Every cell in your body depends on your thyroid gland to function
properly. Specifically, your cells use the hormones produced by your
thyroid to regulate a range of metabolic processes, including getting
energy from the food you eat.
Your thyroid hormones also help
regulate your body temperature and play a role in the proper functioning
of your brain, heart, muscles and other organs. When working properly,
your pituitary gland will release thyroid-stimulating hormone (TSH),
triggering your thyroid to produce the thyroid hormone thyroxine (T4),
which is then converted into triiodothyronine (T3), in the precise
amounts your body needs to thrive.
However, this is a very
delicate system, one that is easily disrupted by outside influences,
including the chemicals that are ubiquitous in our environment. This is
one prominent factor that is increasingly being linked to disruptions of
the thyroid, disruptions that can seriously impact your health.
What Types of Chemicals Can Disrupt Your Thyroid?
There are concerns regarding numerous chemicals that are currently abundant in the environment.
Nine of the chief offenders include:
1. Phthalates
Phthalates
are widely used chemicals often used to make plastic flexible. They're
commonly found in shower curtains, medical tubing and plastic toys, as
well as in numerous personal care products such as fragrances, nail
polish and lotions. Because the chemicals are so widely used, they're
also present in drinking water supplies.
Known to cause
reproductive and developmental toxicity in animal studies, phthalates
can also impact thyroid regulation by decreasing thyroid hormone
receptor activity -- at levels found in drinking water.[1] Currently,
drinking water treatments do not effectively remove thyroid-disrupting
chemicals like phthalates from your drinking water.
2. Flame Retardants
Polybrominated
diphenyl ether (PBDE) are flame retardant chemicals commonly used in
furniture foam, carpets, upholstery, clothing, toys, draperies,
electronics and more. It's estimated that up to 97 percent of Americans
have PBDEs in their blood.
The chemicals easily accumulate in your
fat cells, and increased levels have been linked to a decrease in TSH
levels and an increased risk of subclinical hyperthyroidism in pregnant
women.[2]
3. Bisphenol A (BPA)
BPA is
another plastics chemical commonly used in polycarbonate water bottles,
baby bottles, plastic toys, medical tubing, food packaging, dental
sealants and more. Widely known as an endocrine disrupter that can cause
developmental problems, early puberty, genital deformities and more,
BPA has also been linked to thyroid disruption.
In one study on
frog tadpoles, low levels of BPA exposure -- similar to those found in
human infants -- interfered with the T3 hormone and thereby suppressed
genes controlled by T3, resulting in slowed development and other
changes.[3] Previous animal studies have also linked BPA to disruptions
in thyroid receptors and thyroid function.
4. Dioxin
Dioxin
is a group of chemicals -- including polychlorinated biphenyls (PCBs),
polychlorinated dibenzo dioxins (PCDDs), and polychlorinated dibenzo
furans (PCDFs) -- that are formed as byproducts from industrial
processes like chlorine paper bleaching, pesticide manufacturing and
smelting. Dioxin was also a part of the toxic Agent Orange used during
the Vietnam War.
PCBs, another type of dioxin, were widely used
prior to 1977 when they were banned due to environmental concerns.
However, they and other dioxins still exist in abundance in the
environment, including in your food (especially meat, dairy and
seafood).
Not only is dioxin a known carcinogen, but it also has
been found to interfere with the production, transportation, and
metabolism of thyroid hormones.[4]
5. Perfluorinated Chemicals (PFOA)
PFOA
and a related chemical called PFOS (perfluorooctane sulfonate) --
widely used in nonstick cookware, stain-resistant materials and food
packaging -- can also cause trouble with your thyroid.
One study
found that people with high levels of PFOA in their blood were twice as
likely to have thyroid problems as those with the lowest levels[5] while
past studies have also linked the chemical to decreased thyroid hormone
levels. It's not known how PFOA may cause thyroid disease, or whether
the chemical directly impacts the thyroid or instead the immune system,
causing it to attack the thyroid gland.
6. Fluoride
Most
municipal drinking water supplies in the United States contain added
fluoride, a measure that's intended to reduce rates of tooth decay. It
can also enter water supplies from fluoride-containing rocks and soils.
Studies
have shown that exposure to fluoride can result in decreased thyroid
function, including at exposure levels of 4 mg/L or less, which is the
EPA maximum allowable concentration for fluoride in drinking water.[6]
The effects may be especially problematic for children and people who
drink a lot of water.
7. Perchlorate
Perchlorate
is a byproduct of rocket fuel production that is now a widespread
contaminant in drinking water, certain fruits and vegetables and dairy
products from cows that eat contaminated grasses.
Research
suggests it can inhibit your thyorid's ability to absorb iodine, leading
to an underactive thyroid, or hypothyroidism, even at low-level
exposure. In a study by the Centers for Disease Control and Prevention,
it was estimated that 44 million U.S. women -- including those who are
pregnant, have lower iodine levels or have subclinical hypothyroidism --
could be at increased risk of thyroid problems from perchlorate
exposure.[7]
8. Thiocyanate
Thiocyanate is a
chemical found in cigarettes and certain foods. It may inhibit iodine
uptake by the thyroid, leading to decreased production of thyroid
hormone.
9. Pesticides
Thyroid disease has
also been linked to pesticide exposure from a variety of sources. Among
women whose spouses were licensed pesticide applicators that had used
organoclorine insecticides, rates of hypothyroidism were 1.2 times
higher than in the general population. Increased rates of thyroid
disease were also found among women exposed to fungus killers, herb
killers and other types of pesticides.[8]
How to Reduce Your Exposure to Thyroid-Disrupting Chemicals
Chemicals
are ubiquitous in our environment, but there are steps you can take to
help cut back on your exposure. Some of the top suggestions include:
- Use natural personal care products with ingredients you are familiar with. At the very least look for phthalate-free options.
- Buy children's toys made of natural materials, or at least phthalate-free plastic.
- Avoid exposure to old carpeting and carpet pads and polyurethane foam products (upholstered furniture, mattresses, pillows) manufactured prior to 2005 (these are most likely to contain PBDEs).
- Store your food and beverages in glass or ceramic containers instead of plastic, and do not reheat foods in plastic containers or covered in plastic wrap.
- Limit your use of canned goods and soda cans (the linings often include BPA), or look for BPA-free canned items.
- Trim the fat from your meats to cut back on dioxins stored in animal fats, and choose leaner cuts of meat.
- Avoid polyvinyl chloride (PVC) plastics, such as plastic milk jugs.
- Look for unbleached sources of household products like coffee filters, tampons, diapers, paper towels, etc.
- Avoid using non-stick cookware, opting for stainless steel, ceramic, or other inert materials instead.
- Install a reverse osmosis water filtration system in your home to remove fluoride from your drinking water, and consider a comprehensive filter to also remove other chemicals like perchlorate.
- Avoid smoking cigarettes and exposure to second-hand smoke.
- Choose organic foods as much as possible to limit your exposure to pesticides. Also, do not use the chemicals around your home (including chemical lice treatments and flea and tick products for pets).
With the evidence increasingly showing that exposure to
environmental chemicals, even at low levels, can negatively impact your
thyroid, and the knowledge that even small changes in your thyroid
homeostasis can influence your health, it's important to reduce your
exposure as much as possible.
By making small changes in your food
choices and your personal care products and paying special attention to
finding household goods made from primarily natural sources, you'll be
off to a great start in protecting your thyroid function from these
pervasive toxins.
References
1. Environmental Science and Technology 2010, 44 (17), pp 6863-6868
2. Environmental Health Perspectives October 2010, 118(10)
3. Endocrinology Vol. 150, No. 6 2964-2973
4. Alternative Medicine Review 2009 Dec;14(4):326-46
5. Environmental Health Perspectives 118(5) May 2010
6.
Committee on Fluoride in Drinking Water, National Research Council,
Fluoride in Drinking Water: A Scientific Review of EPA's Standards, 2006
7. Environmental Working Group News Release October 4, 2006
8. American Journal of Epidemiology (2010) 171 (4): 455-464
