High Estrogen: What It Means and What You Can Do

Do you have high estrogen levels? The term “estrogen dominance” gets tossed around a lot in the wellness and functional medicine worlds. It’s a common blanket explanation for many common – and even sometimes more serious – hormone-related issues. But what you’ve heard about estrogen dominance may not be entirely accurate, has some dubious historical underpinnings, and often oversimplifies what’s really going on. 

Let’s unpack what’s meant by estrogen dominance, what’s really going on, and why it’s important to identify and understand. Then we’ll look at how to address estrogen-related issues to reverse common gynecologic symptoms from breast tenderness to menstrual migraine, heavy periods to hot flashes, and more – as well as protecting yourself against the risks of chronic excess estrogen exposure. 

The ‘Queen Bee’ Hormone

Now before you go thinking estrogen is a dangerous hormone, let me explain. Estrogen is the luscious “Queen Bee” of hormones. I know that’s very romantic of me but truly, her influence is so important and so central to our hormonal experience that I think of her as creating a lot of the buzz throughout our lifetime. She’s unquestionably considered the leading lady of female hormones.

Estrogen is best known for helping shape our monthly hormonal cycle, but its role in our life doesn’t end there – not even close. Here are just some of estrogen’s other roles in our health and well-being as women: 

• Influences the development of the female body shape and physical female characteristics 
• Prepares the uterus for pregnancy
• Maintains healthy blood sugar levels
• Stimulates cells growth 
• Controls cholesterol levels 
• Helps produce neurotransmitters like serotonin 
• Assists in the production of our sleep hormone, melatonin 
• Plays a role in empathy and facial expression recognition during our menstrual cycle 
• Helps regulate our stress response 
• Maintains bone health
• Maintains skin tone and hair health 
• Supports vaginal and urinary tract health 
• Supports cognitive health, memory, and executive function 
• Supports cardiovascular health
• Keeps inflammation controlled

Knowing this, it won’t come as a big surprise that both estrogen levels that are too high and too low have been linked to common hormonally-related symptoms – and more serious gynecologic conditions, include uterine fibroids, endometriosis, and uterine and breast cancers. 

There’s More than Just One Estrogen

Estrogen is often thought of as a reproductive hormone; and while estrogen is largely produced in the ovaries, estrogen receptors are found all over the body – in the brain, bones, and even in the immune system. This hormone has major influences on our heart health and our metabolism; it even makes your face more symmetrical during ovulation, enhancing our ‘attractiveness’ at just the right time of month for us to get pregnant. Estrogen’s many roles also explain why women undergo such profound changes during menopause; as overall estrogen levels decline, all of the aspects of health listed above can shift as well, causing us to get to know our bodies once again.

When you get to know estrogen, you understand why this powerful hormone is so much more than just a reproductive hormone. In fact, it’s not just one hormone at all – it’s three:  estrone, which is E1, estradiol, which is E2, and estriol, which is E3 – that are produced in the ovaries, fat cells, and to lesser amounts, in the skin. 

1. Estrone: Think of E1 as the weakest form of estrogen. Some E1 is produced by the ovaries but most of it is produced by the fat cells through something called peripheral conversion (meaning the estrogen production doesn’t happen in a central location like the ovaries). This type of estrogen explains why overweight women tend to experience fewer symptoms during menopause and why certain body compositions can lead to higher levels of circulating estrogen. 
2. Estradiol: E2 is the most dominant and strongest form of estrogen. I like to think of it as the diva of the whole hormone health show throughout most of our maiden and mother life cycle, from the onset of menarche to our reproductive years all the way through to perimenopause. Made in your ovarian follicles, estradiol drives the activity of the first half of your menstrual cycle, making another cameo appearance after ovulation. 
3. Estriol: E3 makes a special appearance and takes over the show in pregnancy when it becomes the dominant form of estrogen. Towards the end of pregnancy it promotes the growth of milk ducts within the breasts and enhances the effect of prolactin, the hormone responsible for lactation. When I was first learning these, the way I remembered them is ‘estriol is 3', so that's mother-baby-placenta.

Shifts in these three types of estrogen, but especially E2, over our life cycles determine when we enter puberty, our fertility, and when and how smoothly we experience the transition to menopause. Predictable estrogen ebbs and flows are responsible for common symptoms that remind us that we are living in a female body, like increased vaginal lubrication and sex drive mid-cycle and breast tenderness, mild bloating, and mood shifts pre-period.

While estrogen levels fluctuate normally throughout the menstrual cycle and throughout your lifetime, the world we live in is a set-up – as you’ll soon learn – for our estrogen levels to get higher than optimal. When this occurs, your healthy hormonal hum may turn into a whole host of annoying symptoms from mood swings, breast tenderness, and heavy periods, to full-on hormonal chaos and even estrogen-driven gynecologic conditions. 

High Estrogen: Symptoms and Risks

Hormone levels fluctuate normally throughout the menstrual cycle and mild signs of this – like tender breasts before your period and changes in mood and energy levels – are notably normal. But if you have higher than normal levels of estrogen, these symptoms can turn into something more; in fact, they can get so intense that they interfere with your ability to function at certain times in your cycle or throughout the whole month. 

If your estrogen levels are too high, symptoms/conditions you might experience include: 

• Cyclic breast tenderness, breast cysts, breast fullness
• Short menstrual cycles (< 21 days)
• Heavy periods
• Uterine fibroids
• Endometriosis
• Water retention
• Mood swings
• Depression, anxiety 
• Hormonal migraines and headaches (as estrogen drops)
• Irregular vaginal bleeding
• Weight gain or weight loss resistance 
• Cervical dysplasia 

These side effects of estrogen might seem puzzlingly broad and far-reaching; but as you learned earlier, estrogen receptors are located all over the body. It makes sense that when estrogen is too high, we feel it just about everywhere. 

Unfortunately, if estrogen levels remain high for too long without being addressed, it can put you at risk for other long-term issues, including: 

• Hypothyroidism: There’s a link between estrogen and thyroid health; If your estrogen levels are too high, it leads to a decrease in the amount of thyroid hormone circulating in your body, which can give your symptoms of a slow thyroid even if your thyroid is “technically” healthy. 
• Worsened endometriosis: Elevated estrogen can trigger the growth of endometrial lesions that can contribute to and worsen your endometriosis. 
• Endometrial hyperplasia: High estrogen can lead to an overgrowth of the uterine lining called endometrial hyperplasia, which can lead to abnormal uterine bleeding. 
• Breast, ovarian, and endometrial cancers: Years of research has shown that unhealthy changes in estrogen can be linked to the progression of certain cancers, including breast cancer and ovarian and endometrial cancers. 
• Heart disease, stroke, and clotting problems: Changes in estrogen levels have been linked to different forms of cardiovascular disease. 

As you can see, there are both immediate reasons (hello, symptoms of high estrogen) and long-term reasons to get estrogen levels to a healthy place. But here’s the key – instead of just using progesterone therapy to increase progesterone levels as many experts suggest, the key to reducing elevated estrogen is addressing the factors causing high estrogen in the first place. 

Is “Estrogen Dominance” a Real Thing? 

As I mentioned earlier, “estrogen dominance” is a common term that we hear all the time in the natural medicine and alternative health world as a blanket term to describe all types of hormone-related issues. But remember when I said it was of dubious origin? Originally, estrogen dominance was a theory about a metabolic state where the level of estrogen in the body outweighs the levels of progesterone. First proposed by John R. Lee and Virginia Hopkins in their 1996 book, “What Your Doctor May Not Tell You About Menopause: The Breakthrough Book on Natural Progesterone,” it was said to be caused by a decrease in progesterone without a subsequent decrease in estrogen. This book criticized estrogen replacement therapy and instead proposed the use of “natural progesterone” as a better way to alleviate symptoms for menopausal women. Unfortunately, Lee's theories have been criticized for being inadequately supported through science, being primarily based on anecdotal evidence, and having no rigorous research to support them. Yikes. 

This is why in my mind, “estrogen dominance” doesn’t mean a whole heck of a lot, and is really part misnomer, part marketing scheme. The reality is that there’s no perfect equation for estrogen and progesterone and “estrogen dominance.” Hormones are also fluctuating all the time and change throughout the course of the month but also throughout the years and decades of our lives as women. We naturally have more estrogen in the first half of our menstrual cycles, for example, but that does not mean we have a hormone imbalance called estrogen dominance. 

That said, our modern lives do create the perfect storm for estrogen problems – particularly chronically and abnormally elevated estrogen levels. Through a combination of lifestyle factors and underlying conditions, estrogen levels can get too high. And if you have too much estrogen in your body, there’s a good chance you’re not feeling great. So while estrogen dominance is not a term I use, nor truly a legitimate condition, it is also true that estrogen-related health complications are at an all-time high, including precocious puberty, hormone-related cancers, endometriosis, infertility, and fibroids, among other conditions. 

What Causes High Estrogen?

The causes of high estrogen don’t form a simple cut and dried list, nor it is an X + Y =  Z equation. Many of the causes of high estrogen overlap, and it’s something that isn’t typically recognized in conventional medicine. Each person has their own hormone ecosystem – the constellation of factors affecting their hormones, and it’s important to look at the overall big picture instead of trying to zoom in on one single cause – though making sure there's no medical problem going on is essential. Here are the common root causes of high estrogen that conventional medicine rarely recognizes or addresses: 

Estrogen-mimicking hormones in your food or environment

Probably the biggest contributing factor to high estrogen levels is exposure to endocrine-disrupting chemicals (EDCs). These chemicals are known for interfering with the body’s hormone system because they can actually mimic the hormones we produce naturally. This means they can get easily absorbed by our body to the point where they are actually found at much higher concentrations in human tissue than our own hormones, which means they can block, overstimulate, and disrupt your body’s natural hormonal processes, including the way your body metabolizes and excretes hormones. There’s even a group of these chemicals called “xenoestrogens” that specifically mimic estrogen. 

Slow gut elimination of estrogens/gut microbiome dysbiosis 

The status of our gut health influences estrogen in more ways than you might imagine. One of the principal regulators of circulating estrogens is the gut microbiome. Here’s how this works: Estrogen is produced in your ovaries and then it circulates in your bloodstream and throughout your body. After it’s done its job, it makes its way to the liver where it’s broken down and neatly packaged so it can be eliminated by the body through – your guessed it – the GI tract. When estrogen is in your GI tract, it interacts with a special subset of your microbiome called your estrobolome (which you can learn more about here) – that has the important job of regulating estrogen levels for excretion. When your gut bacteria become imbalanced, it impairs the estrobolome and you start to reabsorb estrogen. Unfortunately, the type of estrogen you reabsorb is also a more problematic form, which means it adds a lot of stress to your body’s overall estrogen load.

A low-fiber diet

There's a ton of debate in the health world over the importance of carbohydrates, fats, and protein and how much of each we should be eating. There’s so much heated debate, in fact, that it can sometimes cause us to forget that there’s another major nutrient of the utmost importance to our health and hormones – fiber. Fiber is critical for regular bowel movements, which helps remove estrogen from the body after it has been metabolized by the liver. In fact, research has even linked a high fiber diet to a decreased risk of estrogen-positive breast cancer. Unfortunately, most Americans are only getting about 15 grams of fiber a day when our bodies were designed to have nearly 100! This can lead to constipation, which allows estrogen to re-enter circulation and wreak havoc. 

Overwhelmed or undersupport hormone detoxification  

I know the word “detoxification” can conjure images of juice fasts and coffee enemas, but that’s not the true essence of detoxification, nor is it the type of detoxification we’re talking about here. Instead, I’m talking about “metabolic detoxification”, which is the process of eliminating hormones and toxins from your body. This is an inherent physiological process that works on a daily basis without our help, but it’s also a process that can get overloaded by the many estrogen-mimicking chemicals we face on a daily basis. This can be compounded by genetics changes that can make us slower at detoxifying estrogen (like the MTHFR mutation) and increase our vulnerability to elevated estrogen and a diet low in phytochemicals and plant nutrients that help break down and eliminate estrogen.

Obesity  

Okay, sadly, this is probably the only one conventional medicine recognizes – and in a horribly fat shaming way. So lets dispel fat shaming and get to the heart of the matter. I’m thrilled to see that we are entering a new era of appreciating bodies of all shapes and sizes and breaking down stigmas that surround women and body size. I’m also glad to see the myth that being bigger is always unhealthy. That said, obesity or even carrying significantly extra weight increases your likelihood of producing more estrogen because we, in part, create estrogen in our adipose tissue. More adipose tissue means more estrogen production. Further, we store environmental toxins that act as endocrine disruptors in our adipose tissue.

Research suggests that if you are significantly ‘overweight' or obese, losing some weight can help reduce your estrogen levels. And considering the knowledge we have that fat cells can produce estrogen, it makes sense that reducing body fat percentage can help lower estrogen levels in the body. In one study on overweight and obese women, losing an average of 7.7 kiligrams (about 16 pounds) led to 13.4% decrease in average concentrations of free estradiol.   

But instead of focusing on just weight, we can focus in on reducing endocrine disruptor exposure and supporting your microbiome, which can not only help with reducing your overall estrogen body burden, but xenoestrogens and dysbiosis are also obesogenic factors, so the risks – and benefits for hormone health, gut health, and weight are intertwined. 

Estrogen-containing pharmaceuticals (the Pill, HRT)

If we’re trying to reduce our exposure to estrogens and estrogen-like chemicals, the combined birth control pill – which contains synthetic forms of estrogen and/or progesterone – has to be part of the conversation. The pill interferes with our body’s natural hormone production and hormonal communication channels and acts as a daily dose of excess estrogen that the body has to contend with. There are some situations where the pill is still the best treatment approach, but for many it’s worth a second look if you have a problem with high estrogen. Similarly, hormone replacement therapy (HRT) used for perimenopausal and menopausal symptoms, is a common culprit in high estrogen levels, and I’ve prevented more than one hysterectomy in a patient who was having heavy vaginal bleeding secondary to high estrogen levels from HRT prescribed by a well-meaning medical doctor, in too high a dose, or over too long a time. 

The factors above are some of the biggest contributors to elevated estrogen, but they’re not the only ones. Other factors like a sedentary lifestyle, underlying conditions like endometriosis or PCOS, lack of sleep, processed red meat consumption, stress, and deficiencies in specific nutrients can also contribute to estrogen overload and inhibit the body’s ability to metabolize estrogen and excrete it efficiently. That said, all these factors are connected and tend to overlap to cause the bigger picture of high estrogen. For example, a sedentary lifestyle continues to obesity; a lack of fiber typically means more meat consumption; and nutrient deficiencies can lead to imparied detoxification and so on.  

Restoring Healthy Estrogen Levels

Now onto the part you’ve been waiting for – what you can do. These important steps can help to restore healthy hormone levels and help you get out from under the environmental risk factors we all face that are contributing to so many people have high levels of estrogen. 

Reduce Your Xenoestrogen Burden

An important first step toward improving estrogen levels is to reduce exposure to endocrine-disrupting chemicals in your environment  – called xenoestrogens. These are found in cosmetics, cleaning products, food storage containers, and likely the foods you’re putting in your cart at the grocery store, unless they’re organic, as a result of herbicide and pesticide contamination. 

To minimize your exposure to environmental disruptors, follow these tips:

• Choose glass containers for heating and storing food.
• If you’re buying something canned or in glass, make sure it’s marked “BPA-free.” 
• Eat organic and “hormone-free” foods, especially animal-based products like meat. 
• Wash hands well after handling paper receipts (these are coated with BPA).
• Check ingredients in skin and hair care products and buy ones labeled paraben-free” instead.

Also check out my article and podcast on endocrine disruptors here. 

Eat for Healthy Estrogen Levels 

Another important step is to focus on a diet rich in fiber and plant-based nutrients, which prevent you from having eleveated estrogen levels, and can help you to eliminate excess estrogen:

Eat More of These

Greens (especially Brassicaceae vegetables) 

Leafy greens, particularly those in the Brassicaceae family – that includes broccoli, cabbages, kale, Brussels sprouts, cauliflower, and collards – are especially important allies for hormone health. Leafy greens are rich in antioxidants and plant chemicals needed for detoxification of hormones and environmental chemicals and contain the best type of fiber to feed your estrobolome to eliminate estrogen properly. Many studies have shown that a diet high in plant foods like leafy greens can increase estrogen excretion and decrease concentrations of bioavailable estrogen in the body. 

Fiber and Flaxseeds 

As we already know, fiber is critical for the excretion of estrogen metabolites. Flaxseeds are not only a great source of fiber, they’re also a great source of dietary lignans, which are phytochemicals that are precursors to phytoestrogen. Lignans have been shown to increase levels of sex-hormone-binding globulin (SHBG), which decreases the amount of available active estrogen, as estrogen bound to SHBG is rendered inactive. Experimental studies suggest that lignans may exert breast cancer preventive effects through hormonal mechanisms; one study on 48 women who consumed flaxseeds every day for 12 weeks noted a decline in estrone and estradiol levels and these reductions were more pronounced in overweight or obese participants. This means that flaxseeds can help you improve bowel health and regularity thanks to fiber, but they also help your body eliminate harmful estrogens that you may have picked up from the environment. (You can read more about flax seeds and hormones here.)

Reduce or Eliminate 

Dairy

Normally I’m not fanatical about having all my patients go dairy-free. In fact, when you look at some of the healthiest communities around the world, many of them eat some form of dairy in their daily diet. But if you’re overloaded with estrogens, dairy is something to reduce or eliminate at least for the time being. Why? Because it’s one of the most significant sources of human exposure to estrogen. Unlike the pasture-fed animals of the past, modern dairy cows are usually kept pregnant or lactating year-round to raise their milk yield, and they continue to lactate during the latter half of each subsequent pregnancy, when the concentration of estrogens in milk is the highest. Plus, endocrine-disrupting environmental chemicals are also known to bioaccumulate in animal fat, making dairy products a kind of repository for hormone-disrupting toxins.  

Alcohol

I know you might not want to hear this but if you’re trying to reduce estrogen and get your hormones back in balance, alcohol – including beer, wine, liquor, and yes, also that alcoholic kombucha or zero-sugar seltzers – aren’t doing you any favors. After drinking alcohol, your estradiol levels go up and lead to persistently high levels in the luteal phase, which can lead to uncomfortable symptoms like breast tenderness and heavy bleeding. Alcohol is a known hormone disruptor and can contribute to estrogen imbalances. 

Caffeine

There’s no one-size-fits-all approach to caffeine, and coffee may even promote cognitive health in moderation, but if you’re trying to balance estrogen, it’s something to consider hitting pause on. A study published in the American Journal of Clinical Nutrition revealed that the caffeine from just a few cups of coffee can increase our risk of hormonal conditions, though the study was inconclusive and showed variations based on ethnic background. If you’re resistant to decreasing your caffeine consumption, you can at least switch to decaf or green tea. The antioxidants and phytochemicals in green tea boost liver detoxification which may support hormone health.  

Red Meat

There’s an established link between meat consumption and breast cancer and also red meat and increased estrogen levels. And while the estrogen levels in meat are much lower than those in contraceptive pills or other sources,  it still contributes to your overall burden of estrogen, allowing it to accumulate. 

What about Phytoestrogens?

If you’re health-savvy, you might have read the words “estrogen-mimicking” above and immediately wondered about the estrogen-like compounds found in plants like soy. These are called “phytoestrogens” and they do have a structure very similar to estradiol. But here’s the thing: Phytoestrogens contain a weaker form of estrogen that can bind to estrogen receptors and help prevent them from getting overloaded with xenoestrogens, which are much more damaging. In fact, despite years of soy having a major PR crisis, the data clearly shows that moderate soy intake in women does not cause harm to hormonal health. To avoid excess phytoestrogen consumption, limit soy consumption to twice weekly and make sure all soy products are organic and non-GMO.   

Support Gut Health

Nourish your Estrobolome

Nourishing your estrobolome is a key ingredient for healthy estrogen levels. This means eating plenty of vegetables and greens, getting beneficial fiber, and even more importantly, eating plenty of fermented foods. Fermented foods are not only tasty, they’ve been an integral part of just about every traditional diet around the world. Naturally fermented foods like coconut yogurt, sauerkraut, pickled veggies, kimchi, and chickpea and rice miso are important for a healthy estrobolome and proper detoxification and elimination of estrogen. You can also supplement with a probiotic containing at least 10 billion billion colony-forming units (CFUs) of a variety of Lactobacillus and Bifidobacterium species to help restore the normal balance of flora in your gut. 

Poop Regularly

When you’re not pooping regularly, estrogen gets reabsorbed into the bloodstream and increases your circulating levels. To make matters more complicated, estrogen also delays gastric emptying, so high estrogen and constipation can become a vicious cycle. To make sure you’re having regular bowel movements, increase your fiber intake and move your body daily since exercise can help keep things moving. 

Love your Liver

Your liver is also a part of your digestive system. More than 50% of all estrogen metabolism and conjugation occurs in the liver, so it’s critical to support liver detoxification pathways if you want to balance estrogen levels. The good news is that focusing on steps one through three above will help support your liver’s ability to complete metabolic detoxification quickly and efficiently, without getting overloaded with endocrine disruptors or estrogen that’s been reabsorbed. You can learn more about metabolic detoxification here. 

Consider estrogen-clearing herbs and nutrients 

You can reduce the estrogen burden on your body significantly by following the steps above but the truth is that unless you’re willing to live in a bubble, you’ll still be exposed to some endocrine-disruptors. And still, that bubble might be filled with BPA! This truth is a good reason to incorporate estrogen-clearing nutrients into your routine, even if you’re reducing your exposure as much as possible. A few that I can recommend are: 

Broccoli Extracts (DIM and I3C)

This group of nutrients is what makes the Brassicaceae family of vegetables so great for healthy estrogen levels. If you’re not able to get enough of these foods through your regular meals, or you just want to further support estrogen metabolism, you can supplement with DIM or I3C, which are two closely related compounds. 

• DIM: DIM stands for diindolylmethane and is also known as the “estrogen blocker” because of its ability to convert bad estrogens into less harmful forms of the hormone. It also blocks an enzyme called aromatase, which converts testosterone to estrogen in the body. DIM is actually what the body creates when you eat I3C through your food. 
• I3C: Indole-3-Carbinol is what’s actually found in cruciferous vegetables, so it’s essentially a precursor to DIM. I3C aids in healthy estrogen metabolism and detoxification. For example, urine samples collected before and after oral ingestion of 13C showed a significant decrease in estrogen in as little as a few weeks. 

St. John’s Wort

You may know this herb because of its mood-boosting properties, but St. John’s Wort is worth considering for reducing overall estrogen burden as well. It increases liver detoxification of estrogen very effectively. In fact, it’s a well-known fact that you should exercise caution if you take St. John’s Wort with the pill because it can increase your body’s metabolism of estrogen, lower blood estrogen levels, and interfere with its effectiveness.

Bitters

Bitters are a group of plants that are defined by exactly what their name implies – their bitterness. Bitter herbs like dandelion greens, endive, radicchio, and arugula are powerful digestive stimulators and help with detoxification. The simplest way to introduce bitters into your daily life is to eat them, all of which can be incredibly delicious when you know how to prepare them. The trick is to use some “acid” (i.e., citrus or vinegar) and a pinch of salt to make them more palatable. ( I wrote a full article on bitters here.) 

Should You Get Your Hormones Tested? 

When my patients ask about estrogen dominance, I’m sure they are hoping that this is the answer to all their problems, and that there’s a simple test that will reveal exactly what’s going on with their estrogen levels. 

It can be helpful to get your hormone levels tested, though it’s not always necessary and the tests may not provide a conclusive link between your hormone levels and your symptoms. They will mostly often just indicate whether there’s a significant hormone shift going on (i.e, perimenopause) or whether there’s a more overt hormone imbalance. The panel I run in my practice includes: 

• Estradiol
• FSH and LH (best tested on day 3 of your menstrual cycle)
• Progesterone (best tested on day 19–22 of your menstrual cycle)
• Sex-hormone-binding globulin
• Free testosterone
• Prolactin

Running these tests can help identify whether you do have a specific hormone imbalance, and your health care provider can help you understand exactly what the results mean. 

Unfortunately, this still doesn’t tell you why your hormone levels are off. As we already know, there are different types of estrogen that all come from many different sources. In addition, you may have high estrogen levels caused by excess estrogen exposure, but you might also have too much estrogen because of an issue metabolizing or eliminating it. 

How to Know if Your Estrogen Levels Have Improved

Okay – now onto the really fun part. If you follow the advice above, how do you know if your estrogen levels are improving? You’ll notice relief in symptoms related to high estrogen. 

Imbalances in estrogen can affect virtually every aspect of your life. I hope that I’ve cleared up some misconceptions about estrogen dominance, and given you a path toward healthier estrogen levels. If you want a comprehensive plan — not just for healthy estrogen levels — but healthy hormones and a healthy you – whatever your life stage or age – you’ll definitely want to keep my latest book, Hormone Intelligence, on your nightstand or favorite bookshelf!