素食向來被認為是健康的飲食習慣，但美國有研究發現，茹素的人身體為了適應吃素，經幾代遺傳後，會出現基因變異，以適應吸收蔬菜中的脂肪酸，但此舉卻同時增加罹癌與心臟病風險。
美國康乃爾大學研究人員剛公佈一項有關素食的研究結果，該研究對比數百名印度傳統素食者，以及喜歡吃肉的美國人基因，結果發現數代都吃素的人，FADS2基因出現突變，以便讓身體更易吸收蔬菜內的脂肪酸。
如果膳食含有大量植物油，如葵花籽油，這種突變基因會讓脂肪酸加速變成一種叫「花生四烯酸」的不飽和脂肪酸，增加罹癌與心臟病風險。
此外，變異的基因還會阻礙身體製造可降低心臟病風險的Omega-3脂肪酸。這次研究結果正好解釋之前有研究發現，素食者罹患腸癌的風險高於肉食者近四成。研究結果刊登在最新一期《分子生物與演化》期刊。（國際中心／綜合外電報導）
www.appledaily.com.tw/realtimenews/article/new/20160331/828580/
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Long term vegetarian diet changes human DNA raising risk of cancer and heart disease
Populations who have had a primarily vegetarian diet for generations carried a genetic mutation which raised risk of cancer and heart disease
10:00PM BST 29 Mar 2016
Long term vegetarianism can lead to genetic mutations which raise the risk of heart disease and cancer, scientists have found.
Populations who have had a primarily vegetarian diet for generations were found to be far more likely to carry DNA which makes them susceptible to inflammation.
Scientists in the US believe that the mutation occured to make it easier for vegetarians to absorb essential fatty acids from plants.
But it has the knock-on effect of boosting the production of arachidonic acid, which is known to increase inflammatory disease and cancer. When coupled with a diet high in vegetable oils – such as sunflower oil – the mutated gene quickly turns fatty acids into dangerous arachidonic acid.
The finding may help explain previous research which found vegetarian populations are nearly 40 per cent more likely to suffer colorectal cancer than meat eaters, a finding that has puzzled doctors because eating red meat is known to raise the risk.
Researchers from Cornell University in the US compared hundreds of genomes from a primarily vegetarian population in Pune, India to traditional meat-eating people in Kansas and found there was a significant genetic difference.
“Those whose ancestry derives from vegetarians are more likely to carry genetics that more rapidly metabolise plant fatty acids,” said Tom Brenna, Professor of Human Nutrition at Cornell.
“In such individuals, vegetable oils will be converted to the more pro-inflammatory arachidonic acid, increasing the risk for chronic inflammation that is implicated in the development of heart disease, and exacerbates cancer.
“The mutation appeared in the human genome long ago, and has been passed down through the human family.”
To make the problem worse, the mutation also hinders the production of beneficial Omega 3 fatty acid which is protective against heart disease. Although it may not have mattered when the mutation first developed, since the industrial revolution there has been a major shift in diets away from Omega 3 – found in fish and nuts – to less healthy Omega 6 fats – found in vegetable oils.
"Changes in the dietary Omega 6 to Omega 3 balance may contribute to the increase in chronic disease seen in some developing countries,” added Dr Brenna.
“The message for vegetarians is simple. Use vegetable oils that are low in omega-6 linoleic acid such as olive oil.”
The mutation is called rs66698963 and is found in the FADS2 gene which controls the production of fatty acids in the body.
Over many generations vegetarianism can lead to genetic changes Photo: Alamy
Previous studies have shown that vegetarianism and veganism can lead to problems with fertility by lowering sperm counts.
Separate research from Harvard University also found that a diet high in fruit and vegetables may impact fertility because men are consuming high quantities of pesticides.
Many vegetarians also struggle to get enough protein, iron, vitamin D, vitamin B12 and calcium which are essential for health. One study found that vegetarians had approximately five percent lower bone-mineral density (BMD) than non-vegetarians.
However other research suggests vegetarianism lowers the risk of diabetes, stroke and obesity.
The new research was published in the journal Molecular Biology and Evolution.
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