Neck and shoulder stiffness and pain are common complaints, and causative factors include muscle tension and reduced blood flow around the neck and shoulders. NKCP® is as a food supplement that contains bacillopeptidase F, a protease (enzyme) that is isolated and purified from the culture of the probiotic bacterium B. subtilis var. natto, which is used to ferment soy beans to natto, a traditional Japanese food. Various health benefits have been attributed to natto, and NKCP® has been shown to have blood thinning properties. This double-blind, placebo controlled crossover study aimed to evaluate the effects of NKCP® on healthy individuals with neck and shoulder stiffness and pain. Subjects received either NKCP® or placebo for 4 weeks, then had a 4 week washout period where they received neither test supplement, and then received the other test supplement for another 4 weeks. Shoulder and neck symptoms were assessed prior to starting the trial, and at 4, 8 and 12 weeks, through subjective reporting and a muscle hardness meter to measure muscle stiffness. Neck and shoulder stiffness and pain were improved after taking NKCP® but not significantly more than in the placebo group. Headaches improved significantly more in the NKCP® group compared to the placebo group. No significant changes were observed for lower back pain, cold hands and feet, eyestrain, and dry eye.