How Sunlight Could Prevent Alzheimer’s and Cancer

In part one of this series on Vitamin D, Dr. Frank addresses the epidemic of vitamin D deficiency: 30 to 100 percent of Americans don’t get enough of this crucial hormone. This deficiency can play a role in almost every major disease including 17 kinds of cancer, MS, Parkinson’s and Alzheimer’s. He explains that since only about 10 percent of vitamin D comes from diet, the two best sources are the sun and supplements. In part two, Dr. Frank advises us on how to tell if we are vitamin D deficient. In this post, Dr. Frank addresses vitamin D toxicity, tanning beds and more. 

My Doctor told me to avoid the sun, what do you think?

There is an old Italian saying “Where the sun does not go the doctor does.”

For about the last 25 years, doctors (dermatologists in particular) have demonized sun exposure and repeatedly told us it is bad for you and causes cancer. But is that true? In the last few years, numerous studies have shown that modest exposure to sunlight may actually be good for you, helping the body produce the vitamin D it needs to keep bones healthy and protect against cancer, including skin cancer. Though repeated sunburns–in children and very fair-skinned people–have been linked to melanoma, there is no credible scientific evidence that moderate sun exposure causes it. Since it’s almost impossible to get adequate amounts of vitamin D from food alone (including fortified milk and fatty wild fish), sun is your best source. I’m not suggesting you go bake in the sun with your suntan oil or go to tanning salons. But getting some sun without getting sunburned makes healthy sense. We evolved in the sun; we were made to get some sun, not to live our lives indoors and slather on sunscreen every time we go outside. If the sun is shining where you are today, get out and enjoy it, talk about a free natural treatment! All you need is a little common sense when heading outdoors, do it gradually and always avoid sunburn. Special Note: Remember to take antioxidants when you sit in the sun, as these can help prevent skin cells from sun damage.

How much sunshine do you need?

All living things need sun, the key is balance. Too much sun exposure can cause melanoma and skin aging, while too little creates an inadequate production of vitamin D. The amount needed depends on the season, time of day, where you live, skin pigmentation and other factors. As a general rule, if you are not vitamin D deficient, about 20 minutes a day in the spring, summer and fall on your face and arms or legs without sunscreen is adequate. It doesn’t matter which part of the body you expose to the sun. Many people want to protect their face, so just don’t put sunscreen on the other exposed parts for those 20 minutes.

If you live north of 37 degrees latitude (approximately a line drawn horizontally connecting Norfolk, Virginia to San Francisco, California) sunlight is not sufficient to create Vitamin D in your skin in the winter months, even if you are sitting in the sun in a bathing suit on a warm January day! The further you live from the equator, the longer exposure you need to the sun in order to generate vitamin D.

What about the use of tanning beds to get my vitamin D?

I tend not to recommend them because we don’t really know if they are safe. Because the light sources vary with different tanning beds, it makes them unpredictable and possibly unsafe. In addition, most commercial tanning beds emit an unknown amount of EMF and because one is so close to the actual bed, it may be an unnecessary high dose. Theoretically both these problems could be overcome, but in reality they usually are not.

Can I take cod liver oil to get my vitamin D?

Although Cod liver oil contains a fair amount of vitamin D, it also contains high amounts of vitamin A. Vitamin A antagonizes the action of vitamin D and can be toxic at high levels.

Next: What are food sources of vitamin D and what about vitamin D toxicity?

What are food sources of vitamin D?

Fish liver oils, such as cod liver oil.
Fatty wild fish like mackerel, salmon, halibut, tuna, sardines and herring
Fortified milk, orange juice and cereal
Dried Shiitake mushrooms
Egg yolks

(But to get adequate amounts of vitamin D from food, you would have to eat at least 5 servings of salmon a day or drink 20 cups of fortified milk.)

How much vitamin D do I need?

How much vitamin D you need varies with age, body weight, percent of body fat, latitude, skin coloration, season of the year, use of sun block, individual variation in sun exposure, and – probably – how ill you are.

As a general rule, old people need more than young people, big people need more that little people, fat people need more than skinny people, northern people need more than southern people, dark-skinned people need more than fair skinned people, winter people need more than summer people, sun block lovers need more than sun block haters, sun-phobes need more than sun worshipers, and ill people may need more than well people.

What I and many of my colleagues around the country are finding is that even people spending what we thought was adequate amount of time in the sun, are still showing up with low blood vitamin D levels. I am not sure why at this stage, but there is an easy and cheap solution: vitamin D supplementation.

How much vitamin D should I supplement with?

Most important is that you take vitamin D3, (cholecalciferol) the active form of vitamin D. Do not take vitamin D2 as it is not as biologically active nor as effective, and nor as safe as vitamin D3. And taking the right amount is crucial, most doctors tend to under dose. The current recommendations from the Food and Nutrition Board of the U.S. Institute of Medicine (from 200 to 600 IU/day depending on one’s age) are way too low. These values were originally chosen because they were found to prevent osteomalacia (bone softening) and rickets.

Here are some guidelines:

If your blood level is above 45ng/ml and for maintenance, I recommend 2,000-4,000 IU daily depending on age, weight, season, how much time is spent outdoors, where one lives, skin color and obviously blood levels. (If you are older, larger, living in the northern latitudes during the winter, are not getting sun and have dark skin, I recommend the higher maintenance dose.)

If your blood level is 35-45 ng/ml, I recommend you correct it with 5,000 of vitamin D3 a day for 3 months under a doctor’s supervision and then recheck your blood levels.

If your blood level is less than 35 ng/ml, I recommend you correct it with 10,000 of vitamin D3 a day under a doctor’s supervision and then recheck your blood levels after 3 months. It takes a good 6 months usually to optimize your vitamin D levels if you’re deficient. Once this occurs, you can lower the dose to the maintenance dose of 2,000 – 4,000 IU a day.

What about vitamin D toxicity?

It is impossible to generate too much vitamin D in your body from sunlight exposure: your body will self-regulate and only generate what it needs. Although very rare, it is possible to overdose and become toxic with supplementation as vitamin D is a fat soluble vitamin and therefore stored in the body for longer periods of time. Therefore if you are taking 5,000 IU or more daily, you should have your blood levels monitored approximately every 3 months.


William C
William Cabout a year ago


W. C
W. Cabout a year ago

Thank you.

Debbie Crowe
Debbie Crowe6 years ago

I always feel better on sunny days and like to be outside. In the spring, summer and in the fall, that's easy to do. But, on sunny days in the winter with snow & ice on the ground, I don't get out too much!! I'll have to get some Vitamin D tablets.

K s Goh
KS Goh7 years ago

Thanks for the article.

Brenda Towers
Brenda Towers7 years ago

I try to go out doors each day, but of course I use sun protection cream all year round! I try to balance this by taking Vit. D tablets.


When you live in countries with extremely high u/v levels, like here, in Australia ( and as Sa R noted.. Israel!) it is a bit hard to really know what you are doing! I realize that SOME sunshine is good, but many of us, who HAVE to be out in the midday sun, are being slowly fried by the sun, even when you are exposed for just a short period of time. Some day, you go out into the sun and in one or two minutes, you feel as if you are being slowly roasted in an oven!As we have about the highest levels of skin cancer in the world, it is going to be rather difficult to persuade people to quit using their sunscreen and get back out into those rays! There has been so much media coverage of the dangers of exposure to the sun, that maybe we need to have more articles like this, to make us re-think the knowledge we have had drummed into us! It is certainly food for thought. I think I think maybe I will chicken out and use a mineral sunscreen and delve into that pot of D3, just in case the scientists change their minds again!

Angel Sch
Past Member 9 years ago

i've noted, thanks a lot :).

Jane L9 years ago


Izabela Suzuki-kugler

I love this article. Thank you.

Santanita Grogg
Santanita Grogg9 years ago

Its always about moderation.
No matter what it is. To much of anything is bad for us.