Cottonseed as Protein

The white lint that is spun into cotton yarn constitutes roughly a quarter of the raw plant matter sucked into a cotton stripper. Over the years, U.S. producers have learned to squeeze maximum value out the rest, especially the seeds. For every pound of fiber, 1.6 pounds of seed are produced. Once considered garbage and dumped in streams, cottonseed has long been used as cattle feed, fertilizer, and in countless industrial applications.

Cottonseed oil comprises about 16% of a seed, by  weight; is a well-known ingredient in many processed snack foods; and is the most valuable cottonseed product. Current EPA regulations classify it as safe for human consumption after it has been refined to remove volatile compounds such as monoglycerides, some pigments, free fatty acids, fatty oxidation products, pesticide residues and other undesirable compounds.¹

Once most of the oil has been removed, the meal, the second most valuable product of cottonseed, is used principally as livestock feed. Constituting nearly half of a seed’s weight, the meal contains 23% of a high biological-value protein.

Today, nearly 10% of U.S.-produced meal goes to fish farms, where some species thrive on it. Fish farmers praise it as a cheap, highly nutritious alternative to fish meal, which is composed primarily of wild-caught marine species, the price of which continues to climb as natural fish stocks dwindle.

In October, the National Organic Standards Board voted to consider developing organic standards for some farm-raised fish species, while unanimously voting against creating national organic standards for wild-caught fish. Some argue that this could put aquaculturists at a disadvantage to the beef and poultry industries, which are now eligible for organic labeling.

But cottonseed might provide a loophole. In a recent study funded by the National Cottonseed Products Association and the Cotton Foundation, Ohio State University researchers replaced fish meal protein with cottonseed meal protein in up to 100% of the diet of rainbow trout (“Plant-Based Meal Paves Way for “Organically-Grown” Fish,” OSU Extension). The growth of the fish was unaffected by the switch, so the researchers suggest that cottonseed meal could replace fish meal as the main protein source of species such as trout, making them eligible for organic labeling.

Most fish and other non-ruminant animals, including humans, cannot eat cottonseed because it contains a toxin called gossypol. When eaten by people, this polyphenolic anti-nutrient damages the heart and liver.

For years, scientists have tried to breed cotton with gossypol levels safe for consumption. In the 1950s they succeeded, but because the toxin was missing from leaves as well as seeds, the plants proved defenseless against pests. But last November – via a new technique called RNA interference, or RNAi, a gene-silencing mechanism for which its discoverers Andrew Fire and Craig Mello won the 2006 Nobel Prize for Medicine – researchers at the Texas Agricultural Experiment Station succeeded in lowering the gossypol level in seeds while sparing the rest of the plant.

The result of this experimentation (partially funded by Cotton Incorporated) is being hailed by the cotton industry and biotechnologists as a breakthrough in the struggle against world hunger. According to Dr. Keerti Rathore², one of the Texas researchers, the current level of 44 million tons of cottonseed produced globally each year, containing 22% high-quality protein, could feed 500 million people. Studies in animals, including humans, using gossypol-free, glandless cottonseed flour, have shown that cottonseed protein promotes growth, weight gain, and a positive nitrogen balance (less N is excreted through urine, feces and sweat than is taken in). Researchers are already experimenting with lowering gossypol levels in indigenous African cotton strains, as well as employing RNAi technology on other crops with toxic components, such as fava beans.

Solution to Hunger … or Diversion?

Industry estimates put the time-to-market for low-gossypol cotton at 10 years. Scientists maintain that cotton farmers in poor countries will doubly benefit from a crop that can be sold for food (or be eaten directly) and clothing. Supporters of genetic engineering hope that the prospect of “feeding the world” with cotton will win over skeptics and change policies of those poor countries that are, so far, resisting the pressure to give in to genetically engineered (GE) crops.

Concerning cottonseed as fish meal, the problem of crashing ocean populations will put into perspective any satisfaction we derive from fish that will eat, and even thrive, on cotton’s protein. As fish meal, cottonseed might open new channels of discussion around organic food labeling, but as human food, is the science of edible cottonseed a red-herring in the real struggle to feed the world’s poor?

1. Environmental Protection Agency
40 CFR Part 185 [OPP-300335A; FRL-5357-7]
Revocation of Pesticide Food Additive Regulations

2. https://www.pnas.org/cgi/content/abstract/103/48/18054
Engineering cottonseed for use in human nutrition by tissue-specific reduction of toxic gossypol
Ganesan Sunilkumar, LeAnne M. Campbell, Lorraine Puckhaber , Robert D. Stipanovic , and Keerti S. Rathore.