An alarmingly large number of football players, especially in the youth sector, are using food supplements to raise their performances, FIFA says.

The ruling body's medical chief Jiri Dvorak said on Wednesday data gathered over the past decade shows 35 per cent of World Cup players use such substances and the number is up to 50 per cent at the under-17 and under-20 level.

Dvorak said many players sought no medical advice on the issue, that there was no scientific evidence food supplements enhanced performance and that possible contamination of supplements could lead to positive doping tests.

"The marketing strategies of the producers of food supplements are influencing the behaviour of footballers and athletes in general," Dvorak said.

"From different surveys we know that about 60 per cent of U-16 athletes in the USA are using nutritional supplements daily and all of them believe they will increase their performance.

"This is definitely not based upon the scientific evidence or literature, which says the opposite.

"The same scientific studies also show that 70 per cent of these young athletes do not seek adequate advice from a nutritional specialist physician ... For me as a sports physician this is not only surprising, it is alarming!"

Dvorak said not all supplements undergo quality control and that meat products in countries like Mexico and China could be contaminated with substances such as clenbuterol which speeds the growth of cattle.

An examination of urine samples after the 2011 under-17 World Cup revealed 109 of the 208 tests showed the presence of clenbuterol through contaminated meat, affecting players from 19 of the 24 participating teams.

There have also been similar cases in China.

"It is well established and proven that many of the food supplements are contaminated by prohibited substances such as anabolic steroids and other substances," Dvorak said.

"This is, of course, very dangerous because if the athlete is subject to a doping control test and is regularly using that kind of contaminated supplement, he or she can test positive for doping.