Influenced by the tradition or habits in daily diets, there are many ideas which have existed in people's mind for a long time. In fact, most of these ideas are not correct, and even may bring harms to human health.

The first error: kidney stone patients should not supplement calcium.
Most of kidney stones are caused by the deposition of calcium oxalate in the urine. This is mainly due to the intake of too much oxalic acid. When the oxalic acid is excluded out of the urinary tract, it will combine with calcium and form calcium oxalate, which will further lead to kidney stones. The key to prevent kidney stone is to reduce the intake of the foods containing too much oxalic acid, such as spinach and bamboo shoots.

The second error: patients with diabetes should eat carbohydrates as little as possible.
The level of blood glucose is closely related with the intake of carbohydrate. Diabetic patients should properly control the intake of carbohydrates, so as to prevent excessive blood sugar. Under the condition of maintaining normal body weight, they should keep a normal intake of energy, in which the intake of carbohydrates should account for 60% to 65% of the total energy. Diabetic patients should eat more foods rich in dietary fiber, such as oatmeal and fresh vegetables, which can slow down the digestion and absorption of carbohydrates, so that the blood sugar will not rise too quickly and can remain at a stable level.

The third error: old people drink milk will lead to cataracts.
Some people say that milk contains cysteine. When the cysteine is oxidated, it will damage the lens of the eye and cause cataracts. As a result, they hold that old people should not drink milk. In fact, milk is rich in calcium, so it is a very important dietary source of calcium. What's more, the casein contained in milk is also a kind of high-quality protein, which is easily absorbed and utilized by human body. In order to prevent cataracts, the elderly people can supplement more antioxidant nutrients, such as vitamin C, vitamin E, β-carotene, selenium, zinc and other trace elements.

The fourth error: supplementation of vitamin C is easy to cause kidney stones.
Vitamin C is the cofactor of enzyme, which is closely related with the synthesis of collagen, the healing of wound, and the fragility of blood vessel. What's more, vitamin C also has effect, which can promote the absorption of iron and enhance the immune function. As long as the daily intake of vitamin C is less than 1,000 milligrams, it will not cause kidney stones.