Sesame seeds are sometimes added to breads, including bagels and the tops of hamburger buns. Sesame seeds may be baked into crackers, often in the form of sticks. Sesame seeds are also sprinkled onto some sushi style foods. Whole seeds are found in many salads and baked snacks as well in Japan. Tan and black sesame seed varieties are roasted and used for making the flavoring gomashio. Sesame seeds are exceptionally rich in iron, magnesium, manganese, copper, and calcium (90 mg per tablespoon for unhulled seeds, 10 mg for hulled), and contain vitamin B1 (thiamine) and vitamin E (tocopherol). They contain lignans, including unique content of sesamin, which are phytoestrogens with antioxidant and anti-cancer properties. Among edible oils from six plants, sesame oil had the highest antioxidant content. Sesame seeds also contain phytosterols associated with reduced levels of blood cholesterol. The nutrients of sesame seeds are better absorbed if they are ground or pulverized before consumption, as in tahini. Sesame seeds contain a high amount of the anti-nutrient phytic acid. Women of ancient Babylon would eat halva, a mixture of honey and sesame seeds to prolong youth and beauty, while Roman soldiers ate the mixture for strength and energy.