Taipei, June 11 (CNA) Collagen, a naturally occurring animal protein that is believed to be good for human skin, is difficult for human bodies to absorb and excessive consumption may lead to kidney problems or high cholesterol, doctors said Monday.
Hsiao Tun-jen, a doctor who operates a gastroenterology clinic in Jhongli City, Taoyuan and is renowned for weight-loss treatment, said that only collagen with a molecular weight of under 3,000 daltons can be absorbed by human body when taken orally.
However, the molecular weight of collagen in products found in the market is usually higher than 300,000 daltons, he said.
The doctor said studies in Japan have found that collagen between 950 and 1,500 daltons can be absorbed through skin. He did not specify the research he quoted.
Most cosmetic products that contain collagen, such as facial creams or eye gels, comprise collagen of larger molecular units and thus can only be absorbed by the epidermis but not by the dermis, where it actually takes effect and can help reduce signs of aging, Hsiao added.
The amount of collagen, which accounts for one third of protein in a human body, reduces as people age, said Chen Jiun-rong, chair of the School of Nutrition and Health Sciences at Taipei Medical University.
He said some people believe that eating chicken's feet, pig skin or shark fin can increase the amount of collagen in their bodies, but the protein from those food items is of a lesser quality and excessive consumption can lead to kidney problems and/or higher fat and cholesterol levels.
Cosmetic products containing collagen cannot help reduce wrinkles but do have a moisturizing effect on the skin, Chen said.
By eating protein and vitamin C and taking regular exercise, people can help their bodies produce collagen, he added.
(By Lung Jui-yun and Jamie Wang)