Yoga tones muscles and increases flexibility, strength, and stamina.
Science says: Yoga increases flexibility, strength, and stamina, but no studies show that it tones muscles. Still, tone is partially a function of nervous system stimulation of the muscle; any physical activity, done repeatedly, produces muscle tone.
Claim: The twisting postures in yoga release harmful toxins from internal organs and boost the immune system.
Science says: No studies could be found to bolster such claims. There is some evidence showing that yoga postures may help reduce pain and inflammation in people with rheumatoid arthritis and osteoarthritis.
Claim: Yoga aids weight loss.
Science says: Any physical activity, coupled with controlled eating, aids weight loss. Different yoga methods -- vinyasa, hatha, and kundalini, to name a few -- are practiced at different speeds and strength levels, burning calories at different rates.
Claim: Yoga improves circulation, thereby reducing acne, the signs of aging, and other skin disorders.
Science says: No studies yet support these claims. Stress is commonly blamed for causing acne, but most doctors think it has little effect.
Claim: Yoga helps you "stay regular" by stimulating the digestive system.
Science says: A few studies report improvement in bowel patterns among yoga enthusiasts. The mechanism for this effect has not been studied; it's possible that a decrease in stress hormones may have a positive effect on intestinal motility and bowel movements.
Claim: Yoga can help reduce the cause and effects of high blood pressure, diabetes, depression, colds, cancer, backaches, and more.
Science says: Some studies show that practicing yoga can reduce blood pressure, improve blood glucose in people with diabetes, improve mood, improve the pain and discomfort associated with chemotherapy for cancer patients, and reduce the pain from back problems.