Can Multivitamins Cause More Harm Than Good?

By Samantha Gilbert, FNC, CHNP, CNC     Last updated on December 26th, 2021

Everywhere we look, we see doctors, nutritionists, health coaches, and even your “healthy” neighbors touting the importance of multivitamins. They worry that you’re not getting enough nutrients from your food, no matter how healthily you’re eating. 

We tend to look to authority figures (or those who present themselves as such) when wondering what we should do, but even a doctor — when unfamiliar with your personal biochemistry — could give you the wrong advice. 

What if recommending daily multivitamins to everyone is actually creating serious health problems?

What Are Vitamins?

Vitamins are organic nutrients required for biochemical reactions that ensure growth, survival, and reproduction. Some are unable to be synthesized by the body, and must therefore be ingested alone or through your diet.

What Are Multivitamins?

Multivitamins may include herbs, vitamins, and/or minerals, and are usually sold over the counter. They’re not regulated by the government like medications are, so they may or may not be effective, and no list of side effects is required. Additionally, multivitamins that do not undergo rigorous, third-party testing, provide no guarantee they contain the level of ingredients stated on the label — there could be more or there could be less. In fact, I often see this with kelp supplements that contain far higher iodine levels than reported, which can be detrimental in someone with a thyroid condition such as Hashimoto’s thyroiditis. Nutrient levels in some multivitamins can even exceed the suggested daily limits (which, due to individual biochemistry, aren’t relevant to everyone, anyway).

An estimated 200+ million Americans are taking mass-market (a.k.a. consumer-grade) supplements. The majority of them are useless at best, outright harmful at worst. This is due to the use of fillers, preservatives, excipients, antioxidants, glazes, sweeteners, artificial coloring, binders, and deodorizers. These additional ingredients are found in the world’s most heavily promoted and widely used brands, such as Centrum or One A Day. These ingredients are also found in laxatives, hair dyes, herbicides, fungicides, pesticides, fertilizers, cement, glues, and resins. Some of these substances are well-known carcinogens, irritants, allergens, and birth-defect-causing agents.

There are five major categories of supplements to choose from:

  • Consumer-Grade
  • Generic
  • “Natural”
  • Professional-Grade
  • Opportunistic (MLM)

In general, each successive category is more expensive than the previous one. To a large extent, higher prices reflect better quality but not always — there is plenty of expensive junk too. Professional-grade nutraceuticals are the only class of supplements I recommend to my clients due to their strict quality control standards and third-party testing.

You can find consumer-grade supplements on supermarket and drugstore shelves and on Amazon. They are labeled as Centrum, One A Day, Nature‘s Way, Theragran, and generics (Costco’s Kirkland and CVS, for example). The majority of high-end health food stores and specialty websites don’t resell consumer-grade supplements due to quality concerns. They are made from the cheapest, least efficient components to maximize profit. The entire daily “dose” is usually squeezed into one or two hard-pressed tablets and is optimized for extended shelf life. To mask oxidation, spoilage, odor, and discoloration common to all supplements, their manufacturers use artificial colorings, preservatives, and glazes that often cause a lot of allergic reactions and negative side effects.

Clients often report negative reactions to the supplements they are taking, but in many cases, I find it’s not the actual nutrient that is the problem, but rather, the quality of the product and all the additional toxic ingredients.

Buying supplements from Amazon or eBay comes with an even greater risk because many of them are either counterfeit and dangerous, useless and expired products that have been repackaged as new, or they are stolen products released on the black market without any quality control. And I’m sure you know by now that Amazon is more concerned about profit over quality control.

The Importance of Individual Biochemistry 

We are all biochemically unique; as humans, we exhibit great diversity in blood and brain chemistry. We each have our own individual chemistry, so we have our own unique responses and reactions to the same nutrient inputs. No two people will process vitamins and minerals in exactly the same way. 

Most people are deficient in several nutrients and overloaded in others due to their genetics. An individual assessment with lab testing is crucial to determine the appropriate vitamin and mineral recommendations for any given person. 

Are Multivitamins Dangerous?

Anything that is “one size fits all” can be dangerous. Because multivitamins assume that we all need the same specific nutrients in the same specific ratios, you could personally be getting too much or too little. 

Being consistently overloaded with vitamins and minerals can hurt you. Ingesting inappropriate doses becomes even more dangerous when you consume them every day. You could accumulate a buildup of vitamin C or zinc and experience nausea, diarrhea, or stomach cramps. You could get too much selenium and experience hair loss, GI issues, fatigue, or even mild nerve damage. Folic acid can also wreak havoc, especially if you already suffer from cancer, depression, anxiety, or other cognitive impairments. You can read more about that here.

Unfortunately, I still see many practitioners prescribing multivitamins based on faulty testing methods such as MTHFR, which will make a patient worse over time. Before I found my current doctors, my naturopath put me on a multivitamin as well as 5-HTP for depression and a B-vitamin complex. They all contained folic acid (the multivitamin contained both folic acid and copper). Since I was already undermethylated with copper overload, these nutrients made me feel worse. I spent another two years suffering from massive depression and oxidative stress due to this inappropriate prescription.

Please don’t assume that vitamins and minerals are safe simply because they’re “natural.” Your body isn’t like anyone else’s, and the supplements you choose must be calibrated for you, specifically, if you want to avoid negative effects.

Multivitamins and Heavy Metals

Many multivitamins also contain heavy metals (especially cheap, consumer-grade, and generic options from Costco and CVS), which can stay in your body and increase your likelihood of dementia or other issues. An accumulation of heavy metals over time from daily multivitamins could harm your organs and lead to numerous health complications, including:

  • Depression
  • Fatigue
  • Anxiety
  • Headaches
  • Nerve damage

Can Multivitamins Cause Depression? 

Daily use of multivitamins containing high levels of vitamin D over a period of several months is known to be toxic, resulting in symptoms such as depression, confusion, fatigue, and muscle weakness. Too little or too much vitamin A can lead to negative side effects, including depression from too much retinol (derived from Vitamin A). Multivitamins usually contain vitamin A in a combination of beta-carotene and retinol (preformed vitamin A).

Can Multivitamins Cause Headaches?

Some generic multivitamins include large amounts of fat-soluble vitamins, for which excess is stored in the body versus excreted in the urine. These can therefore build up inside the body through consistent multivitamin use over a period of time. The buildup of Vitamin A, for example, may cause headaches — along with dizziness, liver damage, and weakened bones. 

While Vitamin C is water-soluble, large doses over time can prevent it from being completely absorbed, overly deplete copper, and therefore result in a buildup in the intestinal tract. A buildup of Vitamin C (also included in multivitamins) can result in headaches and nausea.

Can Multivitamins Cause Anxiety?

B-complex vitamins (included in most generic multivitamins) are stimulating and have been known to cause anxiety and panic attacks for people whose dosage is too high for their individual needs. Folic acid can be over-activating to the body and brain, resulting in anxiety. The interaction of multivitamins with certain medications can also increase anxiety symptoms. All vitamins are “metabolic activators,” so if you’re prone to anxiety or manic episodes, take multivitamins with caution.

Can Multivitamins Cause Acne?

Many of today’s most popular multivitamins contain vitamins and minerals that, in excess, are known to cause acne. Vitamins B6 and B12, for example, may cause acne. B12 encourages inflammation-causing compounds and alters the gene expression of the skin, and multivitamins tend to contain excessive levels of it. Iodine can also cause acne on the face and upper trunk. Too much calcium, also included in most generic multivitamins, can prevent you from absorbing enough zinc to keep your skin clear.

How to Evaluate Your Multivitamins

  1. Take an inventory of all the supplements you are currently taking, including the brands.
  2. Ask yourself why you are taking each of them.
  3. Take note of any reactions (good or bad) you’re experiencing as a result of these supplements.

Do You Need a Multivitamin?

If you’re generally healthy, you most likely don’t need a generic multivitamin. In fact, more harm can be done by taking too much than by not taking anything at all. 

Keep in mind that nutrients from food and supplements can greatly influence the regulation of genes. I strongly encourage you to save your money and work with a practitioner that really understands biochemistry, and the importance of nutrient-specific protocols for your individual case. 

Do you take multivitamins? I’d love to know what your experience has been in the comments below!


46 thoughts on “Can Multivitamins Cause More Harm Than Good?”

  1. Hi Samantha,

    I just found your website, and it brought me some relief to know it’s not all in my head. Any vitamim b supplement, even as a part of multi, makes me depressed. I don’t understand why, and no naturapth that I met understands me. Do you know what kind of multi would be recommended for people like me? I feel like there is something wrong me. Most supplements make me feel off..

    1. The same happened to me. I am still confused that a vitamin can cause such a negative reaction! When I tried to talk to my doctor, she rolled her eyes, and said she’d never ever heard of that! I’ve had to be my own advocate and do my own research. B can make some of us depressed – and feeling crazy!

    2. I have this same reaction to b vitamins and a nutritionist told me it is due to the MTHRFR gene mutation. I now take a methylated B vitamin supplement and feel AMAZING.

  2. I am taking a B complex with folate because I am extremely folate deficient ( found that out from an OAT .) What do you do if you are folate deficient but are not supposed to take folate? I am an undermethylator…

  3. hi, i am currently taking 1000mg cod liver oil, multivitamins and iron, high strength vitamin D, along with 150mg trazadone, 10mg diazapam, i take these daily, and i am a 29yr old female, and 3 stone over weight, i decided to get active and take vitamins to help with my anxiety and panic disorder, but within a week of starting these, i feel terrible, faint, whoozy, pins and needles constantly in my hands and feet, also my finger nails have changed a dark peachy colour at the tips, i dont see my doctor for another 2 weeks, could something be seriously wrong?

  4. After reading this great article I’m afraid to take another supplement until I know for sure what I need, just for “me”. How does one begin the journey of these answers?

    1. I’m not a doctor, but I’d imagine a blood test. Low levels of B or D can cause a slew of mental and sleep issues.

      I also have been under the assumption that you body just excreted the vitamins it didn’t need. This is first I’ve been reading about negative effects of vitamins and supplements. 😞🔫 depression and anxiety for two years now due to a few big life events. Kind of think the crazy amount of supplants and vitamins I’ve been taking have hindered me from recovering.

  5. Synthetic vitamins are not good for us, and its taken awhile to work this out, hopefully one day they will stop forcing them down our throats by fortifying them in all our foods.

  6. I find that if I take a B-100 complex daily, I am more likely to be in a great mood, and my energy level stays high all day. B-vitamin deficiency has been a problem in my family, especially in relation to depression. My daughter suffered from depression for years. Without vitamins, she would have a “bad” day 80-90% of the time at school. Give her a B-complex with breakfast, and she will have a “good” day 80-90% of the time. Every body is different, but this is one thing I swear by–at least, for us!

    1. Hi Renee,
      I’m so glad you figured out what works best for you and your family. Keep up the great work!

    2. If you have anxiety disorder and or PTSD like I do you had better stay the hell away from multivitamins because it will make your problems much worse especially if they contain folate or folic acid . And both D and B vitamins will also make it worse and it will also affect you sleep pattern

      1. I have ptsd. Was a crime victim. Vitamin B made my depression dangerously worse. I became dizzy, confused, barely able to function- and suicidal. I was shocked that a vitamin could do this!

      2. I totally agree. I recently tapered from my zoloft and was feeling much better after about six weeks. My hair has been thinning due to telegen effluvium from anxiety and stress and my dermatologist told me to try 5000 mg of biotin once a day. Almost immediately my anxiety worsened and I developed insomnia. I just stopped taking them today, so I’m hopeful that I’ll feel back to normal soon.

  7. Darlene McCullough

    I am taking Melaleuca vitamin supplements and I vould immediately tell within a week that I felt the difference. Prior to taking these supplements, I got sick at the holidays 3 years in a row and it took weeks to recover. However, for the last two years I have not been sick at all.

    1. That’s wonderful Darlene! Thank you for sharing your story and I’m so glad you found what works for you!

  8. Hi Samantha,

    I’m actually taking a PreNatal vitamin because I thought it was almost “mandatory” as part of the pre-pregnancy process. I’m feeling fine. Can I get the necessary folic acid from alternative natural food sources?


    1. Hi Stacy,
      I can’t advise you one way or the other without a complete assessment, but I would encourage you to look into high folate vegetables as natural sources.

  9. Hi Samantha,

    Since childhood, I’ve always suffered from Migraines (I’m 55 now). I was taking “Alive” Once a Day vitamins for Men, but they were causing me headaches and at times migraines. I just came across your posts via another link (by luck) and really enjoy reading what you have to say about nutrition. What foods/diet would you recommend for me? Thank you.

    Kind regards,

    1. Hi Esteban,
      Thank you, I’m so glad you are enjoying my posts. Migraines can be caused by a multitude of things, so there’s no way I can make a recommendation without a complete assessment first. If you are interested in becoming a client, please email my assistant Shannon at and she’ll get you set up.

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