This ups and downs make the public more confused: the lead content has not changed, why is this standard once and that standard once again? What effect does this lead have on health?
Lead is a metal element that the human body does not need and can accumulate in the body. Long-term intake of extremely low doses of lead may also cause damage to nerves, kidneys and blood system. The harm to children is more obvious, which easily leads to stunting and low cognitive ability. So the intake target of this substance is zero.
But lead exists widely in our environment. Especially in modern society, they often exist in industrial waste gas and are not difficult to find in soil and drinking water. Many plants can accumulate lead, which makes it difficult to avoid it in food. In other words, when we eat, drink and breathe air, we may take in lead.
Just like aflatoxin in food, we can't completely avoid it, so we can only try our best to reduce it. According to the current scientific data, it is considered that the intake per kilogram of body weight per week is less than 25 micrograms, and the impact on health is acceptable. This "safety standard" is equivalent to an adult's intake of 200 micrograms per day.
Some experts pointed out that excessive lead in spirulina only means that they are "unqualified products" and does not mean that they are "harmful". Just in terms of numbers, there is also a certain basis. According to the lead content of 2 milligrams per kilogram of spirulina, the average person eats about 5 grams a day, and the lead content is about 10 microgram. For an adult, it is roughly equivalent to about 5% of the "daily safe intake".
However, this analysis is not very reasonable. The harm of lead does not depend on the specific source, but on the total intake. If spirulina is only the only way for people to ingest lead, then this 10 microgram is harmless. But the reality is that lead in air, water and other foods is almost inevitable. In order to reduce the risk of "chronic lead poisoning", what we can do is to avoid its intake where it can be avoided.
In order to achieve this goal, mankind has made a lot of efforts. For example, leaded gasoline used to be the main source of lead in air, water and natural environment, but now people have gradually given up this kind of gasoline; Paint often contains lead, which has been banned in many countries for many years; Lead in plastics and paints often makes toys exported from China rejected by Europe and America. According to American statistics, the lead intake of Americans has dropped by about 90% for decades.
Comparing the result of "reducing by 90%", we can see that "5% of safe intake" is not a negligible amount. Because, we may also take more than 5% or even more from other channels. For example, the United States stipulates that the lead content in candy should not exceed 100 micrograms per kilogram, and the lead content in fruit juice should be 50 micrograms. If this amount is reached, then 100 grams of candy or a glass of juice will reach that "5%".
In other words, only the lead contained in spirulina is not necessarily harmful. However, it is only one of many ways for human body to ingest lead. Especially those spirulina with high lead content, the contribution to the "total lead intake" is still considerable.
For food, medicine or health care products, we always seek a balance between "value" and "safety". If spirulina really has all kinds of magic in legend, it is not unacceptable to take this amount of lead. If its "efficacy" is only a mirage, there is no need to take such a risk.
The reality is that the efficacy of spirulina that people "believe" at present basically comes from commercial marketing, but it lacks scientific basis. China's management approved the vague functions of Spirulina such as "regulating immunity" and "anti-fatigue", but the merchants derived various "miraculous effects". If in the United States, this can be regarded as a serious violation of the law and will be punished.
The scientific fact is: Spirulina is a good wild vegetable-it contains high protein, some vitamins and minerals. If it is used instead of regular food, it can really provide quite rich nutrition. However, spirulina, as a "health product", generally eats a few grams every day, and the nutrition it can provide is very limited. For example, merchants like to say "high-quality protein", and 5 grams of spirulina can provide about 3 grams, which is only a drop in the bucket compared with the dozens of grams of protein that the human body needs every day. Other "nutrients" are roughly the same.
If there is no pollution caused by heavy metals such as lead, it is no problem to eat as a dish. But when the content of heavy metals can not be ignored, the risk of "eating too much" is also great.