Digestive Health Supplements Market (2025 - 2033) Size, Share & Trend Analysis Report By Product (Prebiotics, Probiotics), By Form (Capsules, Tablets), By Distribution Channel (Over-the-counter (OTC), Prescribed), By Region, And Segment Forecasts

Table of Contents

Chapter 1. Methodology and Scope
                    1.1. Market Segmentation & Scope
                    1.2. Market Definition
                    1.3. Information Procurement
                        1.3.1. Purchased Database
                        1.3.2. GVR’s Internal Database
                        1.3.3. Secondary Materials & Third-Party Perspectives
                        1.3.4. Primary Research
                    1.4. Information Analysis
                        1.4.1. Data Analysis Models
                    1.5. Market Formulation & Data Visualization
                    1.6. Data Validation & Publishing
Chapter 2. Executive Summary
                    2.1. Market Snapshot
                    2.2. Product Outlook
                    2.3. Form Outlook
                    2.4. Distribution Channel Outlook
                    2.5. Regional Outlook
                    2.6. Competitive Landscape Snapshot
Chapter 3. Digestive Health Supplements Market Variables and Trends
                    3.1. Market Introduction
                    3.2. Industry Value Chain Analysis
                        3.2.1. Raw Material Trends & Outlook
                        3.2.2. Retail/Sales Channel Analysis
                    3.3. Market Dynamics
                        3.3.1. Market Driver Analysis
                        3.3.2. Market Restraint Analysis
                        3.3.3. Market Opportunities
                        3.3.4. Market Challenges
                    3.4. Industry Analysis Tools
                        3.4.1. Porter’s Five Forces Analysis
                    3.5. Market Entry Strategies
Chapter 4. Digestive Health Supplements Market: Consumer Behavior Analysis
                    4.1. Demographic Analysis
                    4.2. Consumer Trends & Preferences
                    4.3. Factors Affecting Buying Decisions
                    4.4. Consumer Product Adoption
                    4.5. Observations & Recommendations
Chapter 5. Digestive Health Supplements Market: Product Estimates & Trend Analysis
                    5.1. Digestive Health Supplements Market, By Product: Key Takeaways
                    5.2. Product Movement Analysis & Market Share, 2024 & 2033
                    5.3. Market Estimates & Forecasts by Product, 2021 - 2033 (USD Million)
                        5.3.1. Prebiotics
                            5.3.1.1. Market estimates and forecast, 2021 - 2033 (USD Million)
                        5.3.2. Probiotics
                            5.3.2.1. Market estimates and forecast, 2021 - 2033 (USD Million)
                        5.3.3. Enzymes
                            5.3.3.1. Market estimates and forecast, 2021 - 2033 (USD Million)
                        5.3.4. Fulvic Acid
                            5.3.4.1. Market estimates and forecast, 2021 - 2033 (USD Million)
                        5.3.5. Others
                            5.3.5.1. Market estimates and forecast, 2021 - 2033 (USD Million)
Chapter 6. Digestive Health Supplements Market: Form Estimates & Trend Analysis
                    6.1. Digestive Health Supplements Market, By Form: Key Takeaways
                    6.2. Form Movement Analysis & Market Share, 2024 & 2033
                    6.3. Market Estimates & Forecasts by Form, 2021 - 2033 (USD Million)
                        6.3.1. Capsules
                            6.3.1.1. Market estimates and forecast, 2021 - 2033 (USD Million)
                        6.3.2. Tablets
                            6.3.2.1. Market estimates and forecast, 2021 - 2033 (USD Million)
                        6.3.3. Powders
                            6.3.3.1. Market estimates and forecast, 2021 - 2033 (USD Million)
                        6.3.4. Liquids
                            6.3.4.1. Market estimates and forecast, 2021 - 2033 (USD Million)
                        6.3.5. Others
                            6.3.5.1. Market estimates and forecast, 2021 - 2033 (USD Million)
Chapter 7. Digestive Health Supplements Market: Distribution Channel Estimates & Trend Analysis
                    7.1. Digestive Health Supplements Market, By Distribution Channel: Key Takeaways
                    7.2. Distribution Channel Movement Analysis & Market Share, 2024 & 2033
                    7.3. Market Estimates & Forecasts, by Distribution Channel, 2021 - 2033 (USD Million)
                        7.3.1. OTC
                            7.3.1.1. Market estimates and forecast, 2021 - 2033 (USD Million)
                                7.3.1.1.1. Supermarkets/Hypermarkets/Food Stores
                                    7.3.1.1.1.1. Market estimates and forecast, 2021 - 2033 (USD Million)
                                7.3.1.1.2. Drug Stores & Pharmacies
                                    7.3.1.1.2.1. Market estimates and forecast, 2021 - 2033 (USD Million)
                                7.3.1.1.3. Convenience Stores
                                    7.3.1.1.3.1. Market estimates and forecast, 2021 - 2033 (USD Million)
                                7.3.1.1.4. Online
                                    7.3.1.1.4.1. Market estimates and forecast, 2021 - 2033 (USD Million)
                                7.3.1.1.5. Others
                                    7.3.1.1.5.1. Market estimates and forecast, 2021 - 2033 (USD Million)
                        7.3.2. Prescribed
                            7.3.2.1. Market estimates and forecast, 2021 - 2033 (USD Million)
Chapter 8. Digestive Health Supplements Market: Regional Estimates & Trend Analysis
                    8.1. Regional Movement Analysis & Market Share, 2024 & 2033
                    8.2. North America
                        8.2.1. U.S.
                            8.2.1.1. Key country dynamics
                            8.2.1.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                        8.2.2. Canada
                            8.2.2.1. Key country dynamics
                            8.2.2.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                        8.2.3. Mexico
                            8.2.3.1. Key country dynamics
                            8.2.3.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                    8.3. Europe
                        8.3.1. UK
                            8.3.1.1. Key country dynamics
                            8.3.1.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                        8.3.2. Germany
                            8.3.2.1. Key country dynamics
                            8.3.2.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                        8.3.3. France
                            8.3.3.1. Key country dynamics
                            8.3.3.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                        8.3.4. Italy
                            8.3.4.1. Key country dynamics
                            8.3.4.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                        8.3.5. Spain
                            8.3.5.1. Key country dynamics
                            8.3.5.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                        8.3.6. Sweden
                            8.3.6.1. Key country dynamics
                            8.3.6.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                        8.3.7. Netherlands
                            8.3.7.1. Key country dynamics
                            8.3.7.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                        8.3.8. Denmark
                            8.3.8.1. Key country dynamics
                            8.3.8.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                    8.4. Asia Pacific
                        8.4.1. China
                            8.4.1.1. Key country dynamics
                            8.4.1.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                        8.4.2. India
                            8.4.2.1. Key country dynamics
                            8.4.2.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                        8.4.3. Japan
                            8.4.3.1. Key country dynamics
                            8.4.3.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                        8.4.4. Australia & New Zealand
                            8.4.4.1. Key country dynamics
                            8.4.4.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                        8.4.5. Hong Kong
                            8.4.5.1. Key country dynamics
                            8.4.5.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                        8.4.6. Singapore
                            8.4.6.1. Key country dynamics
                            8.4.6.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                    8.5. Central & South America
                        8.5.1. Brazil
                            8.5.1.1. Key country dynamics
                            8.5.1.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                    8.6. Middle East & Africa
                        8.6.1. South Africa
                            8.6.1.1. Key country dynamics
                            8.6.1.2. Market estimates and forecast, 2021 - 2033 (USD Million)
                        8.6.2. UAE
                            8.6.2.1. Key country dynamics
                            8.6.2.2. Market estimates and forecast, 2021 - 2033 (USD Million)
Chapter 9. Digestive Health Supplements Market: Competitive Analysis
                    9.1. Recent Developments & Impact Analysis by Key Market Participants
                    9.2. Company Categorization
                    9.3. Participant’s Overview
                    9.4. Financial Performance
                    9.5. Product Benchmarking
                    9.6. Company Market Share Analysis, 2024 (%)
                    9.7. Company Heat Map Analysis, 2024
                    9.8. Strategy Mapping
                    9.9. Company Profiles
                        9.9.1. Bayer AG
                            9.9.1.1. Company Overview
                            9.9.1.2. Financial Performance
                            9.9.1.3. Product Portfolios
                            9.9.1.4. Strategic Initiatives
                        9.9.2. Abbott
                            9.9.2.1. Company Overview
                            9.9.2.2. Financial Performance
                            9.9.2.3. Product Portfolios
                            9.9.2.4. Strategic Initiatives
                        9.9.3. Glanbia plc
                            9.9.3.1. Company Overview
                            9.9.3.2. Financial Performance
                            9.9.3.3. Product Portfolios
                            9.9.3.4. Strategic Initiatives
                        9.9.4. Herbalife Nutrition Ltd.
                            9.9.4.1. Company Overview
                            9.9.4.2. Financial Performance
                            9.9.4.3. Product Portfolios
                            9.9.4.4. Strategic Initiatives
                        9.9.5. Nature’s Bounty
                            9.9.5.1. Company Overview
                            9.9.5.2. Financial Performance
                            9.9.5.3. Product Portfolios
                            9.9.5.4. Strategic Initiatives
                        9.9.6. Amway Corporation
                            9.9.6.1. Company Overview
                            9.9.6.2. Financial Performance
                            9.9.6.3. Product Portfolios
                            9.9.6.4. Strategic Initiatives
                        9.9.7. Garden of Life
                            9.9.7.1. Company Overview
                            9.9.7.2. Financial Performance
                            9.9.7.3. Product Portfolios
                            9.9.7.4. Strategic Initiatives
                        9.9.8. NU SKIN
                            9.9.8.1. Company Overview
                            9.9.8.2. Financial Performance
                            9.9.8.3. Product Portfolios
                            9.9.8.4. Strategic Initiatives
                        9.9.9. Lonza Group Ltd.
                            9.9.9.1. Company Overview
                            9.9.9.2. Financial Performance
                            9.9.9.3. Product Portfolios
                            9.9.9.4. Strategic Initiatives
                        9.9.10. NOW Foods
                            9.9.10.1. Company Overview
                            9.9.10.2. Financial Performance
                            9.9.10.3. Product Portfolios
                            9.9.10.4. Strategic Initiatives

List of Tables

Table 1. Global digestive health supplements market - Key market driver analysis
Table 2. Global digestive health supplements market - Key market restraint analysis
Table 3. Global digestive health supplements market estimates & forecast, by product (USD Million)
Table 4. Global digestive health supplements market estimates & forecast, by form (USD Million)
Table 5. Global digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 6. U.S. macro-economic outlay
Table 7. U.S. digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 8. U.S. digestive health supplements market estimates & forecast, by Product (USD Million)
Table 9. U.S. digestive health supplements market estimates & forecast, by form (USD Million)
Table 10. U.S. digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 11. Canada macro-economic outlay
Table 12. Canada digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 13. Canada digestive health supplements market estimates & forecast, by Product (USD Million)
Table 14. Canada digestive health supplements market estimates & forecast, by form (USD Million)
Table 15. Canada digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 16. Mexico macro-economic outlay
Table 17. Mexico digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 18. Mexico digestive health supplements market estimates & forecast, by Product (USD Million)
Table 19. Mexico digestive health supplements market estimates & forecast, by form (USD Million)
Table 20. Mexico digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 21. UK macro-economic outlay
Table 22. UK digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 23. UK digestive health supplements market estimates & forecast, by Product (USD Million)
Table 24. UK digestive health supplements market estimates & forecast, by form (USD Million)
Table 25. UK digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 26. Germany macro-economic outlay
Table 27. Germany digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 28. Germany digestive health supplements market estimates & forecast, by Product (USD Million)
Table 29. Germany digestive health supplements market estimates & forecast, by form (USD Million)
Table 30. Germany digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 31. France macro-economic outlay
Table 32. France digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 33. France digestive health supplements market estimates & forecast, by Product (USD Million)
Table 34. France digestive health supplements market estimates & forecast, by form (USD Million)
Table 35. France digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 36. Italy macro-economic outlay
Table 37. Italy digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 38. Italy digestive health supplements market estimates & forecast, by Product (USD Million)
Table 39. Italy digestive health supplements market estimates & forecast, by form (USD Million)
Table 40. Italy digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 41. Spain macro-economic outlay
Table 42. Spain digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 43. Spain digestive health supplements market estimates & forecast, by Product (USD Million)
Table 44. Spain digestive health supplements market estimates & forecast, by form (USD Million)
Table 45. Spain digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 46. Sweden macro-economic outlay
Table 47. Sweden digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 48. Sweden digestive health supplements market estimates & forecast, by Product (USD Million)
Table 49. Sweden digestive health supplements market estimates & forecast, by form (USD Million)
Table 50. Sweden digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 51. Netherlands macro-economic outlay
Table 52. Netherlands digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 53. Netherlands digestive health supplements market estimates & forecast, by Product (USD Million)
Table 54. Netherlands digestive health supplements market estimates & forecast, by form (USD Million)
Table 55. Netherlands digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 56. Denmark macro-economic outlay
Table 57. Denmark digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 58. Denmark digestive health supplements market estimates & forecast, by Product (USD Million)
Table 59. Denmark digestive health supplements market estimates & forecast, by form (USD Million)
Table 60. Denmark digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 61. China macro-economic outlay
Table 62. China digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 63. China digestive health supplements market estimates & forecast, by Product (USD Million)
Table 64. China digestive health supplements market estimates & forecast, by form (USD Million)
Table 65. China digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 66. India macro-economic outlay
Table 67. India digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 68. India digestive health supplements market estimates & forecast, by Product (USD Million)
Table 69. India digestive health supplements market estimates & forecast, by form (USD Million)
Table 70. India digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 71. Japan macro-economic outlay
Table 72. Japan Digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 73. Japan digestive health supplements market estimates & forecast, by Product (USD Million)
Table 74. Japan digestive health supplements market estimates & forecast, by form (USD Million)
Table 75. Japan digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 76. Australia & New Zealand macro-economic outlay
Table 77. Australia & New Zealand Digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 78. Australia & New Zealand digestive health supplements market estimates & forecast, by Product (USD Million)
Table 79. Australia & New Zealand digestive health supplements market estimates & forecast, by form (USD Million)
Table 80. Australia & New Zealand digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 81. Hong Kong macro-economic outlay
Table 82. Hong Kong Digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 83. Hong Kong digestive health supplements market estimates & forecast, by Product (USD Million)
Table 84. Hong Kong digestive health supplements market estimates & forecast, by form (USD Million)
Table 85. Hong Kong digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 86. Singapore macro-economic outlay
Table 87. Singapore Digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 88. Singapore digestive health supplements market estimates & forecast, by Product (USD Million)
Table 89. Singapore digestive health supplements market estimates & forecast, by form (USD Million)
Table 90. Singapore digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 91. Brazil macro-economic outlay
Table 92. Brazil digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 93. Brazil digestive health supplements market estimates & forecast, by Product (USD Million)
Table 94. Brazil digestive health supplements market estimates & forecast, by form (USD Million)
Table 95. Brazil digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 96. South Africa macro-economic outlay
Table 97. South Africa digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 98. South Africa digestive health supplements market estimates & forecast, by Product (USD Million)
Table 99. South Africa digestive health supplements market estimates & forecast, by form (USD Million)
Table 100. South Africa digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 101. UAE macro-economic outlay
Table 102. UAE digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Table 103. UAE digestive health supplements market estimates & forecast, by Product (USD Million)
Table 104. UAE digestive health supplements market estimates & forecast, by form (USD Million)
Table 105. UAE digestive health supplements market estimates & forecast, by distribution channel (USD Million)
Table 106. Recent developments & impact analysis by key market participants
Table 107. Company market share, 2024
Table 108. Company heat map analysis
Table 109. Companies undergoing key strategies

List of Figures

Fig. 1 Global Digestive Health Supplements Market Segmentation
Fig. 2 Information procurement
Fig. 3 Primary research pattern
Fig. 4 Primary research approaches
Fig. 5 Primary research process
Fig. 6 Market snapshot
Fig. 7 Product snapshot
Fig. 8 Distribution Channel snapshot
Fig. 9 Regional snapshot
Fig. 10 Competitive landscape snapshot
Fig. 11 Global digestive health supplements market size (USD Million)
Fig. 12 Global digestive health supplements market size, 2021 to 2033 (USD Million)
Fig. 13 Global digestive health supplements market: Penetration & growth prospect mapping
Fig. 14 Global digestive health supplements market: Value chain analysis
Fig. 15 Global digestive health supplements market: Profit margin analysis
Fig. 16 Global digestive health supplements market: Market dynamics
Fig. 17 Global digestive health supplements market: Porter's five forces analysis
Fig. 18 Factors influencing buying decisions for digestive health supplements
Fig. 19 Global digestive health supplements market: Product Movement Analysis, 2024 & 2033 (%)
Fig. 20 Prebiotics market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 21 Probiotics market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 22 Enzymes market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 23 Fulvic Acid market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 24 Others market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 25 Global digestive health supplements market: Form Movement Analysis, 2024 & 2033 (%)
Fig. 26 Capsules market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 27 Tablets market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 28 Powders market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 29 Liquids market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 30 Others market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 31 Global digestive health supplements market: Distribution Channel Movement Analysis, 2024 & 2033 (%)
Fig. 32 OTC market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 33 Supermarkets/Hypermarkets/Food Stores market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 34 Drug Stores & Pharmacies market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 35 Convenience Stores market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 36 Online market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 37 Others market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 38 Prescribed market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 39 Global digestive health supplements market: Regional outlook, 2024 & 2033 (USD Million)
Fig. 40 Regional marketplace: Key takeaways
Fig. 41 North America market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 42 US market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 43 Canada market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 44 Mexico market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 45 Europe digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 46 UK digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 47 Germany digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 48 France digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 49 Italy digestive health supplements market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 50 Spain digestive health supplements market estimates, 2021 - 2033 (USD Million)
Fig. 51 Sweden digestive health supplements market estimates, 2021 - 2033 (USD Million)
Fig. 52 Netherlands digestive health supplements market estimates, 2021 - 2033 (USD Million)
Fig. 53 Denmark digestive health supplements market estimates, 2021 - 2033 (USD Million)
Fig. 54 China market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 55 India market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 56 Japan market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 57 Australia & New Zealand market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 58 Hong Kong market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 59 Singapore market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 60 Brazil market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 61 South Africa market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 62 UAE market estimates and forecast, 2021 - 2033 (USD Million)
Fig. 63 Key company categorization
Fig. 64 Company market share analysis, 2024
Fig. 65 Strategic framework of digestive health supplements market