Hey all! I honestly can’t believe Monday has rolled around so fast! The last week of lectures just wrapped up and now it’s study time as exams start next week. Eeek! So as you can probably imagine I’m slightly stressed, definitely tired, but still very much pumped for today’s post
Today I wanted to talk tuna with all you, so I suggest we start at the very beginning…
If you are a fitness fanatic like me, canned tuna is probably in your repertoire of foods that you eat quite often. It’s cheap, convenient, low in fat, and even comes in yummy flavours. For a good year I’d say I had a can a day habit. Whether it be on a salad at lunch, or with some crackers as a snack, tins of tuna always made a regular appearance on my plate. And I thought nothing of it. I was in the mindset of fish being a healthy addition to my diet, but I was unaware of the hidden dangers lurking in those tins – Mercury.
Mercury occurs naturally in the environment and tends to accumulate in the aquatic food chain, as methylmercury. This is because mercury from the ocean sediment is transformed into methylmercury by microorganisms. The mercury is then absorbed by fish through their gills as they swim, and digestive tract as they eat. So it’s not just Tuna that is affected! All fish will have some level of mercury in them, but the exact amount can vary between species and regions. As a general rule of thumb, the bigger the fish, the more mercury it is likely to have.
But what does methylmercury actually do and why is it harmful to us?
When ingested, methylmercury is completely and readily absorbed in the gut. From here it binds strongly to proteins, and amino acids, such as cysteine. The body mistakes this methylmercury and cysteine complex to be the familiar essential amino acid, methionine. Because of this, the molecule is freely transported across the body, and even goes through the blood-brain barrier, and can lead to damaging effects. Mercury also takes a long time to break down in the body (it has a half life of about 50 days), so accumulation and toxicity is possible.
Symptoms of toxicity are often hard to differentiate from other disease states, but some signs include:
- impairment of the peripheral vision;
- disturbances in sensations (“pins and needles” feelings, usually in the hands, feet, and around the mouth);
- lack of coordination of movements;
- impairment of speech, hearing, and walking;
- and muscle weakness