UK/Europeans need mineral suppplements?

Use an anti mosquito cream to avoid mosquito bites.
NEVER use anti malaria tablets.
A hat is handy against the sun.
Sunblock depending upon your skin.
An ultra light poncho is handy for when it rains ... and it rains big style.

Vitamins are usually only needed when you have a bad diet, same as anywhere else in the world.

Honestly speaking, I don't think there is anything special that you need to consider as far as foods, vitamins and supplements are concerned. If you are already fairly healthy then I'd say there is absolutely nothing to worry about.

By the way, every shopping mall in KL usually has several pharmacists which apart from selling the normal stuff have large sections specialized for food supplements and vitamins. Nearly every mall also has specialist shops like GNC which specialize in selling every kind of supplement and vitamin that you could imagine. It's all available in Malaysia.

The only things that I take from time to time, depending on how motivated I am, is Glucosmine, Chondroitin and MSM for my joints. Then occasionally garlic tablets or fish oil capsules if I'm feeling particularly health conscious. And when I am really concerned about my health I take Caspirin. But most of the time I don't take anything. All of these things are pretty much what people take back home as they begin to age, and they are all readily available everywhere in KL in many different forms and combinations.

Since KL is so hot and there is airconditioning everywhere, the constant change in temperature can cause you to get flu, so consider taking Panadol CF (cold & flu). I haven't seen it in Indonesia where I currently live, but I always stock up on it when I am in KL as it works great.

Apart from that, the only other thing I can think of is using a mosquito repellent if you plan to visit parks or outdoor areas to help avoid getting Dengue Fever from bites from the Aedes Mosqioto. I've had it before and it's not very nice.