Study: Potato protein might help women maintain muscle

Researchers from McMaster University in Canada have found that the potato, primarily known as a starchy vegetable, can be a source of high-quality protein that helps to maintain muscle.

The findings, reported in the journal Nutrients, highlight the potential benefits of what is considered a non-traditional source of protein, particularly as dietary trends change and worldwide demand has increased for plant-based alternatives to animal-derived sources.

“While the amount of protein found in a potato is small, we grow lots of potatoes and the protein, when isolated, it can provide some measurable benefits,” says Sara Oikawa, a former graduate student in the Department of Kinesiology at McMaster and lead author of the research paper. The Hamilton, Ontario university is guided by the Okanagan Charter, which provides a framework for colleges and universities "to promote the importance of health and well-being" through its campus culture as well as local and global collaboration.

The researchers recruited young women in their early twenties who consumed diets containing protein at the recommended dietary allowance (RDA) of 0.8 grams of protein per kilogram of weight each day—approximately 60 grams of protein for the average woman or 70 grams for the average man.

The recruits were between the ages of 18 and 29 years old, with a median age of 21 years. None smoked or had diabetes; they were active, but did not participate in 150 minutes per week of moderate exercises. Sixteen of the 24 participants reported that they use contraceptives.

Applicants who consumed vegetarian or vegan diets were excluded from the study, as were any who participated in any weekly resistance exercises; had significant weight loss or gain in the previous six months; had a history of chronic disease; or ate vegetarian or vegan diets.

One group of participants consumed additional potato protein isolate in the form of a pudding, doubling their intake of the RDA to 1.6g/kg/d.  Another group received a placebo.

The women who consumed the additional potato protein increased the rate at which their muscles made new protein, while the placebo group did not, researchers found.

“This was an interesting finding that we did not expect,” Oikawa says. “But it is one that shows the recommended daily allowance is inadequate to support maintenance of muscle in these young women.”

Perhaps more interesting, she says, was that a form of plant-derived protein, which has generally been thought to be of lower quality than animal-derived protein, can have such a beneficial effect.

To study the impact of weightlifting, the research team then instructed both groups of women to exercise only one of their legs.

“This method is a little unconventional but allows us to see the effect within the same person and not have to add more people who were exercising,” said principal investigator Stuart Phillips, a professor in the Department of Kinesiology at McMaster and a leading researcher on protein and exercise.

In the leg the women exercised, scientists did not find any extra benefits from potato protein.

“That finding, which some may find disappointing, is in line with the rather small effect that protein has compared to exercise itself,” Phillips says.  “In other words, exercise is just such a more potent stimulus for making new muscle proteins compared to protein.”

The demand for protein has risen dramatically to meet the increasing needs of the rising global population. Plant-based proteins could fill that gap.

“This study provides evidence that the quality of proteins from plants can support muscle,” says Oikawa. “I think you’ll see more work on plant-based protein sources being done.”

In addition to Oikawa and Phillips, the researchers were Ravninder Bahniwal and Changhyun Lim from McMaster University's Department of Kinesiology; Tanya Holloway of Applied Health & Community Studies, Sheridan College, Brampton, Canada; Chris McGlory of School of Kinesiology and Health Studies, Queens University, Kingston, Canada; and Steven Baker from McMaster University's Department of Neurology at the Michael DeGroote School of Medicine.

The research was funded by the Alliance for Potato Research & Education, a not-for-profit organization dedicated to understanding the nutritional value of potatoes. The organization, based in Chicago, Illinois, is funded by potato growers and potato-food manufacturers. It doesn't lobby, according to its website.

Source: McMaster University