ConsumerLab.com Answers
Question:
If I buy NAC as a loose powder in a large bag, as opposed to in tablet form, will it spoil? I've heard it can spoil or degrade into a harmful by-product.
Answer:
NAC (N-Acetyl-Cysteine) powder can be stored in a closed container at room temperature (away from high heat or humidity) for at least two months, and possibly longer, without spoiling or degrading. Small amounts of NAC may degrade, over longer periods of time, into a by-product called di-NAC — however, this substance is not known to be harmful. (The sulfur in NAC may cause a "rotten egg" odor, but this does not indicate a problem.) If you are concerned about degradation, consider capsules or tablets, as they will be even more stable than powder. You can see ConsumerLab.com's test reports for NAC supplements, and get more information about NAC's effects, side-effects, and dosage in the NAC Supplements Review >>
ConsumerLab.com Answers
Question:
Is it true that NAC can help clear nasal passages?
Answer:
Although NAC has mucus-thinning properties when directly inhaled, there is little evidence that oral supplementation can reduce the thickness or volume of nasal congestion. More about this is found in the Review of NAC (N-Acetyl Cysteine) Supplements.
If you are suffering from nasal congestion due to a cold, taking a zinc lozenge may reduce the duration of nasal discharge and nasal congestion if taken within 24 hours of onset of symptoms.
Certain probiotics have also been shown to reduce the duration of cold symptoms such as a runny nose.
ConsumerLab.com Answers
Question:
Which supplements reduce the risk of stroke? Which increase the risk of stroke?
Answer:
Certain supplements have been shown to reduce the risk of stroke, while others may increase that risk. In addition, certain nutrients from foods may reduce the risk of stroke — although the benefit does not necessarily carry over to those nutrients when obtained from supplements, as discussed below. Also be aware that some supplements may increase the risk of stroke, as noted below.
Keep in mind that there are different causes of stroke. The most common type of stroke, called ischemic stroke, occurs when blood flow to a part of the brain is blocked, either by a blood clot or plaque build-up in arteries (atherosclerosis), depriving the brain of oxygen. The second, less common, type of stroke is hemorrhagic stroke, which occurs when a blood vessel inside the brain leaks blood or ruptures, creating pressure which damages brain cells. Risk factors for stroke include high blood pressure, diabetes, high cholesterol, atherosclerosis, atrial fibrillation, heart failure, and carotid artery disease (build up of plaque in the main artery in the neck which carries blood to the brain). Lack of physical exercise and being overweight, frequent use of NSAIDS (such as ibuprofen), stress and depression also increase the risk of stroke.
Supplements that may reduce the risk of stroke: (Use the links for more details such as dose.)
Getting a certain amount of vitamin D per day from food and/or supplements may reduce the risk of ischemic and hemorrhagic stroke in men, but this benefit has not been shown in women.
Folic acid (vitamin B-9) supplementation may decrease the risk of stroke in people who have very low or deficient levels of folic acid. However, be aware that there are risks associated with getting too much folate, and current supplement labels may mislead you to consume more folate than you need or is safe for you. It's also important to note that consuming high doses of other B vitamins from supplements, such as B-6 and B-12, may increase the risk of stroke, as well as heart attack and death, in people with diabetes who also have advanced kidney disease.
Nattokinase supplements may decrease blood-clotting factors in the blood, however, there are no published clinical studies in people showing that these supplements reduce the risk of blood clots (which, as discussed above, can cause ischemic stroke).
A daily dose of NAC (N-acetyl cysteine) was found to reduce the incidence of cardiovascular events, including ischemic stroke and heart attack, by 40% compared to placebo in people with end-state renal failure.
As discussed in the Encyclopedia article about Strokes, several other supplements, such as policosanol, vinpocetine and glycine have been proposed to help reduce the risk or improve recovery from stroke, although the evidence for these is not strong.
Be aware that taking a daily multivitamin has not been found to reduce the risk of stroke.
Foods that may reduce the risk of stroke:
The following types of foods may reduce the risk of stroke — although the substances in these foods have not been shown to provide the same benefit when given as supplements.
Higher intakes of calcium from foods are associated with a reduced risk of coronary artery calcification (a form of atherosclerosis), while the use of calcium supplements is associated with an increased risk.
Higher intakes of vitamin K2 from foods are also associated with a reduced risk of coronary calcification — while this benefit has not been shown from vitamin K supplements.
Eating fish has been associated with a 6% to 12% lower risk of ischemic and hemorrhagic stroke, depending on how many servings of fish per week were consumed. However, taking fish oil supplements has not been found to have the same benefit.
Getting more magnesium from your food can help reduce the risk of stroke: One study found that people who consumed more magnesium per day than average had an 8% lower risk of strokes of any kind and a 9% lower risk of ischemic stroke. However, this does not mean that magnesium supplements necessarily have the same risk-lowering effect.
In men and women at high risk for cardiovascular disease, consuming a certain amount of extra-virgin olive oil daily, as part of a Mediterranean diet was found to reduce the risk of ischemic and hemorrhagic stroke, heart attack and death by 30%.
In observational studies, drinking several cups of green tea per day was found to reduce the risk of ischemic stroke by up to 21%.
Supplements that may increase the risk of stroke:
There is concern choline from supplements and foods can increase the risk of stroke. However, a specific form of choline may help to improve recovery from stroke.
People who have had a stroke or are at risk for a stroke, should not take Ginkgo biloba.
Be aware that a case of hemorrhagic stroke associated with the consumption of a popular energy drink has been reported.
Also, be careful if you choose to use a weight loss supplement — the FDA has issued many warnings about weight loss supplements found to contain undeclared sibutramine, a drug which can substantially increase blood pressure and pulse rate in some individuals, and may present a significant risk for people with a history of stroke (Scroll down to the "Warnings" section here for a list of some of these products).
ConsumerLab.com Answers
Question:
Do glutathione supplements work to prevent aging or for other conditions?
Answer:
Although glutathione plays an important role in the body as an antioxidant, supplementing with glutathione has not been shown to slow aging or help with conditions associated with reduced levels of glutathione, such as cancer, cataracts, diabetes, and HIV infection.
Glutathione is a protein normally made in the body from three amino acids: cysteine, glutamic acid, and glycine. We get small amounts of glutathione from foods, and this is normally broken back down to amino acids by enzymes in the digestive tract.
As discussed in the Glutathione article on ConsumerLab.com, taking a very large (3,000 mg) single dose was not shown to raise glutathione levels in the body. However, a study in which large amounts of glutathione were given daily for six months did show an increase in glutathione levels. Taking large amounts of the amino acids of which glutathione is comprised, such as cysteine, or whey protein (which is high in cysteine), may also raise glutathione levels, as may taking other antioxidants, such as vitamin C or lipoic acid, which spare glutathione from being used in the body.
Nevertheless, there are no studies showing a clinical benefit on any disease or medical condition from taking glutathione supplements. For more information, see the Glutathione article on ConsumerLab.com.
Also see answers to the following questions:
Immunocal is much more expensive than other whey protein isolates - is it worth the extra cost? >>
What is the difference between cysteine and cystine? >>
Do any supplements help prevent or treat a cold? >>
Also see this Warning:
Glutathione Supplement Maker Warned For Manufacturing Violations and Drug Claims
ConsumerLab.com Answers
Question:
Which supplements can help treat constipation?
Answer:
A number of supplements may be helpful in treating or preventing constipation. Fiber supplements, such as psyllium and glucomannan (a water-soluble fiber) may help to relieve constipation (Note: there is a safety concern when using glucomannan). Ground flaxseed, another source of fiber, may also be helpful. (See ConsumerLab.com's Fiber Supplements Webinar for more information about these supplements for constipation as well as for other uses.)
A specific probiotic product was found to significantly increase the number of bowel movements per week in people with chronic constipation. (Other strains have been found to be helpful for constipation associated with IBS).
Magnesium and aloe vera juice (with latex) can help to relieve constipation due to their laxative effects (Note: There are safety concerns with aloe latex -- see the "Concerns and Cautions" section of the Aloe Vera Review before using).
See the Encyclopedia article about Constipation for information about other proposed treatments.
Be aware that constipation may be a side-effect of certain supplements, especially iron, and to a lesser degree, calcium (see the "ConsumerTips" sections of the respective ConsumerLab.com Reviews for more about forms of these minerals which may be less likely to have this effect). Other supplements reported to cause constipation, although less frequently, include nattokinase, chlorella, NAC (N-acetyl cysteine) and beta-sitosterol.
Excessive intake of vitamin D as a supplement can cause hypercalcemia (too much calcium in the blood) with symptoms including constipation.
ConsumerLab.com Answers
Question:
Which supplements can cause diarrhea?
Answer:
There are a number of supplements which can cause diarrhea. Discussed below are some of the most common culprits. Diarrhea can also be caused by certain medications, illness and infection, and certain health conditions, such as irritable bowel syndrome (IBS) and lactose intolerance -- so be sure to consult with your physician if you experience severe or chronic diarrhea.
Supplements with a laxative effect:
Magnesium supplements can cause diarrhea and, in fact, are often taken for their laxative effect. However, if you are taking magnesium for other reasons, and want to avoid this effect, certain forms of magnesium are less likely to cause diarrhea. Taking your magnesium supplement with food can also reduce the occurrence of diarrhea.
Aloe supplements containing latex are also known for their laxative effect. If you are taking aloe for a different purpose, be sure to choose a product labeled as aloe gel or vera leaf juice which has been processed to remove the latex.
Be aware that many weight loss supplements contain herbs with laxative properties, such as cascara, frangula, rhubarb root and senna, so be sure to carefully read the label if you are taking a supplement for weight management or "cleansing", such as certain acai supplements and drinks.
Certain types of fiber can also have a laxative effect, but do not necessarily cause diarrhea — some forms of fiber, in fact, may be helpful for diarrhea associated with IBS.
Other common supplements that can cause diarrhea:
Fish oil and other supplements containing omega-3 fatty acids, or a combination of omega-3 and omega-6 fatty acids, such as flaxseed oil and borage oil, can cause diarrhea. Taking smaller doses throughout the day, rather than a single, large dose, may help reduce this effect.
Taking large doses of vitamin C can cause diarrhea. Other supplements which can cause diarrhea when taken in high doses include ashwagandha, NAC (N-acetyl-cysteine), lysine, iodine and kelp supplements which contain iodine, D-limonene, and yacon syrup.
Other supplements which can cause diarrhea include curcumin/turmeric, St. John's wort, berberine, creatine, 5-HTP, nattokinase, chlorella, modified citrus pectin (MCP), and beta-sitosterol, a common ingredient in cholesterol-lowering supplements and prostate supplements.
Unexpected sources:
An often-over-looked cause of diarrhea from supplements can be from added sugar substitutes such as sorbitol. Sorbitol can be found in protein and nutrition bars (ConsumerLab.com lists amounts of sugar alcohols (such as sorbitol and mannitol) in popular bars in its Review) and some protein powders and drinks and meal replacement and weight management meals and shakes. These chemicals can also be found in certain zinc lozenges and some B12 supplements, especially dissolvable tablets, liquids and sprays, although occasionally in regular tablets as well.
ConsumerLab.com Answers
Question:
Can taking NAC (N-acetylcysteine) interfere with blood tests?
Answer:
Although very high doses of NAC can potentially interfere with blood tests for cholesterol, this is unlikely to occur with the dose in typical servings of NAC from supplements. For more details, see Concerns and Cautions in the NAC Supplements Review.
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Product Review: N-Acetyl Cysteine Supplements |
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Initial Posting: 9/26/14 Last Update: 12/4/17
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Choosing the Right N-Acetyl Cysteine SupplementsTests of NAC (N-Acetyl Cysteine) Supplements Show Which Provide Best Quality and Value
— Find Out How Your NAC Supplement Compares —
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NAC (N-acetyl cysteine) is a supplement which the body converts into glutathione, an important antioxidant. Supplementation may be helpful for reducing symptoms of the flu and flare-ups of chronic bronchitis and COPD. NAC may also be beneficial in Sjogren's syndrome, renal failure, schizophrenia, compulsive behavior, and polycystic ovary disease.
We independently and rigorously tested the quality of many popular NAC supplements on the market. Among the products that passed testing, the cost to obtain an equivalent dose of NAC ranged from just 9 cents to 70 cents -- meaning that you can save a lot by shopping wisely. Some products contain added ingredients, but it may not be worth paying more for these. We also found that the daily suggested dose ranged just 500 mg to 1,800 mg, so it's critical that you know how much you really need rather than rely on labels.
You must be a member to get the full test results for NAC supplements along with ConsumerLab.com's recommendations and quality ratings. You'll get results for ten NAC supplements selected by ConsumerLab.com and for four others that passed the same testing through CL's voluntary certification program, as well as information about another product very similar to one of those that passed testing.
In this comprehensive report, you'll discover:
- Which NAC supplements passed or failed our tests
- Which of the best NAC supplements provide the greatest value, i.e., high-quality NAC at lowest cost
- Why additional ingredients are sometimes added to NAC supplements and whether they matter
- What "free form" NAC means and whether it's important to look for it on labels
- Dosage of NAC for specific uses — as well as the evidence for or against these uses
- Concerns, cautions, and potential side effects with NAC
Learn More About Finding the Best N-Acetyl Cysteine SupplementsQuestion:
If I buy NAC as a loose powder in a large bag, as opposed to in tablet form, will it spoil? I've heard it can spoil or degrade into a harmful by-product. Get the answer >>
Question:
Is it true that NAC can help clear nasal passages? Get the answer >>
Question:
Which supplements reduce the risk of stroke? Which increase the risk of stroke? Get the answer >>
Question:
Do glutathione supplements work to prevent aging or for other conditions? Get the answer >>
Question:
Which supplements can help treat constipation? Get the answer >>
Question:
Which supplements can cause diarrhea? Get the answer >>
Question:
Can taking NAC (N-acetylcysteine) interfere with blood tests? Get the answer >>
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