最方便直接的方式,其實就是曬太陽,人體所需的維他命D超過九成都是靠曬太陽而來的,皮膚接受特定波長紫外線照射就能合成維他命D. 於春季、夏季、秋季的 10點-15點之間曬太陽 5-15 分鐘就能讓我們合成足夠的維他命D. 然而,過了5-15分鐘後,就要擦上防曬油了 (SPF>15),以免增加皮膚癌的可能,年紀越大,膚色越深的人(如:黑人),吸收陽光合成維他命D的能力就越差。
由以上敘述,可以知道影響身體合成維他命D的幾個重點:
- 日照強度或日照角度都有關。要曬到一點點紅(slight pinkness to the skin),但又不用到很紅的程度。
- 日照時間不用久,久了會皮膚癌。
- 防曬油一擦上去,就幾乎沒有合成維他命D的能力了。
- 其實若非刻意防曬,年紀不大的人且不完全生活在室內的人其實可能是足夠了,但長期坐辦公室、放假又宅在家中的人就不敢保證了。
再來就是食物的種類,其實並不多,主要在富有油脂的魚類,如鮭魚 ( 100g 中含 360 IU)、鯖魚、沙丁魚都算多;蛋黃中也有,不到 50 IU,但是因為蛋黃中的膽固醇高,所以也不能只靠吃蛋黃來獲取足夠的維他命D;而魚肝油裡頭含有很多,是很好的維他命D食物。另外有少數食品中會添加維他命D,如牛奶、柳橙汁等等,要看食品標籤有沒有囉。以下表格支援!
富有維他命D之食物 | 每一百公克之含量 |
野生鮭魚 | 600–1000 IU |
養殖鮭魚 | 100–250 IU |
沙丁魚 (罐頭) | 300–600 IU |
鯖魚 (罐頭) | 250 IU |
鮪魚 (罐頭) | 236 IU |
魚肝油 | 400–1000 IU (每一茶匙) |
香菇 (新鮮摘下) | 100 IU |
香菇 (乾製後) | 1600 IU |
蛋黃 | 20 IU (每一蛋黃) |
蘑菇 | 76 IU |
奶油 | 52 IU |
起士 (如:Emmental) | 44 IU |
個人結論:要達到每日維他命D建議劑量800 IU,光靠食物是不大可能會夠的,除非你很愛吃很油的魚;至於日曬,曬太久又有皮膚癌的風險,隨便曬曬,又不知道到底夠不夠…因此,適度補充綜合維他命,以保持足夠維他命D的量,可保健康 !
補充:本篇所指的維他命D,是原料維他命D,想知道維他命D在身體裡面,會經過哪些變化,才會變成具有活性的“活性維他命D”嗎?請看“維他命D在體內的旅程與敵人,以及腎臟病患的補充法”
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