It’s pretty obvious to everyone that fruits and vegetables are an essential part of a healthy diet. But do you know exactly how much nutrition is lost from peeling? How about boiling versus stir-fry? You can find most the the answers in yet another very useful study from the Hong Kong Centre for Food Safety, this time reviewing asian fruits and vegetables (Centre for Food Safety – Risk Assessment Studies – Nutrient Values of Fruit and Vegetables) I think it’s a great, readable PDF for all to print out and share with colleagues and family.

This research paper goes into wonderful detail regarding which fruits are higher in fiber, vitamin C, sugar and fat. It also has outstanding graphs, including this one which shows how much fiber is lost by peeling. Pears seem to lose a lot more fiber than apples:

Another graph shows how boiling can decrease vitamin C levels, and that sir-frying is a better preparation but still not as good as raw:

Yet another graph shows the fat content from stir fry vs. boiling. Clearly, stir-frying has a much higher fat content:

Their Bottom Line

There is a lot more information in the paper, but here’s their summary:

The result of the study suggested that fruit and vegetables are good sources of dietary fibre and vitamin C, whilst their energy, total fat, saturated fat and sodium contents are generally low. They are also free from cholesterol. Some fruits have higher energy value, for example, avocado and durian. Therefore, although avocado and durian are high in fibre, their consumption should be limited.

The leaves of Chinese kale and Chinese flowering cabbage contained more calcium than the stalks. Disposal of leaves during preparation is not advisable to those who want to maximize their calcium intake.

Addition of oil and dressings to fruit and vegetables during cooking and seasoning increases their fat content and energy value.

(Much of this article was originally printed in an earlier version; I am reposting some archives as I am on vacation now.)