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Cruciferous Vegetables - Should you avoid them while Breastfeeding?

Updated: Mar 9



Cruciferous Vegetables include kale, broccoli, bok choy, cauliflower, cabbage, brussels sprouts, radishes, kale, collard greens, kohlrabi, rutabaga, and watercress.

They are infamous among breastfeeding moms for making a breastfed baby gassy, and among those with thyroid disease for containing gointrogens.

Is it true? Should breastfeeding moms avoid cruciferous vegetables? Do cruciferous vegetables really make a baby gassy? And should you avoid them if you have hypothyroidism?

1. The Health Benefits of Cruciferous Vegetables

Cruciferous Vegetables are some of the most nutritious foods out there. Let's review:

  • They are a surprisingly high source of Vitamin C! (1 cup of Kale has as much Vitamin C as an entire lemon!)

  • They are one of the highest sources of Vitamin K (Pregnant and lactating women can meet their daily Vitamin K needs with a single cup of Kale!)

  • They contain Folate, an important nutrient for the synthesis of DNA, brain development the prevention of neural tube defects

  • They are a source of ALA Omega-3 fatty acids, and therefore considered to be anti-inflammatory and good for brain and eye development in the fetus!

  • They protect your eyes due to secondary plant compounds such as lutein and zeaxanthin

  • They have a TON of fiber, which helps digestion, blood sugar control, heart health and more

  • They protect against certain cancers, such as bladder, breast, colorectal, prostate, lung and ovarian cancer

With all of these benefits, should breastfeeding moms really avoid cruciferous vegetables as a precaution because they may make a baby gassy? Or moms with thyroid disease because they contain goitrogens?



2. Can Broccoli, Cabbage & Co. make a Baby gassy?

It's the age-old question: Can gassy foods such as cruciferous vegetables make my baby gassy?

The idea is that broccoli, cauliflower, cabbage and the likes make some of us poot more after we eat them, mainly because they have a ton of fiber.

Watching a baby struggle with passing gas (a weird sensation for a newby, for sure) makes some of us wonder whether it was the broccoli soup we had the night before which is to blame.

From all we know about physiology and how our digestive system works, this doesn't make any sense. The whole reason we get gassy from such foods is because the fiber doesn't get absorbed into the blood stream; it travels down the digestive tract and into the colon instead where it is fermented by the gut bacteria, producing the infamous 'gasses'. But, this fiber technically never enters mom's circulation (blood).

Since breast milk is made from components in our blood, the fiber would therefore not have any way to reach the baby; hence, it shouldn't have the same effect on the baby as it has on mom who eats the food directly.

The only study to date on the subject was done in the 1990's. They sent out questionnaires to moms and asked about colic symptoms in babies and what they ate the during that week. This study did find a correlation between a mom's intake of cruciferous vegetables and infants experiencing colic symptoms (1).

What gives? Why do so many moms report gassy foods make their babies gassy, when it technically makes no physiological sense? And why does this study find a positive correlation?

Granted, it could be the placebo effect. We've all been told we should watch our broccoli intake if we have a gassy baby, mainly by the older generation. The above study is, after all, just a survey, not an intervention study, and it's difficult to pinpoint which food, if any, could be to blame.

However, there's a fairly new theory out there which deserves mention here:

There may exist an entero-mammary pathway: A way for bacteria (and other factors?) from mom's gut to translocate to the mammary gland (2). The research in this field is still at the very beginning, so I can't really tell you how (or if) this actually happens, but you bet I'll be following this very closely and update you guys as I have new information. This is definitely a very significant finding!

For now, I recommend you go with 'your gut instinct' on this one (literally). If you think cruciferous vegetables give your baby gas, cut them out for a while and see if this improves the symptoms. If not, leave them in your diet to continue to reap the benefits. There is no reason to cut them out precautionally.

2. Cruciferous Vegetables may boost Milk supply in those with high Estrogen levels

Cruciferous vegetables may have a positive effect on breast milk production in some women. To get to this conclusion, I have to get a big scienc-y so please stay with me:

Cruciferous vegetables contain significant amounts of glucosinolates. Those are the phytonutrients which give cruciferous vegetables this very strong, acric, almost musky smell as you're chopping it up.

One of these break down products is Indole-3-Carbinol, a natural inhibitor of estrogen.

Now, you may think estrogen is important for breastfeeding moms, but it's actually the enemy when it comes to breast milk supply. In fact, while estrogen levels are naturally high during pregnancy (and lactation suppressed as a result of it), the drop in estrogen and progresterone levels in days following birth actually signals the milk to 'come in' (3). Only when estrogen levels are sufficiently low, do we make enough milk for the baby.

Indole-3-Carbonol has been shown to balance female hormones by breaking down and lowering high estrogen levels (4). Numerous studies have also demonstrated, a high intake of cruciferous vegetables may prevent cancers especially in estrogen-dependent tissues such as the breast, endometrium and cervix due to Indole-3-Carbonol's ability to suppress high levels of estrogen (5, 6, 7, 8, 9), and the cells in these organs seem to be especially sensitive to the actions of estrogen.

Some women, especially those with diabetes, obesity, stress, certain dietary habits or those taking 'the pill' often have difficulty establishing and maintaining an adequate milk supply. This is simply because these conditions or habits predispose one to a higher estrogen level, and estrogen suppresses the production of breast milk.

Nature intended for breastfeeding moms to have lower estrogen levels compared to non breastfeeding women.

Cruciferous vegetables have shown to balance the amount of estrogen we have in the body. Including Kale, Broccoli & Co. into your diet while breastfeeding may be one piece of the puzzle for you to establish and maintain a healthy breast milk supply, especially if you struggle with low milk supply from high estrogen levels.


3. Avoid excessive amounts if you have Thyroid problems

With Kale and other cruciferous vegetables being so good for us and baby, especially while Breastfeeding, you may think: The more, the better! Or you may even consider a supplement or green powder. However, as with everything in human nutrition: Moderation is key.

Some glucosinolates in Kale and other cruciferous vegetables are broken down into goitrogens. These are substances which compete with iodine uptake into the thyroid gland, making it more difficult for the thyroid to produce thyroid hormones which the body needs for normal metabolism, heat production and so on.

Goitrogens can be found not only in Kale, but in other cruciferous vegetables, cigarette smoke and soy-based products such as tofu.

When consumed in recommended amounts (1 1/2 to 2 1/2 cups per week), cruciferous vegetables have not shown any negative effects on the thyroid in human studies (9).

While pregnant, breastfeeding or for those with hypothyroidism, you should avoid large amounts of cruciferous vegetables, although it's difficult to reach this threshold of 1 pound per day with real food. Extracts ('green powders' or supplements) on the other hand can easily be overdone.

If you have hypothyroidism like me, stay on the safe side and avoid green powders and supplements, but continue to enjoy your green smoothies, kale salads, broccoli soup and kale burgers if they are made with real food ingredients!

The 2015-2020 Dietary Guidelines for Americans recommend that adults consume 1½-2½ cup-equivalents of dark-green vegetables (which include cruciferous vegetables) per week, and this amount is more than likely safe for your thyroid if you are meeting your iodine intake as well.

​​4. Make sure you balance it out with Iodine

Iodine is an important aspect to thyroid hormone production and may actually protect against negative effects of goitrogens on the thyroid (10).

Therefore, always make sure you are meeting your recommended daily intake for iodine (220 micrograms while pregnant and 290 micrograms while breastfeeding) when increasing your intake of cruciferous vegetables.

5. Cooking reduces Goitrogens

Boiling cruciferous vegetables has been found to help reduce their goitrogen content, since heat deactivates the enzyme myrosinase which is responsible for the break down of glucosinolates into goitrogens and other end products (11).

Boiling, of course, also reduces some of the beneficial effects of cruciferous vegetables, so to reap most of the benefits of Kale, eat some raw and some cooked.

6. Conclusion

Kale and other Cruciferous Vegetables have many proven health benefits. It's most prominent health benefit, the protection against some cancers, may even be passed down via mom's diet during pregnancy and lactation.

Can they make baby gassy? We don't know but cutting them out of your diet 'as a precaution' is not recommended.

While breastfeeding, cruciferous vegetables may assist in establishing and maintaining an adequate milk supply through the suppression of estrogen, particularly in those who have low milk supply due to higher than normal estrogen levels.

Most cruciferous vegetables contain goitrogens, so you should avoid excessive intake of raw cruciferous vegetables (for example, in supplement or powder form). Try to include about 1 and a half to 2 and a half cups of cruciferous vegetables into your diet per week, some of them raw and some of them cooked, while also making sure you are getting enough iodine in your diet!

So, go ahead and enjoy your Green Smoothies and Kale Salads! Reap the benefits of these awesome Greens while Breastfeeding and beyond!