Ray Peat on Vitamin D

January 29, 2026

Effects of an Increase in Parathyroid Hormone on Body Tissues

“When vitamin D or calcium is lacking, or when phosphate is in excess, and in cases of hypoglycemia and stress (Ljunghall et al., 1984), parathyroid hormone rises. This can lead to softening of the bones and hardening of soft tissues, especially the arteries, sometimes also the brain, skin, and other organs. Parathyroid hormone raises blood pressure, even before calcium hardening is detected.”

September 2017 – Ray Peat's Newsletter

Effects of Calcium and Vitamin D on Metabolism

“A moderate increase in calcium and vitamin D reduces obesity and increases metabolic rate, and some of the mechanisms involved are known.”

September 2017 – Ray Peat's Newsletter

Reduction of Parathyroid Hormone in Relation to Overweight and Related Problems

“The reduction of parathyroid hormone through more calcium and vitamin D is closely linked to less overweight and the health problems associated with overweight – high blood pressure, insulin resistance, heart arrhythmias, depression, and various inflammatory diseases.”

September 2017 – Ray Peat's Newsletter

Aging Skin, Progesterone, and Vitamin D

“It has been known for several decades that the production of progesterone and DHEA steadily decreases with age, and in recent years it has been found that older skin produces only about half as much vitamin D in sunlight as young skin. Old skin contains about half as much cholesterol as young skin, so it is not surprising that the substances derived from it are also reduced.”

November 2018 – Ray Peat's Newsletter

Progesterone and Vitamin D in the Restoration of Nerve Function

“Studies on the effects of progesterone on the restoration of nerve function after traumatic brain injuries have found that vitamin D enhances its effectiveness. By improving calcium homeostasis and counteracting the effects of parathyroid hormone, which activates calcium channels, vitamin D (25-hydroxycholecalciferol) is increasingly regarded as a neurosteroid (Groves et al., 2014; Gezen-Ak and Dursun, 2019) – as well as an essential factor for immunity.”

May 2020 – Ray Peat's Newsletter

Environmental Factors That May Contribute to Autism

“Things in the environment or substances that arise in response to environmental stress and could cause autism include prenatal and neonatal radiation exposure, including isotopes from the energy industry, nuclear weapons testing, Chernobyl, and Fukushima; exposure to air pollution, including nitrogen oxides, ozone, carbon monoxide, sulfur dioxide, and particulates (Jung et al., 2013); aluminum (Mold et al., 2018), lead, mercury, manganese, arsenic, cadmium, chromium, manganese, and nickel (Windham et al., 2006); acetaminophen, infections, endotoxin, exogenous and endogenous estrogens, hypothyroidism, progesterone deficiency, agmatine deficiency, serotonin excess, endogenous nitric oxide (Sweeten et al., 2004), and vitamin D deficiency.”

May 2018 – Ray Peats Newsletter

Seasonal Variations in Breast Cancer Diagnoses

“There is a clear seasonality in the diagnosis (occurrence) of breast cancer: a maximum in spring and a minimum in autumn (Cohen et al., 1983). The increased detection in spring coincides with rising gonadotropins (which are associated with breast and prostate cancer), and the lower detection in autumn coincides with higher vitamin D and lower stress hormones.”

May 2016 – Ray Peat's Newsletter

Common Inhibitors of the Enzyme Carbonic Anhydrase

“Common inhibitors of carbonic anhydrase include mildly oxidizing flavonoids such as apigenin and fisetin, some polyphenols, vitamin B1, vitamin D (Mras et al., 2012), progesterone (partly by blocking activation by estrogen and aldosterone), as well as emodin.”

July 2017 – Ray Peat's Newsletter

Effects of Long-Term Low Vitamin D Levels on the Parathyroid Glands

“If your vitamin D level has been very low for a long time, I think your parathyroid glands have probably enlarged and may need some time to normalize under the influence of a generous amount of vitamin D and calcium.”

Email response from Ray Peat

Back to the blog