Tag Archive for: citrus

Does Vitamin C Increase Melanoma Risk?

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Last week’s Memos on citrus fruits raised an obvious question; one reader mentioned it, so I thought I should write about it. Here’s the question: was vitamin C examined for any possible relationship with the development of melanoma? Yes, but take a look at what the researchers wrote in the set-up for the study.

After examining the research, they found that vitamin C is toxic for melanoma cells; it kills melanoma cells via multiple pathways and prevents them from multiplying. These are all test-tube studies but still give some indication of the potential role within the body. Because of the prior research, they hypothesized that any increased risk for getting melanoma was related to other compounds in citrus fruit, such as the phytonutrients, and not the vitamin C.

As you would expect, vitamin C levels increased as more citrus fruit was eaten. However, the risk of melanoma didn’t rise as the vitamin C levels from fruit and supplements increased. That confirmed it was some other aspect of the fruit that led to a higher rate of melanoma.

Let’s be sure that we don’t interpret the results to mean that we should megadose on vitamin C to prevent melanoma; the research definitely does not say that. But the skin is connective tissue, so it may be prudent to take additional vitamin C, glucosamine, and collagen to protect your skin, especially if you’re a sun-lover.

This study is also a reminder that our diet needs to be balanced. Too much of anything—even something as healthy as citrus fruit—can lead to problems. Everything in moderation.

What are you prepared to do today?

        Dr. Chet

Reference: J Clin Oncol 2015; 33:2500-2508.

My Clementine

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In doing the background research on whether citrus increases the risk of melanoma enough to be a real concern, there was one more important study that was published this year. The same basic group of researchers who did the original examination of citrus intake in the two large healthcare professional studies added one more component. They used a database of FURs (furocoumarins) levels from 10 different foods that were included in the food frequency questionnaire and re-examined the data. This time, there was no relationship between FUR and melanoma; there was a small relationship with basal cell carcinoma but nothing of great significance.

I’m still going to eat my clementine every morning and drink my energy drink that has grapefruit juice in it when I want to. But these studies did raise at least two questions.

The Furocoumarins Database

The database was constructed by selecting foods that were suspected of having high FUR levels, which makes sense. The chemical analysis of each food is above my pay grade, but let’s assume it’s accurate since no one questioned it in the years since that study was completed. They purchased the foods for analysis from 17 different grocery stores in Connecticut and then analyzed three different samples of the same food purchased from different stores. All good.

The issue is that phytonutrient content can vary based on the season of the year, the ripeness of the fruit or vegetables, even the time of day it was harvested. FURs are stress-induced molecules. After harvesting, FUR levels can be affected by many factors ranging from ultraviolet light exposure to insect infestation. The levels can also vary by the variety of the fruit or vegetables. Then, when it comes to juice, there are processing and storage factors to consider. None of that was considered in the database study.

To be fair, buying foods that we actually eat is the right thing to do. But as a grocery shopper, you know that you can purchase two identical containers of food with two different expiration dates. That has to be accounted for, even if only to find out it doesn’t make a difference. In the case of FURs, it appears the date matters, based on prior research.

Food Frequency Questionnaires

If you’ve been reading the Memo for any length of time, you know that I’m not a big fan of food frequency questionnaires for the way they’re typically used today. The FFQ was designed to give an overall estimate of what people eat, but it’s not a measurement of what people actually ate. When you want to know the overall servings of citrus a person eats, fine. When you begin to break it down into extremely discrete serving portions, that’s where things fall apart in my opinion. Think of how many of these large studies that have used the FFQ that have gotten results that indicate nutrients are associated with some disease or another. In other studies, the reverse is true.

The reason that these are imprecise is because they were validated with a low number of subjects: 173 for one FFQ and 150 for another. The correlation coefficients are just not high enough to put a lot of faith in the FFQ for anything other than a general idea of diet. I’ve got a lot more to say about the topic but this isn’t the forum.

In addition, I think we’d be foolish to overlook the fact that the places where citrus grows in the backyard, and is therefore more convenient and available, are the same places that get more sunny days every year and more intense sun. The researchers controlled for self-reported sun exposure, but I’m almost as skeptical about that as about FFQs.

The Bottom Line

Based on the sum total of all the research, FURs are in some way related to the development of skin abnormalities, especially if you spend a lot of time in the sun. But given all the issues with the FFQ, at least in my opinion, it isn’t enough to avoid citrus if you typically eat or drink it. Pass my clementine, please.

What are you prepared to do today?

        Dr. Chet

References:
1. J Clin Oncol 2015:33:2500-2508.
2. Nutr Cancer. 2020;72(4):568-575.
3. J Food Science. 2011. doi.org/10.1111/j.1750-3841.2011.02147.x
4. J. Agric. Food Chem. 2017, 65, 24, 5049-5055.

Are Furocoumarins the Problem?

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If you’ve been reading the Memos for any length of time, you know I talk about phytonutrients a lot. They’re chemicals in plants that help the plant protect itself against threats such as bacteria, insects, birds, and anything that wants to eat them—such as humans. You might also believe that all phytonutrients are safe and beneficial. That might not be true. Let me explain.

The purpose of the studies on citrus consumption and skin cancer was related to the observation that a class of phytonutrients called furocoumarins (FUR) could be related to an increase in skin cancer, especially melanoma. It turns out that these phytonutrients are photosensitive; when exposed to light, they may cause damage to cell layers. Furocoumarins have been used as a treatment for psoriasis. And one of the major sources of FUR is citrus fruit.

In the study I mentioned Tuesday, the study found a 36% increase in cases of melanoma in those who consumed the most citrus, specifically grapefruit, compared to those who consumed the least. In a similar study on the subject in the Women’s Health Initiative, eating and drinking citrus resulted in a 12% increase in cases of melanoma over 15 years. That assumes that the fruit and juice actually contained the furocoumarins. More about that on Saturday.

What do the results mean for us? In 2016, 22 out of every 100,000 people had some form of melanoma. A 36% increase in the rate would mean that 30 out of every 100,000 people would be affected, and a 12% increase would be 26 out of every 100,000 people. Remember, that risk is for those who consumed citrus every day for 24 and 15 years respectively. As you might expect, nothing is as ever as simple as it seems as you’ll find out on Saturday.

What are you prepared to do today?

        Dr. Chet

References:
1. J Clin Oncol 2015:33:2500-2508.
2. Nutr Cancer. 2020;72(4):568-575.

Does Citrus Increase Melanoma?

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I could write about COVID-19 every week, but health is more than dealing with a viral pandemic, and it’s important we don’t neglect other aspects of our health while we try to keep ourselves safe. When the news and developments warrant, I’ll do an audio update so you can download it just like the free COVID-19 Bottom Line. But whenever we get to the new normal, we’ll still have some of the same health challenges; cardiovascular disease, diabetes, and cancer aren’t going away just because we have to self-isolate for a while.

A reader asked about a news article that showed eating and drinking citrus, specifically grapefruit, could increase the risk of getting melanoma, a severe form of skin cancer. A 2015 study based on the Healthcare Professionals Study and the Nurses Health Study showed a 36% increased risk of melanoma over 24 years when comparing those who consumed the most citrus with those who consumed very little. In doing the background research on the study, there were two other studies that demonstrated similar results.

Should we skip the glass of orange juice every day? What’s in citrus that could be a factor? I’ll answer those questions the rest of the week.

What are you prepared to do today?

        Dr. Chet

Reference: J Clin Oncol 33:2500-2508.