A growing number of people who are switching to a healthier, whole foods + plant-centric diet often are enthused about their consumption of green smoothies. I suppose this is because of the social media equation of green smoothies to being über health-conscious. It's hard to come across an Instagram page that doesn't have a snapshot of a smoothie from the New Yorker's Juice Generation to L.A. Juice. As much as I am a proponent of these lifestyle + diet changes— especially of those switching from a SAD Diet, more on that here—I do have some concerns about smoothie consumption . . .
I preface this post, just like with other posts on nutrition, with the statement that I am not a health practitioner and that, although it is quite extensive, this is solely my own research. Please consult your own doctor before incorporating lifestyle or diet changes . . .
THYROID HEALTH
The first of my concerns is the affect of raw cruciferous vegetables, which make up the base of most smoothies, on thyroid health. There has been increased research surrounding the consumption of raw vegetables and, more specifically, cruciferous vegetables or Brassicaceae. These include: arugula, bok choy, broccoli, brussels sprouts, cabbage, cauliflower, chinese cabbage, collard greens, daikon radish, horseradish, kale, kohlrabi, land cress, mustard greens, radish, rutabaga, shepherd's purse, turnip, and lastly, watercress.
I have italicised those vegetables that are consumed more popularly, either in the form of a salad or in a smoothie and predominantly in its raw form. I'll focus on kale as it's the hype and is thrown into every other green smoothie possible.
The two issues that arise with kale is the consumption of two substances called goitrogens and oxalates. Let's focus on the former first . . .
A goitrogen is a substance that inhibits the uptake of iodine, which the body cannot make and the thyroid needs in order to produce hormones at optimum conditions. There are certain foods that have a goitrogenic effect when consumed in excess or consumed by a person who already has thyroid issues or is low in iodine. In addition to the cruciferous vegetables mentioned above, other foods that have this effect include sweet potatoes, yuca, millet, + soy products.
Keeping the consumption of these foods at a couple of times a week is healthy for most individuals, but consuming them every day and especially in their raw form can be detrimental, especially for those whom thyroid function is already suppressed or iodine levels are low. At a high level of consumption, even supplementation with iodine or eating foods rich in iodine [such as kelp] won't reverse the effects of these goitrogens as they interfere with its uptake into the thyroid hormone. So, if someone is suffering from Hashimoto's Disease, for example, it is probably not a good idea to have green smoothies with raw kale or dark leafy greens in the morning. It is not a great idea either for even an otherwise healthy individual to consume such a green smoothie every single morning. We all need variety + we need a well-functioning thyroid, and a solid breakfast, but more on that later . . .
Good news is that we can reduce the goitrogenic effect of these foods by cooking them properly. The most effective way to decrease these substances is through steaming these foods, which can reduce goitrogens from thirty to up to around eighty percent. Here is one exemplary study if you're interested.
The problem here that many will raise, however, that cooking sometimes also kills heat-sensitive + beneficial phytonutrients that are present in fruits and vegetables. Yes, although some foods lose certain phytonutrients through cooking, other nutrients are also increased through this process in addition to the reduction of goitrogens.
This is not to say that I believe that one should stop consuming these otherwise very nutritious + delicious foods, even in the case of thyroid dysfunction. I believe in moderation with everything. So, although I would suggest keeping the consumption of, say, raw kale or collard greens to a minimum if you have thyroid issues, I would allow your own body to be your guide. Try steaming these vegetables before putting them in your smoothie and see how your symptoms manifest themselves. If you don't have thyroid dysfunction, I would suggest that you simply keep the consumption of these foods at a moderate level—just a couple of times a week—and cook them properly.
PREGNANCY
Pregnant women should also be extra cautious as those with thyroid dysfunction are when it comes to goitrogenic foods as a developing baby's thyroid hormone uptake is sensitive. Overconsumption of these foods would consequently be more than just possibly detrimental to the mama. I would stick to steaming these foods before consumption + discarding the water.
CHINESE MEDICINE + NOURISHMENT
Chinese Medicine is also another aspect to consider when approaching these foods and the consumption of raw foods in general. Especially during these colder Winter months, we should be increasing the consumption of warmer foods according to Chinese Medicine. This is the case most of the time actually according to TCM as raw foods are very taxing on digestion. You can see this even through most asian cuisine as vegetables are predominantly consumed cooked and it's very unlikely that you'll see a big bowl of cold, raw salad on these tables. Warm foods do just that to our bodies—they warm them up, increase the flow of qi, + deeply ground us. Beginning the day with a raw smoothie with raw vegetables + frozen fruits [which most people also add in] is quite shocking to your digestion that is just barely waking up. Save your sleepy little body the rude wake-up call + nourish it with a wholesome + warm breakfast. You could have some green juice [my go-to includes some romaine, mint, cucumber, ginger, + lemon and follow it with a good, solid breakfast. Think pasture-raised, organic eggs cooked in coconut oil or ghee, for example or even a warm cup of soup. RISE + SHINE!
photo courtesy of Amanda Chantal Bacon