When green beans are frozen and then cooked, retention of some B vitamins (like vitamins B6 and B2) can be as high as 90%! ... More on What's New and Beneficial About Green Beans.
What high-lipoic acid foods can do for you:
Sources of lipoic include: dark green leafy vegetables, including spinach and collard greens; broccoli; animal foods such as beef steak; and organ meats such as calf's liver.
For serving size for specific foods see the Nutrient Rating Chart.
Lipoic acid (also sometimes called thioctic acid) is an enormously important and under-appreciated nutrient whose chemical structure was first discovered in 1951. Our bodies cannot be maximally efficient in producing energy from carbohydrates or fats without the help of lipoic acid. This nutrient is also classified as an antioxidant, and it plays a direct role in protecting our cells from oxygen damage. In addition, our supplies of several different antioxidants, including vitamins E and C, cannot be successfully maintained in the absence of lipoic acid.
An unusual feature of lipoic acid is its ability to function in a water-based or fat-based environment. Some nutrients, like vitamin E, tend to be associated with fat-based areas of the cell (like the cell membrane), and others, like vitamin C, are found primarily in water-based areas (like the inside of the cell, called the cytoplasm). Because lipoic acid can function equally well in both areas, it can support the activity of both types of vitamins.
Lipoic acid cannot be called a vitamin in the traditional sense of the word since our bodies appear capable of producing it. (Nutrition tradition says no substance can be designated a "vitamin" unless it is impossible to produce in the body). The way our cells produce lipoic acid is not entirely clear. We think it gets its two atoms of sulfur from an amino acid (part of protein) called methionine, and we think it gets the rest of its chemical structure from a fatty acid (part of fat) called octanoic acid.
Lipoic acid is nestled into one of the most critical spots in all of the body's energy production pathways. It sits at the end of a process called glycolysis, which our cells use to create energy from sugars and starches. This same spot also occurs at the beginning of the pathways we use to create energy from fats. The placement of lipoic acid at this critical juncture in energy metabolism helps explain its clinical use with conditions like diabetes, where processing of sugar is disrupted, and also with skeletal muscle dysfunction in which muscle cells are unable to produce energy from fats.
The antioxidant function of lipoic acid has been extensively studied, and its ability to help prevent oxygen-based damage to cells is well established. The antioxidant role of lipoic acid may be the key factor in explaining its success in prevent cataract formation in animal studies. Prevention of oxygen-based damage to nerves is also a key area of clinical research on the possible use of lipoic acid.
Because of its two-fold interactions with both water-soluble (vitamin C) and fat-soluble (vitamin E) substances, lipoic acid has been shown to prevent deficiency of both vitamins in both human and animal studies. Other antioxidants seem to benefit equally from the presence of lipoic acid. These antioxidants include coenzyme Q, glutathione, and NADH (a form of niacin).
Because lipoic acid works so closely with many other antioxidant nutrients, deficiency symptoms for lipoic acid alone are difficult to pinpoint. Lipoic acid is required for the maintenance of vitamin C supplies, and symptoms of lipoic acid deficiency can imitate symptoms of vitamin C deficiency. These symptoms can include weakened immune function and increased susceptibility to colds and other infections. In research studies on animals, lipoic acid deficiency has been linked to problems with memory, decreased muscle mass, and failure to thrive (in young animals).
Toxicity symptoms from excessive intake of lipoic acid have not been adequately studied. However, in clinical practice, this nutrient has been given in supplemental form for over 30 years in many European countries as a supportive nutrient for individuals with nervous system damage from diabetes, and no reports of toxicity have been reported in the literature in this regard.
In several animal studies, lipoic acid supplementation has been shown to reduce high blood sugar levels by increasing the activity of insulin and allowing sugar to leave the blood. For this reason, individuals with blood sugar imbalances, particularly hypoglycemia (low blood sugar) may experience toxic effects from excess intake of lipoic acid in the form of insufficient blood sugar. It is important to note that this phenomenon is not well-studied, and that doses of lipoic acid that might cause hypoglycemia are higher than those obtained through diet alone.
One animal study has shown potentially toxic effects of lipoic acid when given simultaneously with thyroid hormone. For this reason, individuals on prescription thyroid hormone medications may want to consult their health practitioner before supplementing with lipoic acid. Once again, the amount of lipoic acid used in this thyroid study was higher than the amount that would be obtained through diet alone.
Although not strictly falling into the category of toxic side effects, individuals with B-complex vitamin deficiencies—especially deficiency of vitamins B1 and B12—should be sure to remedy these deficiencies when supplementing with lipoic acid. Some animal studies have shown a worsening of B-complex vitamin deficiencies when lipoic acid is supplemented in the absence of B-complex vitamins. (Note: All of the above factors involve supplements, not food, and many food sources of lipoic acid—like green leafy vegetables—are also sources of B-complex vitamins.)
At present, there are no studies showing the impact of cooking, storage, or processing on levels of lipoic acid in foods.
Interestingly, because lipoic acid is found in the mitochondria (energy production units) of animal cells, individuals who eat no animal products may be at higher risk for lipoic acid deficiency than individuals who do. Vegetarians who eat no green leafy vegetables may also be at special risk, since the chloroplasts in these leaves house most of the lipoic acid.
Since lipoic acid protects proteins during aging, older individuals may be at greater risk of deficiency.
Similarly, because lipoic acid is used to help regulate blood sugar, individuals with diabetes may be at special risk of deficiency.
Individuals with poor protein intake, and particularly those with poor intake of the sulfur-containing amino acids (the building blocks of protein that contain sulfur, namely, methionine, cysteine, and taurine) may also be at higher risk of lipoic acid deficiency. The reason for this connection is simple: lipoic acid gets its sulfur atoms from these sulfur-containing amino acids.
Because lipoic acid is asorbed primarily through the stomach, individuals with stomach disorders (for example, hypochlorhydria, or low stomach acid) may also be at increased risk of deficiency.
Vitamins C and E, coenzyme Q, glutathione, and NADH all require lipoic acid for their efficient recycling in the body. Deficiency of these antioxidant nutrients will reduce synthesis of lipoic acid in the body.
Lipoic acid gets its two sulfur atoms primarily from the sulfur-containing amino acid methionine. For this reaspon, methionine deficiency can reduce the body's ability to make lipoic acid. Deficiency of other sulfur-containing amino acids, like cysteine and taurine, can also prevent lipoic acid synthesis in our cells.
Food sources of lipoic acid are not well researched. In general, however, two categories of lipoic acid-containing foods have been identified.
Green Plants: The first category includes green plants which have a high concentration of chloroplasts. Chloroplasts are key spots for energy production in plants, and they require lipoic acid for this activity. For this reason, broccoli, spinach, and other green leafy vegetables like collard greens or chard are food sources of lipoic acid.
Animal Foods: Animal foods constitute the second category of lipoic acid sources. Once again, the cell's energy production mechanisms are involved. Mitochondria are critical energy production spots in animal as well as plant cells, and the main location for finding lipoic acid. Body tissues with lots of mitochondria (like the heart, liver, kidney, and skeletal muscle) are good spots for finding lipoic acid, so consumption of these foods (for example, calf's liver or round steak) also provides lipoic acid. Yeast has also been shown to contain this vital nutrient.
There are currently no public health recommendations for lipoic acid.
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