Update: 7/20/22. After over 20 years of investigating supplements, I've come to a couple of conclusions. First, depending on you and your health status, there are some good supplements and not-so-good supplements. The second is everything has side effects. What you will read below are some of the weirdest, most interesting – and sometimes scariest – supplement side effects I've run across. Remember these as you shop for supplements. When in doubt, if you think any of this applies to you, speak to your doctor and pharmacist. As you read this list, ask yourself why nobody ever told you this before…
1 Beta-Alanine
Beta-Alanine is an ingredient found in many pre-workout supplements. Some evidence suggests it might reduce lactic acid levels during exercise and improve exercise performance. But, what you may not be aware of is that beta-alanine may cause the following supplement side effect:
Skin Tingling
When taken in high dosages (2-3 grams, for example) some report feelings of pins and needles or a tingling sensation on the skin. This is thought to be due to beta-alanine interacting with nerves. This side effect is temporary and often goes away after an hour or so.
The tingling sensation plays no role in the results you get from beta-alanine. Whether or not the pins and needles sensation reduces exercise performance requires more study.
2 Beta Carotene
Beta carotene, a precursor to vitamin A is found in carrots, tomatoes, etc. There are hundreds of carotene molecules. It's a powerful antioxidant and is often thought to be safer than vitamin A because it doesn't harm the liver. Yet, studies show beta carotene may promote the following supplement side effect:
Lung Cancer
Studies done in the 1990s noticed a significant increase in lung cancer in those who took high-dose beta carotene supplements for many years. Researchers noted a 20% greater lung cancer risk. The risk of lung cancer was said highest in people who:
- smoked
- former smokers
- those who worked around asbestos
Video: Beta Carotene and Cancer
Watch on my Youtube channel if you like.
The amount used in the research was about 20 mg per day. This is a mega dose and much more than is in most beta carotene supplements – although I have seen some supplements list dosages close to this.
While most beta carotene supplements in the US list their amounts in International Units (IUs) some supplement brands give the amount milligrams.
Based on this, I suggest nobody take beta carotene supplements. Instead, eat a carrot. Then you are getting ALL the carotene molecules – and not just beta carotene.
3 Biotin
Biotin, (vitamin H) is found in pretty much every hair and nails supplement I've ever looked at. While often thought to be harmless, biotin can be associated with the following supplement side effects:
False Positive Hyperthyroidism
Biotin supplements might make it look like you have hyperthyroidism on a blood test. TSH is thyroid-stimulating hormone. It's the hormone that tells you to make thyroid hormone. Testing TSH levels is common for thyroid health.
Lower TSH levels indicate higher thyroid hormones. Biotin supplements make it seem like your TSH levels are lower than they really are. Very low TSH may mean you have hyper-thyroidism. Very high TSH might mean the opposite – hypothyroidism.
If you get thyroid testing, tell your doctor you are taking biotin supplements.
Improved Vision
In people with multiple sclerosis, biotin supplements may improve some aspects of vision.
Video: 7 Supplement Side Effects
Watch on my Youtube channel if you prefer
4 Black Seed
Black seeds (nigella sativa) have the reputation of being the “cure for everything except death.” While generally considered safe, a few black sees may be related to the following supplement side effect:
Reduced Need For Thyroid Medication
One study has noted 2 grams of black seed powder lowered TSH levels and thyroid antibodies and increased thyroid hormone levels (T3) in people who had Hashimoto's hypothyroidism.
Technically, this might mean black seeds were improving hypothyroidism. While I would not call black seeds a cure for hypothyroidism, this finding is interesting. More research is needed.
See black seed oil review and black seeds facts review for more insights.
Video: Black Seeds & The Thyroid
5 Calcium
Calcium supplements are popular for helping bones stay strong, and important to everybody with osteoporosis. While an essential mineral, some research hints calcium may be associated with the following supplement side effect:
Heart Attacks
Various studies have noted an increased risk of heart attacks in middle age and older people who consume more than the calcium RDA (100-1200 mg per day). This can easily occur when you get your calcium from food and supplements.
To be fair, this is controversial with other research finding no association with myocardial infarction. No research links calcium from foods to heart attacks. Until we get to the bottom of this, if you can, try to get most of your calcium from foods.
6 Chondroitin sulfate
Chondroitin sulfate is popular in arthritis supplements. While there is some proof it may help arthritis pain (and some showing it doesn't help), it may be related to the following supplement side effect:
Prostate Cancer
Preliminary evidence (I mean test tubes) suggests a substance in chondroitin sulfate may cause the spread of prostate cancer cells. There is no proof chondroitin sulfate supplements do this in humans. But, until we know more, I feel men should talk to their doctor before using chondroitin sulfate supplements.
See the chondroitin sulfate prostate cancer review.
7 Fish Oil
The omega-3 fatty acids in fish oils – EPA and DHA are well known to reduce triglycerides. They may also have a wide range of other benefits ranging from helping depression to arthritis too. But they may also promote the following supplement side effects:
- Anti-blood clotting effects. High doses (2-3 g) of fish oils may interact with blood thinner medications.
- Increased LDL levels. High dosages of fish oils (more than 3 g) may raise LDL (bad cholesterol) levels. This is unlikely with most supplements.
8 Folic Acid
Folic acid (folate) is one of the B vitamins. Folate is the natural form of this vitamin. Folic acid is the synthetic version. Many supplements contain folic acid because it's better absorbed.
Folic acid plays a very important role in reducing birth defects. It also helps us make red blood cells and reduces homocysteine. The RDA is only 400 to 800 micrograms a day. As critical as folic acid is, in some, it may be associated with the following supplement side effects:
Prostate Cancer
Some research has noted an association between folic acid supplements and prostate cancer. In one such study, researchers saw an almost 10% increase in prostate cancer in men who used folic acid supplements for 10 years.
Colon Cancer
Some research suggests folic acid supplements may raise the risk of colon cancer. One investigation noted an 11% increase in colon cancer in those who took 1 mg of folic acid for 3 years. This is a mega dose of the vitamin.
These findings are controversial. In fact, some research has shown folic acid reduces cancer risk. That said, This should not scare off pregnant women. One thing is certain: If you are pregnant or want to be pregnant, take folic acid.
Folic acid reduces birth defects.
For the rest of us, remember folate -the food version – has never been linked to cancer. Cancer is complicated. Talk to your doctor, pharmacist, or dietitian to see if folic acid supplements are right for you.
9 Garcinia Cambogia
Garcinia cambogia (hydroxy citric acid/HCA) is a popular weight loss supplement, despite proof it really works. What most people don't know is various reports have linked Garcinia Cambogia to the following supplement side effect:
Liver Failure / Liver Transplant
While many reports have involved multi-ingredient products, there is now at least one report of liver failure in someone who took a supplement that had only 1 ingredient – garcinia Cambogia. The person needed a liver transplant. While the risk is low compared to the total number of people who've consumed this herb, even 1 case is too high for me.
10 Glucosamine Sulfate
Glucosamine sulfate is a popular supplement for reducing arthritis pain. While it does have evidence, it may also have the following supplement side effect:
Elevated Blood Sugar
Glucosamine sulfate may raise blood sugar levels. This can be a problem if you have diabetes or pre-diabetes (metabolic syndrome).
To be fair, the research on glucosamine and blood sugar is a bit murky. While I have met diabetics who told me their blood sugar surged after taking glucosamine sulfate supplements, I've met others who had no problems.
To be safe, if you are a diabetic or prediabetic, check your blood sugar levels if you take glucosamine sulfate supplements.
Increased Eye Pressure
One small study has indicated glucosamine sulfate supplements may increase eye pressure in people with glaucoma. Eye pressure decreased when people stopped taking glucosamine supplements. If you have glaucoma and take glucosamine, tell your eye care professional.
11 Hibiscus Tea
Hibiscus tea is technically a food and not a supplement. The tea is healthy and full of antioxidants. Some studies even find hibiscus may reduce blood pressure. While that's great, hibiscus may be associated with the following supplement side effect:
Lower Absorption Of Cholesterol Medicine
Preliminary evidence suggests hibiscus tea may reduce how well statin medications (simvastatin) work by decreasing their absorption. The evidence is preliminary (rats) and needs to be confirmed with human proof. Until more is known, it may be wise to separate statin medicine use and hibiscus tea by a few hours.
12 Red Yeast Rice
Red yeast rice is very popular for lowering cholesterol. While often effective, reports have linked red yeast rice to the following supplement side effects:
Muscle Pain/ Rhabdomyolysis
Muscle pains and aches are somewhat common side effects of statin-cholesterol lowering medicine with about 5% of people experiencing muscle pains from statins. Odds are you have seen TV commercials mention this possibility.
Rhabdomyolysis (rhabdo) is much more serious and occurs when the muscle fibers die. When they die, the stuff in your muscle cells leaks into your blood. This can cause very serious – sometimes fatal -outcomes.
One study has noted at least 27 cases of muscle pain and rhabdo from red yeast rice supplements.
I wrote the first book about exercise and rhabdo. If you exercise and take cholesterol-lowering medicine -or red yeast rice supplements – you may have an increased risk of rhabdomyolysis.
Liver Problems
Red yeast rice can raise liver enzymes. Tell your doctor if you take this supplement.
13 Saw Palmetto
Men with prostate problems may supplement with saw palmetto. Some research suggests saw palmetto is linked to the following supplement side effects:
Early Menstruation
There are at least 2 cases of saw palmetto causing hot flashes and other signs of menstruation in young girls (10-11 years of age) after taking saw palmetto supplements.
Erectile Dysfunction
Saw palmetto inhibits an enzyme called 5 alpha-reductase which takes part in testosterone metabolism. Inhibiting this enzyme is also why the herb is used in hair growth supplements. In men, some report weaker erections (ED) and less ejaculatory volume when taking saw palmetto. While ED seems to be very rare, I bring it up just in case you experience it.
14 St John's Wort
St. John's wort is a popular herbal remedy for depression. But there are also reports, that it may be associated with the following supplement side effects:
Pregnancy
There are at least 5 reports of unplanned pregnancies in women who were taking St Johns's wort -as well as birth control pills. It's thought St. John's wort interferes with birth control pills, making them less effective.
Some women think saw palmetto might also cause unwanted pregnancies. See the Saw palmetto birth control pill review for more insights.
Allergic To Sun Light
People who use St. John's wort sometimes report sunlight-induced rashes.
St. Johns wort & Birth Control Pills
Watch on my Youtube channel if you prefer
15 Vitamin E
What we call vitamin E is actually 8 different types of related nutrients. Most supplements contain only 1 type: alpha-tocopherol. While popular, various studies hint vitamin E supplements may be associated with the following side effect:
Increased Risk Of Death – From Everything
In the studies, they call this all-cause mortality. Some researchers noted an increased association of death in people who took at least 400 IUs per day. It's a slight increase but slight or not, it's too much for my tastes.
What's going on here? I've never seen a good explanation. It may be a fluke. Or it may be something real. More research is needed.
Keep in mind the research doesn't prove “vitamin E kills you.” Rather, it only says there seems to be an association with an increased risk of dying from all causes. The association appears to hold true even if you are healthy.
So if you love vitamin E, what do you do? Well, besides talking to your doctor, you may want to keep your vitamin E dosage to less than 200 IU or take a supplement that has all 8 types of vitamin E (it's called mixed tocopherols). Or, better yet, get your vitamin E from foods like almonds, avocados, sunflower seeds, and wheat germ.
16 Yerba Mate
Yerba mate is popular in some energy supplements, likely because it has caffeine. Drinking yerba mate beverages may have the following side effect:
Cancer
Various studies have linked drinking large amounts of yerba mate beverages (like a gallon a day) to a variety of cancers such as:
- throat cancer
- mouth cancer
- stomach cancer
- lung cancer
It takes years of drinking yerba mate for cancer to show up. The risk of cancer appears to be greater when it's consumed as a hot beverage. Whether or not yerba mate supplements cause cancer is not known.
17 Yohimbe
Yohimbe, is popular in ED supplements. I believe the risk Yohimbe is greater than its benefits. Research finds Yohimbe may have the following supplement side effects:
- elevated blood pressure
- fever and chills
- breathing problems
- kidney failure
- changes in mood
Obviously, the side effects would depend on how much you took as well as your health problems. If you have health disorders, talk to your doctor first.
Should You Avoid Supplements?
My goal in showing you these supplement side effects was not to scare you. Most supplements are pretty safe. My hope is to get you to remember everything has side effects and natural does not mean safe for everybody.
I offer supplement consultations if you want help with the supplements you take.