benefiting the outcomes of cardiovascular disease (25., 26., 27., 28., 29., 30., 31., 32., 33.). However, a new meta-analysis and systematic review published in 2012 found no relation between use of omega-3 FA and reduced risk of major cardiovascular diseases (34). At present, the National Heart Foundation of Australia recommends all Australian adults consume about 500 mg (or 1,000 mg for those who have documented coronary heart disease) of omega-3 FA per day (35). There is also some evidence that omega-3 FA may improve clinical, biological and quality of life parameters amongst patients with advanced cancer (36., 37., 38.). The efficacy of omega-3 FA regarding the following conditions is also suggested, but there is currently insufficient evidence to support these claims: improvement of mental health disorders (39., 40., 41.) asthma (42), cystic fibrosis (43), rheumatoid arthritis, inflammatory bowel disease and osteoporosis (44) and cognitive functions affected by aging, dementia, and neurological diseases (45, 46).

Despite the extensive use of glucosamine and omega-3 FA in contemporary societies, the topic has received little attention to date. While previous broad complementary and alternative medicine (CAM) or nutrition-focused studies have provided prevalence rates for glucosamine (7, 47., 48., 49., 50.) and omega-3 FA use (7, 50), there has been little focused examination of the profile of users of glucosamine (51, 12) and omega-3 FA (10) and the various factors influencing the consumption of these two supplements (8).

Drawing upon analysis of a nationally representative sample of Australian women, this paper reports findings regarding the prevalence and profile of glucosamine and omega-3 FA users providing information of significance for nutrition planning, health promotion and service delivery.

Methods

Sample

This research was conducted as part of the Australian Longitudinal Study on Women's Health (ALSWH) which was designed to investigate multiple factors affecting the health and wellbeing of women over a 20-year period. Women in three age groups (‘young' 18-23, ‘mid age' 45-50 and ‘older' 70-75 years) were randomly selected from the national Medicare database (52). The focus of this study is women from the mid-age cohort. The baseline survey, comprising of 14,099 women, was conducted in 1996 and the respondents have been shown to be broadly representative of the national population of women in the target age groups (53). Analyses for this research is restricted to the survey conducted in 2007, as specific questions on use of vitamins and supplements were asked in this survey only.

Measures of demographic characteristics

Postcode of residence at the time of the baseline survey was used to classify area of residence as urban or non-urban. Women were asked about their current marital status, the highest educational qualification they had completed, and whether or not they have private health insurance for ancillary services. The women were also asked how they manage on the income they have available.

Measure of health status

Women were asked to rate their overall health and were given 5 categories (excellent, very good, good, fair, poor). Women were classified according to the number of cigarettes smoked each day as ‘non-smoker' or ‘current smoker' using a modified version of the Australian Institute of Health and Welfare data dictionary (54) and also classified according to their consumption of alcohol as defined by the National Health and Medical Research Council of Australia (55): ‘risky/high risk drinker' (over 175ml of pure alcohol per week), ‘low risk drinker' (up to 175ml of pure alcohol per week) or ‘non-drinker' (abstaining from alcohol).

Women were asked how often they experienced a list of symptoms in the previous twelve months, including: allergies or hay fever or sinusitis, indigestion, chest pain, headaches or migraines, severe tiredness, stiff or painful joints, back problems, haemorrhoids, other bowel problems, depression, and anxiety. Women were also asked whether a doctor had ever told them that they had any of the chronic medical conditions listed, including: osteoarthritis, rheumatoid arthritis, other arthritis, osteoporosis, diabetes, heart disease (heart attack or angina), hypertension, low iron, asthma, and cancer (excluding skin cancer).

Health service utilisation

The women were asked about their frequency of consultations in the previous twelve months of a general practitioner (GP) and a specialist doctor. In addition, they were asked if they had consulted with a range of CAM practitioners (i.e. chiropractor, massage therapist, acupuncturist, naturopath/herbalist, osteopath, other alternative health practitioner) in the previous twelve months.

Outcome measures

The women were asked to write down the names of all their medications, vitamins, supplements or herbal therapies. Where possible, they were asked to copy the names of these products from the packets. From this information, the Anatomical Therapeutic Chemical (ATC) codes (56) were used to define use of glucosamine and omega-3 FA.

Statistical analyses

Chi-square tests were used to examine the association between glucosamine use, omega-3 FA use and the demographic, health status and health service utilisation variables. Separate logistic regression model building processes were undertaken to determine the statistically significant predictors of glucosamine use and omega-3 FA use. That is, all the demographic, health status and health service utilisation variables listed above were entered into a model and then a stepwise backward elimination process was employed, using a likelihood ratio test, to eventually produce the most parsimonious model. In response to the large sample size, a p-value < 0.005 was adopted for statistical significance. All analyses were conducted using statistical program SAS.

Results

Of the 10,638 women in our study, 26.8% (n=2,847) reported use of omega-3 FA and 15.9% (n=1,685) glucosamine. Table 1 shows the distributions of demographic characteristics amongst women who do or do not consume omega-3 FA or glucosamine. Those women with no formal education or who find it difficult to manage on their income were less likely to use the two dietary supplements (all p<0.005). Women with ancillary health insurance were more likely to use glucosamine and omega-3 FA (all p<0.005) than those without ancillary health insurance. Neither area of residence or marital status was significantly associated with use of these two supplements.

Table 1.

The distribution of demographic characteristics amongst women who do or do not consume omega-3 FA and do or not consume glucosamine

Characteristic		Omega-3 FA		Glucosamine
		Yes	No	Yes	No
		(n=2847)	(n=7791)	(n=1685)	(n=8953)
		%	%	%	%
Area of Residence	urban	41	39	39	40
	rural/remote	59	61	61	60
Education 1,1	no formal	14	17	11	17
	school only	49	48	49	48
	trade/diploma	21	20	23	20
	tertiary	16	15	17	15
Manage on Income 1, 2	impossible/difficult always	10	13	10	13
	difficult sometimes	23	24	22	24
	not too bad/easy	67	63	68	63
Marital Status	married/defacto	79	78	81	78
	separ./widowed/divorced	18	19	16	19
	never married	3	3	2	3
Health Insurance 1,2	yes	62	56	63	57
	no	38	44	37	43

¹Statistically significant association with omega-3 FA (p<0.005);

²Statistically significant association with glucosamine (p<0.005)

The distributions of health status characteristics amongst women who do or do not consume omega-3 FA or glucosamine are presented in Table 2. Women who consume the two supplements were more likely to be non-smokers and low-risk drinkers of alcohol (all p<0.005). They were also more likely to have osteoarthritis, other arthritis, joint pain and back problems (all p<0.005). The women who consume glucosamine were also more likely to have rheumatoid arthritis (p<0.005). In contrast, women with diabetes were less likely to use these two supplements (all p<0.005) and women with hypertension were less likely to use omega-3 FA (p<0.005). There were no statistically significant associations between use of these two supplements and osteoporosis, asthma, cancer, heart disease, anxiety or depression.

Table 2.

The distribution of health status characteristics amongst women who do or do not consume omega-3 FA and do or not consume glucosamine

Characteristic		Omega-3 FA		Glucosamine
		Yes	No	Yes	No
		(n=2847)	(n=7791)	(n=1685)	(n=8953)
		%	%	%	%
Smoking Status 1,2	non-smoker	93	88	93	88
	current smoker	7	12	7	12
Alcohol Status 1,2	non-drinker	7	9	5	9
	low-risk	87	85	88	84
	risky	6	7	7	7
Overall Health	excellent/v. good/good	87	86	88	86
	fair/poor	13	14	12	14
Osteoarthritis1,2	yes	21	14	32	13
	no	79	86	68	87
Rheumatoid Arthritis2	yes	5	4	6	4
	no	95	96	94	96
Other Arthritis1,2	yes	16	13	20	12
	no	84	87	80	88
Osteoporosis	yes	7	6	7	6
	no	93	94	93	94
Asthma	yes	10	10	12	10
	no	90	90	88	90
Cancer	yes	17	16	17	16
	no	83	84	83	84
Hypertension1	yes	26	29	27	28
	no	74	71	73	72
Heart Attack or Angina	yes	4	4	4	3
	no	96	96	96	97
Anxiety	yes	8	8	7	8
	no	92	92	93	92
Depression	yes	24	23	22	24
	no	76	77	78	76
Diabetes1,2	yes	5	7	4	7
	no	95	93	96	93
Joint Pain1,2	yes	70	61	83	59
	no	30	39	17	41
Back Problems1,2	yes	60	53	66	53
	no	40	47	34	47

¹Statistically significant association with omega-3 FA (p<0.005);

²Statistically significant association with glucosamine (p<0.005)

Table 3 shows the distribution of health service utilisation characteristics amongst women who do or do not consume omega-3 FA or glucosamine. The women who used these two supplements were more likely to consult with a GP, specialist, and CAM practitioner (all p<0.005).

Table 3.

The distribution of health service utilisation characteristics amongst women who do or do not consume omega-3 FA and do or not consume glucosamine

Characteristic		Omega-3 FA		Glucosamine
		Yes	No	Yes	No
		(n=2847)	(n=7791)	(n=1685)	(n=8953)
		%	%	%	%
GP visits1,2	yes	95	93	96	93
	no	5	7	4	7
Specialist Visit1,2	yes	50	46	52	46
	no	50	54	48	54
CAM Visits1,2	yes	51	39	53	41
	no	49	61	47	59

¹Statistically significant association with omega-3 FA (p<0.005);

²Statistically significant association with glucosamine (p<0.005)

The multiple logistic regression model for predicting consumption of glucosamine is presented in Table 4. In comparison to women with a tertiary education, women with no formal education were 0.563 (95% CI: 0.444, 0.714) time less likely to use glucosamine (p<0.001), while women with school only education were 0.861 (95% CI: 0.732, 1.026) times less likely to use glucosamine (p=0.003). Women who were current smokers were 0.661 (95% CI: 0.529, 0.826) times less likely to use glucosamine than non-smokers (p<0.001). In comparison to risky drinkers of alcohol, those women who were low risk drinkers were 1.638 (95% CI: 1.153, 2.329) times more likely to consume glucosamine (p=0.001). The women who consulted a CAM practitioner were also 1.432 (95% CI: 1.267, 1.618) times more likely to use glucosamine (p<0.001). Regarding health conditions, the women with osteoarthritis (OR=2.529; 95% CI: 2.190, 2.921), other arthritis (OR= 1.618; 95% CI: 1.375, 1.905), and joint pain (OR= 2.699; 95% CI: 2.305, 3.160) were more likely to use glucosamine (all p<0.001). In contrast, those with diabetes (OR= 0.471; 95% CI: 0.343, 0.646) or depression (OR= 0.764; 95% CI: 0.657, 0.887) were less likely to use glucosamine (both p<0.001).

Table 4.

Multiple logistic regression model for predicting consumption of glucosamine

Factor		Odds Ratio	95% C.I.	p-value
Education	Tertiary	-
	Trade / Diploma	0.987	0.811, 1.203	0.456
	School Only	0.861	0.732, 1.026	0.003
	No Formal	0.563	0.444, 0.714	<0.001
Smoking Status	Non-smoker	-
	Current smoker	0.661	0.529, 0.826	<0.001
Alcohol Status	Risky drinker	-
	Low risk drinker	1.638	1.153, 2.329	0.001
	Non-drinker	1.042	0.815, 1.333	0.032
Consulted a CAM	No	-
Practitioner	Yes	1.432	1.267, 1.618	<0.001
Osteo-arthritis	No	-
	Yes	2.529	2.190, 2.921	<0.001
Other Arthritis	No	-
	Yes	1.618	1.375, 1.905	<0.001
Diabetes	No	-
	Yes	0.471	0.343, 0.646	<0.001
Depression	No	-
	Yes	0.764	0.657, 0.887	<0.001
Joint Pain	No	-
	Yes	2.699	2.305, 3.160	<0.001

The multiple logistic regression model for predicting consumption of omega-3 FA is presented in Table 5. In comparison to women from urban areas, women from rural areas were 0.865 (95% CI: 0.783, 0.955) time less likely to use omega-3 FA (p=0.004). Women who were current smokers were 0.602 (95% CI: 0.505, 0.717) times less likely to use omega-3 FA than non-smokers (p<0.001). The women who consulted a CAM practitioner were 1.612 (95% CI: 1.462, 1.779) times more likely to use omega-3 FA (p<0.001). The women with osteo-arthritis (OR=1.481; 95% CI: 1.297, 1.691) and joint pain (OR= 1.456; 95% CI: 1.306, 1.622) were more likely to use omega-3 FA (all p<0.001). Women who rated their general health as being excellent, very good or good were 1.288 (95% CI: 1.099, 1.510) times more likely to use omega-3 FA (p=0.002), compared to women who rated their general health as poor or fair.

Table 5.

Multiple logistic regression model for predicting consumption of omega3

Factor		Odds Ratio	95% C.I.	p-value
Area of Residence	Urban	-
	Rural	0.865	0.783, 0.955	0.004
Smoking Status	Non-smoker	-
	Current smoker	0.602	0.505, 0.717	<0.001
Consulted a CAM	No	-
Practitioner	Yes	1.612	1.462, 1.779	<0.001
Osteo-arthritis	No	-
	Yes	1.481	1.297, 1.691	<0.001
Joint Pain	No	-
	Yes	1.456	1.306, 1.622	<0.001
General Health	Fair / Poor	-
	Excellent / Very Good / Good	1.288	1.099, 1.510	0.002

Discussion

This paper reports the results of an analysis of the ALSWH dataset regarding the prevalence and profile of glucosamine and omega-3 FA use among mid-age Australian women. The research benefits from having such a large and nationally representative sample, based on probability sampling, and the findings further our understanding of the prevalence and characteristics of users of dietary supplements in Australia.

The study shows that the use of glucosamine and omega-3 FA is common among mid-age Australian women. Specifically, 15.9% and 26.8% of the study participants, who are aged between 55-60 years (at time of the 2007 survey), consume glucosamine and omega-3 FA respectively. These two prevalence rates are lower than the level of use (glucosamine 22.0%; omega-3 FA 32.6%) as recorded by previous studies using the 45 and Up Study dataset (10, 11). One possible explanation for this difference is the age of the participants surveyed across the two datasets. There is evidence that consumption of dietary supplements is associated with increased age (57., 58., 59.) and the previous literature reveal that 62% of participants of the 45 and Up Study are 60 years or over and these older Australians are 2.3 times more likely to consume glucosamine (1.8 times more likely in the case of omega-3 FA) than people aged below 60 (10, 11). Given that the ALSWH participants are younger in age (55-60 years at time of information collection), this difference in age between the two study populations may explain the variation in prevalence rates for glucosamine and omega-3 FA use.

Our analysis shows that use of glucosamine and omega-3 FA among mid-age Australian women is associated with higher education, annual income and private health insurance. These findings are consistent with results of previous studies on dietary supplements (10, 60., 61., 62., 11). This previous literature highlights the importance of socioeconomic factors (such as an ability to seek information/professional advice or afford the cost of dietary supplements) in determining the consumption of these two supplements. Like many dietary supplement products in Australia, glucosamine and omega-3 FA are not subsidised by the Pharmaceutical Benefits Scheme of the Federal Government and as such attract an added 10% goods and service tax. The relatively low prevalence of use of these two supplementations among Australian women with poor socio-economic status may reflect a disparity in access of health services and resources.

One of the important findings of this study is to highlight and provide empirical support to the link between use of glucosamine/omega-3 FA and consultation with a CAM practitioner. Our analysis indicates that women who visit a CAM practitioner are 1.4 times more likely to consume glucosamine (or 1.6 times more likely to consume omega- 3 FA) than women who do not consult a CAM practitioner. Dietary supplements such as glucosamine have long been promoted as a complementary medication or agent (63) and the result of this study underlines the important role of CAM practitioners in prescribing or recommending such supplements to patients. Previous research on prescription style and information needs regarding dietary supplements has focused exclusively upon conventional health professionals such as GPs and pharmacists (9). Our study suggests that there is a need for future investigation to also pay attention to the role of CAM practitioners in the prescription and safe use of nutritional supplements.

The findings of our study that use of glucosamine and omega-3 FA is associated with health conditions such as osteoarthritis and joint pain are also broadly in line with previous studies (10, 11) and the clinical evidence base for the two supplements (44, 15, 17, 22). Our analysis demonstrates that the use of glucosamine and omega-3 FA is associated with healthy lifestyles including not smoking and/or consuming less alcohol. The link of these two supplements use to such health conscious choices/practices highlights the use of glucosamine and omega-3 FA as a preventative practice alongside the treatment of specific health conditions. It would be useful for future studies to provide in-depth examination of the motivations of glucosamine and omega-3 FA users and the role of dietary supplements as a component of a healthy lifestyle approach combining the use of CAM, physical exercises and other nutritional supplementations.

Finally, regarding spatial distribution of consumption of dietary supplements, the finding from our study that omega-3 FA is higher in urban areas is consistent with results of our study in New South Wales (10). In contrast, our study finds no regional difference in the use of glucosamine. This finding is different from the analysis of the 45 and Up Study dataset which suggests a higher level of consumption of glucosamine among residents of rural areas as opposed to non-rural areas across New South Wales (11). Our findings add to the evidence-base on the geographical distribution of supplementary use and highlight the need for further investigation into the complexities of geographical variation in consumption of nutritional supplements.

The interpretation of our findings is limited by the fact that both information about health/disease conditions and omega-3 FA/glucosamine use are self-reported by the ALSWH participants and as such responses may be subjected to recall bias. Moreover, the association between particular health conditions with omega-3 FA/glucosamine use does not necessarily imply that these two dietary supplements have been used specifically for such conditions. Further studies are needed to illuminate the role of omega-3 FA and glucosamine in relation to these health problems.

Implications for Practice and/or Policy

The prevalence of use of omega-3 FA and glucosamine amongst mid-aged women is high. However, the evidence base for the effectiveness of glucosamine as a treatment for osteoarthritis remains inconclusive. Similarly, the evidence base for the effectiveness of omega-3 FA for the treatment of a number of chronic conditions is mixed. Health care practitioners need to acknowledge this high use of omega-3 FA and glucosamine amongst their patients and as such engage in conversation with their patients about the available evidence of effectiveness in treating particular conditions. Long-term use of these supplements can be a costly to patients and it is the health care practitioner who is in the best position to advise them regarding such use. The findings of this study also highlight areas of importance for future research, in particular why women seek out alternative forms of care for their chronic illnesses, and what information sources do they employ in making decision about their use of supplements.

Conclusion

This paper reports the findings of an analysis on the prevalence of use and profile of users of glucosamine and omega-3 FA amongst a nationally representative sample of women aged 56-61. Substantial prevalence rates for use of glucosamine and omega-3 FA amongst these women highlights the need for conventional health practitioners and policymakers to be mindful of the significant possible role of such supplement use within patient health seeking and community health behaviours.

Disclosure of interest:

There is no conflict of interest for the authors of this paper.