For women who spend little time thinking about nutrition, pregnancy usually changes that. In fact, for many women, especially if they are healthy, a prenatal vitamin might be the first supplement they ever take. 

So, if you are taking a prenatal vitamin supplement to ensure the good health of your baby, then it would be very troubling to learn that supplement might contain a heavy metal, such as lead. A recent report1 published by Puremarket™ (a Colorado company that independently tests foods, supplements, and other goods) brought attention to this issue, although in truth it is not a new issue. 

Why is there lead in prenatal vitamins (and other supplements) anyway?

Virtually all risk of heavy metal contamination in supplements is associated with minerals (although we say “prenatal vitamin” most of these products contain vitamins and minerals). Minerals get their start as part of the Earth’s crust. In nature, you don’t just have piles of pure calcium or magnesium or zinc lying around – they tend to be all mixed together. And even though they are harmful, and never helpful, heavy metals are minerals, so the good and bad are naturally present together. 

In addition, minerals that have similar electrical charges tend to cluster together – meaning that heavy metals like mercury and lead tend to be found mixed together with non-toxic minerals like calcium and magnesium. For their use in foods or supplements, minerals are refined or processed in various ways. More processing tends to result in a “cleaner” product with fewer contaminants.2

It is the responsibility of the supplement manufacturer to ensure that levels of heavy metals are risk-acceptable for the ingredients being used and for the final product. Ingredients or products in excess of acceptable limits should be disposed of, although this does not always happen.

It should be understood, however, that even with the best manufacturing methods, it’s almost impossible to get rid of 100 percent of the heavy metals – although you can get pretty close.

What are the limits on lead in prenatal multi-vitamin/mineral supplements and other supplements?

The United States Pharmacopeia (USP) sets the federal limits for lead and other toxic elements (such as mercury, arsenic, and cadmium) in supplements. The USP sets two limits:  one that is acceptable for an ingredient, and one for daily intake. 

Separately, the State of California has stricter limits under the regulation knows as Proposition 65. It was the Proposition 65 limits that Puremarket used as a guideline to evaluate the products in their study.

Proposition 65 limits are significantly lower than federal guidelines, so it is often the case that supplements that are below federal limits still require a Proposition 65 warning notice when sold in California.

In fact, all of the products that were tested for lead in the Puremarket study only tested “high” relative to California’s strict Proposition 65 standard – all of the products had acceptable lead limits per federal USP guidelines.

Most often the numbers provided for defining limits of exposure are given in measures like parts per million (ppm) – which is pretty hard to relate to in daily life. The following table shows you the limits set for “safe” daily intake of various heavy metals such as lead, comparing the USP limits to California’s Proposition 65 limits.

Note that the State of California has never set a safe limit for mercury, although the limits of 0.3 mcg/day and 3.0 mcg/day for methylmercury and mercury, respectively, have been proposed by California’s Office of Environmental Health Hazard Assessment.3


USP Product Limit (mcg/day)

Prop 65 (mcg/day)

Lead

5

0.5

Cadmium

5

4.1

Arsenic

15

10

Mercury

30

Not defined


What’s the risk that lead is in prenatal vitamin supplements?

Lead is a known toxin to the developing fetus, to children, and to adults. If you want to understand your personal risk for heavy metals, you can check them easily at home. Lead can accumulate in a woman’s body and then cross the placenta, with potentially harmful effects on fetal development. Prenatal exposure to lead can have lasting adverse effects on intelligence, behavior, memory, and more.4

According to the Centers for Disease Control and Prevention,5 the biggest risk factors for exposure to lead are old paint, drinking water that comes through lead pipes, cosmetics, and workplace exposures. Traditional herbal medicines and supplements can sometimes be sources too. 

One piece of good news is that a high intake of other nutrients is actually protective – especially calcium, iron, and vitamin C. That’s right – while calcium can have some naturally occurring lead present in it, it also competes with lead for absorption and binding, and helps to keep minerals (including heavy metals like lead) from being mobilized from bone. Iron does as well,6 and possibly zinc.

So, having higher levels of these nutrients from supplements and foods helps lower overall risk. In fact, supplementing with calcium has specifically been shown to help lower blood levels of lead during pregnancy and nursing.7 

Are some prenatal vitamins “cleaner” than others?

Testing of the raw materials and further testing of finished goods is the responsibility of the supplement manufacturer. Some supplement companies take this responsibility much more seriously than others.

This is because testing for heavy metals is time consuming and costly – so it’s not uncommon for companies to take shortcuts. At Thorne, our standards aren’t industry standards — they are much higher. Thorne knows that our name stands for quality and trust – a reputation built over four decades and a reputation that we seek to protect each and every day.

For this reason, we go above and beyond, testing more than we are required to because it matters to us that our customers get the purest possible product when it comes to something they are putting in their bodies. 

What about Thorne’s prenatal supplement and lead? 

Thorne’s Basic Prenatal was not one of the products tested in the Puremarket investigation. Nevertheless, because we test our products extensively, we are confident in what they contain. Here are the heavy metal testing results from a recent batch of our Basic Prenatal vitamin supplement and how we measured up against the federal and California limits on lead:


USP Product Limit (mcg/day)

Proposition 65 (mcg/day)

Thorne’s Basic Prenatal (mcg/day)

Lead

5

0.5

0.176

Cadmium

5

4.1

0.124

Arsenic

15

10

0.096

Mercury

30

Not defined

0.006

 

As you can see, the levels consumed in one day’s use of Basic Prenatal fall far below even the strict levels set by the State of California – and not just for lead, but also for the other heavy metals as well.

Another common supplement taken by women during pregnancy is additional folate (folic acid). Folate is naturally less of a concern, because it is not a mineral, but it’s good to know Thorne’s 1 mg 5-MTHF also conforms to these strict standards.

At Thorne, product quality is our number one concern. It’s not just our reputation, it’s your health, and we truly appreciate that you trust us with your health. We know our products cost a little more than other brands, but we hope you see it as we do – as an investment. We do what we do so you can be confident about what you take – and feel better taking it. 


References

  1. Prenatal Vitamins Archives. Pure Market. https://www.puremarket.com/c/prenatal-vitamins/. Accessed January 15, 2020.
  2. Scelfo GM, Flegal AR. Lead in calcium supplements. Environ Health Perspect. 2000;108(4):309-313.
  3. Steven D. Gillett v. Madison One Acme Inc., a Company doing business as Solstice Medicine Company, 2008. https://oag.ca.gov/system/files/prop65/settlements/2007-00033S800.pdf. Accessed January 15, 2020.
  4. Shah-Kulkarni S, Ha M, Kim B, et al. Neurodevelopment in early childhood affected by prenatal lead exposure and iron intake. Medicine (Baltimore) 2016;95(4). doi:10.1097/MD.0000000000002508
  5. Health NC for E. CDC – Lead – At risk populations – pregnant women. https://www.cdc.gov/nceh/lead/prevention/pregnant.htm. Published July 31, 2019. Accessed January 15, 2020.
  6. Association between blood lead concentrations and body iron status in children | Archives of Disease in Childhood. https://adc.bmj.com/content/88/9/791. Accessed January 15, 2020.
  7. Dietary calcium supplementation to lower blood lead levels in pregnancy and lactation. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2566736/. Accessed January 15, 2020.