吃盐和生育

人体的肾脏每天过滤超过三磅的盐，几乎所有的盐都被肾脏重新吸收了，但这需要耗费大量的能量。

当人体内部的盐含量较低，肾脏吸收盐的力度加大，耗能也随之加大。如果我们吃盐太少，肾脏一直需要高强度吸盐，身体会很累，没有多余的精力來生孩子。古希腊时代，亚理斯多德已经记载吃盐少的羊生育率低。中医也认为肾是先天之本，肾虚影响生育。

大多数人应该吃盐足够多，但少数人，特别是那些跟随低盐食谱的人，可能吃盐太少。如果这些人很难怀孕，也许可以考虑根据自己的口味，而不是根据低盐食谱，来做饭。

更具体的讨论，请参看下面这本书：

The Salt Fix: Why the experts got it all wrong — and how eating more might save your life (Some quotes)

The mechanism of kidney 

On average, our kidneys may filter between 3.2 and 3.6 pounds of salt per day. This is about 150 times the amount of salt we ingest per day. To put this into perspective, most health agencies tell us that consuming just 6 grams of salt is too high, yet our kidneys filter this amount of salt every five minutes.

The salt restriction recommendations hardly make sense from a physiological viewpoint, but seeing these numbers helps to put things further into perspective. The amount of salt we eat per day is truly a drop in the bucket compared to the amount the kidneys filter on a daily basis. In fact, the stress on our kidneys mainly comes from having to conserve salt and reabsorb all of the 3.2 to 3.6 pounds of salt that we filter every day. The reabsorption requires us to use up ATP ... Our sodium pump uses approximately 70 percent of the basal energy expended by the kidneys, making a low salt diet an energy hog and a tremendous stress to the kidneys. This is one way that low salt diets lead to weight gain, by slowly depleting our energy stores and leading us to become more sedentary. What organisms want to move (and sweat out precious sodium) when it has too little salt to begin with? (P 28)

Salt and Sex

One of the salt’s most intriguing properties is its importance for many facets of reproduction — from sexual desire and procreation to gestation and lactation — and this connection has been known at least since the time of ancient Greeks ... 

A low salt diet seems to act like a natural contraceptive in both animals and humans, and in both males and females. A low salt diet causes a reduced sex drive, reduced likelihood of getting pregnant, ... and increased erectile dysfunction, fatigue, sleep problems. (P 30)




General 

The known consequences of salt restriction ... has long been independently known to increase the risk of death. (P 40)


Compared to dramatic changes in the form, structure and function of the organs that occurred during vertebrate evolution, the fact that the electrolyte make up of the extracellular fluid has remained generally constant suggests that salt balance is an evolutionary adaptation. (P 17)

Comment: In physiology classes, we should have learned electrolyte functions first. Instead, the content is put at the end of the textbook and was not taught.

When one exercises, he will sweat and lose salt. If the amount of salt in the body is not enough, he will be reluctant to exercise. This is very much like a starved person is reluctant to exercise. A salt starved person is very much like food starved person. They can’t grow very well and will have a lot of other health problems.