April 15, 2019 by Renee Tavoularis


By Rachel Swanson, MS, RD, LDN

We are well-versed when it comes to reading the recipe directions to add a ‘dash of salt and pepper to taste’, but when was the last time the directions took into consideration the influence of bioavailability on the foods you're preparing? In this context, simply think of bioavailability as the nutritional effectiveness that can take place within our body. Selecting high quality, nutrient-dense produce is a main part of the equation, but there’s another side to the story that typically remains untapped and will open up an entirely new value-add component to your dishes. 

The truths surrounding the debate between consuming raw versus cooked, or the best food prep methods cannot be boiled down to a simple black and white answer. Rather, these answers depend on the nutrient of interest: cooking degrades some bioactive compounds…while simultaneously enhancing others. This is important because it enables us to make elevated choices when it comes to enhancing the food that we eat. The more we can optimize the bioavailability factors of our food, the greater the probability they have to perform incredible services in our body; from scavenging for damaging free radicals, to influencing gene expression.

Time for a little food science and kitchen chemistry lesson, served up hot. 


Going with local, organic options at a farmer’s market means purchasing produce options very close to their actual harvest date. This isn’t just for the freshness factor –  it’s for preserving nutrient bioavailability. This loss of nutrients in any particular fruit or vegetable is referred to as the cellular respiration rate. In fact, research out of Berkeley showed that broccoli had undetectable levels of vitamin C simply after 7-days post-harvest!

Expert takeaway:

  • Produce with the highest respiration rate include broccoli, asparagus, mushrooms, peas, and sweet corn (and therefore will result in the highest moisture loss, quality and nutrient degradation). Best to use within 1-3 days of purchase (the same applies to the produce after it has reached peak ripeness on the countertop)!
  • Don’t fret so much for others like pumpkin, beets, squash, sweet potatoes, onions and full-sized variety carrots – these selections can be going strong for at least one month with proper storage!
  • Don’t hesitate to go for an organic option in the frozen foods section either, since the produce was likely flash-frozen at the peak of season, and can offer pretty viable substitutes in terms of nutritional value. (Besides, not all of us will have the luxury of shopping for the freshest picked ingredients)! 


When we rush home after the local farmers market, we quickly jam all the produce in the fridge to prevent the dreaded nutrient degradation. For all intents and purposes, this is a great habit. However, there are multiple produce selections that simply do not maintain their peak flavor sitting in the fridge. After all – timing is everything, and we can achieve peak nutrition from our produce (vitamins, minerals, antioxidants) when we consume it at their peak ripeness.

Expert takeaway:

  • Avocado, peaches, nectarines, tomatoes, bananas, and melons can be left out on the countertop until they have matured to their peak succulence. (The one fruit that is an outlier are bananas- consuming them slightly less ripe means you’ll be consuming more of the beneficial resistance starch that it contains).
  • For potatoes, onions, garlic, and winter squash, ideally keep them in a cool, dark, dry place to ensure perfect ripeness and readiness for when the meal prep begins.


Generally, the most vulnerable nutrients that are most sensitive to heat degradation are the water-soluble vitamins (vitamins C and B, including folate). We observe the most nutrient losses when boiling, so consuming these choices raw, or those which are cooked at lower temperatures without water, is preferable.

Expert takeaway:

  • Typically, steaming will be your best bet to preserve water-soluble nutrients. This will be important for leafy greens (kale, mustard greens, swiss chard, etc). If boiling is your go-to, then don’t discard - simply use this water as a stock for some homemade soup!
  • Cooking inactivates the potent chemoprotective and anti-inflammatory effects of the nutrients contained in cruciferous vegetables (e.g. broccoli, cauliflower, Brussels sprouts). However, a cool kitchen chemistry hack can be applied to activate the enzyme needed to form the beneficial compound, sulforaphane, so it is not lost in the cooking process. Simply chop up these vegetables before you cook (about 40 minutes prior). Then, you can cook as desired and will be awarded with the powerful nutrient delivery into your body!

Just as some nutrients are destroyed in the cooking process, others are enhanced. Carotenoids fall into this category; these are the brilliant red, orange, and yellow pigments in fruits and vegetables. Carotenoids increase in bioavailability during food processing and cooking because it helps to release the compounds within the food’s matrix. This in turn, increases intestinal absorption. To put it in perspective, this is important because one of the carotenoids found in tomatoes, lycopene, has proven itself as a powerful antioxidant. In fact, it’s been studied for its role in cardiovascular disease, stroke and cancer, exhibiting a clear protective effect, especially for males. (So, make sure you’re serving them up to the important men in your life)!

Expert takeaway:

  • As a general rule of thumb, the use of heat versus eating raw will be the best way to enhance carotenoid absorption; the richest sources include tomatoes, carrots and sweet potato.


Just as a sommelier can pair the perfect wine to enhance your meal, you can do the same thing when it comes to the food combinations on your plate. Pair the produce rich in fat-soluble vitamins, (vitamins A, D, E, or K), like in sweet potatoes, carrots, squash, spinach, and other dark greens with some fat to optimize absorption. This could be as simple as serving up a lunch salad with a drizzle of olive oil, topped with a few avocado slices or a sprinkle of chopped nuts. Or, sautéing tomatoes in olive oil when making a pasta sauce to significantly increase the bioavailability of lycopene. Another notoriously easy pairing can enhance absorption of plant-based iron. Simply combine with vitamin C (e.g. a squeeze of fresh lemon, slices of oranges or strawberries) alongside iron-rich choices like kale, spinach, lentils and soybeans.

Expert takeaway:

  • Get the most vitamins out of your meal by pairing it with healthy fat and a touch of vitamin C to optimize iron absorption.


  1. SELECT A VARIETY OF PRODUCE. This in turn, will maximize nutrient variety. Simple! If you also pick some foods that fight bloating, that’s even better!
  2. MIX UP THE COOKING METHODS. It’s okay if some days you don’t have the bandwidth to consider bioavailability. Just aim to mix it up – it’s a series of tradeoffs, anyway. Consume your purchased produce raw one meal, and cooked the next to have the best of both worlds, which can demonstrate how different food prep methods affect bioavailability. Seriously – have fresh spinach salad at lunch, then sautéed side with dinner (at lunch you’ll have more vitamin C, and at dinner you’ll be increasing the carotenoids)! You can also consider adding ingredients like nutritional yeast to fully reap the benefits.
  3. WHEN IN DOUBT, POP IT IN THE MICROWAVE. Really – when it comes to preserving the amount of antioxidants in a dish… turns out microwaving isn’t all that bad! After all, a few minutes heating up a leftover veggie dish will trump any meal handed out of a fast-food takeout window.
  4. TAKE-HOME MESSAGE: To put it in perspective, the most important fact we can always agree upon… eating vegetables despite the optimal cooking method will still always be better than not eating them at all.

Rachel Swanson is founder of Rachel’s Rx, a preventative medicine private practice and nutrition consultancy. She currently practices at Lifespan Medicine, a concierge medical practice utilizing top technologies, leading edge diagnostics and integrative, natural therapies to help others look, feel and live their best life possible. Prior to starting her company, she was selected twice for professional NFL cheerleading teams — Patriots and Chargers. During this time, she simultaneously led research efforts in sports performance recovery for Harvard Orthopedics, diet and oncology research for a Harvard physician-led foundation, and provided nutrition education and meal plans for professional NFL players. She recently established a community medical rotation for NYU students in Cape Town to assist those with HIV AIDs, diabetes and malnutrition. She is a trusted expert for the Dr. Oz Show, where she is frequently quoted for her advice pertaining to optimal health and nutrition. Rachel is a Licensed, Registered Dietitian Nutritionist, holds a Masters of Science in Clinical Nutrition from NYU, and completed clinical rotations at Mt. Sinai Hospital in Manhattan.

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1 Response


May 22, 2019

Hey, very nice blog. I came across this on Google, and I am stoked that I did. I will definitely be coming back here more often. Wish I could add to the conversation and bring a bit more to the table, but am just taking in as much info as I can at the moment. Thanks for sharing.

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