When respiratory virus season hits, it’s normal to want to do everything possible to support immune health. Supplements come up quickly in that conversation, but it can be hard to work out what actually helps and what is mostly hype.
Vitamin C and zinc are two of the most talked-about options. They play different roles in the body, but neither one acts like a shield against viruses. A supplement will not prevent an infection on its own. However, if a person is low in vitamin C or zinc, supplementing may help bring levels back into a healthier range, which supports normal immune function.
Experts say it helps to focus on the basics first. Food intake matters, and supplements can play a role when diet falls short. For anyone who prefers food-first options, plenty of everyday foods can lift vitamin C and zinc intake too.
What is vitamin C?
Vitamin C, also known as L-ascorbic acid, is a water-soluble vitamin that needs to come from food or supplements. The body cannot make vitamin C on its own, explains nutritionist and registered dietitian Sonya Angelone.
“Vitamin C is an antioxidant vitamin which means it helps quench harmful molecules that get generated every day through exercise, metabolism and that we are exposed to through the environment,” Angelone says. “Vitamin C is important for collagen production, wound healing and iron absorption.”
Daily needs vary by age and sex. Many adults meet vitamin C requirements through diet, but some groups tend to have lower intake. That includes people who smoke, people with a limited diet and people with certain medical conditions.
What is zinc?
Zinc is a trace mineral found in cells throughout the body. It supports many everyday functions, including immune health. “It is crucial for a healthy immune system, for wound healing, for normal taste and smell and for making new DNA,” Angelone says. Zinc also needs to come from food or supplements. “Zinc also needs to come from the diet or supplements since your body does not make or store zinc,” she adds.
Daily needs vary by age and sex. In general, most adult women need 8 to 12 milligrams of zinc per day, while most adult men need 11 milligrams.
Which is better for immune system?
Both nutrients support the immune system in different ways, so it is not a simple one-or-the-other situation.
“Some human and animal studies suggest that vitamin C may modulate the immune response,” says senior scholar Dr Amesh Adalja. That may include supporting the lifespan of T cells, a type of white blood cell involved in fighting infections. “That may translate into protection against certain viral infections,” Dr Adalja says.
“Vitamin C is really critical to optimized immune function,” says professor and chief of infectious diseases Dr Thomas Russo. “It supports all arms of the immune defenses.”
Zinc also plays a direct role in immune cell function. Dr Russo explains that zinc supports immune cells, including T cells and natural killer cells, which can help the body respond to viruses.
So which is better? Dr Russo says it is hard to separate them. “They both play independent, important roles for the immune system,” he says. “You don’t want to be deficient in either.”
For most people who already get enough vitamin C and zinc from food, experts say supplements are unlikely to add much. “If you have an adequate level of vitamin C in your diet, which most well-nourished individuals do, does boosting it with a high-dose supplement do anything? That’s where the data doesn’t exist,” Dr Russo says. “The same is true for zinc.”
Some research suggests zinc may shorten the length of a common cold and vitamin C may make symptoms feel less severe, but the overall evidence is not strong enough to treat supplements as a cure-all.
“A regular balanced diet is sufficient,” Dr Adalja says. “Not many, outside of the malnourished, are deficient in zinc or vitamin C.” Dr Russo agrees. “Taking a multivitamin with zinc and vitamin C is OK,” he says. “But with high-dose supplements, you end up urinating most of it out.”
Signs of vitamin C deficiency
Vitamin C deficiency remains uncommon, but it can happen. People who get little or no vitamin C for weeks may develop scurvy, a condition linked with fatigue, gum inflammation, purple spots on the skin, joint pain, loose teeth and anaemia.
Low vitamin C levels can also show up in subtler ways. People who run low, without being fully deficient, may notice more frequent colds and infections, Angelone says.
Signs of zinc deficiency
Zinc deficiency can affect several systems in the body. “If you’re deficient in zinc, you may struggle with loss of taste and smell, have wounds that are slow to heal and struggle with thinking, reasoning and memory,” according to Angelone.
Vitamin C drug interactions
Anyone taking prescription medicines or undergoing medical treatment should discuss supplement use with a healthcare professional. Vitamin C can interact with certain medicines, including statins and some cancer treatments, such as chemotherapy and radiation therapy.
Zinc drug interactions
Zinc can interact with certain medicines, so a quick check-in with a healthcare professional helps if supplements are on the table. Quinolone antibiotics, such as ciprofloxacin, and tetracycline antibiotics can reduce how much zinc and medicine the body absorbs. Zinc can also interfere with the absorption of penicillamine, which is used to treat rheumatoid arthritis. Thiazide diuretics may increase zinc loss in urine.
What’s the best way to get vitamin C?
Food remains the easiest way to cover vitamin C needs. These options are high in vitamin C:
- Red bell pepper, ½ cup: 95 milligrams
- Orange juice, ¾ cup: 93 milligrams
- Orange, 1 medium: 70 milligrams
- Grapefruit juice, ¾ cup: 70 milligrams
- Kiwifruit, 1 medium: 64 milligrams
- Green pepper, ½ cup: 60 milligrams
- Broccoli, ½ cup: 51 milligrams
What’s the best way to get zinc?
Zinc-rich foods include a mix of seafood, meat, dairy and seeds:
- Oysters, 3 ounces, 32 milligrams
- Bottom sirloin beef, 3 ounces, 3.8 milligrams
- Blue crab, 3 ounces, 3.2 milligrams
- Oat cereal, 1 cup, 2.3 milligrams
- Pumpkin seeds, 1 ounces, 2.2 milligrams
- Pork chops, 3 ounces, 1.9 milligrams
- Turkey breast, 3 ounces, 1.5 milligrams
- Cheddar cheese, 1.5 ounces, 1.5 milligrams
Anyone concerned about low vitamin C or zinc should check in with a healthcare professional. A blood test can help clarify where levels sit and whether supplements are needed.
Newsletter
