Antioxidants and Cancer Prevention

항산화제와 암의 예방

Reviewed: February 6, 2017

갱신 : 2017년 2월 6일

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• What are free radicals, and do they play a role in cancer development?

활성산소란 무엇이며, 암의 발병에 역할을 하는가?

• What are antioxidants?

항산화제란 무엇인가?

• Can antioxidant supplements help prevent cancer?

항산화제 보충제는 암의 예방에 도움이 되나?

• Should people already diagnosed with cancer take antioxidant supplements?

이미 암 진단을 받은 사람은 항산화제를 복용해야 하나?

What are free radicals, and do they play a role in cancer development?

활성산소란 무엇이며, 암의 발병에 역할을 하는가?

Free radicals are highly reactive chemicals that have the potential to harm cells. They are created when an atom or a molecule (a chemical that has two or more atoms) either gains or loses an electron (a small negatively charged particle found in atoms). Free radicals are formed naturally in the body and play an important role in many normal cellular processes (1, 2). At high concentrations, however, free radicals can be hazardous to the body and damage all major components of cells, including DNA, proteins, and cell membranes. The damage to cells caused by free radicals, especially the damage to DNA, may play a role in the development of cancer and other health conditions (1, 2).

활성산소는 세포에 해를 끼칠 가능성이 있는 매우 반응성이 강한 화학물질이다. 활성산소는 원자나 분자(원자가 두 개 이상 있는 화학 물질)가 전자(원자에서 발견되는 작은 음전하 입자)를 얻거나 잃을 때 생성된다. 활성산소는 체내에서 자연적으로 형성되며, 많은 정상적인 세포 과정(1, 2)에서 중요한 역할을 한다. 그러나 고농도에서는 활성산소가 신체에 위험할 수 있으며 DNA, 단백질, 세포막을 포함한 세포의 모든 주요 구성요소를 손상시킬 수 있다. 활성산소에 의한 세포의 손상, 특히 DNA의 손상은 암과 다른 질환(1, 2)의 발병에 영향을 미칠 수 있다.

Abnormally high concentrations of free radicals in the body can be caused by exposure to ionizing radiation and other environmental toxins. When ionizing radiation hits an atom or a molecule in a cell, an electron may be lost, leading to the formation of a free radical. The production of abnormally high levels of free radicals is the mechanism by which ionizing radiation kills cells. Moreover, some environmental toxins, such as cigarette smoke, some metals, and high-oxygen atmospheres, may contain large amounts of free radicals or stimulate the body’s cells to produce more free radicals.

비정상적으로 체내 활성산소의 농도가 높아지는 것은 전리(이온화)방사선 및 기타 환경독소에 노출되어 발생할 수 있다. 전리방사선이 세포 내의 원자나 분자에 부딪히면 전자가 손실되어 활성산소가 형성될 수 있다. 비정상적으로 높은 수준의 활성산소의 생산은 전리방사선이 세포를 죽이는 메커니즘이다. 더구나 담배연기와 일부 금속, 고산소 대기 등 일부 환경독소는 다량의 활성산소를 함유하거나 신체의 세포를 자극해 더 많은 활성산소를 생산할 수 있다.

Free radicals that contain the element oxygen are the most common type of free radicals produced in living tissue. Another name for them is “reactive oxygen species,” or “ROS” (1, 2).

원소 산소를 함유하고 있는 활성산소는 살아있는 조직에서 생산되는 활성산소의 가장 흔한 유형이다. 또 다른 이름은 "반응 산소 종" 또는 "ROS"(1, 2)이다.

What are antioxidants?

항산화제란 무엇인가?

Antioxidants are chemicals that interact with and neutralize free radicals, thus preventing them from causing damage. Antioxidants are also known as “free radical scavengers.”

항산화제는 활성산소와 상호작용하고 이를 중화시켜서 손상을 입히지 못하도록 방지하는 화학물질을 말한다. 항산화제는 "활성산소 청소기"로도 알려져 있다.

The body makes some of the antioxidants that it uses to neutralize free radicals. These antioxidants are called endogenous antioxidants. However, the body relies on external (exogenous) sources, primarily the diet, to obtain the rest of the antioxidants it needs. These exogenous antioxidants are commonly called dietary antioxidants. Fruits, vegetables, and grains are rich sources of dietary antioxidants. Some dietary antioxidants are also available as dietary supplements (1, 3).

신체는 활성산소를 중화시키는데 사용되는 산화방지제를 만든다. 이 항산화제는 내생성 항산화제라고 불린다. 그러나 신체는 필요한 나머지 항산화제를 얻기 위해 주로 식이요법인 외부(외생) 공급원에 의존한다. 이러한 외생 항산화제는 일반적으로 식이 항산화제라고 불린다. 과일, 야채, 곡물은 풍부한 식이 항산화제 공급원이다. 일부 식이 항산화제는 식이 보조제(1,3)로도 이용 가능하다.

Examples of dietary antioxidants include beta-carotene, lycopene, and vitamins A, C, and E (alpha-tocopherol). The mineral element selenium is often thought to be a dietary antioxidant, but the antioxidant effects of selenium are most likely due to the antioxidant activity of proteins that have this element as an essential component (i.e., selenium-containing proteins), and not to selenium itself (4).

식이 항산화제의 예로는 베타 카로틴, 리코펜, 비타민 A, C, E(알파-토코페롤) 등이 있다. 미네랄 원소 셀레늄은 흔히 식이 항산화제로 생각되지만 셀레늄의 항산화 효과는 이 원소를 필수 성분(즉, 셀레늄 함유 단백질)으로 가지고 있는 단백질의 항산화 활성(즉, 셀레늄 함유 단백질)에 의한 것일 가능성이 가장 높고, 셀레늄 자체는 그렇지 않다(4).

Can antioxidant supplements help prevent cancer?

항산화제 보충제는 암의 예방에 도움이 되나?

In laboratory and animal studies, the presence of increased levels of exogenous antioxidants has been shown to prevent the types of free radical damage that have been associated with cancer development. Therefore, researchers have investigated whether taking dietary antioxidant supplements can help lower the risk of developing or dying from cancer in humans.

실험실 및 동물 연구에서는, 외생성 항산화제의 수준의 증가가 암 발병과 관련이 있는 유형의 활성산소 손상을 예방하는 것으로 나타났다. 따라서 연구원들은 식이요법 항산화제를 복용하는 것이 인간의 암에 걸릴 위험이나 사망 위험을 낮추는 데 도움이 될 수 있는지를 조사했다.

Many observational studies, including case–control studies and cohort studies, have been conducted to investigate whether the use of dietary antioxidant supplements is associated with reduced risks of cancer in humans. Overall, these studies have yielded mixed results (5). Because observational studies cannot adequately control for biases that might influence study outcomes, the results of any individual observational study must be viewed with caution.

환자-대조군 연구와 코호트(집단) 연구를 포함한 많은 관찰 연구를 식이 항산화제의 사용이 인간의 암 위험 감소와 관련이 있는지를 조사하기 위해 수행되었다. 전반적으로, 이러한 연구들은 혼란스러운 결과를 낳았다(5). 관찰 연구로는 연구 결과에 영향을 미칠 수 있는 편향(치우침)을 적절히 통제할 수 없기 때문에, 개별 관찰 연구의 결과는 주의하여 검토해야 한다.

Randomized controlled clinical trials, however, lack most of the biases that limit the reliability of observational studies. Therefore, randomized trials are considered to provide the strongest and most reliable evidence of the benefit and/or harm of a health-related intervention. To date, nine randomized controlled trials of dietary antioxidant supplements for cancer prevention have been conducted worldwide. Many of the trials were sponsored by the National Cancer Institute. The results of these nine trials are summarized below.

그러나 무작위 통제된 임상 실험은 관찰 연구의 신뢰성을 제한하는 대부분의 편향이 결여되어 있다. 따라서 무작위 시험은 건강과 관련된 개입의 유익성 및/또는 위해성에 대한 가장 강력하고 신뢰할 수 있는 증거를 제공하는 것으로 간주된다. 지금까지, 암 예방을 위한 식이 항산화 보조제의 무작위 통제 실험 9건이 세계적 규모로 시행되었다. 많은 실험들이 국립 암 연구소의 후원을 받았다. 이 9번의 시험 결과는 아래에 요약되어 있다.

Overall, these nine randomized controlled clinical trials did not provide evidence that dietary antioxidant supplements are beneficial in primary cancer prevention. In addition, a systematic review of the available evidence regarding the use of vitamin and mineral supplements for the prevention of chronic diseases, including cancer, conducted for the United States Preventive Services Task Force (USPSTF) likewise found no clear evidence of benefit in preventing cancer (27).

전반적으로, 이들 9개의 무작위 통제화 임상 실험은 식이 항산화제가 1차 암 예방에 이롭다는 증거를 제공하지 않았다. 또 미국예방서비스대책위원회(USPSTF)에서 실시한 만성질환 예방을 위한 비타민 및 미네랄 보충제 사용과 관련해 이용 가능한 증거들을 체계적으로 검토한 결과 암 예방에 도움이 된다는 명확한 증거는 발견되지 않았다(27).

It is possible that the lack of benefit in clinical studies can be explained by differences in the effects of the tested antioxidants when they are consumed as purified chemicals as opposed to when they are consumed in foods, which contain complex mixtures of antioxidants, vitamins, and minerals (3). Therefore, acquiring a more complete understanding of the antioxidant content of individual foods, how the various antioxidants and other substances in foods interact with one another, and factors that influence the uptake and distribution of food-derived antioxidants in the body are active areas of ongoing cancer prevention research.

항산화제, 비타민, 미네랄의 복합 혼합물(3)을 함유하고 있는 식품에 소비할 때와 달리 정제된 화학 물질로 소비할 때 임상 연구에서 유익성의 결여는 검사한 항산화제의 효과의 차이로 설명할 수 있다. 따라서 개별 식품의 항산화 함량에 대한 보다 완전한 이해를 얻는 것, 그리고 음식 속의 다양한 항산화 물질과 다른 물질이 서로 어떻게 상호작용하는가, 그리고 음식에서 유래한 항산화 물질의 체내 섭취와 배분에 영향을 미치는 요인은 진행 중인 암 예방 연구의 활동적인 영역이다.

Should people already diagnosed with cancer take antioxidant supplements?

이미 암 진단을 받은 사람들은 항산화제 보조제를 섭취해야 하나?

Several randomized controlled trials, some including only small numbers of patients, have investigated whether taking antioxidant supplements during cancer treatment alters the effectiveness or reduces the toxicity of specific therapies (28). Although these trials had mixed results, some found that people who took antioxidant supplements during cancer therapy had worse outcomes, especially if they were smokers.

소수의 환자만을 포함한 몇몇 무작위 통제된 실험들은 암 치료 중 항산화제를 복용하는 것이 효과를 변화시키는지 아니면 특정 치료제의 독성을 감소시키는지를 조사해왔다. 비록 이러한 실험들이 엇갈린 결과를 보였지만, 일부는 암 치료 동안 항산화제를 복용한 사람들이 특히 흡연자라면 더 나쁜 결과를 보인다는 것을 발견했다.

In some preclinical studies, antioxidants have been found to promote tumor growth and metastasis in tumor-bearing mice and to increase the ability of circulating tumor cells to metastasize (29–31). Until more is known about the effects of antioxidant supplements in cancer patients, these supplements should be used with caution. Cancer patients should inform their doctors about their use of any dietary supplement.

일부 임상 전 연구에서는 항산화제가 종양을 가진 생쥐의 종양 성장과 전이를 촉진하고 종양 세포 순환 기능을 증가시키는 것으로 밝혀졌다(29~31). 암 환자들에게 항산화제의 효과에 대해 더 많이 알려질 때까지, 이러한 보충제는 주의해서 사용되어야 한다. 암 환자들은 그들의 의사에게 식이보조제의 사용에 대해 알려야 한다.

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