WARNING!
This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.
The benefits of vitamin D have been well-documented over the years. I believe that getting your vitamin D status optimized to between 60 ng/mL and 80 ng/mL is one of the best things you can do to help protect yourself against the fall infectious disease season, which is expected to include both flu and COVID-19.
Health authorities are warning of a second wave of COVID-19, which means the time to start addressing your vitamin D level is now. But, as important as it is to get your level optimized by fall, it's just as important to keep it there throughout the year.
Ideally, your body makes vitamin D when your skin is exposed to sunlight. This is why it's also called the sunshine vitamin.1 The best indicator of your vitamin D level is a blood test measuring the concentration of 25-hydroxy vitamin D, also called 25-OH vitamin D.2
In addition to the crucial role it plays in your immune system, researchers have also found that it's integral to optimizing leptin levels, which in turn are linked to obesity.3 In one study, researchers measured vitamin D and metabolic markers in two age- and gender-matched groups.4
They learned that individuals with deficient or insufficient vitamin D had a higher risk of metabolic syndrome. The results from several studies have also revealed a link between low levels of vitamin D and nonalcoholic fatty liver disease, although the results have not been consistent.
Foot Pain Associated With Knee or Hip Osteoarthritis
Recently, insufficient levels of vitamin D have been associated with foot pain linked to knee osteoarthritis (OA). Before delving into the results of the research, it's important to understand the relationship between low back pain and foot pain associated with severe knee OA.
In a study from 2010, researchers found that those who had OA in the knee and had pain in other joints in the body, were more likely to experience more intense knee pain.5,6 More specifically, the researchers found that when pain was present in the lower back, foot and elbow on the same side as the affected knee, the individual rated their knee pain as more severe than those who did not have pain in other joints.
The study was led by a physician from Harvard Medical School and involved the use of data from the Osteoarthritis Initiative, a study of knee OA involving people from several locations in the northeastern area of North America. The researchers included 1,389 participants who were between 45 and 79 years of age. The results showed that 57.4% had pain in their lower back, and those same individuals had a higher pain score in their knee.
Another group of participants from the same initiative and in the same age range were gathered for a second study.7 Researchers evaluated 1,255 individuals who had symptoms of knee pain related to OA. They noted that 25% of them had foot pain and the majority of those had pain in both feet.
After adjusting for confounding variables, they discovered that people who had foot pain also had lower scores on other health measures compared to those who did not have pain. Those who had bilateral or ipsilateral pain had lower health scores. This suggested that the side of the body where the foot pain occurred was important.
In a third study published in the Journal of the American Podiatric Medical Association, scientists also evaluated the side of the body where foot pain occurred and compared it to the presence of knee OA.8 One author commented about the importance of this identification:9
"The study shows that a physician evaluating a patient for foot pain should also ask about possible hip or knee pain, and vice versa, so we can address all of a patient's issues. In medicine, many times it comes down to 'what does your MRI look like or what does your x-ray look like?'
But it's really important to conduct a thorough medical history and physical exam. A comprehensive orthopedic evaluation may prompt a broader treatment strategy and possibly a referral to another specialist."
Vitamin D May Reduce Pain Level
People with knee OA may experience mild, moderate or severe pain.10 The Arthritis Foundation compares pain medications used for osteoarthritis listing nonsteroidal anti-inflammatories (NSAIDS), acetaminophen and injections of steroids or hyaluronic acid as treatments.11
In some cases, antidepressants are used to treat chronic pain, such as Duloxetine (Cymbalta).12 In all cases, the medications have a long list of side effects. In one study, comparisons were made between NSAIDs and opioids, a drug with known addictive properties, to relieve OA pain. Researchers found that both types of medication reduced pain and the effects were nearly identical.13
When the use of opioids use has been measured across counties, researchers have found that where there is a higher prevalence of disability and arthritis, there is also a higher rate of opioid prescriptions.14
In a recently published study, researchers sought to determine whether sufficient levels of vitamin D could lower foot pain in those with knee OA.15 Using data from a randomized, double-blind placebo-controlled study they undertook a post-hoc data analysis.16
Members of the group were randomly assigned to receive either a monthly dose of vitamin D3 or a placebo for two years. The participants had a mean age of 63.2 years. Of the 413 who were enrolled, 340 completed the study. The researchers used the Manchester Foot Pain and Disability Index (MFPDI) to rate the patients' perceived pain. At the start of the study 23.7% had disabling foot pain.
The data showed greater improvement in people receiving vitamin D and in those who maintained a sufficient level of vitamin D. They concluded that "supplementation and maintenance of sufficient vitamin D levels may improve foot pain in those with knee OA."17 In an article published in Rheumatology Advisor, it was noted that the study had several limitations, one of which may have significantly underestimated the results:18
"The study had several limitations, including those secondary to a post-hoc analysis, lack of data on the clinical importance of the differences in MFPDI scores, and potential underestimation of the benefits of vitamin D, as >60% of patients in placebo group had sufficient vitamin D levels at the end of follow-up."
Slow Osteoarthritis Progression With Omega-3 Fats
A second nutrient the body uses to prevent or slow the progression of OA is omega-3 fat. Dietary fat is essential to good health. While eating too much or not enough is damaging, without healthy fat your body does not work properly.19
Polyunsaturated fats (PUFA) are one type of essential fat, which means you must eat them since the body doesn't make them. The two main types of PUFAs are omega-3 and omega-6.
Both must be consumed in the right amounts or you may develop chronic inflammation. You'll find high concentrations of omega-6 in processed food, and corn, safflower and sunflower oils. While the ideal ratio is 1-to-1, most who eat a Western diet are getting 16 times more omega-6 than is considered healthy.20
As I've written recently, one of the problems with chronic inflammation may be that it promotes the damaging and dangerous cytokine storm found in those with severe COVID-19. The omega-3 index is a measure of omega-3 fat in the blood, or specifically in the red blood cell membranes. It is given as a percentage, with 8% or higher being ideal, putting you in the lowest risk zone.21
In a global meta-analysis of past studies measuring omega-3 levels, the researchers found areas with "very low blood levels (less than or equal to 4%)" included North, Central and South Americas, Europe and Africa.22
This is important since the balance of omega-3 and omega-6 can help regulate inflammation23 and slow the progression of OA after an injury,24 as demonstrated in animal studies. In naturally occurring OA, animals fed a diet rich in omega-3 reduced OA by 50% over those fed a standard diet.25
In a human trial, researchers found that supplementing with fish oil did not change the cartilage volume in knee osteoarthritis, but it did reduce the participants' pain scores over two years.26 Additionally, researchers have discovered a link between OA and metabolic syndrome.27
While metabolic syndrome increases the risk for OA, balancing your omega-3-to-omega-6 ratio can help reduce the potential risk of metabolic syndrome. The authors of one recent meta-analysis concluded:28
"The present meta-analysis indicates that higher intakes of omega-3 PUFAs, but not omega-6 PUFAs, was associated with lower MetS risk; adding to the current body of evidence on the metabolic health effects of circulating/dietary omega-3 PUFAs."
In a second paper, the authors wrote:29
"Lately, an inverse relationship between omega-3 fatty acids, inflammation, obesity and CVDs has been demonstrated … Omega-3 PUFAs have been shown to decrease the production of inflammatory mediators, having a positive effect in obesity and diabetes mellitus type-2. Moreover, they significantly decrease the appearance of CVD risk factors."
Based on these studies, it's apparent that omega-3 has an impact on OA pain and that it can slow the progression of OA as well as help prevent metabolic syndrome, which also raises the risk of OA.
Number of People With Osteoarthritis Has Doubled
The authors of a study published by Harvard University found that people currently living in America were more than two times more likely to have knee osteoarthritis than those who lived there before World War II. They looked at more than 2,000 skeletons with the goal of determining the age of the disease.30
Interestingly, there was a rise in disease after confounding factors were accounted for, such as longer life and the meteoric rise in rates of obesity since 1940.31 The researchers controlled for age and body mass index and still found a significant rise in people with OA. One author was quoted in the Harvard Gazette, saying:32
"We were able to show, for the first time, that this pervasive cause of pain is actually twice as common today than even in the recent past. But the even bigger surprise is that it's not just because people are living longer or getting fatter, but for other reasons likely related to our modern environments. Knee osteoarthritis is not a necessary consequence of old age. We should think of this as a partly preventable disease."
In the skeletons of people over the age of 50, the data showed knee osteoarthritis was 2.6 times more common in those who were born in the post-industrial age, as compared to those born in the late 1800s.33 The researchers also found the rate of OA in both knees in the post-industrial era was 1.4 times higher.
If you are among those who have OA, consider using vitamin D3 supplements to raise your serum levels. It is important to include vitamin K2 MK-7 for reasons I discuss in "What Are the Health Benefits of Vitamin K2?", including reducing your risk of atherosclerosis.
For a list of natural pain relievers and anti-inflammatory supplements that also have demonstrated the ability to reduce pain, see my article, "Number of People Suffering From Osteoarthritis Has Doubled."