Can getting too much of a vitamin/mineral be bad for you?

It is extremely easy to reach your RDAs (besides B12) for every mineral/vitamin with a properly balanced vegan lifestyle. I consume a lot of spinach because Riboflavin is a bit harder to get for optimal muscle building and I also eat a bunch of kale for its antioxidants post workout to detox the inflammation.
Sometimes, my vitamin K, A, folate, iron, or other categories go red and i go over anywhere from 600-1000% of the RDA for that category. Can this be detrimental for my health?
Only supplement I take is B12. Most I'll eat are 2 cups of spinach and kale a day.

Best Answer

  • When they go red, it means that you are approaching or have passed the TUL (Tolerable Upper Limit), or where leading nutrition authorities report that negative consequences may occur.

    For instance, with A it is

    liver abnormalities, notably abnormal liver pathology


    For K, there is some debate if a real upper limit exists.Fue to absorbtion falloff, many agree that

    No adverse effects have been associated with vitamin K consumption as food or supplements in humans

    and thus, I have personally turned off the TUL for K.


    General toxicity . . . increased carcinogenesis . . . and adverse reproductive and developmental effects


    and finally, iron:

    gastrointestinal symptoms


    However, the TUL is not where negative things may happen, it's just where they recommend sticking under, as you may be approaching negative consequences. For instance, the lowest recorded adverse effect level for iron is 70mg, and the TUL is 45.


  • @VeGains There are only two nutrients that we can't get from plants; one is B12 (glad you are supplementing) and the other is vitamin D. In Canada, we have a hard time making enough vitamin D from the sun, so it's a good idea to supplement.

    In general, I don't worry about exceeding nutrient targets from food alone; your body has pretty good systems in place to enhance/reduce absorption. @tf2manu994 gave a great overview of the UL which is the highest level of intake of a nutrient (from food and supplements) that poses no adverse affect. Above this level, negative health outcomes may occur which can be mild (i.e. diarrhea) or more significant (changes to the liver).

    Hope this helps!

    Susan Macfarlane, MScA, RD
    Registered Dietitian Nutritionist
    As always, any and all postings here are covered by our T&Cs:

  • tf2manu994 gave some examples of acute toxicity (though I would caution that the toxicity of vitamin A is for preformed vitamin A (retinol): beta-carotene has no such toxic effect — it just turns your skin orange. Similarly, the possible cancer-promiting effect of folic acid is for folic acid per se (the form found in most dietary supplements): food folates (5-methyltetrahydrofolate and related compounds) have not been linked to such potential risks).

    Epidemiological studies and clinical trials on dietary supplements have revealed long-term negative health impacts that are much harder to link back to excessive exposure to some nutrient. from high-dose selenium raising the risk of diabetes (and possibly some cancers), to the possible increases in lung cancer mortality amongst smokers supplementing with beta-carotene (when the trial was based on epidemiology associating high dietary beta-carotene with reduced risk of lung cancer amongst smokers), to increased mortality in mice administered a human-equivalent full dose of Life Extension Mix®, and other cases discussed in my 2004 CR Society presentation — as well as concerns that are not yet confirmed but that merit caution, such as the potential cancer-promoting effect of folic acid and the hypothetical cancer promoting effect of benfotiamine and other high-dose or high-bioavailability forms of thiamine. And just recently, vitamins B6 and B12 were linked to higher risk of lung cancer in smokers at doses at the low end of those found in health-food-store and online multivitamins.

  • I'm glad you don't have problems meeting your RDA. Unfortunately, I do since I typically do not take in a lot of calories (1300 for maintenance). I've often wondered if the RDA should be scaled - since I'm smaller and not as active as some people, I should think I would need less micronutrients.

    Here's a journal article you might be interested in:
    Low intake of calcium, folate, nicotinic acid, vitamin E, retinol, β-carotene and high intake of pantothenic acid, biotin and riboflavin are significantly associated with increased genome instability—results from a dietary intake and micronucleus index survey in South Australia

    I use nutritional yeast for niacin, since I tend to miss the target for niacin (nicotinic acid) more often than not, but hate the fact that it contains so much riboflavin, which gives it that nice yellow color. Another one that I miss often is pantothenic acid, but maybe that's a good thing.

  • @LH1

    You make a good point! It's hard to know the exact amount of a vitamin and mineral our body needs without detailed testing. Nutrient targets are set to meet the needs of 97-98% of a healthy population, but it's likely that some people simply need more and some less of a nutrient due to their genetics, physical activity, and diet.

    Susan Macfarlane, MScA, RD
    Registered Dietitian Nutritionist
    As always, any and all postings here are covered by our T&Cs:

  • I'm a lacto-ovo vegetarian and I started the LCHF/Keto way of eating in May. Because I have lowered my carbs I started taking a multivitiamin as I usually do in the winter here in Canada, along with D3. Calcium + Magnesium, now adding K. Because of the major change in my way of eating and the excessive urination that comes with this way of eating, I increased potassium, magnesium citrate, sodium, biotin . I've always been concerned about my B12 but now I that I'm tracking my multivitamin and supplements, I see it puts me over many of limits -- Folate especially. B1, B2, B, B12, Folate is in the red.

    On the product label, Folic acid 1,000 mcg described as Folic acid (Folate). When I created my custom food I put 1000 ug in the Folate field. Is this correct?

    Thank you in advance.

  • @Maggie yes, μg and mcg both stand for 'micrograms'.

  • edited December 2017

    A reddit thread spooked me into getting more Vitamin D (especially this time of year in the UK [let's all move to Cape Town]). I picked up some tablets (not sure of the bv of D3 in this form), but they came with vitamin C also. I wanted to take ~4k of VitD, but this site suggests no more than 1k of C is prudent. So, I'm stuck with a couple of these pills (2k), plus some cod liver oil (~250), and some small fish.

    That sort of turned into a diatribe. The moral of the story is not to buy supplements while surrounded by bright lights and christmas music from the darkest period of 'British culture'. (I was keen to gtfo).

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