The vegan mathematician responded to one of her followers, who had tweeted her an article from The Daily Mail claiming vegan diets could lower a person's IQ due to lack of a nutrient that is critical to brain health.
Riley, who has remained plant-based during her pregnancy, replied: "Choline's in my prenatal vitamins, all fine then."
Pro-meat advocate Dr. Emma Derbyshire, a nutritional consultant who sits on the Meat Advisory Panel, made the claims in a piece published in the BMJ Nutrition, Prevention & Health journal - which has since been cited by a plethora of tabloids.
She warned that vegans may be missing out on choline, as the best dietary sources are beef, eggs, dairy products, pork, chicken and salmon. However, it can also be found in nuts, beans, and cruciferous vegetables and can be supplemented.
According to Professor Emeritus of Nutrition and Dietetics at King's College London, Tom Sanders, choline can be made in the body and is 'abundant' in many plant-based foods.
"There is no justification for suggesting that plant-based diet risk damaging brain development," Sanders said.
"My own research on vegans and those of others in Europe and USA find the growth and development of vegans and vegetarians is normal.
"The main hazard of a vegan diet with regard to neurological development is vitamin B12 deficiency which can readily be avoided by consuming food fortified with the vitamin derived from microbial sources."
The Vegan Society also addressed the current concern over choline, stating: "The leading authority on nutrition in the UK, the British Dietetic Association, shares the message that well-planned vegan diets can support healthy living in people of all ages, including children and pregnant women."