Antioxidant Intake and Antitumor Therapy: Toward Nutritional Recommendations for Optimal Results

Abstract

The role of the induction of oxidative stress as the mechanism of action of many antitumor drugs is acquiring an increasing interest. In such cases, the antitumor therapy success may be conditioned by the antioxidants present in our own body, which can be synthesized de novo (endogenous) or incorporated through the diet and nutritional supplements (exogenous). In this paper, we have reviewed different aspects of antioxidants, including their classification, natural sources, importance in diet, consumption of nutritional supplements, and the impact of antioxidants on health. Moreover, we have focused especially on the study of the interaction between antioxidants and antitumor therapy, considering both radiotherapy and chemotherapy. In this regard, we found that the convenience of administration of antioxidants during cancer treatment still remains a very controversial issue. In general terms, antioxidants could promote or suppress the effectiveness of antitumor treatment and even protect healthy tissues against damage induced by oxidative stress. The effects may depend on many factors discussed in the paper. These factors should be taken into consideration in order to achieve precise nutritional recommendations for patients. The evidence at the moment suggests that the supplementation or restriction of exogenous antioxidants during cancer treatment, as appropriate, could contribute to improving its efficiency.

Figure 1

Oxygen reactive species (ROS) and derivatives. ROS includes superoxide anion, hydroxyl radical, singlet oxygen, hydroperoxyl radical, peroxyl radical, hydrogen peroxide, and hypochlorous acid. There are other reactive species which result from the reaction between ROS and nitric oxide (reactive nitrogen species, RNS), or with thiols (reactive sulfur species, RSS) [–6].

Figure 2

The antioxidant defense. The human antioxidant defense is composed of exogenous and endogenous antioxidants that can be classified into three different lines regarding their mechanism of action. The first line prevents the formation of new free radicals and includes SOD, CAT, GPX, ferritin, ceruloplasmin, Se, Cu, and Zn. The second line captures free radicals to prevent the oxidative chain reactions and includes gluthatione, vitamins C and E, carotenoids, and flavonoids. The third line repairs the damage caused to biomolecules by free radicals and includes DNA repair enzymes, lipases, proteases, transferases, and methionine-sulfoxide reductases [–21].

Figure 3

Influence of antioxidants on human health. Antioxidants can influence many aspects of human health such as diabetes, aging, cardiovascular and neurodegenerative diseases, cancer, and other illnesses. Antioxidants produce several beneficial effects, promoting a healthy status, reducing the oxidative stress caused by ROS [89, 90].