BACKGROUND:One of our readers asked for a review of trimethyl glycine (TMG) because it was recommended to lower cholesterol levels. The compound is also called betaine because it was first discovered in sugar beets. This continues to be the main source of commercial betaine, although it is produced by many plants and animals, including humans. Good dietary sources of betaine include various beets, legumes, whole grains, liver, eggs and fish.
We require betaine for normal metabolism and usually obtain enough from dietary sources or by making it in the body from other compounds. People with a condition called homocystinuria may require much more betaine than others. This condition can be caused by a genetic problem, insufficient folic acid in the diet, or by alcoholism. When it occurs, an amino acid called homocysteine accumulates in the blood and urine. Betaine is involved in one mechanism that lowers these levels. Betaine is approved in many countries as a medical treatment for homocystinuria.
High blood levels of homocysteine have been found in people with many diseases, including cardiovascular disease, osteoporosis, arthritis, depression and dementia. The precise role of homocysteine in these conditions is not known. Given these associations, betaine or TMG supplements are popularly recommended to treat these conditions, and others.
EVIDENCE FROM STUDIES
Most of the betaine produced from sugar beets is used in animal feeds. It is believed to produce better meat by increasing lean muscle mass and decreasing tissue fat. Because of this, TMG supplements are increasingly promoted for body builders and people seeking to lose weight. However, only one small study has examined this in humans. It found no impact on obesity or body fat after 12 weeks of betaine supplementation.
These alleged changes in body fat have led to claims that betaine supplements lower blood cholesterol and lipid levels and thus reduce the risk of cardiovascular disease. Most of the research in this area has focused on people with elevated homocysteine levels.
People taking 6g betaine per day were found to have blood homocysteine levels reduced by about 10-15 per cent. This would somewhat reduce their risk of cardiovascular disease – although this is for people with high homocysteine levels.
Some of these studies also measured cholesterol levels and found that 4-6g of betaine led to a 3-4 per cent increase in cholesterol and triglyceride levels. Such studies led one researcher to conclude that people should be warned against using betaine to lower cholesterol levels. However, others have questioned these results, claiming the percentage changes are not large and occurred with high doses of betaine.
On the other hand, population studies found that people with higher blood levels of betaine tended to have lower cholesterol levels. One possible explanation for these inconsistencies is that betaine from the diet and produced by the body has a different effect than betaine available from food supplements. Another explanation is that population studies ask people about lifestyle factors and, in this case, cannot show what caused the different cholesterol levels. The results of the controlled studies would be more reliable indicators of the true effect of betaine on cholesterol levels.
PROBLEMATIC ASPECTS
The reader who inquired about betaine mentioned that she had experienced nausea and diarrhoea after taking it. These are the most common adverse effects, along with abdominal cramps and body odour.
RECOMMENDATIONS
Betaine plays a role in several biochemical pathways, including those involving cholesterol. Much remains unclear about all its functions. Given that these metabolic pathways are complex and interconnected, uncertainty about all the supplement’s effects is not surprising.
The evidence to date suggests that betaine’s effect on cholesterol is at best negligible, but may be detrimental. While betaine is an important nutrient, a balanced diet should provide an adequate intake for most people. Those with particularly high homocysteine levels can benefit from betaine supplements. Apart from these conditions, betaine supplementation cannot be recommended in general.
Dónal O’Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University
