암위험을 포함한 총체적 식단 연구

2018년 10월 25일 질 리드 박사

우리가 먹고 마시는 것들이 암 발병의 위험에 영향을 미치는가?

많은 연구들이 이 질문을 했지만, 대답하기는 어렵다. 음식을 먹고 음료를 마시면 그것들이 함유하고 있는 영양분과 식이 성분이 함께 소화될뿐더러 결코 서로 분리시킬 수가 없다.

이를 설명하기 위해, 그리고 식이요법과 질병의 연관성과 관련된 연구의 질을 향상시키기 위해, 연구 업계에서는 식이요법의 건강 영향과 식이요법과 암 위험을 평가하는 방법에 대해 우리의 사고방식을 바꾸고 있다. 우리는 좀 더 전체적인 접근법을 취하면서 전 생애에 걸쳐 개별적인 음식이나 영양분들과 비교해서 식생활 패턴을 관찰하고 있으며, 이러한 변화를 반영하기 위해 식생활 패턴을 통합할 수 있는 도구를 개발하고 있다.

다시 말해서, 우리는 브로콜리나 치즈버거를 먹는 것이 건강에 어떤 의미가 있는지 평가하는 데 관심이 있지만, 더 큰 식생활 패턴과 우리가 무엇을, 언제, 왜 그리고 어떻게 먹는지를 포함하는 전반적인 식생활 질의 맥락에서 평가한다.

식이 연구 접근법의 확장

식이요법과 암 위험성에 대한 연구는 종종 특정한 식이 성분에 초점을 맞춘 환원주의적인 접근법을 취해왔다. 그러나 그러한 접근법은 다른 동반 식품이나 영양소를 고려하지 않고 식품과 영양소만으로 암세포의 형성과 성장을 촉진할지도 모르는 특정한 생물학적 효과를 도출할 수 있다고 가정한다.

그러나 이 접근법만 사용할 경우, 한계와 예상치 못한 결과가 있다. 예를 들어, 1980년대 후반, 알파-토코페롤, 베타-카로틴 암 예방 연구는 특정 비타민이 많이 함유된 식단이 폐암의 위험 감소와 관련이 있다는 일부 연구결과가 나온 후 시작되었다. 그러나 이러한 비타민을 알약으로 복용하는 것(식품에 포함되지 않은 것)은 흡연자들 사이에서 폐암의 발생을 줄이지 않았으며, 실제로 약간의 해를 끼쳤을 수도 있다.

이러한 역설적인 발견은 영양소와 음식 섭취가 밀접하게 연관되어 있어서 어떤 하나의 식이 요인과 만성 질환 사이의 연관성을 조사하기 어렵다는 것을 인식함으로써 설명될 수 있을 것이다. 보충제를 복용함으로써 한 영양소의 섭취를 극적으로 증가시키는 것은 다른 유익한 영양소의 흡수나 순환 농도를 감소시키는 것과 같은 예상치 못한 효과를 유발할 수 있다.

음식물과 영양소들 사이에 상호 작용 또는 시너지 효과가 있을 가능성이 높으며, 이는 식단의 전체가 누적된 영향을 미칠 수 있다. 이는 NIH가 식이 접근법(연구)으로 고혈압을 중단시키는 연구에 자금을 지원한 이유 중 하나일 수 있다. 단일 식품이나 영양소가 아닌 전반적인 식사 패턴을 바꾸는 효과를 조사한 이 임상시험이 건강에 긍정적인 결과를 보여주었다.

전체 식단의 질을 살펴봄으로써, 우리는 다양한 퍼즐 조각들을 함께 맞추려고 노력할 수 있다. 우리는 특정한 음식이나 영양분을 넘어서서 음식을 어떻게 먹는지, 식사 시기와 주기 리듬과 같은 다른 문제들에 대해 배울 수 있다. NCI는 이미 이러한 요소들과 전체 식단을 규정할 수 있는 다른 요소들을 조사하는 연구에 자금을 지원하고 있다.

Studying “Total Diet” and Its Impact on Health, Including Cancer Risk

October 25, 2018, by Jill Reedy, Ph.D., M.P.H., R.D.

Does what we eat and drink affect our risk of developing cancer?

Many studies have asked this question, but answering it is challenging. Foods and beverages, as well as the nutrients and dietary constituents they contain, are consumed together, never in isolation of one another.

To account for this, and to improve the quality of research related to the connection between diet and disease, the research community is shifting how we look at the health impact of diet, and how we assess diet and cancer risk. We’re taking a more holistic approach and looking at dietary patterns versus individual foods or nutrients across the lifespan, and we are developing tools that can incorporate dietary patterns to reflect this shift.

In other words, we’re interested in assessing what eating broccoli or a cheeseburger means for your health—but in the context of a larger dietary pattern and overall diet quality that includes the what, where, when, why, and how we eat.

Expanding the Approach to Diet Research

Research on diet and cancer risk has often taken a reductionist approach, focusing on specific dietary components. That approach, however, assumes that a food or nutrient alone, without consideration of other accompanying foods or nutrients, can induce a specific biological effect that can fuel the formation and growth of cancer cells.

But there are limitations—and unanticipated findings—when only using this approach. For example, in the late 1980s, the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study was initiated after some studies found that diets high in certain vitamins were associated with a reduced risk of lung cancer. However, taking these vitamins as pills (and not packaged in foods) did not reduce the incidence of lung cancer among smokers, and may actually have caused some harm.

These apparently paradoxical findings might be explained by recognizing that nutrient and food consumption is closely connected, making it difficult to examine associations between any one dietary factor and chronic disease. Dramatically increasing intake of one nutrient by taking a supplement could have unanticipated effects, such as decreasing the absorption or circulating concentrations of other beneficial nutrients.

There are also likely interactive or synergistic effects among foods and nutrients, such that the totality of diet may have cumulative effects. This may be one of the reasons the NIH-funded Dietary Approaches to Stop Hypertension studyExit Disclaimer, a clinical trial that examined the effect of changing an overall dietary pattern rather than a single food or nutrient, showed positive health outcomes.

By looking at total diet quality, we can try to fit the different puzzle pieces together. We can look beyond a certain food or nutrient and learn how that food was consumed and what other issues might be at play, such as the timing of meals and circadian rhythms. NCI is already funding research investigating these and other factors that can define a total diet.

How NCI is Working to Improve Dietary Patterns Research

Every 5 years, the US Department of Agriculture (USDA) and NCI collaborate to update a dietary tool called the Healthy Eating Index (HEI). This tool is used to assess how closely an eating pattern, or any set of foods in the food supply chain, aligns with the most recent Dietary Guidelines for Americans.

The HEI has been applied by researchers to describe diet quality among the US population. It has also been used to evaluate the quality of foods you’d find in different environments: for example, in a fast food restaurant, a federal food distribution program, a food bank, or a school cafeteria.

The most recent Dietary Guidelines (for 2015–2020) reflect this shift toward focusing on total diet. For example, the guidelines now stress an overarching approach to diet, such as following a healthy eating pattern across the lifespan; eating a variety of foods, with a focus on nutrient density and amount; and limiting calories from added sugars and saturated fats and reducing sodium intake.

Our most recent updates to the HEI, described in three articles in the Journal of the Academy of Nutrition and Dietetics, also reflect this emphasis on total diet.

The fact that tools like the HEI can now be applied to any set of foods in the food supply chain is important because large segments of the population don’t have access to, or can’t afford, healthy food. If we assess how well a set of foods—for example, those provided by a food bank—align with dietary guidance focused on total diet, we can then work toward improving that set of foods to minimize the risk of cancer and other health conditions.

In an editorialExit Disclaimer accompanying our articles on the HEI, Barbara Millen, Dr.P.H., R.D., chair of the 2015 Dietary Guidelines Advisory Committee, wrote that “the evidence base is stronger than ever before linking the total diet—its dietary patterns, nutrient density, and overall quality—to health promotion and disease prevention across the human life span.”

We agree with Dr. Millen that the updated HEI is a “powerful tool to assess total diet quality” and hope other researchers will use the HEI and other evidence-based tools that fully embrace this total diet approach.

And the time is ripe for this shift. There is a growing interest in online platforms and apps for diet and physical activity monitoring that may be integrated with assessment tools like the HEI, providing opportunities for new research, tools, and technologies that eventually will help in the design of tailored nutrition interventions at the individual and community levels.

To assist in measuring dietary patterns, for example, NCI has supported the development of a freely available dietary assessment tool, the Automated Self-Administered 24-Hour Dietary Assessment Tool (ASA24), which enables research participants to report what they’ve consumed within the last 24 hours or in real time as a food record. This tool provides information that previous tools don’t, such as when food was eaten, where, and with what other foods and beverages.

It’s been exciting to see the field of diet and cancer research expand, and we’ll continue to improve methods to incorporate this new approach of looking at the total diet. Our biggest hope is that research like this can better guide efforts to understand how and what we eat affects health, and in turn inform policies and practices that reduce risk and improve health for everyone.

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