Most people know amino acids are the building blocks of proteins. What they may not realize is that amino acids play roles independent of their proteins, and some amino acids are never protein components at all. Essential amino acids are those required in the diet because they cannot be synthesized by the body. These essentials are leucine, isoleucine, threonine, methionine, tryptophan, valine, histamine, phenylalanine and lysine.1

Two nonessential amino acids with independent therapeutic values are taurine and carnitine. They are both valuable for the heart, especially as people age, but they also have other physiologic functions--placing them in the category of "conditionally essential" nutrients. Typical doses of both taurine and carnitine are from l,000 mg up to 4,000 mg daily in divided doses.

Taurine Taurine, a sulfur-containing amino acid derived from the amino acid cystine, is a component of the bile salts produced in the liver (it was first isolated from ox bile). It is important for proper digestion of fats and absorption of fat-soluble vitamins. But only a fraction of available taurine is used to make bile salts,2 while an enormous amount floats freely inside cells.

Taurine is not incorporated into proteins but remains free in the tissues, especially muscle and nerve tissues. It has a number of therapeutic uses including acting as a membrane stabilizer and reducing arrhythmias of the heart. Taurine also enhances the contractile strength of heart muscle (called a positive inotropic effect)3, and thus can help treat heart failure--which is a decreased ability of the heart to pump out all the blood that flows into it. When the heart is failing, the blood backs up and forces fluid out into the tissues (edema) by osmosis. This leads to either swelling of the legs or fluid in the lungs and shortness of breath, depending on which part of the heart is more involved.

In a 1984 animal study, taurine protected against heart failure, reducing mortality by 80 percent in the taurine-treated group with no diminishment of cardiac function.4 In a later animal study in 1988, taurine was shown to lower blood pressure.5 My own clinical experience confirms some of these effects of taurine, and I commonly give it to patients with heart failure and high blood pressure.

Taurine is also beneficial for the eyes--enhancing the rods and cones (the pigmented epithelial cells in the retina of the eye that serve as visual receptor cells). The greatest visual acuity occurs in the macular area of the retina near where the optic nerve enters from the back of the eye. With aging, the macula commonly degenerates as rods and cones die, often causing blindness. What causes the degeneration is not clear, but it is more common in diabetics and may be the result of free radical damage from ultraviolet light or oxygen exposure.6

A review of animal studies reveals that taurine appears to protect the eyes from macular degeneration.7 In one 1975 research report, a diet deficient in taurine was associated with retinal degeneration in cats.8 Thus, taurine can be part of a comprehensive approach to macular degeneration that also includes antioxidant nutrients, minerals, flavonoids, botanicals and chelation therapy (an intravenous therapy done in a doctor's office).

Because taurine is a neuroinhibitory amino acid, it may help treat seizure disorders. Some animal studies have suggested a role for taurine in controlling seizures, but the results are not consistent. In 1977, a cat with chronic epileptic seizures was successfully treated with taurine both orally and intravenously.9 Other studies have also suggested taurine's supportive role for seizures, but some clinical trials have shown limited benefits or have not confirmed this effect of taurine. I have used taurine, in combination with magnesium and other nutrients, in my seizure patients with some success. It seems to enhance the effects of some of their seizure medications so they can take a lower dose.

Carnitine Carnitine is not an essential amino acid because it can be synthesized in the body from lysine and methionine, providing there is available vitamin C and iron for the synthesis. Even if they apparently have enough of the lysine and methionine precursors, some people do not make enough carnitine, especially as they get older. People who have conditions such as arteriosclerosis (hardening of the arteries) may also need more carnitine.

One of carnitine's important roles is in fat metabolism. To burn fat molecules for energy, the fat has to be moved into the mitochondria, the energy-producing engines of the cells--a process that requires carnitine. In this way, carnitine works with Co-Q10 (required for burning the fat once it is inside the mitochondria) to make the energy storage molecules. Carnitine thus provides energy for the cells and also helps burn off fats so they do not accumulate.

In this regard, carnitine has been shown to help lower serum lipids. In a 1983 clinical trial where patients were given approximately 1 g of carnitine per day, cholesterol was lowered from 295 down to 234, with an increase of the good HDL cholesterol and a decline of triglyceride levels.10

As with taurine, one of the clinical values of carnitine is supporting heart muscle tissue. In one study, heart patients had reduced angina pectoris (heart pain from lack of oxygen) when given 6 g/day of carnitine.11 These patients also had fewer palpitations and improved cardiograms. A 1996 study showed improvement in patients with a myocardial infarction (heart attack) when they were given 2 g/day for 28 days carnitine compared to placebo.12 The extent of the infarction (death of the heart muscle) was significantly reduced, and the blood enzymes, which go up during an infarction, did not increase as much in the carnitine group. Angina was less than half, and both heart failure and arrhythmias were better in the test subjects. In fact, subsequent heart attacks and heart attack-related deaths were cut almost in half in the carnitine group.

Administering carnitine to cells in the laboratory shows that it can stabilize the fluidity of red blood cell membranes.13 Healthy cell membranes are important for transporting nutrients into cells and removing waste materials from cells. Also, circulation depends on red cells being able to squeeze through capillaries, and to do this they must maintain their flexibility. Carnitine researchers theorized that this maintenance of membrane flexibility could be the reason that carnitine reduces heart muscle damage during a heart attack.

In another study, heart-failure patients were given 2,000 mg/day of carnitine. Compared to placebo, these patients improved subjectively and had lowered heart rate, less fluid accumulation and improved breathing.14 The carnitine subjects also needed less heart medication than the control group. In addition, carnitine reduced patients' cholesterol and triglyceride levels and very importantly, there were no side effects.

In my own experience, carnitine has helped reduce angina and increase exercise tolerance in heart patients. Of course, I recommended a number of supplements to these patients, so it may have been the combination that was important and not just carnitine. It would seem safe to conclude, though, that my clinical experience does support the controlled clinical trials.

Several studies have shown that carnitine can increase exercise tolerance in heart patients. There are also several reports of this effect in normal subjects, but for healthy subjects the results are inconsistent. In one report, 110 elite athletes in a variety of endurance and strength sports showed improved performance and blood tests after exercise when given carnitine, either as a single dose or over a period of weeks.15 My colleagues and I typically recommend from 1,000 mg to 4,000 mg of carnitine daily as therapeutic levels. In these doses there is no evident risk from taking carnitine supplements.

There are many valuable supplement therapies that have significant scientific support, although in some cases the research is still equivocal. In the case of taurine and carnitine, there is enough information to recommend them in a variety of conditions, especially considering their excellent safety record and the potential benefits to patients. Any time you can reduce dependence on medication, it is worth exploring the benefits of dietary supplements.

Michael Janson, M.D., F.A.C.A.M., is president of the American Preventive Medical Association and a fellow and president-elect of the American College for Advancement in Medicine. Janson is the author of The Vitamin Revolution in Health Care. He practices nutrition, chelation therapy and preventive medicine at the Center for Preventive Medicine in Barnstable, Mass.

REFERENCES

1. Linder, M., Ed. Nutritional Biochemistry and Metabolism, 2nd edition, Elsevier Scientific Publishing, 1991.

2. Chesney R.W. "Taurine: Its biological role and clinical implications," Adv Pediatr 32: 1-42, 1985.

3. Pisarenko, O.I. "Mechanisms of myocardial protection by amino acids: Facts and hypotheses," Clin Exp Pharmacol Physiol 23(8): 627-33, August, 1996.

4. Azuma, J., et al. "Beneficial effect of taurine on congestive heart failure induced by chronic aortic regurgitation in rabbits," Res Commun Chem Pathol Pharmacol 45(2): 261-70, August, 1984.

5. Fujita, T., Sato, Y. "Hypotensive effect of taurine. Possible involvement of the sympathetic nervous system and endogenous opiates," J Clin Invest 82(3): 993-97. September 1988.

6. Gaby, A.R., Wright, J.V. "Nutritional factors in degenerative eye disorders: Cataract and macular degeneration," J Adv Med

6(1): 27-4O, Spring 1993.

7. Chesney, R.W. op. cit.

8. Hayes, K.C., Carey, R.E., et al. "Retinal degeneration associated with taurine deficiency in the cat," Science l88(4191): 949-51, May 30, 1975.

9. van Gelder, N.M., Koyama, I., et al. "Taurine treatment of spontaneous chronic epilepsy in a cat," Epilepsia 18(1): 45-54, March, 1977.

10. Pola, P., et al. "Statistical evaluation of long-term L-carnitine therapy in hyperlipoproteinaemias," Drugs Exptl Clin Res 9: 925-34, 1983.

11. Orlando, G., Rusconi, C. "Oral L-carnitine in the treatment of chronic cardiac ischaemia in elderly patients," Clin Trials J 23: 338-44, 1986.

12. Singh, R.B., Niaz, M.A., et al. "A randomised, double-blind, placebo-controlled trial of L-carnitine in suspected acute myocardial infarction," Postgrad Med J 72(843): 45-50, January 1996.

13. Kobayashi, A., Watanabe, H., et al. "Effects of L-carnitine and palmitoylcarnitine on membrane fluidity of human erythrocytes," Biochim Biophys Acta 986(1): 83-8. Nov. 17, 1989.

14. Ghidini, O., Azzurro, M., et al. "Evaluation of the therapeutic efficacy of L-carnitine in congestive heart failure," Int J Clin Pharmacol Ther Toxicol 26(4): 217-20, April l988.

15. Dragan, I.G., Vasiliu A., et al. "Studies concerning chronic and acute effects of L-carnitina in elite athletes" Physiologie 26(2): 111-29, April-June, 1989.