Is it better to buy supplements which are combination formulas or single-ingredient?
It's generally best to buy and use single-ingredient supplements. There are several reasons for this.
First, you are more likely to get what's listed on the label with a single-ingredient supplement. Years of testing by ConsumerLab.com have shown that combination products are more likely to contain incorrect amounts of one or more ingredients -- and they are more likely to be contaminated.
Second, with a single-ingredient supplement, the recommended daily serving of that ingredient is more likely to be clinically relevant than if the ingredient is part of a combination formula, where a tiny amount may be included merely as "window dressing." In addition, most combinations on the market have not been clinically tested.
Third, using single-ingredient supplements gives you a better idea of which ingredients work and which do not, as well as which are causing side-effects. This allows you to adjust your supplements and dosage to better suit your needs.
Finally, you may find it actually costs less
to purchase ingredients as separate supplements than in a combination formula. Many single-ingredient products of high quality and low cost are identified in the ConsumerLab.com's Product Reviews
With that said, an appropriate time to use a combination formula is when that exact combination has been shown to work in a well-controlled clinical trial and it is less expensive to purchase (or much more convenient to use) than the corresponding collection of single-ingredient supplements.
Please tell me which types of vitamins should not be taken together and which should be taken together for maximum effect.
Is it important to take calcium and magnesium together?
If vitamin K absorption appears to be reduced by other fat-soluble vitamins, like vitamin D, why do some "bone health" supplements combine them? Should they be taken separately?
This CL Answer initially posted on 12/22/2016.
Last updated 7/25/2017.