Walk into a typical health food shop and you are confronted by a multitude of products, each claiming to reduce the risk of heart attacks, strokes, Alzheimer’s Disease and cancer, alleviate migraine, depression and irritable bowel syndrome, build up your body, improve mental performance and counter the effects of ageing. Often, many different versions of a product exist and there are little safety or efficacy data. In addition, the products can be costly and you are advised to take several doses daily for the rest of your life. The internet site of a well-known health food shop in the UK, for instance, lists 30 different categories of nutraceuticals, many with more than 40 different choices each. 

From a healthy diet to a functional one

To understand why such health food shops have been so successful, it is necessary to remember that nutritional research has changed dramatically over the last few decades, since it established the concept of a healthy balanced diet to prevent diseases such as rickets (by providing calcium in milk) and scurvy (by recommending intake of vitamin C in fruit). However, with increased human longevity, chronic conditions, such as cancer and cardiovascular disease, have become more prevalent and there has been great interest in their prevention by promoting healthy eating. This has resulted in the emergence of an industry which markets foods or food supplements for consumption, in addition to the normal balanced diet, in response to an almost obsessional demand by the public. Such foods have variously been called, nutritional (dietary) supplements, functional foods, herbal medicines and nutraceuticals, since they occupy the borderline between normal foods and pharmaceuticals.

Nutraceuticals cover an enormous range of foods including dietary fibre, polyunsaturated fatty acids, proteins (peptides, amino acids and keto acids), minerals, vitamins and other antioxidants. Nutraceuticals have also been referred to as phoods to reflect the fact that they based on foods which have been supplemented with an ingredient or chemical to enhance health. Such foods include breakfast cereals with added vitamins, iodised salt (e.g. Morton Salt) containing iodine to reduce the risk of goitre and calcium-containing orange juice. 

Big business

The term, nutraceutical, was first coined in 1989 in the USA in response to growing medical and public interest, particularly in relation to the practice in Japan of eating bread with various supplements to combat depression. Nutraceuticals have continued to be extremely popular in Japan. A nutraceutical was defined by Dr Stephen DeFelice in 1992 as: ‘any substance that is a food or a part of a food, and provides medical or health benefits, including the prevention and treatment of disease.’ The simplest nutraceuticals are vitamin or multi-vitamin pills, which are swallowed by millions of people daily. Make no mistake, nutraceuticals are now big business. In 2007, a Business Communications Company (BCC) report, based on market research, put the global market worth at US$117.3 billion, of which nutraceutical foods were US$39.9 billion, nutraceutical supplements, US$39.0 billion, and nutraceutical beverages US$38.4 billion. The global figure is expected to increase to US$ 176 billion by 2013 (a compound annual growth rate of 7.4 percent), with the greatest growth being in beverages. The largest market is in North America, followed by the EU, then Japan. 

Preventing disease

So, what is the basis for the use of nutraceuticals? Many chronic diseases are thought to be due to an accumulation of damage to cells in tissues resulting from attack by a form of oxygen called reactive oxygen species (ROS). Oxygen, of course, is the molecule used by most living organisms to generate energy, but not all of it is used in this process. The body has protective mechanisms against ROS, and also normal foods can soak up or quench them by containing constituents that act as anti-oxidants. However, these mechanisms can become overwhelmed and the intake of extra anti-oxidants, particularly to prevent and treat cancer, is considered beneficial. Many chemicals found in plants (phytochemicals) act as anti-oxidants, an example of which are anthocyanins found in the nutraceutical, raspberry juice. 

Some diets increase the risk of cancer, while others decrease it. Many years ago, it was noticed, in a population of Japanese that had gone to live in the USA, that the incidence of gastric cancer began to decrease while the frequency of bowel cancer increased over time, exactly the opposite situation to the prevalence of the two cancer types found in Japan and the same as the prevalence of the cancers in the USA. These changes were attributed to the immigrants adopting a western style diet, with less raw fish and more red meat, rather than the opposite situation. It marked one of the first demonstrations that cancer could be influenced by environmental factors, in this case, diet. This also explains why dietary fibre (another type of nutraceutical) could protect against colon cancer, because it stimulates bowel movement, reducing the time during which cells lining the bowel are exposed to dietary constituents that could induce tumours (carcinogens).

Evidence

The study of the incidence of disease in a population in relation to exposure to risk factors is called epidemiology There are many other examples in which epidemiologists have noticed that dietary intake and lifestyle can affect the incidence of chronic diseases. For example, the Hunzakuts, in the Hunza valley in Pakistan, often live healthily to great old age. Autopsies have very rarely revealed signs of cancer. They eat mainly fruit, vegetables and grains, particularly apricots and a preparation made from the ground pits of apricots, very rich in vitamin B-17 (laetrile). 

Other epidemiological studies have shown that Eskimos have low incidences of many cancers, heart disease and strokes, and this was linked with their consumption of cold-water fish rich in omega-3 fatty acids. These, and other, fatty acids, found in many foods, are essential for cell membrane formation and other processes in the body. Nutraceuticals based on them are recommended for treating atopic dermatitis and psoriasis and to prevent inflammatory disease.

Problems

There have been many clinical trials to investigate claims for the beneficial effects of nutraceuticals (efficacy). For example, by 2002, a series of clinical trials had suggested a positive association between omega-3 fish oils and protection against cardiovascular disease. This prompted the American Heart Association to recommend increased fish consumption and the use of fish oil supplements for patients with the disease. However, a review of more than 800 scientific studies cast doubt on these conclusions. Similarly, the results of clinical trials with laetrile are confusing, and vitamin B-17 therapy for cancer has been discontinued. Many other examples exist where the indications from epidemiology have not been substantiated by clinical trials for the use of nutraceuticals. These include lycopene (from tomatoes) for treating prostate cancer and glucosamine (with or without chondriotin) for treating osteoarthritis. 

Success

While these problems detract from the original claims for efficacy, problems could be due to difficulties in interpreting clinical trial data and extrapolating the results to the whole population, particularly when small numbers of volunteers are involved. In addition, many factors can affect the aetiology of chronic diseases and we do not know how many nutraceuticals are supposed to exert their claimed effects. However, some clinical trials clearly demonstrate beneficial effects of nutraceuticals. For example, studies have shown that Benecol margarine, launched in 1995 in Finland, lowers the risk of heart attack by almost a third. This nutraceutical contains a plant chemical called a sitostanol ester that was shown to reduce absorption of dietary cholesterol from the gut by as much as 14 percent. There are also numerous studies suggesting beneficial effects from dietary supplementation with amino-acids, the building blocks of proteins. For example, tryptophan is marketed as a treatment for depression, because it enters the brain and is a precursor of serotonin, a molecule mediating the transmission of electrical signals in the brain, which promotes happiness. 

Nutraceuticals are also recommended for treating acute diseases. Evening primrose oil (EPO), extracted from seeds of the Evening Primrose plant, is rich in essential omega-6 fatty acids and is used to treat many ailments, from pre-menstrual tension (PMT), eczema and asthma to arthritis. However, many of the clinical trials for PMT have generated conflicting evidence, and the other benefits of EPO are questionable. Another example is live yogurt cultures for intestinal complaints. These contain bacteria that live in the gut and make it less favourable for toxin-producing bacteria. 

Customisation

Susceptibility to chronic disease is also genetically determined. Completion of the human genome project, which involved characterising all 25,000 genes in the human body, means that you can now have your genetic pre-disposition to a range of diseases assessed by having your DNA analysed. At least one company offers this service, in conjunction with suggestions for how you could change your life style accordingly. Such changes include taking nutraceuticals. So, technology has raised the possibility of tailoring food intake to individual needs to reduce risks of future disease. 

The future

Many other clinical trials on the use of nutraceuticals for specific purposes are being conducted, and will be undertaken in the future, particularly due to recent legislation in Europe and the USA requiring more pre-clinical and clinical testing to substantiate claimed benefits and to assess safety. These regulations are justified since, even though a nutraceutical product is based on a constituent in the normal diet, it should not be assumed to be safe. This is because it could contain small amounts of toxic contaminants, used in, or resulting from, its production, and also many natural chemicals are highly poisonous or toxic (botulinum toxin produced by a bacterium and aflatoxin produced by a fungus being two good examples). However, due to their extremely wide diversity and nature, the effective testing of nutraceuticals poses many problems that still have to be resolved. 

There would seem to be little doubt that the public’s focus on nutraceuticals will continue to grow, and the market will continue to expand, despite the often equivocal evidence supporting the claims for their many benefits, and the problems with assuring their safety. This, together with their relatively high cost and the frequent need to take high doses for long periods, suggests that one should be very cautious before relying on nutraceuticals to provide the panacea for preventing chronic disease. It would seem that some benefits are real, while others are very definitely not. So, the evidence suggests that there is no substitute for a balanced diet and adequate exercise as the basis of a healthy lifestyle.