The Stomach is a Yang organ but it frequently suffers from Yin deficiency. Indeed, I would say that Stomach-Yin deficiency is very common in the patients we see. The cause of Stomach-Yin deficiency is irregular eating habits. That includes eating late at night, eating in a hurry, eating while working, eating standing up, etc. all very common habits in the patients we see.
Another less common cause of Stomach-Yin deficiency is eating too drying foods. The Stomach likes warm but moist foods such as soups, porridge or rice congee. “Drying” foods includes broiled or baked foods which would include bread. Broiling and baking makes foods dry and causes dryness when eaten in excess. That dryness can eventually lead to Stomach-Yin deficiency. Interestingly, there is very little broiling and baking in Chinese cooking and even bread is steamed (man tou) rather than baked.
How do we know there is Stomach-Yin deficiency? Primarily from lack of coating on the tongue. The normal tongue coating derives from the Stomach rotting and ripening and it indicates a normal functioning of the Stomach. When Stomach-Yin is deficient, there is no coating on the tongue.
However, there are some intermediate stages before reaching a full-blown Stomach-Yin deficiency and no coating on the tongue. The very beginning of Stomach-Yin deficiency will manifest with a coating without root. A coating without root looks likes it is resting on the tongue rather than growing out of the tongue body the same way grass grows out of the soil.
The next stage of Stomach-Yin deficiency is manifested with a tongue that lacks a coating in patches, wherever the patches may be: they may not necessarily be in the Stomach area in the centre of the tongue.
The tongues below all lack a coating in patches.
Please note that when the tongue lacks a coating but has a normal colour, it indicates Stomach-Yin deficiency without Empty Heat: it is only when the tongue lacks a coating and it is red, that it indicates Empty Heat deriving from Stomach-Yin deficiency.
The tongue below is a good example of a tongue that lacks a coating but is not red.
The two tongues below are without coating and red, therefore indicating Stomach-Yin deficiency and Empty Heat. The tongue on the right indicates an extreme degree of Empty Heat.
Another sign of Stomach-Yin deficiency is a Stomach crack (or cracks) on the tongue. However, Stomach cracks may indicate a constitutional tendency to Stomach-Yin deficiency rather than the actual pathology. In any case, when I see such cracks I nourish Stomach-Yin.
The tongues below show Stomach cracks.
The treatment depends a lot on the tongue: if there is coating but it is either rootless or in patches, I use Shen Ling Bai Zhu San Ginseng-Poria-Atractylodes Powder.
If the coating is missing entirely, I use Sha Shen Mai Dong Tang Glehnia-Ophiopogon Decoction.
With acupuncture, the points to nourish Stomach-Yin are very simple: Ren-12 Zhongwan, ST-36 Zusanli and SP-6 Sanyinjiao.
Obviously treatment must include also a change in eating habits.