Vitamin D May Not Be Disease-Fighter Low levels a symptom, not a cause of illness, researchers say By Rob Quinn, Newser Staff Posted Dec 6, 2013 3:22 AM CST 14 comments Comments Sales of vitamin D supplements are worth around $600 million a year in the US. (AP Photo/Brigham and Women's Hospital) (Newser) – Is there any point in healthy people taking vitamin D supplements? New research suggests that while low levels of the "sunshine vitamin" are linked to many illnesses, the deficiency is a result, not a cause of sickness, reports Reuters. French researchers who reviewed hundreds of other studies were unable to find any link between taking vitamin D supplements and having a reduced risk of contracting illnesses including cancer, diabetes, and cardiovascular disease. The review suggests "decreases in vitamin D levels are a marker of deteriorating health," the lead researcher says. Experts not involved in the study say that while it shows that more long-term studies of the vitamin's effects are needed, it shouldn't be a reason for people ceasing to take supplements—especially among groups at risk of deficiency, including older people, pregnant and breastfeeding women, young children, and people with darker skin. The French study also failed to look at bone health, critics note. "It has been known for almost a century that vitamin D supplements given to those with deficient vitamin D levels results in improved bone health, preventing hypocalcemic seizure and rickets," a leading pediatrician tells the BBC.