Fucoxanthin is a botanical pigment that absorbs light energy necessary for plant growth. It is a xanthophyll — an oxygenated carotene, or plant pigment — that researchers are studying as a possible weight-loss treatment. Fucoxanthin is a chemical compound particularly receptive to the more yellow wavelengths of light’s green-to-blue spectrum. Plants containing it are characterized by a greenish brown or dirty yellow color.
Brown algae is an abundant class of plants, with most species living in the ocean and employing fucoxanthin for photosynthesis. The substance is sensitive to shorter wavelengths of light, so most brown algae live in shallow water. Rather than being unicellular and colonial, most brown algae are multicellular plants. Those species anchored in relatively deep ocean beds can grow to more than 160 feet (49 meters) tall.
Some coastal cultures of the world, particularly off colder waters of the Northern Hemisphere where the plants thrive, have adopted edible brown algae into their diet. The Japanese consume wakame, hijiki, and other marine algae in such quantities as to be a daily staple. Along with red and green algae, they have been collectively somewhat — and unappetizingly so — misnamed "seaweed." Seaweed is particularly rich in iron, iodine and dietary fiber.
In 2005, researchers at Hokkaido University on Japan’s northernmost island reported on an intriguing laboratory animal study that implicated fucoxanthin as an anti-obesity substance. In 1979, a substance now called uncoupling protein 1 (UCP1) was discovered in brown adipose tissue (BAT), the only mammalian tissue to undergo thermogenesis, a self-regulatory process in which excess fat is oxidized to generate heat. The bulk of abdominal fat in humans, however, is stored in white adipose tissue (WAT), and the substance had yet to be detected there.
The researchers extracted fucoxanthin from the algae wakame, or Undaria pinnatifida, and added it to the diet of mice for four weeks. The test mice measured a 10 percent loss of both overall weight and specific weight of their white adipose tissue, compared to control mice fed the same diet without fucoxanthin. The messenger RNAs within the WAT fat cells of test mice were sequenced, with positive detection that the UCP1 protein had been expressed.
A variety of dietary substances, including caffeine and beta-carotene, has been shown since 1979 to increase thermogenesis in brown adipose tissue. The presumption of biochemists, and the fervent wish of nutritional supplement companies, has been that there is, as yet undiscovered, an equivalent carotenoid for white adipose tissue. Thermogenesis is the regulatory mechanism by which bears survive winter hibernation, losing a lot of weight in the process. A substance that can induce thermogenesis in white adipose tissue would be the equivalent of ingesting a pill at night to burn away unwanted excess pounds while asleep.
Such a pill containing concentrated fucoxanthin has been created. Another available variation is a time-released skin patch. An abundance of herbal and nutritional supplements containing extracts of a variety of seaweed have come to market, offering weight-loss or weight-gain-prevention benefits. While these remedies sometimes lack rigorous testing, many users testify to their efficacy. Laboratory human studies on the metabolic and nutritional characteristics of the seaweed carotenoid fucoxanthin are ongoing.