[Note - This is the 4th post in a series of posts on popular diets and their usefulness for PCOS. Previous posts covered the ketogenic diet, the Mediterranean diet, and the low glycemic index diet.]

During summer 2020, I tried once more to come off of hormonal birth control. It went well for several months, and then my cycle started getting longer and longer. Around the same time, Karen Hurd was featured on a podcast I listened to regularly. The podcast host had used Karen’s bean protocol to help with her own health issues.

Beans and other legumes are filled with soluble fiber. When our bodies are trying to get rid of anything it doesn’t want in it (excess hormones, pesticide residues on food we’ve eaten, pollution we’ve inhaled, etc.), it packages them up in bile. Our liver sends this bile to our gallbladder where it’s stored until we consume fat. When we consume fat, the gallbladder releases the bile into the small intestine, where it helps us digest that fat.

After filling that role, the bile, still containing the junk our body is trying to get rid of, continues down into the large intestine. If soluble fiber was consumed with that meal, the bile binds to the soluble fiber, and you poop out the bile, the junk in the bile, and the soluble fiber. If soluble fiber isn’t present, the unbound bile gets reabsorbed into your body from the large intestine, and so does the junk your body was trying to get rid of.

When we don’t get enough soluble fiber, our body’s mechanism to get rid of things it doesn’t want stops working.

There’s a lot more to PCOS than just having excess hormones in our bodies, but in the podcast episode, PCOS was one of the many things Karen brought up that could be helped by the bean diet.

So I started adding beans into every meal, as the protocol recommends.

I had HORRIBLE gas!

I tried to stick it out, and I think I made it at least 2 months, but the gas never went away, and my cycle wasn’t getting more regular.

Knowing the benefits of soluble fiber, I still try to eat beans or lentils once a day, and I use a fiber supplement from Thorne that has a lot of soluble fiber. But I abandoned the three servings of beans a day.

Given my experience, I was curious what the literature says about the use of beans for managing PCOS. Sadly, there is only one real study on the topic. The research team has split the results of the study up into multiple publications, which is honestly kind of poor research practice, and makes it look like there has been more research done on the diet than has actually been done.

However, given the popularity of Karen Hurd’s bean diet and Unique Hammond “Bean Protocol,” I think it’s important to at least discuss what little we know for sure.

Beans and PCOS: What does the literature say?

The single study recruited women with PCOS between the ages of 18 and 35 from Saskatoon, Canada. Women who were on hormonal birth control, fertility medications, or any cardiovascular medications were excluded as were those with any thyroid disorders.

Of those women who made it through the study, 31 had been assigned to follow Canada’s National Cholesterol Education Program therapeutic lifestyle changes diet (TLC) while 29 followed a pulse-based diet (McBreairty et al. 2017). Pulses include peas, lentils, beans, and chickpeas.

In addition to providing a good source of soluble fiber, as discussed above, pulses have also been shown to reduce fasting blood glucose, fasting insulin, and blood pressure. This makes them a promising intervention for those with PCOS who usually have some degree of insulin resistance and are at higher risk for cardiovascular issues like high blood pressure.

In the protocol, all the participants followed the TLC diet for two weeks. This diet included:

7-8 servings of fruits and vegetables per day
6-7 servings of grains per day
2 servings of lower-fat milk or milk alternatives per day
2 servings of lean meat or meat alternatives per day

Healthy fats were encouraged while salt, sugar, and alcohol were discouraged.

After the two-week baseline period, the group was split into those who continued on the TLC diet and those who switched to a pulse-based diet.

The pulse-based diet group consumed:

pulse-based lunches and dinners that were provided by the study team and amounted to 150g of pulses (by dry weight) per day which is about 3 servings of pulses per day.
breakfasts and snacks that were based on the TLC principles outlined above.

All participants did 45 minutes of aerobic activity five days per week. Participants were asked to train at 60% or higher relative to their maximum heart rate.

The table below reports all of the measures reported by the research team across three of their publications (Kazemi et al. 2018, Kazemi et al. 2020, and McBreairty et al. 2020).

Both the TLC diet and the pulse-based diet were effective at inducing weight loss and body fat loss, with no statistically significant differences found between the two groups of participants. In terms of reproductive hormones, all moved in beneficial directions after the diet, and the pulse-based group had a larger improvement in sex hormone-binding globulin levels. This hormone is important for women with PCOS because it binds to testosterone, reducing free testosterone (not measured by the study), which is responsible for the acne, oily skin, and excessive facial and/or body hair that women with PCOS experience.

Women with PCOS generally have excessive follicle counts in their ovaries when measured by ultrasound, which increases ovarian volume. Both diets led to improvements in these metrics, with no difference between the two diets. Similarly, both groups experienced reductions in menstrual cycle length, but the changes were not statistically significantly different from each other.

Both diets improved various measures of insulin resistance and reduced fasting blood sugar, with the pulse-based diet leading to bigger improvements in one measure of insulin resistance.

Lastly, in terms of both good and bad cholesterol levels, the pulse-based diet led to greater improvements than the TLC diet.

Effects of a 16-week diet and exercise intervention with either the Therapeutic Lifestyle Diet (TLC) or a pulse-based diet on body weight, body composition, reproductive health, insulin resistance, and cardiovascular health. Results compiled from Kazemi et al. (2018), Kazemi et al. (2020), and McBreairty et al. (2020).

From these results, we can see that the pulse-based diet does have some benefits above and beyond what one would get from the TLC diet. However, I would argue that they are relatively small. If you’re someone like me who can’t handle that volume of pulses, there are other dietary options that can lead to the same or better improvements than seen here with the bean diet.

That said, beans, lentils, and chickpeas are nutritional powerhouses, so if tolerated, I think they should be a daily staple.

take-home points

Consuming 3 servings of pulses (beans, lentils, split peas, and chickpeas) may improve cholesterol levels and levels of sex hormone binding globulin more than the TLC diet (a standard “heart healthy” diet).

This diet would be best done by easing into eating three servings per day, and some individuals may still struggle to handle this volume of pulses.

References

Kazemi M, McBreairty LE, Chizen DR, Pierson RA, Chilibeck PD, and Zello GA. 2018. A comparison of a pulse-based diet and the Therapeutic Lifestyle Changes Diet in combination with exercise and health counselling on the cardio-metabolic risk profile in women with polycystic ovary syndrome: A randomized controlled trial. Nutrients, 10:1387 https://doi.org/10.3390/nu10101387

Kazemi M, Pierson RA, McBreairty LE, Chilibeck PD, Zello GA, and Chizen DR. 2020. A randomized controlled trial of a lifestyle intervention with longitudinal follow-up on ovarian dysmorphology in women with polycystic ovary syndrome Clinical Endocrinology, 92:525–535 https://doi.org/10.1111/cen.14179

McBreairty LE, Chilibeck PD, Chizen DR, Pierson RA, Tumback L, Sherar SB, and Zello GA. 2017. The role of a pulse-based diet on infertility measures and metabolic syndrome risk: protocol of a randomized clinical trial in women with polycystic ovary syndrome. BMC Nutrition, 3:23 https://doi.org/10.1186/s40795-017-0142-6

McBreairty LE, Kazemia M, Chilibeck PD, Gordon JJ, Chizen DR, and Zello GA. 2020. Effect of a pulse-based diet and aerobic exercise on bone measures and body composition in women with polycystic ovary syndrome: A randomized controlled trial. Bone Reports, 12:100248 https://doi.org/10.1016/j.bonr.2020.100248