Currently browsing posts about: Vitamins

Nothing about nutrition is simple.

I was intrigued by the Observatory column in the New York Times last week.  USDA researchers showed that supermarket spinach stored under continuous fluorescent light retained more vitamins than spinach stored in the dark for at least 9 days.  Their hypothesis: the light promotes continued photosynthesis and protects against degradation.

I was curious to know whether they measured vitamin C.  I checked the article in the Journal of Agricultural and Food Chemistry (February 2010, DOI: 10.1021/jf903596v).  Indeed they did.  This seems odd because this vitamin is well known to be degraded by light.  That is why orange juice is usually stored in opaque containers.  One explanation might be that orange juice is stored a lot longer than 9 days.

Cooking also destroys vitamin C.  While I was looking for that article I came across this one, which describes experiments looking at the effects of common cooking practices (boiling, microwaving, and steaming) on beneficial antioxidants and phytochemicals in Brussels sprouts.

Steaming increased phytochemicals in fresh and frozen sprouts.  Boiling did too, but only in the fresh vegetables.  Cooking reduced phytochemical content in frozen samples.  Microwaving was the best cooking method for retaining color and vitamin activity.  As expected, all cooking methods destroyed vitamin C.

So what to make of this?  Eat a mixture of cooked and uncooked vegetables and the vitamins will take care of themselves.  If you do cook, steaming is great and microwaving is better for preserving vitamin activity.  For vitamin C, raw wins every time.

Happy weekend!

It’s hard not to think of multivitamin supplements (which also include minerals) as perfectly safe, since the amounts of specific nutrients rarely exceed recommended levels.  But according to recent reports, formulation mistakes get made and these don’t always get caught by quality controls.  Here are two examples.

According to FoodProductionDaily.com, 25% of Adverse Event Reports (AERs) sent into the FDA last year concerned multivitamin supplements. This, says one supplement trade association, should not be interpreted to mean that there is anything wrong with the supplements.  Maybe not, but how about checking?

I say this because of the high zinc levels in the Nutro pet food recently recalled by Mars (see previous post).  Thanks to Sophie for sending a link to a report that some bags of the kibble contained zinc at more than 2000 ppm as compared to the 75 ppm that is supposed to be there.   This, of course, is why I keep insisting that everyone, not just pet owners, should be concerned about the quality of pet food.  We only have one food supply.  If a problem exists with pet food, it’s quite likely that something similar could happen to ours.

The take-home lessons:

• For food manufacturers: Don’t trust the suppliers of vitamin/mineral mixes; test them!
• For the government: How about requiring all supplement manufacturers to follow HACCP (science-based food safety) plans, with testing and quality control.
• For customers (this means you): Contact the consumer affairs representative listed on the package label, ask if the company tests vitamin and mineral levels in finished products, complain if it doesn’t, and demand to see test data if it does.

Addendum: October 16, 2009: Thanks to Anthro for sending a link to this October 7 article from the website of the New England Journal of Medicine: “American roulette – contaminated dietary supplements.”   This is only to be expected from deregulated industries.

My latest column for the San Francisco Chronicle tackles today’s vexing questions about vitamin D.  How much do we need? How much is safe? How much of the fuss about it is due to marketing hype? No easy answers on this one, alas.

Evidence continues to accumulate, little bit by little bit, that fat-soluble antioxidants and antioxidant vitamins–in this case, lycopenes, lutein, and beta-carotene vs. vitamin E–interfere with each other’s absorption. Here’s the short description and here’s the original paper so you can see how the little bits accumulate. For me, the take-home lesson is easy: eat food, not supplements.

A writer for a women’s magazine asks: If you want to get more of a specific nutrient (lycopene, for example), is it better to take a dietary supplement or to eat foods containing that nutrient? What benefits do you get from eating a whole food that you might miss if you took a supplement instead?

My response: Unless you have been diagnosed with a vitamin or mineral deficiency and need to replenish that nutrient in a great big hurry, it is always better to get nutrients from foods—the way nature intended. I can think of three benefits of whole foods as compared to supplements: (1) you get the full variety of nutrients—vitamins, minerals, antioxidants, etc–in that food, not just the one nutrient in the supplement; (2) the amounts of the various nutrients are balanced so they don’t interfere with each other’s digestion, absorption, or metabolism; and (3) there is no possibility of harm from taking nutrients from foods (OK. Polar bear liver is an exception; its level of vitamin A is toxic). In contrast, high doses of single nutrients not only fail to improve health but also can make things worse, as has been shown in some clinical trials of the effects of beta-carotene, vitamin E, and folic acid, for example, on heart disease or cancer. And foods taste a whole lot better, of course. For more on this, see chapter 37 in What to Eat on “Supplements and Health Food.”