418: Are Peptides Safe? Truth About The Side Effects of Peptides And The Risk Of Cancer (Yes, This Is A Legit Concern)

Last Updated on June 11, 2026

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Are peptides safe? There’s a reason so many people are talking about peptides right now. From men who are hoping to heal old injuries to push workouts harder in the gym, to women navigating perimenopause, stubborn weight gain, chronic inflammation, poor recovery, fatigue, or brain fog, peptides sound incredibly appealing.

And while peptides can be really helpful, using them safely can be tricky. Most conversations online completely skip over the safety concerns, the importance of testing, and the fact that these compounds may not be appropriate for everyone. Instead, people are often handed peptide recommendations from social media influencers, online forums, or even their gym friends without anyone looking at the bigger picture.

That’s a problem. Because your health history and labs matter. As does your level of inflammation. And according to today’s guest, Dr. Elena Zinkov, there are situations in which certain peptides could potentially do more harm than good if used incorrectly.

Dr. Elena Zinkov is redefining how women navigate their health journey with a science-backed, healthspan-forward approach. As a naturopathic medical doctor & entrepreneur, Dr. Elena has dedicated her career to empowering women to thrive at every stage of life. Her clinic is at the forefront of progressive therapies, offering personalized solutions for hormone optimization, longevity and regenerative medicine.

Her passion for transforming healthcare stems from her own experiences with the limitations of conventional medicine. Dr. Elena focuses on democratizing women’s health, ensuring that women worldwide have access to solutions that optimize longevity, vitality, and well-being.

If you’ve been considering peptides or growth hormone therapies (ie. HGH peptides), don’t miss this conversation. Let’s get into it.

In This Episode:

• Why peptides are becoming so popular
• The surprising connection between growth hormone decline and skin, hair, sleep, and muscle recovery
• The hidden risks of using peptides without proper lab testing
• Why IGF-1 levels matter before starting growth hormone HGH peptides
• How certain peptides could potentially fuel underlying cancer growth
• Differences between injectable, oral, sublingual, and topical peptides
• Why peptide “stacks” like GLOW Peptides and Wolverine Peptides may not be safe

Quotes

“There are some people who have never experienced a reduction in food noise until they've been on a GLP-1.”

“Peptides are a tool, but they need to be used individually, they need to be part of personalized medicine.”

Links

Find Dr. Zinkov online | Instagram

Healthy Skin Show ep. 384: Peptides For Skin Problems: Do GLP-1 + BPC-157 Peptides Really Stop Inflammation? w/ Nathalie Niddam

Healthy Skin Show ep. 392: Improving Hidradenitis Suppurativa HS Treatment With GLP1 Weight Loss Meds (NEW RESEARCH) w/ Dr. Steven Daveluy

 

418: Are Peptides Safe? Truth About The Side Effects of Peptides And The Risk Of Cancer (Yes, This Is A Legit Concern) {FULL TRANSCRIPT}

Jennifer Fugo (04:38)

Dr. Elena, I'm so excited to have you here. We're going to talk about peptides and I think just based off of our little conversation beforehand that this is going to be something that maybe people haven't quite considered because there's some pros and we hear a lot of pros about why peptides are so good and why they have so many uses that could be helpful for health. But I also think it's worthwhile talking about where we need to be careful. So thank you so for being here so that we can dive into this topic.

Dr. Elena (05:12)

Thank you so much for having me. I'm excited.

Jennifer Fugo (05:14) 

So I would love to know, just quickly, how did you get into doing peptides and utilizing them in your practice?

Dr. Elena (05:23) 

So peptides are a tool. And just like we use hormone replacement therapy and some of the other therapies that we have access to, I got to a point in my practice where I was just hitting a wall with my patients. And what I mean by that is let's use GLP-1s as an example. I have a lot of patients who come to me and we work on their hormones, we work on the foundations of health. They have a personal trainer, they're counting their macros, but they have the experience of a typical woman who's going through perimenopause or menopause where the metabolism is not the same. It's hard to gain lean muscle mass, it's hard to lose fat. And this is where I started to use peptides a while back before they blew up and are everywhere now.

Dr. Elena (06:12) 

But this is where I would use them very selectively to improve metabolism, to reduce inflammation. Because we know GLP-1s and the different varieties that we have of GLP-1, they're not just for weight loss, but we have cardiovascular benefits, cancer protective properties, as well as the improved metabolism that we see. One of the things that is frequently ignored in women's health is actually growth hormone. So frequently when a woman is going through perimenopause and the other hormonal transitions, we look at estrogen, progesterone. We're lucky if the testosterone actually gets addressed. But rarely does anyone actually talk about growth hormone. And when I started looking into my patients' growth hormone levels, because let's say they were not recovering well after a workout. They're on testosterone, they're eating well, their other hormones are balanced.

Dr. Elena (07:15) 

When I started looking at their growth hormone levels — and it's hard to measure growth hormone directly, but we can use markers like IGF-1 as an example to understand what the potential growth hormone levels are — I realized that in a lot of my patients, both men and women, that IGF-1 was low. And that potentially it's not just the other hormones that are struggling, but growth hormone is one of the first hormones that actually starts to decline, potentially even before the sex hormones start to decline. So I would use gentle growth hormone releasing hormones and peptides to stimulate our own ability to produce growth hormone. And then we see improvements in skin and sleep, in hair, in recovery, in lean muscle mass. It is like turning on a switch and everything becomes easier. It's like the missing piece.

Dr. Elena (08:07) 

So for me, peptides are another tool that I use when the outcomes are plateauing and I'm not seeing the results that I want to see in my patients.

Jennifer Fugo (08:19) 

So I think this is a good question to ask because I do think there is the question of safety, which I want to get to in a little bit. But so that people understand where we are right now, are peptides actually legal? And I've heard things about the FDA kind of reclassifying them, that there's a whole reclassification process. So are peptides legal for us to buy and use?

Dr. Elena (08:47) 

Right, and that's a really important question. At one point there were a lot more peptides available for pharmacies to compound and then for healthcare providers to prescribe. And then the FDA reclassified peptides and said we need to understand the safety of these compounds and pulled a lot of them off the shelf, including the ones that we used for a long time, like BPC-157 and Semax and Selank and so forth. There's quite a few of them that got pulled and now the FDA is reclassifying those peptides again based on their safety, meaning that a lot of them that I just mentioned — at one point their safety was questionable — now they're coming back and some pharmacies have continued to compound them, and that becomes more of an issue.

Dr. Elena (09:44) 

Sometimes, you know, you use what you have until the FDA tells you not to compound anymore. But are peptides legal? There are a lot of peptides that are legal. Are they FDA approved? No. But it comes down to the similar issue that we have with supplements. There are many supplements that we use that are legal, that we have access to, and even oral peptides — they're legal. You can buy them online through reputable sources. But are they FDA approved? No, they're not.

Jennifer Fugo (10:21) 

So interestingly, I'm curious about the combination of HRT with peptides. It sounds like — am I correct in what you had said before — that you actually do utilize peptides and HRT together? And is that something that is the same for men and women?

Dr. Elena (10:40) 

Absolutely. So for example, I mentioned growth hormone releasing hormone and peptides, and the classical ones are Sermorelin and Ipamorelin. As an example, when I put someone on HRT — let's say estrogen, progesterone, testosterone, just sort of the classic trio of HRT — for men, it may be just testosterone, as an example. Most men don't need any more estrogen or progesterone, except in a few situations. But if I'm seeing that the patient is feeling great overall but they're still having issues with sleep or recovery post-workout, or trouble losing weight, I will use — if warranted — growth hormone releasing hormones and peptides, Ipamorelin and Sermorelin, to help them achieve body composition goals, to help reset their circadian rhythm. But I don't do it blindly. I test their IGF-1 levels, I test their inflammatory markers, I test their metabolic markers.

Dr. Elena (11:44) 

This is not something that I just throw into the mix purely on subjective information. I need the objective data to validate and verify that this is the smart decision, because you and I talked a little bit offline about this — peptides have become more popular and a lot of people are being started on them without fully understanding their biochemistry and physiology. And everything is in balance when it comes to hormones and peptides. You know, in a lot of cancer cases, IGF-1 can rise. And some healthcare providers actually argue that IGF-1 rises as a protective mechanism — not necessarily that it is something that happens when you have cancer, but potentially as part of the body's effort to protect the cells from cancer.

Dr. Elena (12:45) 

Now the flip side to that is, okay, if IGF-1 rises with cancer and if we put someone on growth hormone and it increases that IGF-1 further, are we adding more fuel to the fire? It's scary to me to actually see a lot of online peptide companies and hormone telemedicine companies prescribing growth hormone peptides without even testing IGF-1. That's the scary thought to me — are we doing more harm in some situations, unknowingly and unintentionally? But the other way that I use peptides with HRT is of course because of weight loss. And a lot of women struggle with weight loss for a number of reasons, and men too, with androgen decline through different stages of life. It's not just macros and it's not just exercise. And I know a lot of people want to debate this because of the calories in, calories out argument.

Dr. Elena (13:48) 

But it becomes a vicious cycle where as our hormones decline and the lean muscle mass declines, we want to be able to build muscle. But if we have metabolic resistance that we cannot correct with just nutritional changes or with exercise — unless we become a personal trainer and a nutritionist and make it our full-time job to eat the protein and exercise two hours per day — it can be really hard for people with the busy lives that they live to be absolutely perfect and lose weight and build muscle. And this is where I think GLP-1s can be really effective. One thing that I think a lot of people who are against GLP-1s don't understand is that everything declines, including our own GLP-1 function and GLP-1 receptor function.

Dr. Elena (14:40) 

So not just like our hormone receptors decline in their function over time, GLP-1 receptors can also decline and their functionality can diminish. And so people will say, well, you can just naturally stimulate them — but it depends on the amount that you have, because that can also decline. And so I love using GLP-1s in different ways, from using amounts that are well below the conventional milligram doses to provide that anti-inflammatory effect, cardiovascular protective effect, brain protective benefits, along with improving metabolic outcomes.

Jennifer Fugo (15:17) 

I wanted to ask because I do think this is a valid question — there's topical in terms of delivery systems, there's oral so like a supplement or a pill, and there's injectables. What are your thoughts on the three? Are there some general rules of thumb if someone is starting to dive into this area or consider this? I assume there are some peptides that you just cannot take orally, and you probably shouldn't go and buy a vial of peptides and just smear it on your skin. I'm just kind of wondering — is there a rule of thumb here that we can go by that'll help us understand better the reason why some may be topical versus oral versus injectable?

Dr. Elena (16:09) 

Absolutely. It really depends on the end goal and what we're trying to move the needle on. So I'll start with the easiest, and the easiest is: you do not want to buy a peptide mix. The famous ones that have been circulating for some time are the GLOW peptide mix and the Wolverine mix. Now these two mixes combine TB-500, copper peptides — which gives them this purple look — as well as BPC-157 and KPV. The problem with that is that individually those might be fine, but when you mix them together and you mix them with a reconstitution solution, usually bacteriostatic water, you don't know what you're injecting anymore. Those peptides do not belong together in the same vial.

Dr. Elena (17:12) 

So to answer your question, don't buy those peptide mixes because you then don't know one, what you're injecting, but two, what reaction you're going to get. And these peptides — like the GLOW peptide and the Wolverine peptide stack — they've been marketed as a silver bullet. Like this is the thing that's going to fix your collagen issues, get rid of your wrinkles, contribute to hair growth, you're going to lose weight, you're basically going to be like a 25-year-old athlete. And unfortunately, as you know, there are so many other things that go into improving hair and skin and longevity medicine. But a lot of people have been told that this is the miracle peptide mix. And unfortunately, from a safety perspective, I don't recommend using them. And I'm not the only one that says this.

Dr. Elena (18:12) 

A lot of my colleagues in the field and pharmacists who spend a lot of time researching these topics and compounding peptides don't recommend this combination either. But let's talk about what we can use. Topical peptides — can you use copper peptides topically to improve, let's say, hair growth or to improve collagen production? Topically, absolutely. And I think even using something like a topical estriol cream, which is a weaker estrogen, paired with copper peptides is a fantastic option for people who are looking to improve collagen production, improve skin texture, firmness, whatever it is. Topically, that's totally fine to do. It's not going to cross the blood-brain barrier, as injectable peptides can. This is why safety is so important.

Jennifer Fugo (19:04) 

Recently, maybe two weeks ago, as I was preparing for our conversation, I was scrolling through Facebook and happened to notice a video of someone being interviewed about a potential problem with peptides that I had never heard. Any person that I follow who's praising peptides left and right all over social media — I have heard no one even broach this concern that they could potentially fuel cancer growth. So the question is then, are these different peptides, some of which you've even described as research grade, possibly dangerous?

Dr. Elena (19:45) 

Yes. So one thing I want to mention is cancer is complicated. There's never one thing that can cause cancer — it's usually a perfect storm. And we know that in terms of cancer, metabolic health matters. We know that women who are obese, for example, have a 50 to 60% more likelihood of developing breast cancer, as an example. We know that hormones don't cause cancer, and that's been debunked many times. But having said that, we need to still screen people for cancer and we need to make sure that whatever we're prescribing — whether it's hormone replacement, whether it's a GLP-1 or any other peptide — we need to understand the environment into which we're introducing these peptides. So let's take something like IGF-1 and measuring IGF-1 before starting growth hormone peptide therapy or growth hormone releasing hormone therapy.

Dr. Elena (20:46) 

If someone, let's say, is in early stages of cancer and does not know it, and we don't test their IGF-1 or their other panels including their metabolic panel, or do any of the other screening tests, and we start them on a growth hormone releasing hormone, we're potentially doing something very dangerous where, yes, we could be fueling cancer. Now, growth hormone peptides and hormones do not cause cancer. But can they fuel cancer growth? Absolutely. And so this is where even doing basic testing matters. If I am looking at a patient who is five years post breast cancer — technically we know it's safe to incorporate certain forms of hormone replacement at that point — but I'm looking at their IGF-1. Even though they've been cleared from cancer, they're up to date on their screening, their labs don't show any signs of cancer.

Dr. Elena (21:52) 

Their IGF-1 is still at 300, as an example. Am I going to add a growth hormone peptide to that because they want to build more muscle and lose weight? Absolutely not. But if she goes and signs up for a telehealth company appointment that's prescribing peptides and hormones, and they don't check her IGF-1, and they want her to build muscle and lose weight and they know that Sermorelin as a growth hormone releasing hormone is going to do the trick — now they just did that woman a disservice by putting her on that peptide. And there are so many ways for us to accomplish muscle growth and weight loss and everything else in much safer ways. And like I said, peptides are a tool, but they need to be used individually, they need to be part of personalized medicine.

Dr. Elena (22:40) 

It's not for every person and it's not for everyone. I work with my patients and I use hormones and I use peptides and I use a variety of tools, but I've never created the same treatment plan twice. Not every single one of my patients is on a growth hormone peptide. Not everyone needs it. And I make that clinical judgment of who I think could benefit from it or not. So the other thing is when it comes to research peptides — besides peptides and amino acids, we don't really know what is in that vial. If you think about it, a research peptide company can put a certificate of quality assurance analysis on its website, but it's not for human use. It's technically 99.9% pure. What is that other 0.1%? I have no idea.

Jennifer Fugo (23:44) 

That is true.

Dr. Elena (23:45) 

And they can say it's manufactured in the United States, but the original product could be from China, as an example. So again, it's 99.9% pure. Well then I would like to know what's that 0.1% that's impure, right? Is it heavy metals? Is it pesticides? Is it mold? Like what are we dealing with here? Because that 0.1% — it doesn't take much. You're injecting these things into your body and a lot of this can cross the blood-brain barrier. And there are some things that are just simply irreversible.

Jennifer Fugo (24:23) 

So what I'm gathering from this conversation — because this has been my sort of hesitancy — first of all, as a clinical nutritionist, a lot of this education is new. Injectable things are also outside of my scope of practice. These are things where even when I think about my own health, I think long and hard and reach out to my network. A lot of times, even when I was considering HRT, I considered it for two years and I can't even tell you how many people I spoke to about it before I decided to do it. And I don't regret making that decision because HRT for me has been wonderful. But peptides is where I feel like there's a lot of gray.

Jennifer Fugo (25:08) 

And you really should work with someone who has a knowledge base about all of this, because that mention of not knowing what these peptides may be fueling — you could say, oh, but I have a shoulder injury. How do you know that it's just going to the shoulder injury?

Dr. Elena (25:31) 

Right.

Jennifer Fugo (25:31) 

You don't.

Dr. Elena (25:32) 

Yes. Yeah.

Jennifer Fugo (25:34) 

So when you — it sounds like you do a lot of testing, a lot of analysis of the patients that you see before making a decision about what the actual action plan is. Do you feel like that is one of the most crucial pieces right now that's sort of being overlooked in the industry?

Dr. Elena (25:54) 

Absolutely. I think people are getting peptides without actually understanding if they need them or not, and which peptides. Because peptides have become more of a conversation like, “oh, you should try this peptide,” instead of actually working with someone to understand — is that the best peptide? Is injectable form better, or can you actually get away with an oral form? And I'll give you an example. One of my most favorite peptides is actually the Thymosin family of peptides. Now these peptides we technically make on our own. The thymus gland is a very important gland that regulates the immune system. And what can happen — just like with everything else — is that gland function can decline with time, or you can be in a more pro-inflammatory situation for whatever reason.

Dr. Elena (26:48) 

You know, hormone decline or hormonal changes can put you in a more pro-inflammatory state. And we know that women are two times more likely to develop autoimmune conditions. That's why in my practice I see this a lot — I actually developed two autoimmune conditions postpartum in my 30s, and it was a rough ride trying to figure out my own hormones and what works and what doesn't work. But I do utilize quite a bit of Thymosin peptides, specifically Thymosin Alpha-1 and Thymosin Beta-4 and its fragment TB-500.

Dr. Elena (27:22)

But I don't necessarily lead with that. When I look at a patient and sit down with them and I see that there are a lot of nutrient deficiencies and their thyroid is off and clearly the inflammation markers are through the roof and their progesterone is low — and progesterone is very anti-inflammatory — we correct their nutrient imbalances, we work on their gut health, we correct the hormonal imbalance and then reevaluate in six to eight weeks. Did we move the needle? Because if they're feeling better and they're on their way and all of a sudden they don't need to take Tylenol or ibuprofen daily along with their immunosuppressant medications, we're moving in the right direction.

Dr. Elena (28:05) 

If I take a similar patient and I see them in four to six weeks and they say, “Elena, I feel about the same, maybe I'm feeling 10% better but the joint pain is still pretty aggravated and I'm still relying on Tylenol daily plus all the other medications I'm on,” then I'll say okay, let's introduce this peptide in. But I have the data — I have both subjective and objective data to validate that this is the right direction. I have a cancer patient right now who was actually recommended by one of our colleagues to start on Thymosin Alpha-1 as part of his chemo and radiation treatment. And I've used Thymosin Alpha-1 in both autoimmune conditions.

Dr. Elena (28:49) 

I've used it as part of cancer-protective treatments in both men and women who are now on the other side of cancer and we want to be able to regulate the immune system. And I've also used it now with patients who are in the thick of it, undergoing chemo and radiation, to protect the healthy cells — because as you know, chemo and radiation don't care what kind of cell you are. It's going to kill everything in its sight like a bulldozer. But with Thymosin Alpha-1, it protects the cells that are healthy, and it can help the immune system by influencing the T-reg cells — the regulatory cells of our immune system — to get rid of the pro-inflammatory cells and the cells that are not functioning properly, while at the same time supporting a healthy immune response.

Dr. Elena (29:42) 

It's like we need the fighters, but we also don't want everything to be destroyed inside. So that's an example of being able to utilize peptides in a really smart, targeted way versus, “well, my girlfriend is using the GLOW peptide, I should do it too,” or “my personal trainer thinks I should be injecting CJC-1295 growth hormone peptide three times per day” and they've never even seen your lab work.

Jennifer Fugo (30:06) 

Yeah, I really appreciate your approach because like I said, I'm very cautious. Especially since I feel like I've been around integrative and functional medicine long enough — since about 2009 — that what happens is we get these trends where everybody's like, “oh my gosh, let's do this or let's talk about this,” and everyone rushes to do it. And then four or five years later it's like, “ooh, probably shouldn't have done it that way.”

Dr. Elena (30:37) 

Exactly. Yeah.

Jennifer Fugo (30:38) 

I've learned enough to be like, hold on, we need to look at the pros and cons and then your personal landscape, your personal environment, and decide from there — is this the right decision for you, knowing the potential risks involved? Because that's really what's most important. And it sounds to me like you're actually going a step even further than a lot of people even consider, because they're just going on the internet and researching this and they're like, “oh, it was in a forum.” I have a client who said, “I was in a forum and I researched this and this is the dosing they suggested for this peptide.” And I was like, did you talk to somebody about that? Because I don't know if that's appropriate. And he just said, “well, everybody in the forum, this is what they recommend.”

Dr. Elena (31:22) 

Yeah, but you might — this is my take on research studies. I use research studies for guidance. But unless my patient was one of whatever number of people they enrolled, and unless I know that's what my patient responded to, I'm still going to listen to my patient and look at their unique physiology. Because even in research studies, they cannot take into consideration all the possible variables. You cannot enroll thousands of people in a study and account for everything. And so to your point, someone could be in a forum and they say inject 500 micrograms of BPC-157 or whatever the number is. But are you that person that needs that? And do you even need BPC-157?

Dr. Elena (32:15) 

And I hear people — I totally want people to understand how challenging the healthcare system is. And I know that compounded peptides are expensive. My peptides are also compounded — I pay the same amount and the same fee for these peptides and for hormone replacement and everything else. And I know that people are desperate for answers and there are many success stories of people even using research peptides and having incredible results. But there are also cases where it backfired on people. And not only was it a waste of time and a waste of money, but it backfired in a way that had major consequences — whether it's an infection because of how those peptides were stored or sourced, or like you said, potentially cancer-fueling properties that someone was not aware of.

Dr. Elena (33:10) 

And so I can empathize with people who are desperately in need of relief. But there are ways that you can invest in your health to at least know what's safe and what's not, and what to watch out for.

Jennifer Fugo (33:27) 

Yeah. Dr. Elena, I want to make sure too that people can find you, because this has just been such a fascinating conversation. I feel like you and I could have three more hours talking about this. I have so many questions, but I also want to be respectful of your time. So everybody can visit you at your website, drelenazinkov.com. You have a newsletter and you also have a guide for people to download if they sign up.

Dr. Elena (33:56) 

Yeah, I'm always updating those guides so that depending on when they hear our conversation, they'll either get our hormone guide — the Six Hormone Guide — that basically explains in detail the six key hormones. There are a lot of hormones, but there are six key power players. And we're also working on a testosterone guide for women at the moment.

Jennifer Fugo (34:16) 

Awesome, awesome. And do you also see patients, or do you have a clinic where you work with patients directly?

Dr. Elena (34:23) 

Yeah, so my clinic is Proactive Health ND and it is a concierge practice for both men and women. I do accept a limited number of patients every year just because I take a lot of time with each and every one of my patients. As I mentioned, there's a lot of in-depth analysis that goes into understanding unique physiology and metabolism, so I only take on a limited number of patients every year.

Jennifer Fugo (34:52) 

Awesome. Well, thank you so much for having this conversation today. I love that you are just as concerned with the nuance, the pros and cons, and helping a singular person decide what is best for them. Because I think that is the conversation that is most important. Because like you said, there are some bridges we can't uncross, some bells we can't unring. And those are the situations where it's like, well, it's just 1% or it's this tiny percentage of people that end up with bad outcomes — it doesn't feel like that if it happens to you.

Jennifer Fugo (35:29) 

And I think this is an incredible opportunity for people to learn more about the work that you do and get connected with you, and learn from the things that you're helping to create wisdom around, so that as we move forward into this new landscape, we do so safely and informed.

Dr. Elena (35:52) 

Thank you so much for having me today.

 

Frequently Asked Questions About Peptides

Are peptides safe to use?

Peptides can be helpful when prescribed appropriately, but safety depends on the individual, their health history, lab work, and the specific peptide being used. Currently most are considered to be research peptides. Certain peptides may not be appropriate for people with elevated IGF-1 levels, cancer risk factors, or underlying inflammatory issues.

What is the difference between injectable, oral, and topical peptides?

Different delivery methods serve different purposes. Injectable peptides are often used for systemic effects like growth hormone support, topical peptides may target skin and collagen health, and some oral or sublingual peptides are designed for cognitive or gut health support, depending on how they are formulated.

What’s the best peptide stack to support longevity and help with inflammation?

Popular peptide stacks that you might come across on the internet are GLOW peptides or Wolverine peptides. While these are marketed as a “silver bullet”, you can have a reaction to something in the stack. Medical professionals as well as pharmacists have concerns about their safety profile and caution people to stick with single peptides instead.

How can I be sure of what’s in the peptides bought online?

Yes, it’s possible for vials of peptides to be contaminated with various things including heavy metals.