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Being a vegetarian may be partly in your genes
From the Impossible Burger to “Meatless Mondays,” going meat-free is certainly in vogue. But a person’s genetic makeup plays a role in determining whether they can stick to a strict vegetarian diet, according to a new Northwestern Medicine study.
The findings open the door to further studies that could have important implications regarding dietary recommendations and the production of meat substitutes.
“Are all humans capable of subsisting long term on a strict vegetarian diet? This is a question that has not been seriously studied,”said corresponding study author Dr. Nabeel Yaseen, professor emeritus of pathology at Northwestern University Feinberg School of Medicine.
A large proportion (about 48 to 64%) of self-identified “vegetarians” report eating fish, poultry and/or red meat, which Yaseen said suggests environmental or biological constraints override the desire to adhere to a vegetarian diet.
“It seems there are more people who would like to be vegetarian than actually are, and we think it’s because there is something hard-wired here that people may be missing.”
Several genes involved in lipid metabolism, brain function
To determine whether genetics contribute to one’s ability to adhere to a vegetarian diet, the scientists compared UK Biobank genetic data from 5,324 strict vegetarians (consuming no fish, poultry or red meat) to 329,455 controls. All study participants were white Caucasian to attain a homogeneous sample and avoid confounding by ethnicity.
The study identified three genes that are significantly associated with vegetarianism and another 31 genes that are potentially associated. Several of these genes, including two of the top three (NPC1 and RMC1), are involved in lipid (fat) metabolism and/or brain function, the study found.
“One area in which plant products differ from meat is complex lipids,” Yaseen said. “My speculation is there may be lipid component(s) present in meat that some people need. And maybe people whose genetics favor vegetarianism are able to synthesize these components endogenously. However, at this time, this is mere speculation and much more work needs to be done to understand the physiology of vegetarianism.”
The study was published Oct. 4 in the journal PLOS ONE. It is the first fully peer-reviewed and indexed study to look at the association between genetics and strict vegetarianism.
Why do most people eat meat?
Religious and moral considerations have been major motivations behind adopting a vegetarian diet, and recent research has provided evidence for its health benefits. And although vegetarianism is increasing in popularity, vegetarians remain a small minority of people worldwide. For example, in the U.S., vegetarians comprise approximately 3 to 4% of the population. In the U.K., 2.3% of adults and 1.9% of children are vegetarian.
This raises the question of why most people still prefer to eat meat products. The driving factor for food and drink preference is not just taste, but also how an individual’s body metabolizes it, Yaseen said. For example, when trying alcohol or coffee for the first time, most people would not find them pleasurable, but over time, one develops a taste because of how alcohol or caffeine makes them feel.
“I think with meat, there’s something similar,” Yaseen said. “Perhaps you have a certain component — I’m speculating a lipid component — that makes you need it and crave it.”
If genetics influence whether someone chooses to be a vegetarian, what does that mean for those who don’t eat meat for religious or moral reasons?
“While religious and moral considerations certainly play a major role in the motivation to adopt a vegetarian diet, our data suggest that the ability to adhere to such a diet is constrained by genetics,” Yaseen said. “We hope that future studies will lead to a better understanding of the physiologic differences between vegetarians and non-vegetarians, thus enabling us to provide personalized dietary recommendations and to produce better meat substitutes.”
注释：
vogue: n
表示" 时尚；流行"，means " the popular fashion or custom at a certain usually not lasting time"，如：Hoop skirts were once the vogue. 圈环裙一度曾是时尚。
subsist: v
表示"；维持生活；生存"，means "support oneself;"，如：He subsisted mainly on vegetables and fruit. 他主要靠蔬菜和水果维持生命。
emeritus: adj; n
表示"名誉退休的;"，means "honorably retired from assigned duties and retaining your title along with the additional title `emeritus' as in `professor emeritus';a professor or minister who is retired from assigned duties"，如：Perhaps I can introduce Mr. Lake Kirby, an emeritus professor from Washington University.请允许我介绍华盛顿大学名誉教授莱克柯尔比先生。
pathology: n
表示"病理学"，means "he branch of medical science that studies the causes and nature and effects of diseases"，如：Pathology is the study of disease. 病理学是研究疾病的科学。
override: v
表示"推翻；无视；凌驾"，means " take precedence over; prevail over (sb's opinions,decisions,wishes,claims,etc.)"，如：The appeal court overrode the decision of the lower court.上诉法院撤销了下级法院的裁决。
lipid: n
表示" 脂质；油脂"，means "an oily organic compound insoluble in water but soluble in organic solvents; essential structural component of living cells (along with proteins and carbohydrates)"，如：Dietary fiber would also benefit people with hypercholesterolemia because of its possible lipid lowering effect.膳食纤维对血胆脂醇过多的人也有好处，因为它能降低人体内的油脂含量。
Homogeneous: adj
表示"同质的；同种的；相似的"，means "all of the same or similar kind or nature"，如：More of the hitherto homogeneous societies are becoming plural ones.越来越多的单一种族社会逐渐变得多元化。
synthesize: v
表示" 合成；综合"，means "combine so as to form a more complex, product;"，如：The two elements are synthesized by a chemical process.这两种元素已经化学合成。
physiology: n
表示"生理学；生理机能"，means "the branch of the biological sciences dealing with the functioning of organisms"，如：We had studied physiology in middle school.我在中学就已经学过生理学。
metabolize: v
表示" (使)产生代谢变化"，means "produce by metabolism"，如：Our bodies constantly metabolize the food we eat.
我们吃的食物在体内不停分解产生代谢变化。
中文简要说明：
很多人加入「无肉星期一」行列是为了健康或跟流行，没多久就发现自己无肉不欢而宣告放弃，更加觉得长年茹素甘之如饴的人实在不可思议。美国西北大学研究发现，除了宗教与道德考虑，吃素不单纯是意志力问题，有3个基因可能与人们能否长期严格吃素显著相关，有助抵挡肉类的诱惑。
综合美国《新闻周刊》、国家广播公司（NBC）报导，堪萨斯州立大学调查显示，至2022年1月，全美成年人约1成自认是素食主义者，动机包括健康、动保、环境问题、宗教。已有研究显示，自称素食者约半数实际上也吃肉，至少偶尔会吃。
研究论文第一作者、伊利诺伊州西北大学（Northwestern University）医学院病理学教授雅辛（Nabeel Yaseen）说，环境或生物层面的限制，凌驾了严格坚持素食的意愿，导致许多人放弃，真正贯彻的人相对少很多。以往有几项研究显示，遗传影响人们对于食物的喜恶，例如有些人不敢吃香菜。研究团队决定从遗传层面探究坚持茹素的能力是否也与遗传有关。
研究团队从英国人体生物数据库（UK Biobank）找出5324名严格素食主义者（vegan，食物以外的动物产品也不使用）、32万9455名吃肉的人，以全基因体关联分析（GWAS）比较，想找出可能与吃素有关的基因。两组均为白人，以获得同构型样本。
研究人员找到3个与严格素食主义者显著相关的基因、31个可能有关的基因。3个显著相关的基因位在同一条染色体上，其中2个与脂质代谢、大脑功能有关，其他31个基因也有一部分与这两者有关，素食者带有基因变异的机率高很多。
雅辛说，研究结果重点在于，一个人是否适合素食很可能取决于遗传基因，「若实在无法坚持到底，没必要自责」。他指出，植物食品与肉类的差异之一是复杂的脂质，「肉类可能存有某些人需要的脂质成分，带有支持素食基因的人也许能自行合成这些成分」。研究团队由此假设，严守素食的能力可能与身体如何处置脂质、脂质如何影响脑部功能有关。这些仍待更多研究证明。
研究论文指出，这项研究仅强调遗传基因与能否坚持素食之间的关联，并未断言特定基因直接导致人们偏爱素食，盼未来研究进一步了解素食者与非素食者的生理差异，进而提供更贴近个人需求的饮食建议、生产更优质的肉类替代品。研究成果已于本月发表于美国《公共科学图书馆期刊》（PLOS ONE）。
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