完整飲食可避免憂鬱和焦慮

作者：Caroline Cassels  
出處：WebMD醫學新聞

　　January 15, 2010 — 新研究認為，富含蔬果、全榖類與優質肉類及魚類的傳統或完整飲食，有助於預防心智疾病—特別是憂鬱和焦慮，相反的，富含精緻或加工食物與飽和脂肪酸的西式飲食則會增加憂鬱風險。
　　
　　澳洲墨爾本大學研究者進行的一個大型橫斷面研究顯示，相較於攝取西式飲食者，經常攝取所謂的傳統飲食的婦女，有超過30%比較不會發生重度憂鬱、輕鬱症(dysthymia)與焦慮異常，此外，西式飲食與憂鬱可能性增加50%有關。
　　
　　主要研究者、Felice Jacka博士向Medscape Psychiatry表示，簡而言之，如果你習慣食用包括蔬果、全榖類與優質瘦肉的健康飲食，那麼你憂鬱和焦慮的風險就降低了。
　　
　　Jacka博士表示，但是有一個警告，在美國難以獲得優質肉類，這是因為在北美飼養的牛隻多數是使用玉米為主的飼料餵養。
　　
　　Jacka博士表示，這種牛隻飼養方式對於肉類品質有「重大影響」。她表示，這種飼養方法會增加飽和脂肪酸，減少很重要的好的脂肪酸，而在澳洲，牛羊肉等紅肉來自放牧的動物，所以有比較健康的脂肪酸資料。
　　
　　文章中未發表的研究發現之一是，在澳洲的飲食建議指引範圍內(每週不超過4次)食用較多牛羊肉者，比較不會有憂鬱和焦慮。
　　
　　根據Jacka博士表示，最近的澳洲研究顯示，個人飲食攝取的omega-3脂肪酸主要來自紅肉。
　　
　　她表示，我們傳統上認為omega-3脂肪酸主要來自魚類，但是，實際上，自然圈養的優質紅肉也有相當多的omega-3 脂肪酸，而來自飼育場的紅肉含較多的omega-6脂肪酸—這是一種比較不健康的脂肪酸，事實上還可能與較多心智健康問題有關。
　　
　　這項研究線上發表於1月4日的美國精神病學期刊(American Journal of Psychiatry)。
　　
　　【缺乏證據】
　　根據研究者指出，不同於許多醫療狀況，多數值得注意的心血管疾病、精神異常缺乏實證基礎的飲食調控一級預防和治療策略，之前有關飲食和憂鬱疾病之間關聯的研究著眼在個人的營養或食物類型，但是他們指出，這些研究都沒有探討完整飲食的影響。
　　
　　他們指出，不過，個人營養或食物的有限研究，對於飲食和心智健康的關聯提供了一個尚不完整的描述，Jacka博士表示，我們不吃個別的營養成分，我們吃的是完整的飲食。
　　
　　她指出，直到前不久，都沒有任何針對完整飲食對一般心智異常的研究，而在過去10年左右，有關飲食對於心血管疾病、糖尿病與代謝症候群的影響的文獻大量增加。
　　
　　Jacka博士指出，有趣的是，這些疾病受到許多相同的潛在機轉影響，例如免疫失調和持續發炎，而這些也曾被指出會影響憂鬱症。
　　
　　為了評估個人的日常飲食和心智異常發生率的關聯，研究者使用「Geelong Osteoporosis Study」這項大型流行病學研究的資料。
　　
　　【意料之外的發現】
　　該研究包括了1,046名年紀在20-93歲的婦女，研究者使用Cancer Council Victoria飲食問卷分析研究對象的飲食，針對過去12個月的飲食，以10分為範圍對74種食物和6種酒精性飲料進行綜合的飲食頻率評量。
　　
　　為了診斷目前有無心智異常，使用「精神疾病診斷與統計手冊[第四版，文字修訂]研究版、非病患版結構式臨床訪談」評估研究對象。此外，使用12問題版的綜合健康問卷(GHQ-12)測量心理症狀，研究的主要結果為GHQ-12的分數、重度憂鬱異常、輕鬱症與焦慮異常。
　　
　　校正年紀、社會經濟狀態、教育與健康行為之後，結果發現，傳統或完整的飲食與憂鬱及焦慮風險降低有關，勝算比(ORs)分別是0.65(95%信心區間[CI]為0.43 – 0.98；P < .05)和0.68 (95% CI，0.47 – 0.99；P < .05)。
　　
　　相對的，食用加工或炸類食物、精緻榖類、糖製品與啤酒的西方飲食者，GHQ-12的分數較高，這些分數較高者傾向有50%更容易有憂鬱(OR，1.52；95% CI，0.96 – 2.41)，不過，研究者發現，西式飲食與增加焦慮風險之間沒有關聯。
　　
　　有一個意料之外的發現，研究者發現所謂的現代飲食(包括水果、沙拉、魚、豆腐、堅果、優格與紅酒)與年輕、教育程度高之婦女的憂鬱可能性較高有關。
　　
　　研究者推論，這或許是倒果為因，Jacka博士表示，我們認為，這些婦女可能是試圖藉由較健康的飲食來改善她們的憂鬱症狀。
　　
　　【公共衛生警覺提升】
　　Jacka博士指出，最近在澳洲一線照護機構進行的研究顯示，憂鬱症患者有多達30%改變他們的飲食習慣，作為改善其憂鬱症狀的一種方法，她將這個發現視為大眾對於飲食和心智健康之間關聯的警覺提升。
　　
　　雖然一線照護醫師通常鼓勵病患改變飲食和增加運動來幫助改善心血管風險因素，Jacka博士指出，但是在精神科還沒有這樣的建議。
　　
　　她表示，這有一大部份是因為缺乏實證支持「健康飲食可以幫助預防和/或治療心智疾病」這個假設，不過，情勢有所轉變，Jacka博士指出，最近發表於2009年底的兩篇研究[Br J Psychiatry. 2009;195:408-413, Arch Gen Psychiatry. 2009;66:1090-1098]也支持飲食與心智健康及憂鬱風險之間的關聯。
　　
　　Jacka博士表示，好消息是，她們可以用這些研究排除以倒果為因來解釋她們的發現，換句話說，她們發現，如果你的飲食品質不佳，你比較可能會在接下來的歲月中發生憂鬱，這支持了我們的橫斷面研究結果，但是，憂鬱症本身不會造成不佳的飲食。
　　
　　【公共政策的影響？】
　　Jacka博士表示，這些資料相當一致，我認為該是開始討論飲食對於公共衛生之可能影響的時候了，特別是憂鬱症的治療和一般的心智健康。
　　
　　她指出，她的研究團隊有一篇印製中、探討飲食和青少年憂鬱的關聯文章，顯示飲食品質和出現憂鬱之間有相當清楚的關聯。
　　
　　她表示，我的感覺是，應讓加工食品業界實際上感到它們對年輕一代的生理和心理健康的負面影響，營養對於發育中的腦部有影響，有75%的精神疾病發生在25歲之前。
　　
　　Jacka博士表示，我相信，這些飲食研究支持「飲食與憂鬱有因果關係」的假設，但是我們需要更多研究來確定這些發現不是偶然，我們也需要檢視對早期憂鬱進行飲食介入是否有用。
　　
　　【飲食的「深切影響」】
　　加州大學洛杉磯神經營養研究實驗室的Fernando Gomez-Pinilla博士為Medscape Psychiatry發表評論時表示，該研究令人印象深刻且有重要貢獻。
　　
　　Gomez-Pinilla博士表示，這是控制良好的研究，且顯示出完整飲食的重要性，不只對生理健康有益，也對心理健康有幫助。
　　
　　Gomez-Pinilla博士等人進行的動物研究顯示，飲食對於腦衍生神經滋養因子(BDNF)有重要且迅速的影響，在一般的精神疾病，特別是憂鬱症扮演關鍵角色。
　　
　　促進神經營養物是抗憂鬱藥物的主要方法之一。Gomez-Pinilla博士的團隊顯示，以富含精練糖和飽和脂肪的飼料餵養老鼠，對於降低BDNF值有立即且明顯的影響，而導致對學習和記憶的影響。
　　
　　如同Jacka博士，Gomez-Pinilla博士表示，精神醫學界在提倡將飲食作為心智疾病的預防和/或治療策略上有些微沉默，不過，他表示，這個研究以及其他最近的研究，將有助於說服醫師們，這些有「深切影響的」飲食對於心情和一般的精神異常有幫助，或許也會因而改變臨床實務。
　　
　　Jacka博士報告指出，她接受澳洲與奧勒岡Sanof-Synthelabo藥廠的旅費資助， 以及來自Eli Lilly藥廠的不設限教育資金的支持。其他作者們的宣告請見原始文獻。
　　
　　Am J Psychiatry. 線上發表於2010年1月4日。


Whole Diet May Ward Off Depression and Anxiety

By Caroline Cassels
Medscape Medical News

January 15, 2010 — A traditional or whole diet characterized by vegetables, fruit, whole grains, and high-quality meat and fish may help prevent mental illness — specifically, depression and anxiety. Conversely, a Western diet high in refined or processed foods and saturated fats may increase the risk of depression, new research suggests.

A large, cross-sectional study conducted by investigators at the University of Melbourne in Australia shows that women who regularly consume a so-called traditional diet were more than 30% less likely to have major depression, dysthymia, and anxiety disorders compared with their counterparts who consume a Western diet. In addition, the Western diet was associated with a 50% increased likelihood of depression.

"Simply put, if you habitually eat a healthy diet that includes fruit, vegetables, whole grains, and high-quality lean meat, then you may cut your risk of depression and anxiety," principal investigator Felice Jacka, PhD, told Medscape Psychiatry.

But one caveat here, said Dr. Jacka, is high-quality meat, which is difficult to come by in the United States. This is because most of the cattle in North America are raised — from birth to death — in feed lots, where they are fed a corn-based diet.

This method of raising cattle may have a "profound impact" on the quality of the meat, said Dr. Jacka. "It increases saturated fat and decreases very important good fatty acids. Whereas in Australia, red meat, such as beef and lamb, comes from pasture-raised animals, so it has a much healthier fatty acid profile," she said.

One of the findings that was not published in the article is that people who consumed more beef or lamb within Australia's recommended dietary guidelines (not more than 4 times per week) were less likely to have depression and anxiety.

According to Dr. Jacka, recent Australian studies show that a good proportion of individuals' dietary intake of omega-3 fatty acids actually comes from red meat.

"We've traditionally thought of omega-3s as only coming from fatty fish, but actually good-quality red meat, that is, naturally raised, has very good levels of omega-3 fatty acids, whereas red meat that comes from feedlots tends to be higher in omega-6 fatty acids — a fatty acid profile that is far less healthy and may in fact be associated with more mental health problems," she said.

The study was published online January 4 in the American Journal of Psychiatry.

Lack of Evidence

According to the investigators, unlike many medical conditions, most notably cardiovascular disease, psychiatric disorders lack evidence-based primary prevention and treatment strategies based on dietary modification. Previous studies that have looked at a potential link between diet and depressive illness have focused on individual nutrients or food groups, but they note that none has looked at the impact of a whole diet.

However, they add, that limiting studies to individual nutrients or foods may provide an incomplete picture of the relationship between diet and mental health. "We don't eat individual nutrients, we eat a whole diet," said Dr. Jacka.

"Up until very recently there really haven't been any studies that have looked at the impact of whole diet on common mental disorders, which is really interesting since over the past 10 years or so there's been a real burgeoning in the literature regarding the impact of diet on cardiovascular disease, diabetes, and the metabolic syndrome," she added.

Interestingly, many of the same underlying mechanisms that influence some of these conditions, such as immune dysfunction and subsequent inflammation, have also been shown to influence depression, Dr. Jacka pointed out.

To assess the association between individuals' regular diet and the prevalence of mental health disorders, the investigators used data from the Geelong Osteoporosis Study, a large epidemiologic study.

Unexpected Finding

The study included 1046 women ages 20 to 93 years. Participants' diets were assessed using the Cancer Council Victoria dietary questionnaire, a comprehensive food frequency tool that reports on 74 foods and 6 alcoholic beverages during the preceding 12 months on a 10-point frequency scale.

To diagnose current mental disorders, participants were assessed using the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition, Text Revision) Research Version, Non-Patient Edition. In addition, psychological symptoms were measured with the 12-item version of the General Health Questionnaire (GHQ-12). Scores on the GHQ-12, major depressive disorder, dysthymia, and anxiety disorders were the study's primary outcomes.

After adjustment for age, socioeconomic status, education, and health behaviors, the results revealed that a traditional or whole food diet was associated with a reduction in depression and anxiety risk, with respective odds ratios (ORs) of 0.65 (95% confidence interval [CI], 0.43 – 0.98; P < .05) and 0.68 (95% CI, 0.47 – 0.99; P < .05).

In contrast, those who consumed a Western diet of processed or fried foods, refined grains, sugary products, and beer had higher GHQ-12 scores. Those who scored higher on the Western-type or processed food diet tended to be approximately 50% more like to have depression (OR, 1.52; 95% CI, 0.96 – 2.41). However the researchers found no link between the Western diet and an increased risk of anxiety.

In an unexpected finding, the researchers also found a tendency for a so-called modern diet — which consisted of foods such as fruits, salads, fish, tofu, beans, nuts, yogurt, and red wine — was associated with a higher, rather than lower, likelihood for depression among younger, more educated women.

The researchers speculate that this may be due to reverse causality. "We think these women may have been attempting to improve their depressive symptoms by consuming a healthier diet," said Dr. Jacka.

Growing Public Awareness

Dr. Jacka pointed out that recent research conducted in primary care practices in Australia show that up to 30% of individuals with depression change their dietary habits as a way of improving their depressive symptoms, a finding she views as an indication of a growing public awareness about the potential relationship between diet and mental health.

Although primary care physicians often encourage their patients to improve their diets and increase their exercise level to help improve cardiovascular risk factors, the field of psychiatry "is just not there yet," said Dr. Jacka.

In large part, she said, this is due to a lack of evidence to support the hypothesis that a healthy diet can help prevent and/or treat mental illness, but the tide is turning, said Dr. Jacka. Two recent studies published late in 2009 [Br J Psychiatry. 2009;195:408-413, Arch Gen Psychiatry. 2009;66:1090-1098] also support the link between diet and mental health and depression risk.

"The good thing about these studies is that they were able to rule out reverse causality as an explanation for their findings. In other words, they found if you had a poorer-quality diet you were more likely to develop depression over the ensuing years, which supports what we found in our cross-sectional study, but depression itself did not lead to a poorer diet," said Dr. Jacka.

Public Policy Implications?

"The data are fairly consistent, and I do think it's time we started a conversation about public health messages about the potential role of diet in prevention as well as the treatment of depression particularly and mental health in general," said Dr. Jacka.

She added that her group currently has a paper in press investigating a link between diet and depression in a cohort of adolescents that shows "a very clear" relationship between diet quality and the presence of depression.

"My feeling is that the negative impact of the processed food industry is really going to make itself felt [in terms of the physical and mental health] on the younger generation," she said. She pointed out that nutrition has an impact on the developing brain, adding that 75% of psychiatric illnesses begin before the age of 25 years.

"I believe that these dietary studies support the hypothesis that diet is causally related to depression, but we need to do more research to be sure that these just aren't chance findings. We also need to test whether [dietary] interventions in the early stages of depression may be of use," said Dr. Jacka.

Diet's 'Profound Impact'

Commenting on the study for Medscape Psychiatry, Fernando Gomez-Pinilla, PhD, at University of California Los Angeles' Neurotrophic Research Laboratory, said the study is impressive and makes an important contribution to the literature.

"This is a very well-controlled study and demonstrates the importance of a whole diet, not only on physical health, but also mental health," Dr. Gomez-Pinilla said.

Animal research by Dr. Gomez-Pinilla and colleagues has demonstrated that diet has a significant and rapid impact on brain-derived neurotrophic factor (BDNF), which plays a key role in psychiatric illness in general and depression in particular.

Boosting levels of neurotrophins appears to be one of the main ways antidepressant medications work. Dr. Gomez-Pinilla 's group has shown that feeding rats a Western diet high in refined sugars and saturated fats has a very immediate and obvious impact in reducing BDNF level, which has a resulting impact on learning and memory.

Like Dr. Jacka, Dr. Gomez-Pinilla said the psychiatric community has been somewhat reticent about advocating diet as a preventive and/or treatment strategy for mental illness. However, he said, this research, as well as other recent studies, may help convince clinicians about the "profound impact" diet can have on mood and psychiatric disorders in general and perhaps help shift clinical practice.

Dr. Jacka reports she has receive travel funding from Sanof-Synthelabo Australia and Organon and research support from an unrestricted educational grant from Eli Lilly. Disclosures of the other authors can be found in the original article.

Am J Psychiatry. Published online January 4, 2010.