Arsenic,Cadmium,Lead,and Mercury in Lactation Foods and Prenatal Vitamins: Potentially Avoidable Exposure for Breastfeeding Mothers and Infants

Abstract

Background:

Human milk is a biofluid that can contain heavy metals such as arsenic, cadmium, lead, and mercury. These toxins can adversely affect endocrine, respiratory, immune, and nervous systems. Infants may have higher dietary arsenic exposure than adults due to their more restricted diets and greater intake per unit body mass. We identified commonly purchased vitamins, lactation bars, and supplements, to measure the concentration of heavy metals. The goal of the study was to measure and determine if vitamins and lactation foods could be a source of exposure.

Methods:

We tested 9 popular vitamins and 16 lactation bars and supplements all marketed toward breastfeeding mothers to determine the presence of heavy metals. All vitamins, bars, and supplements were analyzed using inductively coupled plasma mass spectrometry, for the total concentration of arsenic, mercury, cadmium, and lead, with the lowest detection limit of 0.001 μg/L.

Results:

The majority of the samples had total arsenic levels below detectable quantities (detection limit of 1 part per trillion [0.001 μg/L]), one sample of syrup had a concentration of 0.112 ± 0.005, 0.132 ± 0.009, and 0.108 ± 0.010 μg of arsenic/g. We also tested nine popular prenatal vitamins for the amount of arsenic in one serving of vitamins per day and showed exposure to arsenic in one vitamin of 7.108 μg of arsenic/day. All lactation foods and vitamins tested had undetectable amounts of cadmium, mercury, and lead.

Conclusion:

Most of the vitamins and bars that were tested had below the detectable limit of arsenic, cadmium, lead, and mercury; we did find one vitamin and one rice syrup that had significantly higher levels. Our data suggest that it is highly feasible to manufacture vitamins and lactation foods and supplements with significantly lower concentrations of heavy metals.

Introduction

Arsenic is a ubiquitous potent metalloid that can easily contaminate and disperse through water, enabling exposures from soil, groundwater, and crops.¹ Arsenic exists in organic and inorganic forms. The organic forms of arsenic are not harmful²; however, the inorganic forms are both known toxins and carcinogens that adversely affect cardiac, respiratory, endocrine, immune, and nervous systems.³ Arsenic is ranked as one of the most common toxic compounds found in everyday life⁴ and animal studies show a greater risk of lung, bladder, kidney, and skin cancer in addition to increased fetal mortality, decreased birth weights, and diminished cognitive functioning.^5–8

Arsenic contaminated water used for irrigation results in the bioaccumulation of arsenic in edible plants, crops, and grains.⁹ Children and infants are more vulnerable to arsenic exposure because their intake per unit body mass is larger, and they have less varied diets.^6,10 Not only are infants particularly sensitive to toxins as they absorb metals to a higher extent than adults, they are less capable of detoxifying their bodies as their liver has not matured.^5,11–13

The AAP, CDC, and WHO all recommend exclusive breastfeeding for the first 6 months of life and ideally until age 1 or beyond as long as the mother and infant are willing.^14–16 Lactating women are often advised by their health care providers to increase their caloric intake during breastfeeding¹⁷ and to take prenatal and postnatal vitamins.¹⁸ Many lactating mothers also search for foods, snacks, and supplements to increase their milk supply.¹⁹ Awareness of potential fetal arsenic exposure in utero and during lactation is essential to identify sources and potentially reduce exposure.

Inorganic arsenic metabolites are thought to cross the placenta and exert epigenetic effects by methylation of DNA, which may silence the expression of specific gene sequences.^5,20 A meta-analysis showed a positive correlation between total arsenic concentrations in food, water, and breast milk levels.^7,21 One animal study showed that gradually increasing the arsenic concentration in drinking water in a sample of pregnant and breastfeeding rats led to proportionally increased concentrations of inorganic arsenic metabolites such as dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA) in the breast milk of the mother rats and the brains and livers of the pups.⁸ Furthermore, a separate study measuring the concentration of arsenic metabolites in the urine of Bangladeshi breastfed infants showed that arsenic levels consistently increased in the infant's urine and mother's breast milk as maternal arsenic exposure increased.^7,12 Maternal dietary intake of arsenic influences the breast milk arsenic concentration and subsequent health of the breastfed infant.²²

The exact mechanism of transfer of arsenic and its metabolites to the mammary glands and breast milk is unclear.^22,23 The ability to identify and limit the concentration of toxins and carcinogens is crucial for the development and health of infants. One concern is the high concentration of total arsenic in organic brown rice syrups and its common use as a sweetener in prepared foods as an alternative to high-fructose corn syrup.²⁴

We quantify the potential arsenic exposure to nursing mothers by testing popular prenatal vitamins marketed toward lactating mothers and measuring total arsenic, cadmium, mercury, and lead in common foods used for lactation support. Our goal was to see if commonly purchased vitamins and foods by lactating mothers could be a source of additional heavy metal exposure to the lactating mother and consequently add to exposure of toxins to developing infants.

Methods

Nine popular prenatal vitamins and 16 commonly purchased lactation supplements were purchased online through Amazon (Tables 1 and 2, respectively). Inductively coupled plasma mass spectrometry (ICP-MS, NexION 2000; PerkinElmer) analysis was performed to detect heavy metals (e.g., arsenic, mercury, lead, and cadmium) in the vitamins and foods. All samples were used as received without further purification or modification. Each sample is transferred to a clean Teflon vessel for acid digestion. Digestion was carried out with a mixture of concentrated HNO₃ (65–70%, Trace Metal Grade; Fisher Scientific) and H₂O₂ (30%, Certified ACS; Fisher Scientific) at 200°C for 45 minutes in a microwave digestion system (Titan MPS; PerkinElmer). Once the sample was cooled to room temperature, it was subsequently diluted to make a final volume of 50 mL by adding filtered deionized water for analysis. The calibration curve was established using a standard solution while the dwell time was 50 mseconds with 30 sweeps and 3 replicates with background correction.

Table 1.

Daily Amount of Arsenic Exposure in Commonly Purchased Prenatal Vitamins

Sample				Arsenic (mg/kg)		Cadmium (mg/kg)		Lead (mg/kg)		Mercury (mg/kg)		Arsenic		Cadmium		Lead		Mercury
Sample				Arsenic (mg/kg)		Cadmium (mg/kg)		Lead (mg/kg)		Mercury (mg/kg)		Estimated maximum daily exposure from consumption (μg/day)
Sample No.	Manufacturer	Product name	Type	Average^*	SD	Average^*	SD	Average^*	SD	Average^*	SD	Average^*	SD	Average^*	SD	Average^*	SD	Average^*	SD
1	VitaFusion	1 First Response Multivitamin PreNatal & PostNatal	Gummies	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
2	IWI	Vegan Prenatal Multivitamin+DHA	Softgel	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
3	Nature Made	Prenatal Multi+DHA		n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
4	Nature's Bounty	Prenatal Multi Healthy Mom		n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
5	Nature's Way	Alive! Prenatal Multi-Vitamin with Plant DHA		n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
6	GNC	Women's Prenatal Formula without Iron	Caplet	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
7	Garden of Life	Mykind Organics Women's Once Daily Whole Food Multivitamin	Tablet	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
8	Nature's Products	Rainbow Light Prenatal One		3.843	0.031	n/d	n/d	n/d	n/d	n/d	n/d	7.108	0.057	n/d	n/d	n/d	n/d	n/d	n/d
9	Target Corporation	Up&Up Prenantal Vitamins		n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d

n/d at a level of 0.001 μg/L.

Sample measured in triplicate with background correction.

n/d, not detectible; SD, standard deviation.

Table 2.

Commonly Purchased Lactation Bars and Snacks Tested for Heavy Metals

Sample					Arsenic (μg/g)		Cadmium (μg/g)		Lead (μg/g)		Mercury (μg/g)
Sample No.	Manufacturer	Product name	Flavor	Replicates	Average^*	SD	Average^*	SD	Average^*	SD	Average^*	SD
1	Upspring Milk Flow	Supplement Drink	Chocolate	1	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
2				2	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
3				3	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
1	Bob's Red Mill	White Rice Flour	NA	1	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
2				2	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
3				3	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
1		Brown Rice Flour	NA	1	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
2				2	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
3				3	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
1	Kroger	Long Grain Brown Rice	NA	1	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
2				2	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
3				3	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
1	Rauyeed	Brown Rice Syrup	NA	1	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
2				2	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
3				3	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
1	Lundberg	Organic Brown Rice Syrup	NA	1	0.112	0.005	n/d	n/d	n/d	n/d	n/d	n/d
2				2	0.132	0.009	n/d	n/d	n/d	n/d	n/d	n/d
3				3	0.108	0.010	n/d	n/d	n/d	n/d	n/d	n/d
1	Milkful	Lactation Oat Bar	Maple Walnut	1	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
2				2	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
3				3	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
1		Lactation Oat Bar	Blueberry Almond Coconut	1	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
2				2	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
3				3	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
1		Lactation Oat Bar	Chocolate Banana Nut	1	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
2				2	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
3				3	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
1	Traditional Medicinals	Herbal Supplement Bar	Honey Cashew Crisp	1	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
2				2	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
3				3	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
1	Munchkin Milkmakers	Lactation Cookie Bites	Oatmeal Raisin	1	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
2				2	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
3				3	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
1		Lactation Cookie Bites	Chocolate Chip	1	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
2				2	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
3				3	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
1		Lactation Bar	Mix Berry	1	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
2				2	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
3				3	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
1		Lactation Bar	Chocolate Chip	1	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
2				2	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
3				3	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
1	Upspring Milk Flow	Lactation Cookie	Oatmeal Raisin	1	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
2				2	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
3				3	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
1			Double Chocolate Chip	1	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
2				2	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d
3				3	n/d	n/d	n/d	n/d	n/d	n/d	n/d	n/d

Results

We tested nine popular prenatal vitamins for the amount of arsenic in one serving of vitamins per day (Table 1). None of the vitamins had any measurable amount of cadmium, lead, or mercury. The detection limit was 1 part per trillion (0.001 μg/L). Our analyses did show a daily exposure to arsenic in the Rainbow Light Prenatal One by the Nature's Products at 7.108 μg of arsenic/day.

We also tested 16 commonly consumed lactation bars, bites, and cookies by breastfeeding women for the total concentration of arsenic, cadmium, lead, and mercury (Table 2). None of the samples had measurable levels of cadmium, mercury, or lead. The detection limit was 1 part per trillion (0.001 μg/L). Although the majority of the samples had total arsenic levels below detectable quantities (detection limit of 1 part per trillion [0.001 μg/L]), one sample of Lundberg's Organic Brown Rice Syrup had a concentration of 0.112 ± 0.005, 0.132 ± 0.009, and 0.108 ± 0.010 (μg of arsenic/g of syrup) when measured in triplicate.

Discussion

The concentration of arsenic in this syrup is close to the maximum allowed in food as established by China (0.15 μg/g) and the United States rice food inorganic arsenic limitation (0.1 μg/g), yet this product is marketed to a sensitive population of lactating women who could expose their infant to toxic levels of arsenic through breast milk.²⁴ Several countries have published established toxicant limits in supplements per day. Both the WHO and European Union recommend a daily arsenic exposure in supplements of <12.85 μg/day for an average adult weighing 60 kg.^24,25

Although the literature suggests a correlation between dietary arsenic intake, maternal concentration, and breast milk levels, numerous studies have concluded that arsenic in water does not easily enter the mammary glands from the maternal bloodstream.²⁶ Moreover, some scientists propose an evolutionary adaptation whereby the infant is protected from arsenic exposure in breast milk by the mammary glands increased methylation and inactivation of toxic arsenic derivatives during pregnancy and lactation.^22,27 It should be noted that these studies looked at arsenic exposure only based on water intake. First, these studies suggest a limited transfer of arsenic to breast milk only focused on water-based maternal intake of arsenic and did not include dietary sources such as foods and vitamins. Despite the limited transfer of arsenic into breast milk, more than half of the infants in another study documenting the amount of arsenic in samples of breast milk from lactating women were exposed to detectable arsenic quantities through breastfeeding.²⁷ Thus, these limitations suggest that a study of arsenic levels in lactation foods and prenatal vitamins provided to women is necessary to ascertain the subsequent effect on arsenic levels in their breast milk.

Another concern regarding the potential effects of maternal consumption of lactation foods with rice ingredients from areas with high arsenic levels on breast milk arsenic concentration is that the FDA does not establish a set limit on the amount of arsenic adults should consume.²⁸ The FDA monitors and regulates levels of arsenic in rice and rice products; however, there are no published allowable limits of arsenic in adult foods. Instead, the FDA tests arsenic levels in food eaten directly by infants such as rice products, apple juice, and bottled water.²⁸ In other words, there are currently no U.S. regulations regarding arsenic concentrations in adult food supplies.²⁹ Unfortunately, an important source of exposure to inorganic arsenic derivatives (more toxic than organic arsenic) is from food grown in areas that use arsenic-contaminated groundwater for crop irrigation.⁷ Rice is typically grown in these environments and is notoriously high in arsenic, including in infant rice cereal products.²⁹ These foods may contribute to unusually high arsenic levels in breast milk because brown rice syrup, the main ingredient in the lactation foods being studied, contains more arsenic per grain since the outer hull that is not stripped off stores of arsenic through contaminated groundwater as the crop grows.³⁰

Our findings are concerning as just one serving of the “Rainbow Light Prenatal One” vitamin already exceeds half the maximal recommended amount of daily arsenic and Lundberg's Organic Brown Rice Syrup is close to the maximum recommended daily intake amount. These products in combination with foods containing organic rice syrup, for example, can lead to extremely high levels of arsenic in maternal blood and potentially harmful levels in breast milk.

One limitation of our study is that we did not account for individuals consuming vitamins in combination with lactation foods, which could result in higher levels of arsenic exposure. Finally, our findings are also limited by measuring total arsenic and not distinguishing between inorganic and organic arsenic species.

Our data suggest that it is feasible to manufacture vitamins and lactation foods and supplements with less than one part per trillion concentrations of arsenic, lead, cadmium, and mercury, and we recommend further studies investigating the manufacturing process and regulations. We also recommend further longitudinal studies looking at the long-term effects on low-dose arsenic exposure in infancy over time and its effects on development, behavior, and cognition correlating pregnant and breastfeeding mother's dietary intake with serum concentrations and breast milk levels.

Footnotes

Acknowledgment

The authors acknowledge the use of ICP-MS facility within the UC Center for Environmental Implications of Nanotechnology in CNSI at UCLA.

Disclosure Statement

No competing financial interests exist.

Funding Information

No funding was received.

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