Pumpkin seeds have long been valued as a source of the mineral zinc, and the World Health Organization recommends their consumption as a good way of obtaining this nutrient. More on the Health Benefits of Pumpkin Seeds.
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Can you please direct me to where I can find a list of alkaline foods to help balance the excess acidity?

The issue of acid and alkaline foods is a confusing one, because there are several different ways of using these words with respect to food.

Acidic and alkaline foods

In food chemistry textbooks that take a Western science approach to foods, every food has a value that is called its "pH value." pH is a special scale created to measure how acidic or alkaline a fluid or substance is. It ranges from 0 (most acidic) to 14 (most alkaline) with 7.0 being neutral. One way of thinking about it is that as you get closer to 7.0 from either end, the food becomes less acidic (6.0 vs 5.0, for example) or less alkaline (8.0 vs 9.0, for example).

Limes, for example, have a very low pH of 2.0 and are highly acidic according to the pH scale. Lemons are slightly less acidic at a pH of 2.2. Egg whites are not acidic at all, and have a pH of 8.0. Meats are also non-acidic, with a pH of about 7.0.

Many vegetables lie somewhere in the middle of the pH range. The pH of asparagus, for example, is 5.6; of sweet potatoes, 5.4; of cucumbers, 5.1; of carrots, 5.0; of green peas, 6.2; of corn, 6.3. Tomatoes fit on the pH scale on the lower end of most vegetables. Their pH ranges from 4.0 to 4.6. This range is higher (less acidic) than pears, for example, with a pH of 3.9, and also higher (less acidic) than peaches, with a pH of 3.5, or strawberries (3.4) or plums (2.9).

Acid-forming and acid-ash, alkaline-ash foods

Another way to talk about food acidity is not to measure the acidity of the food itself, but the body's acidity once the food has been eaten. In other words, from this second perspective, a food is not labeled as "acidic," but instead as "acid-forming."

Similar to this "acid-forming" concept is the "acid-ash, alkaline-ash" concept, in which a food is not chemically broken down in the body, but instead burned, leaving an ash residue, which is then measured for its mineral content. Acid-ash foods are foods that leave high concentrations of chloride, phosphorus, or sulfur in their ash. These foods are called "acid-ash" because chloride, phosphorus, and sulfur are minerals that are used to make acids in the body (namely, hydrochloric acid, phosphoric acid, and sulfuric acid). Alkaline-ash foods are foods that leave high concentrations of magnesium calcium, and potassium in their ash. These foods are called "alkaline-ash" because these minerals are used to form alkaline compounds (called bases) in the body (including magnesium hydroxide, calcium hydroxide, and potassium hydroxide).

The acid-ash model of measuring food acidity is not, of course, what happens inside a living person. We don't burn our food, and ash is not all that's left after we eat. In fact, the whole concept of acid-forming foods is a much more complicated idea than the pH idea, since "acid-forming" is process that happens inside a living body.

How well a food is digested, for example, can influence the degree to which it is acid-forming or not. Many foods, including tomatoes, have preformed acids in their composition that would normally be altered during digestion. However, in a person with problematic digestion, these acids might not get transformed, and the acid-forming properties of the tomato would be increased.

Research on the acid-forming and acid-ash, alkaline-ash foods principle

Although there are many popular diets that revolve around the principle of acid-forming foods, there are virtually no research studies that have focused on this issue. A survey about dietary patterns and lifestyles carried out in China in the early 1990's has shown that higher intake of animal foods and animal-derived proteins results in increased loss of calcium and acids in the urine, while increased intake of plant foods and plant proteins results in lower calcium and acid loss. Presumably, the loss of acids in the urine reflected increased formation of acids in the body that needed to be excreted, and decreased urine acids reflected less formation of acids in the body. Vegetables were one of the major groups of plant foods focused on in the study, and vegetables are a group of food that have been described in many alternative dietary approaches as being non-acid-forming.

List of alkaline foods

You asked us where to find a list of alkaline foods, and according to this second way of looking at alkalinity and acidity, you can find lists at the following websites:



Macrobiotic eating plans often focus on this issue of acid-forming foods, and the need to find balance in the diet and avoid extremes.

Concerning tomatoes

Finally, on to your question about lowering the acidity of tomatoes. First, from a pH perspective, tomatoes fall into the 4.0-4.6 range, and are not nearly as acidic as most fruits. From a strict pH perspective, reducing excess acidity in the diet would mean eliminating foods with the lowest pH, including limes, lemons, vinegars, cranberries, plums, soft drinks, grapefruit, strawberries, raspberries, oranges, peaches, cherries, olives, pears and grapes. All of these foods have a lower pH than tomatoes.

We would not recommend that all of these foods be eliminated from a person's diet! (We might be o.k. with the elimination of soft drinks, however). Many of these foods are among the World's Healthiest Foods and they have been shown to have cancer-preventing and cancer-treating properties. But tomatoes are unlikely to be the most acidic components of most meal plans, if you are evaluating these meal plans from a pH perspective.

Second, the acidity of tomatoes is closely associated with their degree of ripeness. The more mature and ripe, the lower the acidity, approaching the 4.6 pH end of the range described earlier. For this reason, if a person is looking for ways to lower the pH of his or her tomatoes, we would suggest buying only the ripest ones, and steering clear of anything less than fully ripe.

Canned tomatoes are almost always more acidic than fresh tomatoes because of the impact of the canning process. The pH of canned tomatoes can dip down into the 3.2-3.5 pH range. For this reason, avoiding canned tomatoes would be another recommendation if a person were trying to consume foods with a higher pH.

Finally, from a pH perspective with respect to cooking, we haven't seen any evidence that cooking of tomatoes can significantly increase their alkalinity above the 4.5 range. But we also don't think of the 4.5 range of fully ripe, fresh, organically grown tomatoes as a problem, particularly when combined with other vegetables in our recipes that bring in plants whose pH is in the 5-6 range.

If we switch to consider tomatoes from an acid-forming perspective, it's important to realize that tomatoes are actually considered non-acid forming, i.e., alkaline, in most macrobiotic and Chinese medicine traditions. For example, tomatoes are often viewed as being able to alkalize the blood in these traditions and are sometimes recommended to lower the excessively acidic blood that is understood to be characteristic of gout and rheumatic conditions. From this acid-forming perspective, tomatoes would already be considered alkaline and you would not need to worry about doing anything to them on the stove to increase their alkalinity.


Hu, J. F.; Zhao, X. H.; Parpia, B., and Campbell, T. C. Dietary intakes and urinary excretion of calcium and acids: a cross- sectional study of women in China. Am J Clin Nutr. 1993 Sep; 58(3):398-406.

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