Vitamin D may be crucial to fending off infection, according to a recent report. But as many as 70 percent of the U.S. population may be D-deficient, says report author Adrian Gombart, a principal investigator with the Linus Pauling Institute at Oregon State University.

The report highlights vitamin D's role in inducing the expression of cathelicidin, a compound integral to the immune system's first line of defense against wounds, bacteria, and viruses. The report also underscores vitamin's D's role in reducing risk for conditions such as cancer, multiple sclerosis, rheumatoid arthritis, psoriasis, and influenza. Vitamin D appears to curb inflammation, keep blood pressure in check, and protect against heart disease as well.

D deficiency may be particularly prevalent during the winter months, when lack of sunlight exposure slows up the body's synthesis of the vitamin. In order to maintain optimal levels of vitamin D, many health experts recommend taking a daily supplement.

The supplement S-methylmethionine (SMM) may help defend against a common cause of liver damage, according to a recent study. SMM is a molecule found at high levels in a number of plants, including cabbage and wheat.

In tests on mice, researchers discovered that SMM protected against liver toxicity induced by intake of acetaminophen, a pain reliever found in Tylenol and other over-the-counter medicines used to treat conditions like headache, muscle aches, arthritis, back pain, toothaches, colds, and fevers. While acetaminophen isn't considered harmful when consumed at normal levels, excessive intake may lead to the buildup of byproducts known to cause severe liver damage. In fact, acetaminophen overdose is the most common cause of liver failure and liver transplantation in the U.S., according to the study's authors.

If you're looking to reduce your use of acetaminophen, consider trying an herbal remedy that may help ease pain-triggering inflammation. A number of anti-inflammatory herbs (including white willow bark and devil's claw) have proven useful in managing pain-causing conditions in previously published studies.

Flaxseed oil may shield bone health in women at risk for osteoporosis, according to a recent animal study.

In tests on female rats that were in a post-menopausal state and/or had diabetes, scientists found that adding flaxseed oil to the diet helped raise levels of osteocalcin (a protein known to build bone). What's more, levels of urinary deoxypyridinoline (a marker of osteoporosis-related bone breakdown) appeared to fall when rats were fed flaxseed oil.

The study's authors suggest that taking a dietary supplement of flaxseed oil may reduce osteoporosis risk among women with diabetes. While diabetes appears to hamper the process of bone mineralization, the authors explain, intake of the omega-3 fatty acids found in flaxseed oil may help build bone and prevent osteoporosis.

In past studies, a number of other natural substances (including vitamin D, vitamin K, and calcium) have been found to strengthen bone and lower osteoporosis risk. Performing weight-bearing exercises also appears to preserve bone health.

Green tea may help protect liver health, according to a new animal study. In tests on rats, scientists discovered that green tea prevented the development of liver fibrosis (a condition marked by buildup of collagen and other proteins in the liver). The study's results suggest that green tea may help reduce the deposition of collagen fibers in the liver (an organ responsible for aiding in digestion and clearing waste products from the blood).

Occurring in most types of chronic liver disease, liver fibrosis may lead to life-threatening problems like cirrhosis and liver failure. Typically triggered by inflammation, liver fibrosis causes no symptoms and usually affects people who have an underlying liver disorder.

In past studies, natural remedies such as milk thistle and probiotics have also been shown to boost liver health. However, if you have a liver disorder, it's crucial to work with a physician in treating your condition rather than attempting to self-treat with herbs and other natural substances.