The reason for this recommendation was that any vitamins and minerals lost from cooking the vegetables would end up in the water. This cooking water could then be added to homemade soups or sauces with the nutrition benefiting those that consumed them.
This notion took hold and has not let go to this day. Unfortunately, reserving vegetable cooking water can do more harm than good. If the vegetables that are cooked are not organic, pesticides and nitrites from commercially produced fertilizers can end up in the cooking water. Even low to no spray veggies such as asparagus would not be safe bets as these crops are still typically fertilized with commercial preparations that are high in nitrites.
Cooking cruciferous vegetables such as broccoli, cauliflower, cabbage, Brussels sprouts and kale would add goitrogenic (thyroid blocking) substances to the cooking water which should be discarded. Water used to boil potatoes would contain chemicals called hemagglutinins that disrupt red blood cell formation.
Dark green, leafy vegetables such as beet greens, raw spinach and chard contain oxalic acid that blocks calcium and iron absorption. This irritating substance also can cause distress to the sensitive mucous membranes in the mouth and intestinal tract and contributes to the formation of kidney stones.
Consuming raw crucifers or dark, leafy greens is not an alternative either as the substances that cause problems when in the cooking water also cause problems if consumed directly with the vegetable in an uncooked state such as a raw green smoothie.
Legume Cooking Water Not Safe Either
Since 2015, the vegan community has popularized the trend of using legume cooking water for cooking, particularly from chickpeas. It is called aquafaba and is used as an egg replacement particularly in dessert recipes. It whips up foamy just like egg whites.
Cooking water from legumes is also dangerous to consume but for a different reason. Research published in 2018 revealed that chickpea cooking water contains saponins, a potent anti-nutrient that contributes to leaky gut. It is also not advisable for pregnant women to consume this substance as it is a miscarriage risk.
Vegetable Cooking Water that IS Safe
As a result, only the cooking water from organic root vegetables (carrots, turnips, potatoes, parsnips, and beets), organic squash (including zucchini), and organic vegetables from the lily (onions, leeks, and garlic) and nightshades (tomatoes, eggplant and peppers) families can safely be used. For example, this potassium broth recipe uses vegetables simmered in water that do not release toxins.
If you find it confusing as I do to remember the distinctions of which organic veggies are safe to use the cooking water for and which are not or if you mix you veggies together when you steam them, it is best to just adopt the practice of not using the cooking water at all.
It is of particular importance NOT to use vegetable cooking water for use in pureeing homemade baby food.
One final word of caution: All vegetables tend to form nitrates after cooking and during storage. These nitrates can transform into strong carcinogens in the intestines, so it is best to avoid refrigerating and reheating vegetables, particularly leafy, green vegetable which concentrate nitrates when grown commercially.
Sarah, The Healthy Home Economist
References
Homemade Coconut Milk Kefir Recipe (+ VIDEO)
Sarah…. You stated, “If the vegetables that are cooked are not organic, pesticides and nitrites from commercially produced fertilizers can end up in the cooking water”. Does this mean that NO non-organic vegetables should be cooked in soup or cooking water saved and only the vegetables that you stated and if are organic can be cooked in the soup you are making? So even if the cruciferous vegetables or dark green, leafy vegetables are organic, you still should not use the water or cook them in soup? I just need to clear this up in my mind.
Thanks so much!
I am just reading Tamar Adler’s Everlasting Meal. She highly recommends cooking your vege’s in advance, and then using them as you go during the week. She loves reusing water from vege’s or pasta, and I was actually beginning to be converted to this idea! Now I am not so sure. In fact, I am quite confused!
From her website: http://www.tamareadler.com/book/about/
Another one: http://www.thekitchn.com/video-cook-a-we-163999
Sarah I’ve not really understood this concept. Is this not technically what soup is? And if so, does it not make soup any good then?
Soup base comes from homemade bone broth not vegetable cooking water. If you want a vegetable stock base, use miso paste.
What about freezing lightly-blanched kale and swiss chard? I always discard the blanching water. I occasionally add some frozen greens to soups. Does freezing inhibit nitrate production?
What about soup that is made from vegetables cooked in the liquid that eventually IS the soup? I am really confused and concerned about this as I have multiple auto-immune diseases and never seem to get well… no matter how ‘healthy’ I eat. Could my soup be making me sick???
I’ve heard of this before, but then I’ve also heard of people boiling certain vegetables to make a potassium-rich soup which is supposed to be health-promoting.
And what about slow-cooked, hearty vegetable soups or veggies as part of a stew? Is that unhealthy? Thanks.
Yes, I use bone broth as base. I also add carrots, celery and onion while making the bone broth. Then, I’ll add more veggies to cook in the broth for whatever soup I’m making. Is there a danger in this?
I used to use it to water plants. Also the water that I hard boil eggs in.
I think this is one of the most irresponsible articles I have ever read. In a day and age when 95 percent of Americans are eating nothing but processed crap, here we have someone scaring the crap out of us about … vegetable stock? This is even worse than Joseph Mercola writing incessant idiocy warning us against eating fruit. Luckily you don’t have nearly the audience that Mercola has, warning us against LEAFY GREENS?? Seriously? Do just a LITTLE bit of research instead of parroting the articles warning us about oxalates. Are there ANY studies showing a correlation between kale eating and kidney stones? Are there ANY studies correlating the consumption of kale and thyroid issues? No, and no. Kale and spinach are GOOD FOR YOU, hello? Just as with any food on the planet, if you eat pounds of leafy greens every day, you might find yourself with some nutritional issues– a balanced diet is important– but kale and spinach have endless positive health benefits. I’m not going to disagree that we should be buying organic vegetables , but I’d way rather see someone making vegetable stock with non-organic veggies than eating, say, 90 percent of the other stuff you can buy at a basic grocery store. This article is irresponsible and it’s quite disturbing to me that I saw it posted three times on Facebook. Use your noggins, folks, and please ignore this stupidity.
I depends on the vegetables. Some vegetables contain high amounts of oxalic acid and the soluble portion leaches into the cooking water. Its better to throw the water out.
Almost makes you afraid to eat anymore.. I was wondering about dehydrating left over veggies for later use. I heard a lady say that she does this so as to not be wasteful. What are your thought on dehydrating left overs?
Thanks Sarah for informing us once again:)
Great info – thanks for sharing! I use my veggie water for my plants, so there is no question.
I just read that you water your plants with vegetable water. I was asking the same question on wikihow.com now I know someone else is doing it, i’ll try it in my front garden. I’ve got a lot of vegetable water.. I use the clippings from vegetables and boil in water for 45 minutes and strain. then I throw out the clippings. and wala I have vegetable water.
I think that the best practice for using water leftover from cooking or steaming vegetables is to pour into the soil of your garden or yard. That way any nutrients in the water can go into the yard instead of down the drain.
For a more rational look at goitrogens, try here. http://www.whfoods.com/genpage.php?tname=george&dbid=250
Some people who get too far into certain “diets” get to the point where they cannot see the forest for the trees. This article from Sarah is one of those.
I think this is one of the most irresponsible articles I have ever read. In a day and age when 95 percent of Americans are eating nothing but processed crap, here we have someone scaring the crap out of us about … vegetable stock? This is even worse than Joseph Mercola writing incessant idiocy warning us against eating fruit. Luckily you don’t have nearly the audience that Mercola has, warning us against LEAFY GREENS?? Seriously? Do just a LITTLE bit of research instead of parroting the articles warning us about oxalates and “goitrogens”. Are there ANY studies showing a correlation between eating kale or spinach and kidney stones? Are there ANY studies correlating the consumption of kale and thyroid issues? No, and no. Kale and spinach are GOOD FOR YOU, hello? Just as with any food on the planet, if you eat pounds of leafy greens every day, and nothing else, you might find yourself with some nutritional issues— a balanced diet is important— but kale and spinach have endless positive health benefits. I’m not going to disagree that we should be buying organic vegetables , but I’d way rather see someone making vegetable stock with non-organic veggies than eating, say, 90 percent of the other stuff you can buy at a basic grocery store. This article is irresponsible and it’s quite disturbing to me that I saw it posted three times on Facebook. Use your noggins, folks, and please ignore this stupidity .http://www.whfoods.com/genpage.php?tname=george&dbid=250
Sarah,
Thank you for continuing to answer questions on this post after all this time. My question is about frozen kale, chard, and spinach. The recommendation I have always seen for freezing these veggies is to blanch them and then freeze. Once that is done, will the nitrates increase in cold storage? So my question is threefold: 1) My family typically puts the frozen kale in smoothies. Would that cause us to consume bad nitrates? 2) Would we be better off re-heating and water and then discard that water? Or 3) Is there no way to safely preserve kale by freezing it?
Thanks again!
Thanks,
Albert
The tradition in my family is to make a broth from discarded vegetable pieces. Do you have an opinion on boiling onion and garlic papers for broth? Thanks!
Kristen Davenport Katz The readers of my blog are not the average processed food eating people. They are interested in maximizing their health and want to know and understand the nuances of traditional cooking. Using vegetable cooking water has some cautions that go along with it that the majority of my readers will appreciate understanding.
Leslie Delamater Anderson Aitken My Mom is 84 and never saved the vegetable cooking water for anything! LOL