Not all supplements are safe. In fact, some can be harmful to your...
Dr. Eric Berg DC@dr_ericberg
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Oct 03, 2025
~2 min read
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Not all supplements are safe.
In fact, some can be harmful to your health.
Here are 10 vitamins you should never take… and why: 🧵
In fact, some can be harmful to your health.
Here are 10 vitamins you should never take… and why: 🧵
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1/ Synthetic Vitamin A
(often labeled as retinyl palmitate or retinyl acetate)
Builds up in the liver and fat tissue.
Linked to toxicity, birth defects, and bone loss.
In skin creams, it can become carcinogenic under UV light.
Better sources: egg yolks, liver, cod liver oil.
(often labeled as retinyl palmitate or retinyl acetate)
Builds up in the liver and fat tissue.
Linked to toxicity, birth defects, and bone loss.
In skin creams, it can become carcinogenic under UV light.
Better sources: egg yolks, liver, cod liver oil.
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2/ Synthetic Beta-Carotene
Manufactured from petroleum byproducts.
In studies, smokers taking it had a higher risk of lung cancer.
Natural carotenoids protect health, synthetic versions can damage it.
Best sources: carrots, leafy greens, sweet potatoes.
Manufactured from petroleum byproducts.
In studies, smokers taking it had a higher risk of lung cancer.
Natural carotenoids protect health, synthetic versions can damage it.
Best sources: carrots, leafy greens, sweet potatoes.
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3/ Folic Acid (synthetic B9)
Many people cannot convert folic acid into folate.
This leaves unmetabolized folic acid in the blood.
It has been linked to immune dysfunction and increased cancer risk.
Better choice: folate from dark leafy greens.
Many people cannot convert folic acid into folate.
This leaves unmetabolized folic acid in the blood.
It has been linked to immune dysfunction and increased cancer risk.
Better choice: folate from dark leafy greens.
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4/ Synthetic B12 (Cyanocobalamin)
Contains trace amounts of cyanide.
Depletes key antioxidants and is less bioavailable than natural forms.
Choose methylcobalamin from red meat, liver, or high-quality supplements.
Contains trace amounts of cyanide.
Depletes key antioxidants and is less bioavailable than natural forms.
Choose methylcobalamin from red meat, liver, or high-quality supplements.
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5/ Calcium Carbonate
Poorly absorbed and essentially chalk.
Can accumulate in the arteries and kidneys.
Excess calcium without magnesium raises the risk of heart disease.
Best sources: cheese, yogurt, kefir, leafy greens.
Poorly absorbed and essentially chalk.
Can accumulate in the arteries and kidneys.
Excess calcium without magnesium raises the risk of heart disease.
Best sources: cheese, yogurt, kefir, leafy greens.
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6/ Iron (Ferrous Sulfate)
Highly oxidative and difficult for the body to eliminate.
Excess iron has been linked to diabetes, liver disease, Parkinson’s, and Alzheimer’s.
If deficient, choose food sources like liver or red meat, not synthetic supplements.
Highly oxidative and difficult for the body to eliminate.
Excess iron has been linked to diabetes, liver disease, Parkinson’s, and Alzheimer’s.
If deficient, choose food sources like liver or red meat, not synthetic supplements.
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7/ Magnesium Oxide
Poorly absorbed, at a rate of only about 3%.
Higher doses often cause diarrhea and electrolyte loss.
Better option: magnesium glycinate, absorbed up to 80%.
Poorly absorbed, at a rate of only about 3%.
Higher doses often cause diarrhea and electrolyte loss.
Better option: magnesium glycinate, absorbed up to 80%.
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8/ Vitamin D2 (Ergocalciferol)
Produced by exposing fungus or yeast to UV light.
Poorly converted into the active form of vitamin D.
Still prescribed, but much less effective than D3.
Best option: vitamin D3 combined with sunlight.
Produced by exposing fungus or yeast to UV light.
Poorly converted into the active form of vitamin D.
Still prescribed, but much less effective than D3.
Best option: vitamin D3 combined with sunlight.
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9/ Omega-6 Oils (Linoleic Acid)
Most people already get too much omega-6 from their diet.
Excess intake promotes inflammation and disrupts the balance with omega-3.
Better sources of omega-3: fish, cod liver oil, grass-fed meat.
Most people already get too much omega-6 from their diet.
Excess intake promotes inflammation and disrupts the balance with omega-3.
Better sources of omega-3: fish, cod liver oil, grass-fed meat.
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10/ Copper (in isolation)
Required only in tiny amounts.
Excess copper without zinc can cause oxidative stress, brain inflammation, and may increase Alzheimer’s risk.
Better sources: shellfish, dark chocolate, liver. Always pair with zinc.
Required only in tiny amounts.
Excess copper without zinc can cause oxidative stress, brain inflammation, and may increase Alzheimer’s risk.
Better sources: shellfish, dark chocolate, liver. Always pair with zinc.
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Most inexpensive supplements use synthetic forms because they are profitable, not because they are safe.
Focus on food-based or highly bioavailable nutrients, and always read labels carefully.
To learn more about these supplement risks, watch this video:
youtu.be/P9XwBGk3ZiQ
Focus on food-based or highly bioavailable nutrients, and always read labels carefully.
To learn more about these supplement risks, watch this video:
youtu.be/P9XwBGk3ZiQ
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A bit about me:
I’m the creator of Healthy Keto® and Intermittent Fasting protocols, helping over 100M people make healthier choices.
Follow me @dr_ericberg for more evidence-based insights to improve your health and longevity.
I’m the creator of Healthy Keto® and Intermittent Fasting protocols, helping over 100M people make healthier choices.
Follow me @dr_ericberg for more evidence-based insights to improve your health and longevity.
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What is one key takeaway you gained from this thread? Share it in the comments below.
I read every comment and often use them to create future content that matters to you.
I read every comment and often use them to create future content that matters to you.