When you scrape your knee, swelling around the cut is healthy. It's the result of your immune system marshaling forces against invading germs. A swollen ankle after you sprain it is also evidence of healing.
But inside your body, where you can't see it or feel it, ongoing inflammation can trigger heart disease, cancer, diabetes, and autoimmune diseases like rheumatoid arthritis and psoriasis.
Research points to certain vitamins that have anti-inflammatory potential. Many of the studies were done with supplements, so amounts could be accurately measured and controlled. To take advantage of the possible benefits, you should start by eating foods with these vitamins. (Bonus: If you're overweight, a healthy diet can help you drop pounds, which can tame inflammation, too.)
Keep in mind that more isn't always better. Large amounts of certain vitamins can be risky. Talk to your doctor before you take a supplement.
Vitamin A
It seems to play a role in keeping your immune system from overreacting and causing inflammation. Some studies on beta-carotene point to a slower progression of rheumatoid arthritis. Not getting enough vitamin A may put you at risk for Alzheimer's disease, but research isn't firm yet.
What seems to be surer: A diet rich in beta-carotene-containing fruits and vegetables. Supplements don't seem to do the trick.
What to eat:
There are basically two forms of this vitamin -- preformed vitamin A and provitamin A -- and they have different jobs in your body.
Preformed vitamin A is in animal products, including milk, liver, and certain fortified foods. Beta-carotene, the most common type of provitamin A, is what gives orange vegetables and some fruits -- sweet potatoes, carrots, cantaloupe, papaya -- their hue. Spinach and other dark-green, leafy veggies also have a lot.
What else you need to know:
Too much vitamin A can cause liver damage and birth defects. Beta-carotene supplements have been linked to a higher chance of lung cancer in smokers, including those who've given up cigarettes.
Several weight-loss medicine orlistat (Alli, Xenical) can make it harder for your body to get vitamin A, even when you eat enough.
Some pills you take for skin problems, including acitretin (Soriatane) for psoriasis, bexarotene (Targretin) for side effects of T-cell lymphoma, isotretinoin (Absorica, Amnesteem, Claravis) for severe acne, or tretinoin (Vesanoid) for a type of leukemia, are man-made forms of vitamin A. So, do not use vitamin A supplements if you're on these medications.
B Vitamins
Vitamin B6, folate (B9), and B12 can lower your levels of homocysteine, an amino acid that's linked to a greater risk for heart disease and rheumatoid arthritis. But we can't say for sure that lowering homocysteine will also lower your risk for disease.
The same is true for C-reactive protein, a sign of inflammation. These B vitamins can bring levels of it down, but whether that cuts the risk of heart disease remains to be seen.
What to eat:
Beef liver has all three. Fish, red meat, and poultry will help with B6 and B12. Eggs are good for folate and B12. Fruits and vegetables, beans, peas, and nuts will give you B6 and folate. Milk and dairy products will boost your B12.
These vitamins are added to many breakfast cereals. Grain products like bread and pasta often have extra folic acid.
What else you need to know:
Overdoing B6 supplements can cause skin sores, a sensitivity to light, nausea, and heartburn. If you take too much for more than a year, you could have problems with your nerves and lose control of movements.
You could also get nerve damage without enough B12.
High levels of folic acid could raise some people's risk of cancer.
Some drugs lower levels of B vitamins, and sometimes a vitamin can affect how a medication works. You could have a problem with metformin for diabetes, methotrexate (Rheumatrex, Trexall) for cancer, rheumatoid arthritis, or psoriasis. Also check with your doctor if you take a prescription for seizures, asthma or lung disease, acid reflux, or a stomach ulcer. Don't stop taking any medicine unless your doctor says it's OK.
Vitamin C
This antioxidant helps get rid of free radicals that can damage cells and tissue, which means fewer triggers for inflammation.
Regularly eating a variety of fruits and vegetables, which have antioxidants, can lower your chance of heart disease. But studies on supplements have been back-and-forth, with some showing benefits for heart disease and cancer, others not.
Vitamin C, like the B vitamins, may also lower levels of C-reactive protein.
What to eat:
Citrus fruits -- oranges, grapefruit, tangerines -- are what most people think of. But bell peppers, broccoli, and Brussels sprouts have high amounts of vitamin C as well. Leafy greens and berries are also good sources.
What else you need to know:
Your body can only handle so much vitamin C daily, so taking a lot doesn't really make a difference. And high doses may cause tummy troubles. It's more important to eat a mix of vegetables and fruits every day.
If you're being treated for cancer or you're taking a statin drug for high cholesterol, don't take a supplement until you've talked to your doctor about it.
Vitamin D
Low vitamin D levels have been linked to inflammatory diseases including rheumatoid arthritis, lupus, inflammatory bowel disease, and multiple sclerosis. But it's unclear whether raising D levels will stave off these illnesses or prevent some age-related diseases.
In the lab, this vitamin shows a significant anti-inflammatory effect on cells. There's also some evidence that D can lessen the ongoing pain from inflammation.
What to eat:
Only a few foods found in nature contain much vitamin D. Your body makes it when your skin is in sunlight. But it's also in fatty fish, liver, beef, and egg yolks. And it's added to some foods, such as milk.
What else you need to know:
You might not get enough if you're older, have dark skin, are obese, don't get out in the sun much, have inflammatory bowel disease or trouble absorbing fats, or have had gastric bypass surgery.
Steroids, which doctors often prescribe to fight inflammation, can make it hard for your body to use vitamin D. Other drugs that may cause low levels are the weight-loss drug orlistat (Alli, Xenical), the cholesterol medicine cholestyramine (LoCholest, Prevalite, Questran), and either phenobarbital or phenytoin (Dilantin, Phenytek) for seizures.
Too much vitamin D can upset the calcium balance in your body which can affect how certain heart and blood pressure medicines work. Check with your doctor if you take any medicines or have any chronic diseases before taking a supplement.
Vitamin E
This is another antioxidant that's also an anti-inflammatory.
There were hopes that it might head off heart disease, but so far, researchers have been disappointed with their trials. Some experts think they may have better luck with younger people and higher doses over a longer time. We need more tests to know If it has any benefits..
Some research points to a connection between low levels of vitamin E and a greater risk of Alzheimer's disease.
What to eat:
Crunch on sunflower seeds, almonds, and other nuts, and use oils made from them. You can't go wrong with green, leafy vegetables, either.
What else you need to know:
You'll have a higher chance of bleeding if you're taking a blood thinner medicine like warfarin (Coumadin) or daily aspirin and vitamin E supplements.
Many doctors don't recommend taking it if you're getting chemotherapy or radiation for cancer.
Vitamin K
It lowers levels of inflammatory signs. But we don't know yet if that also lowers your risk for related diseases.
What to eat:
Leafy greens, including kale, spinach, collards, and chard are outstanding sources. Broccoli and Brussels sprouts are very good, too.
What else you need to know:
People who take the blood thinner warfarin need to eat a steady amount of vitamin K to make sure their medication keeps working right. Talk to your doctor about what that means for you.