如果你已經成為一位素食者一段時間，妳大概聽過這樣的說法：
- 過多的蛋白質攝取，特別是動物性蛋白質，是造成骨質酥鬆症的原因。
- 乳製品不僅無法使我們免於骨質酥鬆症，它甚至是造成它的主因。
- 鈣質的攝取對預防骨質酥鬆症來說並不重要。
最後，妳很可能會導出一個結論，就是：對於全素者來說，攝取少量的蛋白質是能夠避免罹患骨質酥鬆症的。十年來，素食推廣機構Vegan Outreach對這議題有著不同的意見，但仍建議全素者應攝取接近美國衛生署所建議的鈣質攝取量標準。近幾年來，不斷的有證據在反駁上述的陳述。然而，在2007年二月，一份首次針對這個議題所做的研究報告出爐了，它給了這些問題很好的答案。
這份由「歐洲癌症與健康研究組織牛津分部」(EPIC-Oxford)所做的研究召集了57,000參與者，其中包含從1993年到2000年超過1,000名的素食者與近100,000的奶蛋素食者(lacto-ovo vegetarians , 簡稱LOV)。這份研究要求他們以填寫問卷的方式來測量他們所吃過的食物，在約五年之後進行後續的追蹤，並詢問所有受測者在這五年之間是否曾經骨折過。
在排除因上了年紀所造成的骨折的因素後，全素者比肉食者骨折的比率高出了37%。而在排除其他例如年齡、吸煙、飲酒、體重指數(BMI)、運動量、婚姻狀況、出生時間以及接受女性荷爾蒙治療等因素後，全素者仍然比其他受測者高出了30%的骨折率。>_<
這個結果對於素食者來說真是個壞消息，事實上，由於素食團體長期以來對動物性蛋白質、鈣質以及骨質資訊在做負面宣傳，我擔心它已經讓許多素食者們對於鈣質和維生素D的攝取充滿成見了。
然而，慶幸的是，當全素者在攝取足夠的鈣質後，他們骨折的比率不再偏高了。在受測者們攝取過525毫克的鈣質後（相較於其他飲食群的95%，素食者中僅有55%的人達到這個標準），全素者和其他飲食群的骨折比率相同（如果妳想知道其他飲食群的骨折比率，整體來說，這幾個飲食群之間彼此並沒有太大的差異）
難道這表示單單鈣質的攝取量不足是造成骨質酥鬆症的主要原因嗎？事實上，可能是其他飲食群的受測者在攝取足夠的鈣質時或多或少也攝取到蛋白質，以及足夠的維生素D。他們也在這個研究中發現，蛋白質或是維生素D的攝取並不與骨折率的高低有關連，相信現在，我們已經可以假設鈣質的缺乏，是造成全素者容易骨折的原因了。
這個研究並沒有對有額外攝取鈣質補充品的飲食群做過測試，我不確定在增加這個飲食群後，測試結果會不會有所不同，但我現在先假設它不會。
美國衛生署所建議的每日成人鈣質攝取量為1,000毫克，而在英國方面則是700毫克，你只需每天食用三份高鈣的食物，就能夠達到這些標準了（營養補充飲品、大量富含鈣質的深綠色蔬菜和鈣片），我幾乎每天都喝富含高鈣的豆奶，並且在每日睡前會吞一顆含有500毫克鈣質的鈣片。
你可以在「素食者健康」網站上得到更多關於鈣質、維生素D和骨質的資訊，請參閱以下網站：page: http://www.veganhealth.org/articles/bones
註釋：研究報告全文如下：http://tinyurl.com/2ms6kq
英文原文：
New Study Answers Questions about the Vegan Diet, Calcium, and Bone Health-Jack Norris, RDIf you’ve been a vegan for long, you’ve probably heard that:
- Too much protein, especially animal protein, is the major cause of osteoporosis.
- Not only does dairy not protect against osteoporosis, it actually contributes to it.
- Calcium intake isn’t very important for protecting against osteoporosis.
Finally, you might have come to the conclusion that the lower levels of protein in a vegan diet protect against osteoporosis. For almost ten years now, Vegan Outreach has cautioned vegans that the jury was still out on these issues and that vegans should try to meet the U.S. recommended intakes for calcium. In recent years, the evidence has been mounting against the above statements. In February of 2007, a study was released, the first study of its kind, that gives us pretty good answers to these questions.
(1)The EPIC-Oxford study recruited 57,000 participants, including over 1,000 vegans and almost 10,000 lacto-ovo vegetarians (LOV), from 1993 to 2000. They were asked to fill out a questionnaire to measure what they ate. About 5 years after entering the study, they were sent a follow-up questionnaire asking if they had suffered any bone fractures.
After adjusting for age alone, the vegans had a 37% higher fracture rate than meat-eaters. After adjusting for age, smoking, alcohol consumption, body mass, physical activity, marital status, and births and hormone replacement therapy for women, the vegans still had a 30% higher fracture rate.
That’s not good news; in fact, it’s something I’ve feared for some time now given the vegan propaganda about animal protein, calcium, and bones which has fostered complacency among vegans about calcium and vitamin D.
Yet, there is some good news in this study. When calcium intake was adjusted for, the vegans no longer had a higher rate of fractures. And among the subjects who got 525 mg of calcium a day (only 55% of the vegans compared to about 95% of the other diet groups), vegans had the same fracture rates as the other diet groups. (And if you’re wondering about how the other diet groups (meat-eaters, fish-eaters, and LOV) fared over all, none of them differed from each other in any of the analyses performed.)
Does this mean lower calcium intakes are the cause of the fractures? It could be that people who eat more calcium also eat more or less protein or get more vitamin D. The authors noted that fracture rates did not correlate with protein or vitamin D intake among the people in this study. For now, we should assume that calcium is what the vegans with higher fracture rates were lacking.The study did not measure calcium intake from supplements. I’m not sure if this affected the results, but for now I would assume it did not.
The US recommended intake for calcium is 1,000 mg for most adults. The UK’s recommended intake is 700 mg. You can get this much calcium by having 3 servings of high calcium foods (fortified drinks, large portion of high calcium greens, and calcium tablets) each day. I drink soymilk fortified with calcium on most days and take a 500 mg calcium pill each night before bed.
More information on calcium, vitamin D, and bones can be found at VeganHealth.org on this page: http://www.veganhealth.org/articles/bones
Footnote
Appleby P, Roddam A, Allen N, Key T. Comparative fracture risk in vegetarians and nonvegetarians in EPIC-Oxford. Eur J Clin Nutr. 2007 Feb 7; [Epub ahead of print]http://tinyurl.com/2ms6kq
