What are "broad-spectrum micronutrient" supplements, and do they have greater health benefits than multivitamin/multimineral supplements?

Answer:

The term "broad-spectrum micronutrients" appears to be a marketing term being used to describe supplements that contain all, or nearly all, essential vitamins and minerals that you need in small amounts. But so do many multivitamin/multimineral supplements and, usually, at lower cost.

Both types of products would typically provide about 100% or more of the Daily Value of essential micronutrients (those needed at microgram or low milligram amounts), and smaller percentages of the Daily Values of macronutrient minerals (potassium, phosphorus, calcium, and magnesium), for which relatively large amounts (hundreds or thousands of milligrams) need to be consumed daily (preferably from food).

Below, we compare one "broad-spectrum micronutrient" supplement, Daily Essential Nutrients by Hardy Nutritionals, to a general multivitamin for adults, Kirkland Signature (Costco) Daily Multi, which was our Top Pick general multivitamin for adults in 2021.

In short, Kirkland's provides at least 100% of the recommended daily intake of most vitamins and minerals without exceeding any Tolerable Upper Intake Levels (ULs). Hardy Nutritionals' Daily Essential Nutrients, which is marketed as a "clinical-strength broad-spectrum micronutrient," contains even higher amounts of most nutrients (like a "megadose" multivitamin/multimineral), but this does not necessarily make it better and certainly not safer — although, fortunately, it does not exceed ULs. Most Americans are not deficient in the vitamins and minerals provided in higher amounts in Daily Essential Nutrients. For instance, Daily Essential Nutrients contains more than 5 times as much vitamin E as Kirkland, but vitamin E deficiency affects less than 1% adults in the U.S.

Most striking is the difference in cost between these products: Kirkland costs about 4 cents per day ($19.99 for 500 daily tablets). Daily Essential Nutrients costs about $1.50 per day ($44.95 for 30 daily servings of 4 capsules).

Daily Essential Nutrients claims to be "clinical strength." The significance of this is not clear, but the term may relate to the fact that an iteration of the product was used in at least two small clinical trials that suggested modest and limited benefits in people with ADHD (Rucklidge, J Child Psychol Psychiatry 2018) and for people trying to quit smoking (Reihana, Nicotine Tob Res 2019). On the other hand, a study among adults (average age 38) with self-reported symptoms of anxiety and depression showed that taking 4 capsules (a suggested serving) of Daily Essential Nutrients three times daily for 10 weeks did not increase the percentage of participants who achieved clinically significant improvements compared to placebo. Those in the supplement group appeared to improve more quickly than the placebo group but were also more likely to report diarrhea (Blampied, J Affect Disord 2023).

A potential advantage of Daily Essential Nutrients relates to magnesium. Kirkland provides 100 mg as magnesium oxide, which is not absorbed as well as chelated forms, such as magnesium bisglycinate chelate, or magnesium citrate, and is more likely to have a laxative effect. Daily Essentials Nutrients provides 200 mg of magnesium in a chelated form, although it does not specify the type of chelate. The label only says that the magnesium is part of a "chelation complex" — as are all of the other minerals in the supplement. Is this worth the extra cost of Daily Essential Nutrients? Probably not. ConsumerLab has found that you can get 200 mg of high-quality magnesium as magnesium citrate from a supplement for as little as 8 cents.

Interestingly, Daily Essential Nutrients provides only 4.6 mg of iron, which is only about half the recommended daily allowance for men and older women (8 mg) and much lower than the requirements for women under 51 (18 mg) or who are pregnant (27 mg). In contrast, Kirkland provides 18 mg — which is more than needed by older adults need but appropriate for younger women and adolescents. Daily Essential Nutrients also provides less iodine than Kirkland (45% vs. 100% of the Daily Value), although it does provide a small amount of choline, while Kirkland has none.

Comparison of Vitamins and Minerals in Kirkland Signature Daily Multi versus Daily Essential Nutrients