Posted by kathryn in Fruit, Vegetables and Q & A Thursday

Next on Q & A Month is a BIG and difficult question. Steve wants to know:

What is the deterioration rate of nutrients in fruit and vegetables – from the time they are picked, sold to you, kept in your fridge and finally eaten? Is it the same rate for all fruits and vegetables or do some lose their nutrients faster than others?

This is a really hard question to answer, as there are so many ifs, buts and variables. And at the moment my answer is going to be incomplete at best.

Why is it so hard?

The deterioration rate of nutrients depends on many, MANY things:

• how the food is grown
• how it’s harvested
• how it’s transported
• how it’s stored before and after purchase
• which nutrient we’re talking about
• which food we’re talking about

Plus, how much goodness you get from fruit and vegetables also depends on how you prepare them.

Different nutrients deteriorate at different rates

Vitamins, antioxidants and minerals all have different levels of stability. Vitamins C, most of the B vitamins and folate are really fragile. The minerals tend to be more robust. While some nutrients like the antioxidant lycopene, can actually increase in intensity and availability after picking. In some foods.

There’s some good information on this at the Choice website. They’ve tested the vitamin C and beta-carotene levels in six different vegetables. The results compares fresh vs cooked vs frozen. And they also show the difference between fresh and week old vegies. As you’ll see the deterioration rates vary quite significantly.

Choice also has this report on the freshness of the fruit and veg we buy. In it they note:

• English spinach retains only 53 percent of its folate and 54 percent of its carotenes after just eight days stored at fridge temperature.
• Frozen peas typically have 60 percent more carotene than ‘fresh’ peas and the vitamin C content is comparable with fresh peas that have been stored and then cooked.

There’s ongoing research into these issues. As far as I can tell it’s mostly being conducted by agricultural scientists. And much of it’s ultimately geared towards improving farming and food transport and handling practices.

But we’re a long way from a definitive answer to these questions.

What should you do?

1. Eat your fruit and vegies. It’s still vital to eat two serves of fruit and at least five serves of vegies. In fact, given some deterioration does occur, it’s even more important to have plenty of fruit and veg.
2. Try to shop seasonally. This ensures you’re getting fruit and veg at it’s peak. And minimises the amount of time it’s been stored.
3. If you do a weekly shop, use the more perishable fruit and veg first. I try to use spinach and Asian greens within a couple of days of purchasing. While pumpkin, onions and carrots can be left until later in the week.
4. Buy the freshest stuff you can. Go to farmers’ markets or shops that have a high turnover of fruit and veg.
5. Don’t hesitate to use frozen vegies – they can have nutritional benefits.

What is Q & A Month?

This post is part of Q & A Month. For those of you new to Limes & Lycopene, I usually run a fortnightly question and answer forum, called Q & A Thursday. But for the next four weeks, it’s Q & A Month. If you have a question, or there’s a topic you’d like me to cover, leave a comment below or send me an email. For more information you can take a look at the Q & A Thursday archives.

Broccoli photograph by caro lines under the terms of a creative commons license.

14 February, 2008