What happens to nutrients when cooked or frozen, etc?

Greetings to all! I just wrapped up a presentation/cooking demonstration for UC students taking part in the Foundations for Integrative Health pilot course, which aims to shift the focus of primary care to one of whole body wellness and disease prevention. It is inspiring to see that the old adage “health is the absence of disease” is finally giving way to a more comprehensive definition of what it means to be healthy. I commend students and organizers for taking part in the course, and would like to publicly thank them for allowing me to borrow their precious free time to show some examples of how to prepare vegetables and herbs, a bit about spices, and the benefits of these ingredients.

It was a whirlwind of a class for me, as I could lecture for an hour on the vitamins, minerals, antioxidants, enzymes and phytonutrients in a head of cauliflower alone, not mention how these substances affect our bodies on the cellular level. Alas, we had so much fun chopping, sautéing, adjusting spices, and enjoying the feast of our labors that I could only give a very basic overview of the benefits of some of the ingredients. (Welcome to the rabbit hole of nutrition!)


At the end of the presentation, I took questions, and I was very impressed by the inquisitive nature of many of them. I conceded that some of the questions were a bit complicated to answer with the short time we had, and promised I would answer them for everyone somehow.


I decided it would benefit everyone to be able to learn from these great questions and their answers, and that there’s no better place for this than my blog.  Many of my subscribers are at different degrees of inquiry about nutrition and physiology, so I attempt to walk a fine line between academia and accessibility. The first question has such a complex answer that it gets its own post. Let’s get to it!



Question: How does freezing, cooking, drying, or any manipulation of food affect its nutrients?

As it turns out, this answer is so complex that it begs its own textbook. Data is abundant from research on the effects of just about anything you can do with food, including shelf life and the dramatic loss of certain nutrients. (I highly recommend perusing your medical research databases). Each component of a specific produce item behaves differently. Where to begin?


Big Picture:  Vitamins and minerals fare much better in all methods of preparation and storage than antioxidants, enzymes, and other active phytonutrients and chemicals. I will thus address them separately.


Shelf Life: If you had a device that displayed the current nutrient levels of a fruit or vegetable (a dream of mine), you would be able to see noticeable decreases for every mile travelled between the farm and your kitchen table.


“For example, if you keep spinach at room temperature (20°C) for two days it loses half of its vitamin C,” explains Tara Diversi, a lecturer in the Human Nutrition Unit of the University of Sydney. Many of the B vitamins also decrease, as well, since B and C are water soluble. Fruits and vegetables that last for weeks on the counter, such as the more firm squashes and citrus fruits, have higher retaining ability for nutrients due to less evaporation.


Freezing: Vitamins can be ‘frozen in’, as well. In fact, where vitamins are concerned, it makes sense to freeze vegetables while they are still fresh, rather than finally getting around to them after they’ve begun wilting or becoming more pliable. A freshly harvested vegetable that is instantly frozen tends to retain nutrients better than one that’s been sitting on a shelf for a while, although it is still raw.


You can always lightly saute your greens and freeze them, too, along with any other vegetable for that matter. I find that this preserves both the flavor and texture qualities much more efficiently, and if I may conjecture, this more than likely means that the nutrient qualities are also better preserved, or unlocked.


Freezing vegetables can unlock, quite literally, many nutrients trapped in the thick cellulose skins of vegetables like peppers and tomatoes. Pugliese, et al. (2014) showed that freezing chili peppers increased the bioaccessiblity of mixed carotenoids (beta-carotene, beta cryptoxanthin, alpha-carotene, lycopene, astaxanthin, lutein and zeaxanthin) – also generally referred to as vitamin A.


Boiling: The most detrimental thing you can do to the nutrients in your produce is boil them and drain the water. Most of the benefits, other than the fiber, are extracted as the boiling water replaces the nutrient dense water in the food. Even the minerals, which otherwise are relatively safe, are left in the water. Unless it’s a starchy potato or squash, theres no reason to boil produce when you can simply use a very small amount of water to steam the vegetable while covered briefly, and consume any water left over. If you mess up and go overboard with the water, now’s a great time to invent a soup!


Microwave – Firstly and without question, I recommend against plastics in the microwave, although high quality, food grade plastic containers like tupperware, cambro, and lexan are significantly more safe than plastic wrap, bags, cheap food storage containers, or even the plastic bowls that many microwavable foods come in.


The January/February 1990 issue of Nutrition Action Newsletter tested and reported the ” . . . leakage of numerous toxic chemicals from the packaging of common microwavable foods, including pizzas, chips and popcorn. Chemicals included polyethylene terpthalate (PET), benzene, toluene, and xylene. Microwaving fatty foods in plastic containers leads to the release of dioxins [known carcinogens] and other toxins into your food” (Watanabe, et al. 1998).


One of the worst contaminants is BPA, or bisphenol A, an estrogen-like compound used widely in plastic products. In fact, dishes made specifically for the microwave often contain BPA, but many other plastic products contain it as well.


Luckily, glass, ceramic, porcelain, pyrex, paper, or pressed board based containers pose no risk. Just make sure you don’t obliterate the food. If you are going to use your microwave for food often, get cozy with its settings and power levels. I recommend to HealthSavor clients who prefer the microwave to never go higher than the REHEAT setting. The microwave can actually help retain some nutrients, but you have to be very careful not to over cook them. In light of this, and the fact that all microwaves are different, and have hot spots that tend to overcook one part while the rest is still cool, I try to avoid using it. Keeping food prepped and on hand can help with this, whether it is a lightly precooked meal you can bake or already chopped veggies you can saute or steam quickly.



Dehydrating/freeze drying – Vitamins B and C see a modest decrease in a food dehydrator, while freeze drying retains them both, as well as beta-carotene. All of the fiber, minerals, and many of the phytochemicals are retained.


All of the above methods, however, either retain, unlock, activate, or deactivate the myriad of beneficial polyphenols, flavonoids, and other phytonutrients (For a quick 101 on phytonutrients, click here). This is where this answer could truly become a novel, and is much more interesting to consider due to its complexity and cutting edge data. I’d love to do a presentation on these constituents while sampling a rainbow of fresh produce (wink wink). Every color carries its own specific benefits. I did a presentation for the Cancer Support Community that highlighted the effects of different phytonutrients on individual genes and other amazing functions. In fact, I blogged about it right here.



See what I did here?

See what I did here?

Best Practices

Freshly harvested produce: Nothing could ever beat fresh produce from your garden, or fresh produce in general (keyword: fresh). The one year I had time to tend a garden, I could instantly notice the bold flavors. The amplified flavors and wonderful texture of freshly harvested produce are noticeable even to the least discerning of us, and the amplified nutritive qualities cannot be beat. This is where you will find the highest concentration of many essential elements for health. Strive for it.



Extend shelf life with natural preservatives.

We all know that sugar, salt, and pickling are natural ways of preserving foods, but these have obvious downsides. Keeping food fresh just requires an eye on oxidation and microbes. Here is an example of each.


-Vitamin C is a powerful antioxidant, and lemon juice can be diluted with water to coat any food and slow the oxidation reaction. Similar to salt, lemon juice draws out water content, balancing the pH factor and natural acids in food. C6H807, or citric acid, is an acid found in lemons, which is used in beverages, foods, cosmetics and pharmaceuticals for preserving color, flavor and taste. It provides many of the same benefits, and more, to our bodies.


-Rosemary extract is made from the distillation of rosemary leaves and is a powerful preservative. Its anti-microbial composition contains carnosic and rosmaranic acid, antioxidants that act as shields to decay. The Phytochemical Database supervised by Dr. James Duke from the U.S. Department of Agriculture, states that rosemary has over 24 antioxidants that have a longer life span of activity than most other types of antioxidants. I would imagine that this extract would impart the taste or essence of Rosemary considerably.

-Cloves, or lavang as they are known in Hindi, have been used for thousands of years in Indian and Chinese medicines as a natural preservative. Containing high amounts of phenolic compounds, which have antioxidant properties, they keep food from going bad by preventing the growth of fungus and bacteria.

-Common herbs such as thyme, oregano, cinnamon, and sage also have protective benefits which are equally as powerful, but the oils are too intense to douse your food with… way too intense (I’ve tried).

Cook as lightly as possible to preserve as many nutrients as possible, while still unlocking others.

Most importantly, EAT MORE VEGETABLES!!! Don’t feel like you need bread, pasta, or rice at every meal. “But what about carbs?” –  A lot of people tend to forget that vegetables are made up mostly of carbohydrates. The difference is that vegetables are loaded with significantly more nutrients, fiber, and water content than grains. Grains also often carry a higher glycemic load and can contribute to inflammation. Remember the cauliflower rice we talked about?  Get out your grater and give it a try instead of rice, bread, or pasta at your next meal. Simply steam or saute it briefly with any seasoning you like, or simply a dash of salt and pepper.

The cumulative effect of using fresh ingredients and herbs is higher quality nourishment, longer fridge-life, and the kinds of benefits that I briefly touched on here. Whether you are sauteing, baking, or freezing, follow one rule of thumb: Eat real food, not too much, emphasizing fresh vegetables and lean proteins, fruits, some whole grains, nuts, seeds, and legumes of as many varieties as possible.

I think this scratches the surface of this complex issue. There are as many answers to this question as there are vegetables, fruits, phytochemicals, and food prep/storage methods. Exponentially complex questions deserve blog posts, but if you still feel like part of this question is left unanswered for you, please let me know using the contact form link below.

Thank you for reading!

Have a question or would like an elaboration?  Use our contact form HERE and I will blog it all for everyone’s benefit!  






Pugliese A, O’Callaghan Y, Loizzo M, et al. In vitro investigation of the bioaccessibility of carotenoids from raw, frozen and boiled red chili peppers ( Capsicum annuum). European Journal Of Nutrition[serial online]. March 2014;53(2):501-510. Available from: Health Source: Nursing/Academic Edition, Ipswich, MA.

Watanabe F, Takenaka S, Abe K, Tamura Y, and Nakano Y. J. Agric. Food Chem. Feb 26 1998;46(4):1433-1436



About Chef Braedon

bkaleNutritionist-Chef Braedon Firebrand is the creator of Temptology, an elite-yet-accessible general health, sports nutrition, disease prevention meal-prep program focused around delicious recipes he creates for his celebrity clients. Braedon was also founder and co-owner of HealthSavor, a Cincinnati Ohio based healthy, organic, gluten-free meal delivery service, created to help busy families, individuals and children eat nutritious meals easily and affordably (2010-2017). Chef Braedon focuses on helping his customers lose weight, optimize performance on field or in gym, lower their blood sugar/blood pressure, control chronic conditions and feels very honored to have earned the trust of many doctors, students, parents, actors, musician, athletes, and on-the-go businessmen and women all over the country. Chef B also enjoys hanging out with his daughter, fiance, and rescue dogs, as well as playing music, strength training, and continuing his education in nutrition.

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