June 29, 2010— -- Gwyneth Paltrow's announcement that she has osteopenia, a possible precursor to the bone-thinning disease osteoporosis -- conditions usually found in older women -- has some wondering if her extreme diet and exercise regimen is to blame.
In her online newsletter GOOP, Paltrow, who is 37, revealed that she was diagnosed with the early stages of osteopenia after suffering a leg fracture.
"I suffered a pretty severe tibial plateau fracture a few years ago (requiring surgery) which lead the orthopaedic surgeon to give me a bone scan, at which point it was discovered I had the beginning stages of osteopenia," she wrote in a recent post.
Osteopenia is the term used for bone density that falls somewhere between less than normal and osteoporosis. People with osteopenia have a greater chance of developing osteporosis, a bone disease which leads to an increased risk of fractures. Both ailments are more common in post-menopausal and elderly women.
For pre-menopausal women diagnosed with osteopenia or lower bone mass, the causes can vary between genetics, eating disorders, crazy diets, excessive exercise or conditions that affect calcium intake, according to Dr. Stephen Honig, director of the Osteoporosis Center at NYU Hospital for Joint Diseases.
Calcium is crucial for good bone health. And vitamin D aids in the absorption of calcium.
"It's always good to have good calcium and vitamin D intake and exercise judiciously," Honig told ABCNews.com.
Some have speculated that Paltrow's lifestyle could be to blame for her diagnosis.
In her newsletter, Paltrow said doctors tested her levels of vitamin D, "which turned out to be the lowest they had ever seen (not a good thing)."
"I went on a prescription strength level of vitamin D and was told to…spend a bit of time in the sun!" she said.
Gwyneth Paltrow's Extreme Diet, Exercise Regimens
Vitamin D is commonly found in dairy products. Exposure to the sun can also boost levels of vitamin D.
Honig said most people -- children and adults -- are deficient in vitamin D and will require some supplements.
Paltrow began following a macrobiotic diet of mostly vegetables, grains, soup and fish in 1999. She took a break between 2003 and 2006 while having her children, Apple, now 6, and Moses, now 4. Though she follows a less intense version of the diet now, she still does not consume much dairy.
Paltrow has also followed more extreme diets at times.
"I need to lose a few pounds of holiday excess," she wrote on GOOP last year. "Anyone else? I like to do fasts and detoxes a couple of times during the year, the most hardcore one being the Master Cleanse I did last spring. It was not what you would characterize as pretty. Or easy. It did work, however."
The master cleanse, which Beyonce claimed helped her lose 20 pounds for her "Dream Girls" role, is a trendy liquid diet, also known as the maple syrup diet. Dieters drink a concoction of syrup, lemon juice, water and cayenne pepper.
Keith Ayoob, a registered dietician and director of the nutrition clinic at the Albert Einstein College of Medicine in New York, is not a fan of fasts or cleanses. "The calorie deficiency might not be harmful but it's not likely to be all that beneficial either," he told ABCNews.com.
Nor is he thrilled with the macrobiotic diet, because he's opposed to "anything that gets rid of whole food groups," he said. "It's basically dairy-free and meat-free."
In recent years, Paltrow has also followed a strict exercise regimen devised by her trainer, Tracy Anderson, who also trained Madonna. Paltrow told Oprah Winfrey in 2008 that she exercises six days a week, using stretchy bands and light weights. In addition to a 40-minute cardio dance routine, she does leg crunches and arm exercises in a heated room.
Paltrow's condition could be a cautionary tale for young women.
"I tell mothers to tell their teen daughters," Honig said, "to drink milk, exercise, don't smoke, no crazy fad diets, keep their body weight where it should be and they are going to protect themselves against a lot of issues."
For women in their late 20s and 30s, he added, "check things out and don't get too crazy."