Last night on Instagram, I asked you to send questions about nutrition or fitness that you have been dying to know. The first question I received was "How long do the nutrients really last in the refrigerator?". The short answer is that is depends on the vegetable, but they all immediately begin to lose nutrients after harvest. The long answer is that there are many factors that either speeds up the process or can impact the vegetables nutritional value upon consumption. This is a big question with lots of conflicting information (as is most of the nutrition industry) but here are a few points to be aware of. For the sake of this article, I'll refer to both vegetables and fruits.
1. What causes nutrient loss?
Produce is grown. It needs light, water and oxygen to thrive, ripen, sprout and be ready for harvesting. Once the produce is harvested though, it doesn't stop this process, called respiration. Essentially, the fruit or veggie is using its own nutrients to continue to produce carbon dioxide, water and heat. Certain produce has higher rates of respiration than others, which is why some vegetables (onion, garlic) take ages to rot, while others (berries) rot and mold rapidly. The rate of respiration can cause produce to spoil anywhere from 1-2 days to 2-3 weeks. The rates are available to research but it's only a piece of the puzzle. Once harvested, heat, light, oxygen and moisture cause the depletion of nutrients also.
2. How to reduce the depletion of nutrients?
There are many ways to impact the loss of nutrients in your fresh fruits and vegetables; the simple answer is by reducing the amount of damage they are exposed to. Cutting, washing, cooking, juicing or bruising all impact the rate at which the nutrients breakdown and the produce begins to rot; the more damage, the more loss. Keeping produce in a cool, dark place that is free of excess moisture will keep them fresher longer. Boiling can cause nutrients to leach into the water, whereas steaming lightly is more effective at retaining nutrients. Since nutrients begin breakdown as soon as the produce is harvested, the best way to reduce nutrient loss is to shop local. Reducing the transit time between harvesting and consumption is the best way to ensure the maximum amount of nutrients.
3. What can impact nutritional value?
As listed above, heat, oxygen, moisture, damage and the rate of respiration can all impact the nutritional value of the fruits and veggies you are consuming. What impacts the final nutritional value is also the starting value of the produce. Several studies have shown that organically grown produce has a higher nutritional value than commercially grown produce. Other factors that impact nutrient levels are soil quality (ie. nutrients in the soil, location), harvesting methods (hand picked vs. mechanical), water sources used (chemicals in the water) and the storage methods used once harvested. Storage methods range for each type of fruit or vegetable and some can be stored for up to a year before being brought to your local supermarket (ie. apples).
Again, its not a straight answer but if you are concerned about your nutrient consumption, the best way to ensure you receiving the most nutrients possible is to shop local, organic and consume as quickly as possible. Limiting the cooking process and choosing less destructive means to heat foods (ie. steaming vs. boiling or warming in the oven vs. the microwave) will also impact the nutrients you are consuming.
Thank you for your question and I hope this was helpful! Please leave any comments/questions about this article or any other articles you want to see!
xo Shawn
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