There is no religious requirement to eat certain foods in Asatru. However, some Asatruars observe personal taboos. These personal taboos are based on personal gnosis or group gnosis, which are just as valid for determining an individual person's religious path as the teachings of the wider tradition of which they are a part. There are also traditional foods and beverages associated with holidays and sacrifices to specific gods in Asatru and other heathen sects, both in the Lore and in modern practice based on personal and group gnosis.

Some modern devotees of the goddess Sif avoid buying GMO wheat or GMO corn. This is a personal or group taboo observed as an act of devotion to the grain goddess. This practice is not about what the person eats, but about what the person supports with their purchasing power. Those who follow Sif can eat whatever random grain they are given or provided. When they have the opportunity to buy wheat products or corn products with their own money and make their own purchasing decisions, they will buy non-GMO wheat and corn if it is available. If certified non-GMO wheat and corn products are not available, it is also acceptable to purchase the waste products of a bakery, factory, or store, usually termed day-olds, markdowns, bakery leftovers, outlet goods, damaged, expiring, etc. The point is not about healthy eating, it is about refusing to support the damaging agricultural practices of GMO factory farming with one's money. Monsanto may be gone as a separate company, but everything it was still exists within the agricultural economic sector.

Obviously no one honored Sif in this way in ancient times because GMOs didn't exist. This is a modern practice in response to modern environmental issues.

The main story about Sif is the story of the cutting and regrowth of her golden hair, which is a transparent agricultural metaphor. Sif represents grain. Her husband Thor is the god of thunder, storms, and therefore the rain that helps the crops grow. Thor's mother Jord is the earth herself. Most people get those associations, but the other main characters in the story are Loki and the Dwarves. When Loki cuts the hair, he is representing the farmer who cuts the grain, and thus, he stands in the place of humans in the story. However, there is a long sequence in the story in which Loki goes to another world to get new hair for Sif from those who make things. Loki is then on a shamanic journey to retrieve the ideal or soul of wheat from the otherworld and bring it back so it will grow again.

The question this brings up is, why is the fire god in the role of preparing the fields for the return of wheat? It is probable that the story of Sif's hair looks back to the very earliest days of agriculture. Early European farmers practiced slash-and-burn agriculture. Fire was a necessary part of the agricultural cycle, the part that turned death into new life. This may be how Loki became associated with human funereal cremation, in analogy to what crops go through.

Image: a basket of wheat and a representation of the goddess Sif.