Chemical compound BPA, present in can linings, can affect the reproductive, hormonal activities in the body.

During festive seasons, it is not uncommon for many to reach out for their favourite canned drinks and down cans of beverages in larger quantities as inhibitions disappear and the usual caution is thrown to the wind. While many assume that consumption of readily available canned drinks are safe, there is nevertheless a lingering doubt on the wisdom of this habitual pursuit in the minds of the health conscious individuals.

A 2015 paper published by Korean researchers in the Hypertension journal examined the impact of habitual consumption of canned drinks. The inner coating of cans has a layer of epoxy resin of which one of the components is a chemical compound known as Bisphenol A (BPA). BPA has been used an agent to harden plastics. In addition to can linings, BPA is found in plastic bottles, plastic food containers and dental sealants.  Hence, it is not surprising that in developed countries like the United States (US), BPA is detected in more than 95% of the population.

Contaminating food

There have been studies that have shown that the BPA present in the epoxy lining of the cans can leach into the food contents in the can. A randomized crossover trial by researchers led by Carwile, published in the Journal of the American Medical Association in 2011, showed that eating canned soup for 5 consecutive days increased the BPA levels in the urine by more than 1000% as compared with consumption of freshly cooked soup.

The 2008 US Food and Drug Administration (FDA) report on BPA also stated that BPA levels were 10 fold higher when baby milk bottles were thermally sterilised as compared to usage of plastic milk bottles which were not thermally sterilised. Hence, it appears that BPA may leach out of plastic coatings more readily when the plastic is subject to higher temperatures.

Potential adverse health impact

Epidemiological studies have reported an association between BPA exposure and adverse health risks BPA has an affinity for the same sites in the body where the female hormone, estrogen, binds to enable the hormone to exert its effect. By attaching itself to the same sites in the body where estrogen is usually attached, it can alter or mimic the actions of estrogen. Hence, it can affect the reproductive and hormonal activities in the body.

These binding sites for estrogen in the body are also thought to have an impact on blood pressure. Hence, it is not surprising that a 2012 study on the data from the US National Health and Nutrition Examination Survey published in the Journal of Environmental Public Health, reported that increased concentration of BPA in the urine was associated with high blood pressure.

The US Food and Drug Administration (FDA) report on the Draft Assessment of Bisphenol A for Use in Food Contact Applications, 2008, and the   Scientific Peer-Review of the Draft Assessment of Bisphenol A for Use in Food Contact Applications, 2008, summarised the evidence on the impact of BPA on health. The reports also made reference to the hormonal impact of BPA in the young, its effects on brain development and behaviour and cancer risk, especially in babies and the young. Most of the data on the impact of BPA on health were from animal studies.

Unlike the majority of the previous animal studies, this recently published 2015 randomised study by the Korean researchers on humans examined whether the increase in BPA levels resulting from consuming canned beverage affect blood pressure. Those who consumed the same beverage from 2 cans had elevation of the BPA levels in the urine by more than 1600% when compared to the BPA levels in the urine when they consumed the same beverage from 2 glass bottles. There was also an elevation of the upper or systolic blood pressure by about 4.5 mm Hg. What the study demonstrated was that consumption of canned beverages can cause a sudden increase in the blood pressure.

It also reinforces the belief that some of the findings seen in animal studies on BPA exposure may also be seen in humans. In 2010, the US FDA changed its stance on BPA from one that considered that BPA was safe to one that expressed “some concern” about the potential effects of BPA on the brain, behaviour, and prostate glands in foetuses and the young. This current 2015 study adds to the growing body of evidence that excessive BPA exposure can be harmful to health.

Calorie extravaganza

Beyond BPA, canned beverages often contain high levels of sugar. Many canned or packaged fruit drinks contain 8 to 10 teaspoons of sugar per 330 millilitres (serving per can) including soursop, apple, pineapple, mixed fruit, water chestnut, blackcurrant juices, calamansi. Canned drinks containing grapes may even exceed 10 teaspoons of sugar per can serving. Soft drinks such as Coke drinks and Sprite are within the range of 8 to 10 teaspoons of sugar per can serving. Data from the American Heart Association has shown that average calorie intake has increased by an average of up to 300 calories per day in the last 30 years and about half of this additional calorie consumption comes from consumption of sugar sweetened beverages. Excessive sugar consumption leads to many adverse outcomes including obesity and the complications that accompany it.

Be prudent

The next time you go to the supermarket, reach for a glass bottled drink instead of a canned one or one that is stored in plastic container. If your favourite beverage only comes in a canned version, be prudent in your consumption.  Do not be misled to believe that drinking a canned fruit juice from a well known brand is a healthy choice – well known brands with fruit juices often have high calorie content. Scrutinise the label carefully and check the sugar and calorie content; one teaspoon of sugar is equivalent to 16 calories of energy. Check the source and production date of your canned product.  If your canned beverage or canned food is likely to have been exposed to heat as a result of a long period of transportation via containers or have been on the shelf for a long period after the production date, it may be possible that more BPA may have leached out from the can lining into the beverage or food product. Finally for those who are pregnant or have young children, avoiding exposure to BPA goes beyond milk bottles. Avoid buying food packed in cans or plastic containers for pregnant women, babies and young children – food cooked from fresh ingredients are the best choices for pregnant mothers and babies.