Functional foods and dietary supplements: Products at the interface between pharma and nutrition

Abstract

It is increasingly recognized that most chronic diseases of concern today are multifactorial in origin. To combat such diseases and adverse health conditions, a treatment approach where medicines and nutrition complement each other may prove to be the most successful. Within nutrition, apart from (disease-related) dietetic regimes, an increasing number of functional foods and dietary supplements, each with their own health claim, are marketed. These food items are considered to be positioned between traditional foods and medicines at the so-called ‘Pharma-Nutrition Interface’. This paper encompasses aspects related to the regulatory framework and health claims of functional foods and dietary supplements. The use of functional foods or dietary supplements may offer opportunities to reduce health risk factors and risk of diseases, both as monotherapy and in combination with prescription drugs. Nevertheless, the potential caveats of these products should not be overlooked. These caveats include the increased risk for food-drug interactions due to the elevated amounts of specific functional ingredients in the diet, and the stimulation of self-medication potentially resulting in lower adherence to drug therapy. Health technology assessments should be used more to compare the cost-effectiveness and benefit–risk ratios of drugs, functional foods and dietary supplements, and to evaluate the added value of functional foods or dietary supplements to drug therapy.

Introduction

Since ancient times plants, herbs and other natural products have been used as healing agents. Advances in organic chemistry from the early 19th century have enabled the preparation of numerous synthetic medicines. Yet, the majority of the medicinal substances available today have their origin in natural compounds. The best known example is aspirin (acetylsalicylic acid), originally derived from the bark of the white willow tree (Leroux, 1830, Mahdi et al., 2006). Other examples include the immunosuppressive cyclosporines (Borel et al., 1990), the anthracycline antibiotics (Nadas and Sun, 2006) and the HMG-CoA reductase inhibitors, commonly known as statins (Endo, 2004).

Traditionally, pharmaceuticals have been used to cure diseases or to alleviate the symptoms of disease. Nutrition, on the other hand, is primarily aimed to prevent diseases by providing the body with the optimal balance of macro- and micronutrients needed for good health. Due to the emerging knowledge of disease, medicines are now increasingly being used to lower risk factors, and thereby to prevent chronic diseases. Prime examples are blood pressure lowering and blood lipid-lowering agents which reduce the risk of cardiovascular disease. The appearance of functional foods and dietary supplements on the market has further blurred the distinction between pharma and nutrition (Fig. 1). Functional foods are foods that are claimed to improve health, quality of life or well-being beyond basic nutritional functions (Henry, 2010, Howlett, 2008; ILSI Europe, 1999, van Kreijl et al., 2006). Examples of functional foods are margarines enriched with cholesterol-lowering phytosterols, cereals fortified with soluble fibres and yoghurts with specific bacterial cultures added. Thus, functional foods resemble conventional food products in appearance and are consumed as part of the usual diet. In contrast, dietary supplements are typically marketed in the form of a capsule, pill, powder or gel and are not presented for use as a conventional food, meal or diet. Dietary supplements contain one or more dietary ingredients (e.g., vitamins, minerals, amino acids, herbs or other botanicals) and are intended to supplement the diet (http://ods.od.nih.gov/) (U.S. Food and Drug Administration, 1994, van Kreijl et al., 2006).

Today's functional foods and dietary supplements are typically marketed to large (sub)groups of the total population. For example, phytosterol-enriched functional foods are targeted to all adults with (moderately) elevated cholesterol levels and products with claimed pre- and probiotic activity are aimed at general healthy populations. The recent advances in pharmaco- and nutrigenomics have formed the basis for developing the concepts of ‘personalized medicine’ (Personalized Medicine Coalition, 2009) and ‘personalized nutrition’ (Kaput, 2008, Kussmann and Fay, 2008). These emerging fields rely on targeted therapies based on a person's genetic risk profile. Pharmaceuticals (Caskey, 2010, Pravenec and Kurtz, 2007), as well as several dietary components (Afman and Müller, 2006), have been recognized to modulate gene and protein expression and thereby metabolic pathways, homeostatic regulation, and presumably health and disease. In addition, genes also contribute largely to different responses to diet or drug exposure, including interindividual variations in the occurrence of adverse drug reactions (Friso and Choi, 2002, Lee et al., 2010).

In the following sections we will first address the regulatory framework for drug and food safety and efficacy. In particular, we will focus on functional foods and dietary supplements, and the health claims related to these food products (2.1 Safety and efficacy of drugs, 2.2 Safety of food, 2.3 Efficacy of food: nutrition and health claims). Within the extensive regulatory framework, some (herbal) dietary supplements fall in between food and drug regulations, though (Section 2.4). Subsequently we describe the opportunities for functional foods and dietary supplements to reduce health risk factors and risk of diseases (Section 3.1), and discuss potential caveats of these food products (Section 3.2). Section 4 explains how health technology assessments, i.e. cost-effectiveness and risk-benefit analyses, can be used to make evidence-based decisions about which therapy, or combination of therapies, will result in the most successful and cost-effective management of health risk factors and chronic diseases. Finally, conclusions are drawn at the end of this paper (Section 5).