Friday Q&A: does everything cause cancer?; joint stiffness and menopause; eggs and cholesterol; & full body MRIs

TGIF 🔥

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Photo by Coffeefy Workafe on Unsplash

The following questions have been lightly edited for length and clarity.

QUESTION #1: DOES EVERYTHING CAUSE CANCER?

Dear Dr. McBride, It seems like every week we hear about a new product category that causes cancer or has some correlation to it. No black plastic, no non-stick, no aluminum antiperspirant, only all natural makeup and skincare, and on and on and on. How can we know which swaps are really worth making, and which are fueled by someone selling something?

—Shira

Hello Shira,

I hear you. Making sense of medical headlines can be exhausting, and sorting signal from noise is a challenge—even for doctors!

As someone who fields questions about fear-based headlines all the time, I can tell you that the words “correlation” or “association” do a lot of heavy lifting in most of these headlines. An observational study showing that people who use product X have higher rates of deadly disease Y tells us almost nothing about cause and effect. It doesn’t account for what else those people eat, do, or are exposed to, and the association may be coincidental, confounded, or vanishingly small in absolute terms.

The question worth asking isn’t Is there a link between X and Y? but How strong is the evidence that X causes Y, how large is the effect, and does the causal relationship hold up across multiple well-designed studies?

By that standard, tobacco, alcohol, processed meat, excessive UV exposure, and radon all have strong, replicated links to cancer. PFAS chemicals found in certain non-stick cookware, food packaging, and water supplies have a substantial and growing body of evidence behind them. But most of the weekly headlines about diet sodas, black plastic, aluminum in deodorant, your favorite moisturizer, etc do not clear that bar.

The upshot: it’s reasonable to choose products with fewer synthetic chemicals where it’s easy and affordable, but the swaps that matter most for cancer risk are almost never the ones being sold to you (e.g., not smoking, limiting alcohol, maintaining a healthy weight, getting screened appropriately). I hope that gives you a useful filter for the next headline.

PS. Weighing risks and benefits and sorting through medical information is covered in my forthcoming book, Beyond the Prescription—preorder here!

QUESTION #2: JOINT STIFFNESS AND MENOPAUSE

Hi Doc - when I turned 50 last year, I feel like a switch flipped. I am suddenly so stiff and achy, mostly when I get up after sitting or laying down. Overnight, I have terrible hip pain that I don’t have during the day. I’m a pretty active person, and I usually sleep on my side with a pillow between my knees. I should add I’m a cisgender woman who has been on menopause hormone therapy for a year. Can you tell me why this stiffness issue came on so suddenly and what I should do about it (stretching more seems obvious, right? Anything else?)

-Aimee

Hi Aimee,

Joint pain and menopause are indeed related. How so? Estrogen plays an important role in maintaining joint and tendon health. The decline in estrogen levels during menopause can cause tissues that were previously supple and well-lubricated to become stiffer and prone to irritation. The fact that you’re active, on HRT, and still experiencing this suggests either that your estrogen dose may need to be adjusted (ie. increased), and/or that you’re dealing with a structural issue at the same time.

Note that a condition called gluteal tendinopathy (aka irritation of the tendons that attach the glute muscles to the outer hip) is extremely common in postmenopausal women, often causes exactly the kind of pain you’re describing at night, and is frequently missed. It’s not arthritis and it’s not a structural problem with the joint itself; it’s a tendon issue that responds well to targeted physical therapy, specifically exercises that strengthen the glutes and improve hip stability. Sleeping on your side, even with a pillow between your knees, can actually aggravate it.

If that’s what you’re dealing with, stretching alone won’t fix it and can actually make things worse. Strengthening is the intervention with the best evidence. A physical therapist who works with women in midlife can assess your hip mechanics specifically and give you a targeted program.

Most importantly: be sure to mention hip pain to your HRT prescriber. Joint symptoms are one of the less-discussed effects of the hormonal transition, and it’s important you are getting enough estrogen to protect them.

PS. We cover a ton of topics around menopause in my conversation with Dr. Mary Claire Haver here!

QUESTION #3: EGGS & CHOLESTEROL

Dr. McBride, I have high cholesterol and have been advised to cut back on cholesterol in things I eat. Can you set me straight - are eggs good for you or not?

-Rachel

Hi Rachel,

Ah! This is a great question I get a lot. The relationship between eggs and cholesterol is a topic of ongoing debate. The short story: egg yolks are high in cholesterol, however, recent research suggests that dietary cholesterol doesn’t have as big an impact on blood cholesterol levels for most people as previously thought. Research has shown that eggs can raise both LDL (”bad”) cholesterol and HDL (”good”) cholesterol, but the effect on LDL is usually less significant than the effect on HDL. Importantly, the ratio of LDL to HDL (which is more important for heart health) may not worsen with moderate egg consumption.

In 2015, the Dietary Guidelines Advisory Committee released a report that removed the previous restriction on dietary cholesterol, suggesting that cholesterol from foods like eggs may have a minimal effect on blood cholesterol levels for most people. This was supported by evidence from several studies showing that saturated fats, not dietary cholesterol, are the main culprits in raising blood cholesterol.

Of course, there are always exceptions. Some people—often referred to as “hyper-responders”—may experience a significant increase in blood cholesterol when they consume cholesterol-rich foods like eggs.

Bonus points for egg-lovers: eating more eggs could reduce your risk of developing Alzheimer’s disease by nearly 50%. For women, eggs may mitigate changes in cognitive function due to old age. This is what a pair of new studies suggest. In one study, a higher egg intake was associated with less of a decline in verbal fluency among women only during a 4-year period (sorry, men!), with those consuming 5 or more eggs per week experiencing the greatest benefit. In the other study, eating 2 or more eggs per week was associated with a 47% reduction in Alzheimer’s disease risk over a nearly 7-year follow-up period.

Clearly more studies are needed to confirm the causal relationship between egg consumption and brain health but personally I can’t wait for breakfast. 🍳

QUESTION #4: FULL BODY MRI’S

Hi Dr McBride! My Dad was recently diagnosed with kidney cancer which we were told he likely has had for a decade or more due to the slow growing nature of the tumor. This has me considering paying out of pocket for a full body MRI every few years as a preventative measure. What are your thoughts on companies like Prenuvo and why are we not offering preventative MRIs more broadly when the technology is available and it could save lives and millions in treatment by catching something like this years earlier?

-Layla

Hello Layla,

I’m so sorry about your father’s diagnosis. That kind of news has a way of making us look at our own health very differently.

The appeal of full-body MRIs is intuitive: more information feels like more protection, right? But the evidence doesn’t bear that out, and this is worth understanding before spending several thousand dollars. Up to 40 percent of people who get these scans will have findings that require follow-up testing. Fewer than 1 percent will have findings that actually change their health outcomes. The problem isn’t the technology itself. MRIs are powerful and precise for specific diagnostic purposes. The problem is that a scan of the whole body finds everything: benign cysts, normal anatomical variations, incidental findings that look alarming but aren’t, and things that genuinely need attention but that the scan can’t reliably distinguish from the noise. The cascade of anxiety, follow-up testing, and sometimes unnecessary procedures that follows is real and not trivial.

Your father’s situation is also worth examining closely. His cancer was likely discovered for a specific reason—a symptom, a scan ordered for something else, or a clinical concern. That’s a different context from a healthy, asymptomatic person paying out of pocket for a full-body sweep.

The better investment is a physician who knows your family history, assesses your individual risk factors, and orders targeted screening based on what actually makes sense for you. That’s less satisfying than a whole-body image, but it’s what the evidence supports. I feel for you, though, because the tension between wanting certainty and what medicine can actually provide is one of the central challenges patients face today.

Wishing your father and your whole family all the best as you navigate this.

My book, Beyond the Prescription, comes out on August 11! I wrote it with you in mind.