Multi-Vitamin and Mineral Supplements and Autism Ranking: Insufficient/Mixed evidence

Risks and Safety


The quality of multi-vitamin/mineral supplements can vary enormously depending on the specific supplement, the manufacturer, the ingredients and the manufacturing process.  

Although the doses of vitamins and minerals found in most multi-vitamin/mineral supplements are thought to be safe, very high levels can be harmful and you are likely to experience some harm if you take vitamins in large amounts over long periods of time.  For example, there have been several cases (Boyd and Moodambail, 2016; Vyas and White, 2011) of young children on the autism spectrum being admitted to hospital with hypercalcaemia. This is a potentially fatal condition caused by excessive calcium levels which can be brought about by taking excessive amounts of vitamin A and vitamin D. 

For this reason, we suggest that you do not exceed the RNIs(Reference Nutrient Intakes) recommended by the Food Standards Agency in UK or the RDAs (Recommended Dietary Allowances) recommend by the Office of Dietary Supplements in the USA.

The Office of Dietary Supplements (2011) noted that multi-vitamin/mineral supplements with very high levels of vitamin A, beta-carotene and iron should be avoided.

“Taking a basic MVM is unlikely to pose any risks to health. But if you consume fortified foods and drinks (such as cereals or beverages with added vitamins and minerals) or take other dietary supplements, make sure that the MVM you take doesn’t cause your intake of any vitamin or mineral to go above the upper levels. Pay particular attention to the amounts of vitamin A, beta-carotene (which the body can convert to vitamin A), and iron in the MVM. “


There are very few known contraindications (something which makes a particular treatment or procedure potentially inadvisable for a particular group of people) for most multi-vitamin/mineral supplements. However the Office of Dietary Supplements (2011) in the USA noted that some people should avoid multi-vitamin/mineral supplements with very high levels of vitamin A, beta-carotene and iron.

  • “Women who get too much vitamin A during pregnancy can increase the risk of birth defects in their babies. This risk does not apply to beta-carotene, however. Smokers, and perhaps former smokers, should avoid MVMs with large amounts of beta-carotene and vitamin A because these ingredients might increase the risk of developing lung cancer. 
  • Adult men and postmenopausal women should avoid taking MVMs that contain 18 mg or more of iron unless their doctor has told them that they have iron deficiency or inadequacy. When the body takes in much more iron that it can eliminate, the iron can collect in body tissues and organs, such as the liver and heart, and damage them. Iron supplements are a leading cause of poisoning in children under age 6, so keep any products containing iron (such as children’s chewable MVMs or adults’ iron supplements) out of children’s reach.”

The Office of Dietary Supplements also recommended that anyone taking an anticoagulant drug (which reduces blood clotting) such as warfarin should seek medical advice before taking multi-vitamin/mineral supplements that contain vitamin K.

“MVMs with recommended intake levels of nutrients don’t usually interact with medications, with one important exception. If you take medicine to reduce blood clotting, such as warfarin (Coumadin and other brand names), talk to your health care provider before taking any MVM or dietary supplement with vitamin K. Vitamin K lowers the drug’s effectiveness and doctors base the medicine dose partly on the amount of vitamin K you usually consume in foods and supplements.”

If you have concerns about your diet or your child’s diet, you should seek advice from a responsible health professional such as a GP or pharmacist. This may lead to a referral to a dietitian, in particular one with experience of working with individuals on the autism spectrum.

19 Dec 2017
Last Review
01 Nov 2017
Next Review
01 Nov 2020