Is Cooking Vegetables In A Slow Cooker Healthy?

Slow cookers are a great way to get lots of vegetables in your diet as it’s so simple to add them to your recipe. But how does this cooking method fare in terms of nutrients when it’s left to simmer for hours? I did some research to find out if cooking vegetables in a slow cooker was healthy.

Slow cooking vegetables is healthy as the low heat means they can retain more nutrients than more aggressive cooking. Some vegetables’ nutrients are more accessible after cooking, while some vitamins are sensitive to heat. The enclosed environment means more nutrients stay in the dish.

The key is also not overcooking your vegetables in the slow cooker, which I give some guidance on in this post. If you use your slow cooker correctly, you can serve nutritious vegetables with minimal effort.

The slow cooker helps veg retain more nutrients and flavor than ordinary boiled vegetables. It also makes it easier to incorporate more vitamin-rich vegetables into your family’s diet.

Do Slow Cookers Destroy Nutrients?

Slow cooking does not destroy all the nutrients. Some water-soluble nutrients like vitamin C and B vitamins leach into the liquid but it is generally seen as more healthy than boiling because you usually eat the juices in slow-cooked recipes like stews.

And that’s a great thing about slow cookers. They can be easy to use and more healthy than boiling or steaming vegetables which lose water-soluble vitamins. I’m sure you’ve seen when you boil green vegetables and the liquid turns green – that’s nutrients going down the drain.

It’s worth noting that lots of vitamins are not soluble in water so have no effect. The site Beyond Veg has some info on what vitamins are sensitive to heat or liquid.

Keep The Setting On Low

Most sources tell me that lower temperatures are beneficial in retaining nutrients and the longer cooking times of slow cookers don’t have a huge impact. So try to keep your slow cooker on the lowest setting.

Most slow cookers have a high setting or low setting. The high gets to a boiling point faster than the low and seams to simmer more vigorously. The low setting just needs a bit more time so get your food started a few hours earlier.

Slow Cookers Make Nutrient-Rich Sauces

Vegetable juices will cook into the sauce of the dish you’re cooking, most obviously if you’ve made a dish like a casserole or stew. When you enjoy your dinner, you are taking in all those nutrients which might have been lost in other cooking methods.

If you strain the cooking water from your veg, reserve it as a healthy stock that can become the base of a sauce, marinade, risotto, or soup.

Slow Cookers Enclose The Steam

Keeping the lid on the slow cooker traps the steam and prevents it from evaporating so no nutrients can escape. Make sure that the cover of your slow cooker fits tightly and that there are no cracks where steam could escape.

Also, try to resist the temptation to lift the lid before the end of the cooking period. Opening the crockpot releases steam and slows down the cooking process. Don’t open the cover just to check on the food, but only add ingredients.

What Happens To Food When You Slow Cook For A Long Time?

Food Will Get Mushy

Pretty much all food will get too soft if you cook it for too long. Meat fibers will shred and lose their pleasant texture and even hard root veg will disintegrate.

Slow cooking does not suit some vegetables well at all. Vegetables with very high water content (like spinach, cucumber, and zucchini) and delicate veg (like asparagus) and mushrooms don’t do well in slow cookers. The long, slow cooking method leaves them mushy, watery, and tasteless. 

You Lose Some Nutrients

There are a few vitamins that are sensitive to heat and water (like vitamin C) so any unnecessary long cooking will cause losses. The best advice for nutrition is to not cook food any longer than it needs. Slow cooking is beneficial in that you usually eat the whole dish and throw nothing away.

The slower, more gentle temperatures used by a slow cooker prevent the loss of antioxidants, vitamins, and minerals in vegetables. The lowest setting on most slow cookers is about 200⁰F (93⁰C), ideal for vegetables.

Slow Cooking Can “Unlock” Some Nutrients

When you slow cook vegetables for a long time, it can help to release nutrients like carotenoids in yellow and red veg (such as carrots and tomatoes) and polyphenols in cruciferous vegetables (like cabbage, kale, and broccoli).

The slow cooking process helps make some nutrients more available to our bodies, allowing us to absorb them more easily.

Avoid Overcooking

Many slow cookers have programmable settings that allow you to leave the crockpot on for up to 24 hours, either cooking or warming. However, the fact that you have the setting doesn’t mean you should use it for vegetables or that it will yield the best results.

Always follow a recipe for cooking vegetables to learn how long they should cook – the cooking time could be one to eight hours. 

To avoid overcooking vegetables in your slow cooker, choose a machine with a timer that can switch off automatically or turn to the warmer setting.

Can You Overcook Vegetables In A Slow Cooker?

It is possible to overcook vegetables in a slow cooker, especially if you don’t layer them correctly and know when in the cooking process to add them to the crockpot. Overcooked vegetables will become spongy or squishy, with an unattractive texture. 

To prevent overcooking vegetables in a slow cooker, layer the vegetables in your crockpot: place robust veg (like potatoes, swedes, turnips, or winter squash) nearest the bottom of the slow cooker where it’s hottest, and other vegetables near the top to retain their texture. Greens like spinach go right on top of the food at the end of cooking.

Vegetables cook more quickly if added to a hot crockpot. Adding vegetables later in the cooking process means they cook for a shorter time. Canned vegetables will cook quickly, so add them late to prevent overcooking. Check out my other article to avoid overcooked, dry meat – can you overcook meat in a slow cooker?

Know when to add different veggies so that they can cook for the optimum time and avoid overcooking:

  • The bottom layer of vegetables goes in at the beginning of the cooking time – root vegetables and squashes. Carrot and potatoes, in particular, need to reach a high internal temperature to cook through, so they need the most extended cooking period.
  • When you only have three hours of cooking time remaining, add green beans, tomatoes, cabbages, and peppers. 
  • Veggies that need only half an hour include broccoli, cauliflower, and brussels sprouts. Also, add fresh herbs at this stage.
  • Add green vegetables like bok choi, baby spinach, and snow peas last. These soft, leafy vegetables only need to be heated to wilt and soften. It is easy to overcook greens, so take care to give them the briefest cooking period.

Can You Put Raw Veg In A Slow Cooker? 

You can put raw vegetables in a slow cooker. If you put the veggies in at the optimum time, the slow cooker will cook them through as it reaches the required temperature. Onions are best browned in a pan first to add flavor.

The idea of a slow cooker is that you put raw food into it, leave it for a few hours, and you’ve got a cooked meal.

For best results, chop the vegetables into uniform sizes to cook evenly. If possible, leave the peels on to add nutrients.

If you want to use frozen vegetables, thaw them first, as adding frozen veg to the crockpot will lower its temperature and upset the cooking time. It can also add too much liquid – see my post on preventing too much liquid in the slow cooker.

Vegetables To Cook Before Slow Cooking

There are a couple of vegetables that are best to precook before adding to the slow cooker.

Onions and leeks need to be cooked first, as they won’t brown and caramelize in the slow cooker, so you’ll lose that fragrant note they provide. The slow cooker will soften them during cooking, however.

Aromatics like garlic, ginger, and spices also benefit from precooking to release their flavors. Remember to deglaze the frying pan to capture the goodness and add it to the slow cooker.


Cooking vegetables in a slow cooker is very healthy and convenient, saving you time and effort. With no precooking needed, vegetables benefit from the moist, long, slow cooking environment, releasing nutrients and remaining tender and delicious. A slow cooker helps you produce healthy cooked veg with little attention, intervention, and clean-up.

Have any questions? Ask me in the comment section below and I’ll get back to you.

Tom Hambly

Tom Hambly is the founder of Boss The Kitchen. With a background in cooking and building websites, he enjoys running this site to help other cooks improve. About Tom Hambly.

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