Cruciferous Vegetables And Indirect Antioxidants

Previously we talked about how antioxidants are poorly understood at present. We know a lot about how high potassium foods help prevent high blood pressure and osteoporosis. But a lot remains to discover about all the effects of foods. Many of the high potassium foods are also high in antioxidants, both the direct antioxidants and the indirect antioxidants. Researchers feel both these types of antioxidants are important. But finding out how they help is a slow process with missteps along the way.

Broccoli and cross section edit
Broccoli – A Cruciferous Vegetable
Photo by Fir0002 [GFDL 1.2 (], via Wikimedia Commons

Antioxidant Tests Misleading

Recently the USDA has taken down its prior antioxidant ratings of foods because the ratings don't relate to how the antioxidants behave in people. Many studies of antioxidant supplements have shown no helpful effect on health. Most of these studies were limited to vitamins A, C, and E, the direct antioxidants. They are considered direct because they directly counteract free radicals.

The indirect antioxidants, though, play a major role in combating free radicals. They may turn out to be even more important than the direct antioxidants. They act by turning on or off genes that can enhance or diminish the effect of the direct antioxidants. Or they may act by enhancing enzyme systems even without direct antioxidant influence. Researchers cannot measure these effects by the indirect antioxidants by the test tube antioxidant tests, such as ORAC.

Researchers can only measure them by studying what goes on inside the cell. This means studying the enzymes and breakdown products from molecules injured by the free radicals. And then researchers have to try to figure out how all these activities inside the cell combine to produce the favorable effects.

Why Indirect Antioxidants Are Important

Many of the studies of indirect antioxidants occurring during the past 10 or so years have tried to find the pieces of this puzzle. And some are trying to put the puzzle together. A good review (1) from this past January points out how one group of direct and indirect antioxidants interact with each other. And it discusses the interactions with the genetic code in each of us, as well.

The review examines the evidence of how cruciferous vegetables, such as broccoli, help protect against cardiovascular disease and cancer. Epidemiological studies show that eating cruciferous vegetables reduces heart disease and cancer. But how these foods do it is largely unknown.

The epidemiological studies show us that we should eat our broccoli. But most of us want to know WHY we have to eat our broccoli. It can't be just “because I say so.” The studies discussed in the review sort out what happens in our cells when we eat our broccoli. Much of the evidence points to substances in the food, such as sulforaphanes and other glucosinolates, that improve our health by enhancing the activity of enzymes in the cell. When these enzymes ramp up, they improve the action of the direct antioxidants.

So the antioxidants themselves can only do so much on their own. But when you add the sulforaphanes or other glucosinolates, the antioxidants become more powerful. And they stop the free radicals better. This may explain why the antioxidant supplement studies did not show any positive effect. Most people taking the supplements probably did not change their diet. Without the boost from the indirect antioxidants, the effect from the direct antioxidants is limited.

Genes Are Important Too

The sulforaphanes do not work for everyone equally. This is because not everyone has the genes that will respond to them. There are several genes known to influence antioxidant enzymes. And there are probably others not yet discovered. One set of genes producing enzymes that ramp up the antioxidants are absent in about 10-20% of Caucasians, and as high as 64% of Asians.

Several epidemiological studies showed those without the genes benefited most from eating broccoli. Another set of studies showed those with the genes benefited most. Eventually scientists will know all the genes affected by eating broccoli (and other foods). And this knowledge will resolve this type of discrepancy. When we better understand the nutritionally influenced genes, a personalized diet designed to maximize your health will be possible.

Nutrigenomics (the study of the interaction of nutrition and genes) is a rapidly growing field of study that will answer a lot of nutritional questions. It provides tests to guide individuals' nutritional choices. As researchers perform more studies like the ones mentioned, we will know what foods are best for each of us.

Eat Your Broccoli

In the meantime, the best bet is to follow the eating patterns of the people with the best health in the epidemiological studies. Those patterns include eating high potassium foods with several good helpings of cruciferous vegetables every day. So EAT YOUR BROCCOLI, or cauliflower, cabbage, asparagus, brussel sprouts, turnip, rutabaga, cress, bok choy, kale, collard greens, kohlrabi, mustard seeds, arugula, radish, or wasabi.

See the raw vegetables table for the potassium content of these powerful foods. The “Links to Food Potassium Tables” tab at the top of the page will have a link to the raw vegetables table, as well as to tables for other food groups.
1. Induction of Phase 2 Antioxidant Enzymes by Broccoli Sulforaphane: Perspectives in Maintaining the Antioxidant Activity of Vitamins A, C, and E. Sekhar Boddupalli, Jonathan R. Mein, Shantala Lakkanna, Don R. James, Front Genet. 2012; 3: 7. Published online 2012 January 24. doi: 10.3389/fgene.2012.00007 PMCID: PMC3264924

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