Flavour of the Week

Bisphenol A: Less is More, None is Better


“A new study has provided additional evidence that exposure to the chemical bisphenol A, commonly known as BPA, can increase the risk of heart disease.” The Globe and Mail

A new study by Galloway et al. corroborates what several cross-sectional studies have previously shown: higher urinary BPA (as a way to measure BPA intake) is associated, independent of other risk factors, with increased risk for heart disease (1). The UK team found that urinary BPA concentration at healthy baseline and at 10-year follow-up was higher among the 758 participants who developed heart disease as compared to the 861 men and women who remained free of heart disease; this connection persisted when other risk factors were controlled for, such as socioeconomic status, BMI, blood pressure, blood lipids and exercise.

Mounting evidence suggests that BPA may be linked to a variety of health conditions, and in 2010 Health Canada was the first country to declare BPA a toxic substance… so why is it still in our food?

What exactly is BPA? Bisphenol A, also known as BPA, is a water-insoluble organic compound discovered in the late 19th century. It is used in hard, clear plastics and food packaging (including the liners of most tin cans), as well as the print on most receipts. Initial concerns regarding the estrogen-like activity of BPA were first raised in the 1930s but it wasn’t until the late 1990s when BPA in vivo testing indicated toxic effects at doses previously thought to be “safe” (2).

Recently, BPA has been linked to altered behaviour and emotional regulation in children  exposed to BPA in utero, increased body fat in rats, reproductive issues, increased risk of hormone-dependent cancers and, now, heart disease (2-4). While more research is needed to elucidate the mechanisms, BPA has been shown to alter gene expression through several pathways including: potent endocrine disruption properties due to estrogenic properties; thyroid hormone antagonism; neurotoxicity; and carcinogenesis (2). The current maximum tolerated dose of 1,000 mg/kg body weight was set in 1987 (2), yet the provisional daily dose from Health Canada has been set at 25 mcg/kg body weight given the growing body of work supporting drastic intake reductions (5); that’s a 40,000-fold reduction! Just because it isn’t overtly toxic, doesn’t mean it’s good for you!

Water bottle manufacturers rose to the challenge in recent years, and you will be hard-pressed to find BPA plastic in any bottles now… but there are other, more stubborn, sources. So, how much BPA is still in our food? Based on work by Cao et al. (6,7), canned tuna had the highest BPA content; at 137 ng/g, that’s 16.44 mcg in a 120 g can, or 1% of provisional amount for a 65 kg woman. Tomato paste had lower BPA content than plain, canned tomatoes and canned veggies remain quite low at < 10 ng/g. Canned soft drinks contain 4.5 mcg/L, so drinking two cans of pop per day would provide 3 mcg of BPA (7). Interestingly, condensed soup contained more BPA than ready-to-serve options (6), and previous research shows that simply eating a serving of canned soup for five days can increase urinary BPA excretion by 1,000% compared to eating fresh soup daily (8).

Health Canada’s Food Directorate states that the current dietary exposure to BPA through food packaging uses is not expected to pose a health risk to the general population, including newborns and infants.” But we would rather err on the side of caution!

Given where the evidence is taking us, it seems prudent to limit BPA whenever possible. Though it’s unlikely, and possibly unneccesary, you’ll be able to eliminate absolutely all BPA from your diet, here are some tips to reduce your intake:

  • Toss any BPA containing food containers in the recycling bin! Most brands make BPA-free options now, so need to keep your toxic containers around. You can also purchase glass containers – your lunch bag will be a lot heavier, but reheating in plastic still makes us nervous…
  • Buy BPA-free canned beans. To save on sodium, you can always use dried beans. Though they do take some preparation (we suggest you keep some BPA-free canned beans in the pantry in cases of emergency), you can also cook dried beans in a slow cooker and then freezer them in BPA-free plastic bags.
  • Limit your intake of canned soups. You’ll slash your BPA intake AND your blood pressure will thank you! Look for BPA-free versions available in cans, tetrapaks and BPA-free plastic sleeves.
  • Find tomatoes in glass containers. Because of the acid content of canned tomatoes, there is really no way they can be canned with a BPA-free liner. Glass jarred options are available, but they can be pricey. Look for less expensive options at Italian markets. If you are extremely industrious, you can always can your own!

References:

  1. Melzer D et al. Urinary bisphenol A concentration and risk of future coronary arter disease in apparently healthy men and women. Circulation 2012 [epub ahead of print].
  2. Vandenberg LN, Maffini MV, Sonnenschein C, Rubin BS, Soto AM. Bisphenol A and the great divide: a review of controversies in the field of endocrine disruption. Endocrine Rev 2009; 30:75-95.
  3. Braun JM et al. Impact of early life bisphenol A exposure on behaviour and executive function in children. Pediatrics 2011; 128:873-82.
  4. Somm E et al. Perinatal exposure to bisphenol A alters early adipogenesis in the rat. Environ Health Perspect 2009; 117:1549-55.
  5. Lakind JS, Levesque J, Dumas P, Bryan S, Clarke J, Naiman DQ. Comparing United States and Canadian population exposures from National Biomonitoring Surveys: bisphenol A intake as a case study. J Expo Sci Environ Epidemiol 2012 [epub ahead of print].
  6. Cao XL, Corriveau J, Popovic S. Levels of bisphenol A in canned soft drink products in Canadian markets. J Agric Food Chem 2009; 57:1307-11.
  7. Cao XL, Corriveau J, Popovic S. Bisphenol A in canned food products from Canadian markets. J Food Prot 2010; 73:1085-9.
  8. Carwile JL, Ye X, Zhou X, Calafat AM, Michels KB. Canned soup consumption and urinary bisphenol A: a randomized crossover trial. JAMA 2011; 306:2218-20.
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4 thoughts on “Bisphenol A: Less is More, None is Better

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