5 April 2018
15 October 2014
“Around 11 million people are diagnosed with cancer each year around the world. The most common forms of cancer include colon and rectal cancer, lung cancer and – depending on sex – breast or prostate cancer. By 2030 the number of cancer patients is expected to double because of demographic changes (1). After a period of stagnation, conventional medicine has once again achieved substantial improvements in treatment outcomes in recent years, and for some tumor entities has even achieved longer survival rates. These successes are due in part to new principles of medicinal treatment, and in part to improved diagnostic methods and radiation technology. At the same time, therapies have become more intense and in some cases more aggressive, and in consequence their side effects are often worse (2). Simultaneously, the desire of oncology patients for gentler therapeutic procedures and complementary treatments has greatly increased over the past 15 years.
Today, many cancer patients take vitamins and other micronutrients to augment their standard treatment or to reduce the side effects associated with the illness or its treatment (3). Among oncologists there are justified concerns that dietary supplements could impair the effectiveness of chemo- or radiotherapies (4). The use of micronutrients as complementary medical treatment must therefore always be designed and timed to avoid diminishing the effectiveness of oncological therapies.
The success of treatment and the healing processes in cancer patients are greatly influenced by nutritional status. This is of major clinical relevance, because depending on the type of tumor, its location and the stage of the disease, 30% to 90% of patients will be malnourished. The most severe form of tumor-associated dietary deficiency is cancer cachexia, a wasting condition with loss of weight, appetite and muscle mass. It is especially common among patients with bronchial, gastric, pancreatic or prostate carcinomas. Nutritional deficiencies weaken the immune status, reduce tolerance to treatment and interfere with several organic and metabolic functions. The response to and effectiveness of tumor destruction treatments (chemotherapy, radiotherapy) may be diminished, while the rate of side effects and the risk of therapy-associated complications rise. In consequence patients face a poorer quality of life and prognosis (5). Malnourished cancer patients have increased morbidity and higher mortality rates; fatalities are around 30% higher in cancer patients with malnutrition. Malnutrition does not only relate to energy-providing macronutrients (carbohydrates, proteins, lipids), but also involves the biocatalytic and immunomodulatory micronutrients. Since macronutrients are the natural carriers for micronutrients, malnutrition is one of the main causes of inadequate micronutrient status in cancer patients. Moreover, inflammatory processes as well as the side effects of chemo- or radiotherapy (e.g. vomiting, diarrhea, loss of taste) can increase micronutrient requirements and utilization.
Cancer patients generally have a poorer nutritional status than healthy people – indeed their provision with several vitamins and trace elements is often insufficient at the time of diagnosis and before the appearance of clinically relevant changes to the nutritional status. It deteriorates even more after starting cancer therapy. However, the availability of micronutrients with antioxidant and immunomodulatory activity (e. g. vitamin C, vitamin E, beta-carotene, selenium and vitamin D) and those with a low storage or reserve capacity (e. g. B vitamins and vitamin K). Since a micronutrient deficit in cancer patients due to a tumor or therapy exacerbates the course of the disease and detracts from the efficiency of tumor destruction treatments, as well as increasing the risk of associated complications (e. g. diminished immunocompetence, poor wound healing, exhaustion, depression), care should be taken to ensure an adequate intake of energy substrates (proteins, lipids, carbohydrates) and also an optimum intake of immune stabilizing micronutrients like selenium and vitamin D. The importance of antioxidant micronutrients as an adjunct to nutritional therapy is substantiated by results from several studies which have shown that consuming multivitamin and mineral preparations can enhance both the quality of life and the prognosis for cancer patients (6, 7). Antioxidant micronutrients like vitamin C, vitamin E, vitamin A derivatives and selenium not only act as radical scavengers, but also perform a number of other essential metabolic tasks apart from their antioxidant cell-protective functions. Foremost among these are their immunomodulatory, apoptosis (cell death) inducing and cell division and differentiation regulating properties (1).
Supplementation with antioxidants during tumor destruction treatments is still the subject of controversy, since the ability of radiotherapy and of some cytostatic agents to destroy tumors is based in part on the formation of free radicals. However, the effect of most of the cytostatic agents currently used in cancer treatment, such as antimetabolites (e.g. methotrexate), nitrogen mustard derivatives (e. g. cyclophosphamide), platinum complexes (e. g. cisplatin), vinca alkaloids (e. g. vinorelbine), taxanes (e. g. paclitaxel) or anthracyclines (e. g. epirubicin) is not primarily brought about by oxidative stress. If antioxidants did have a significant influence on the ability of standard therapies to destroy tumors, consumption of fruit and vegetables rich in antioxidants and phytamin or green tea (which is rich in epigallocatechin) would not be allowed during the treatment phase. There is consequently no justification for the frequently sweeping and uncritical rejection of supplementation with antioxidant and immunomodulatory micronutrients during the chemotherapy phase of treatment (8). Systematic reviews of randomized controlled studies on the influence of antioxidants on chemotherapy conclude that supplementation with antioxidants does not adversely affect chemotherapy. Rather, it has a positive influence on the rate of side effects and tumor response. None of the studies examined in this context showed evidence of a significant adverse effect on the chemotherapy. However, many studies did show that supplementation with antioxidants increased either survival times, tumor response or both, and that they reduced the rate of side effects as compared with the control groups (9, 10).
The American Institute for Cancer Research (AICR) recommends that cancer patients undergoing chemo- or radiotherapy should not take multivitamin and mineral preparations containing daily doses of antioxidants greater than the corresponding tolerable upper intake levels (UL) for each individual micronutrient. According to AICR, supplementation with multivitamin and mineral preparations can generally be considered safe if the doses of vitamins and minerals are within the range of the recommended daily amounts (RDA) (11). We recommend cancer patients with eating problems or weight loss in general to take a multivitamin/mineral combination based on RDAs in order to ensure the basic provision of essential micronutrients. This is principally to compensate for potential deficits, and not intended as a high-dose micronutrient therapy. Patients could benefit from taking some micronutrients, such as vitamin D, selenium and L-carnitine, in higher doses, depending on their tumor destruction therapy and laboratory status.”
Based on: Gröber U. et al. Mikronährstoffe in der Onkologie [German: Micronutrients in Oncology]. MMP. 2013; 36(4): 133-143.
5 April 2018
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