Green foods and juices have been around for a long time as health supplements, but these days some restaurants are serving up glasses of lawn-redolent wheat grass juice, or spirulina, with your lunch.

A sip of what is essentially ground-up meadow (same bright green color, same revivifying pastoral scent) has become a very hip power drink. Some even say a cup of chlorella beats coffee. To a coffee lover, that’s quite a challenge.

So what are chlorella, spirulina, wheat grass and barley grass, and why are we ingesting them?

They’re billed as detoxifiers and energy foods, and if you’ve tried one or another of these you’ll know that they do indeed seem to charge you up.

The “greens” are available as tablets or powders which can be mixed with water; purists insist that they be taken in the latter form, as drinks, to enjoy their full benefits. The powders are essentially dried grasses or algae that must be mixed with water to make juice. If you have access to one of the aforementioned green juice-serving restaurants, you might even be served the fresh stuff. Whether the agent is microscopic algae (chlorella, spirulina) or young cereal grasses (barley, wheat), the source of their power is similar: lots of vitamins, minerals, enzymes, chlorophyll, digestible protein and carotenoids.

One advantage of these green power drinks is that they are not likely to have unexpected side effects. Of course, consulting your medical specialist before adding something new to your diet is always advisable. If you want to prepare your green juice from fresh leaves, be absolutely certain that you can identify the plant you want. When in doubt, use of clearly labeled, commercially purchased dried leaves, free of pesticides and undesirable chemicals.

As is often the case when something becomes trendy, people rarely realize that it is just the tip of the iceberg. Juices made from crushed leaves have been part of folk medicine for centuries. Here are some old stand-bys:

Basil leaf juice: This is used to counter a chill. In Europe, it is mixed with a decoction of cinnamon and clove. In Ayurvedic medicine, basil leaf juice is prescribed to treat snakebite, as a general tonic, as a cough remedy and to cure skin problems and earache. Basil leaf is useful in conditions involving nervous exhaustion.

Nettle leaf juice: This European tonic remedy is used to treat weakness and anemia, while it is applied topically to soothe nettle-stings. Rich in iron, the high level of vitamin C in the nettle leaf conveniently aids iron absorption. Beneficial in cases of gout and arthritis, nettle leaf juice is considered a blood cleanser.

Dandelion leaf juice: A diuretic known in the East as well as the West, 20 ml of dandelion leaf juice can be taken three times a day as short-term cures for detoxification or for urinary tract infections. Rich in potassium, the juice replaces this important mineral which is often lost in abundance in diuresis. A good liver tonic and digestive.

Plantain leaf juice: Used to treat inflammations of the urinary tract, gastrointestinal infections and chest infections, plantain leaf juice is prescribed in doses of 10 ml a day, three times a day.

Celery juice: Used commonly to treat urinary tract infections, celery juice may also be prescribed in cases of joint inflammation, rheumatoid arthritis, nervous exhaustion and stress. The entire plant is used.

Borage leaf juice: For depression, sadness and anxiety, this juice is prescribed in doses of 10 ml three times a day. This is an adrenal tonic useful in cases of stress.

Cabbage juice: Used to soothe and treat gastric and duodenal ulcers, cabbage juice may be used topically as well to treat many types of skin problems and promote healing. Folk medicine has found numerous uses for cabbage juice, including the treatment of migraine, digestive problems, chest infections, water retention and a variety of other problems.

Many of these green drinks share a detoxifying function, though each has a slightly different effect on the body. They are worth exploring perhaps, if you are seeking a specific cure and want a simple remedy.