Americans are on a vitamin kick to combat the coronavirus. In many grocery stores, health food stores and pharmacies — even online — there is a dearth of vitamin C and the mineral zinc, mirroring the scarcity of other pandemic-driven items like toilet paper and disinfectants.

Sales of orange juice jumped 27% in March while sales of vitamin C skyrocketed 146%. While there has been no concrete evidence that adding supplements to your diet can help boost immunity to the virus, experts say that good nutrition along with exercise and adequate sleep, form the cornerstone of a healthy immune system.

Nutritional compounds such as vitamin C, antioxidants and zinc have been touted by many experts as reasonable additions to our daily diet to boost immunity. Lona Sandon, an associate professor in the department of clinical nutrition at the University of Texas Southwestern Medical Center told the Latin Times:

“These nutrients work with our immune system and can help it function more effectively. But if you are already getting them from food, evidence and research does not promote the need to take more.”

Michael Roizen, chief wellness officer for the Cleveland Clinic, suggested splitting the vitamin dose, taking half in the morning and the other half in the evening.

“You urinate out the water-soluble components within 12 hours or so, so to keep a steady level take part in the morning and the other part at night,” he told the Times.

According to Healthline, the average adult woman requires 70 milligrams of vitamin C a day, while the average man needs 70 milligrams daily. The maximum recommended amount, or upper limit, is 2,000 milligrams per day.

If you overdose on vitamin C, the side effects could include abdominal pain, cramps, diarrhea, headaches and nausea as well as insomnia. Vitamin C supplements can also interact with heart medications and cancer treatments, according to Healthline.

Medical News Today says taking too much zinc can also be harmful. The Office of Dietary Supplements (ODS) says that women need 8 milligrams daily while men require 11 milligrams. The upper limit is 40 milligrams for adults.

Exceeding that limit can cause zinc toxicity characterized by nausea, vomiting, stomach ache, diarrhea and headaches. Over a prolonged period of time, taking too much zinc can lower the levels of HDL, or the “good’ cholesterol, decrease your immune function and create a copper deficiency.

Sandon says that the best approach is getting your vitamins through basic nutrition.

“Start with a healthy baseline diet, and if you can’t get your needs met, maybe you do need a vitamin,” she told the Latin Times.