This is a response to a warning that someone gave in a recent thread:
"Be careful about taking Vitamin K. The following study suggests that long-term use of a Vitamin K ANTAGONIST may DECREASE the risk of prostate cancer by 17%:
"Based on that, I would be wary of increasing Vitamin K intake."
The coagulation cascade is quite complex and involves many factors - see list after my signature.
If you want to be amused/bemused for 5 minutes, here is a video that claims to be: "Coagulation Cascade SIMPLEST EXPLANATION !!"
The point is, one can interfere with coagulation at many points in the cascade.
Warfarin (Coumadin) is the classic vitamin K antagonist. Why antagonize vitamin K?
"Warfarin decreases blood clotting by blocking an enzyme called vitamin K epoxide reductase that reactivates vitamin K1. Without sufficient active vitamin K1, clotting factors II, VII, IX, and X have decreased clotting ability."
As you can see, Warfarin creates a vitamin K deficiency in order to prolong clotting time. Vitamin K is never the reason someone is on Warfarin. People ask: "Will I get a clot if I take too much vitamin K?" Does spinach come with a warning?
What are the consequences of vitamin K antagonist use?
[1b] Arterial calcification.
"Long-term warfarin therapy may be associated with bone mineral loss and vascular calcification in 60-80 year old hypertensive patients."
 A bleed out on the way to the ER, following a serious accident involving blood loss (carry the antidote at all times - vitamin K)
For those with the misfortune to be on a vitamin K antagonist, vitamin K deficiency is the norm.
Everyone else should avoid insufficiency, since that will lead to osteoporosis & arterial calcification.
Is there particular benefit for those with PCa?
"Our results suggest an inverse association between the intake of menaquinones, but not that of phylloquinone, and prostate cancer." i.e. use vitamin K2.
The study cited in the other thread states:
"This meta-analysis indicates that VKAs use may be associated with a decreased risk of prostate cancer, especially in long-term users."
It's possible, but one has to be crazy to want to go on Warfarin. And the protection would be due to clot inhibition - not vitamin K restriction. One could simply cut out all sources of the vitamin from the diet, of course. Let me know if that affects your PSA.
That meta-analysis was from last month. There was another one just 3 months earlier:
"In conclusion, we did not observe a reduced risk of prostate cancer associated with VKA use in this nationwide study and, taken together with previous study findings, a major protective effect of VKAs against prostate cancer seems unlikely."
In a Danish study from 2016:
"This study, which included a larger number of PCa cases with warfarin exposure than previous studies, does not support previous notions of decreased risk of PCa among warfarin users."
An Italian study from 2011:
"These results support the hypothesis that anticoagulation might have a protective effect on cancer development, especially prostate cancer."
Choose the studies you like!
The PCa benefit of coagulation inhibitors - not specifically VKAs - is that they may prevent metastasis, rather than incidence. But in population with a low rate of screening, that may appear as a drop in incidence.
Coagulation factors and related substances
Number and/or nameFunctionAssociated genetic disorders
I (fibrinogen)Forms clot (fibrin)Congenital afibrinogenemia, Familial renal amyloidosis
II (prothrombin)Its active form (IIa) activates I, V, X, VII, VIII, XI, XIII, protein C, plateletsProthrombin G20210A, Thrombophilia
III (tissue factor or tissue thromboplastin )Co-factor of VIIa (formerly known as factor III)
IV CalciumRequired for coagulation factors to bind to phospholipid (formerly known as factor IV)
V (proaccelerin, labile factor)Co-factor of X with which it forms the prothrombinase complexActivated protein C resistance
VIUnassigned – old name of Factor Va
VII (stable factor, proconvertin)Activates IX, Xcongenital factor VII deficiency
VIII (Antihemophilic factor A)Co-factor of IX with which it forms the tenase complexHaemophilia A
IX (Antihemophilic factor B or Christmas factor)Activates X: forms tenase complex with factor VIIIHaemophilia B
X (Stuart-Prower factor)Activates II: forms prothrombinase complex with factor VCongenital Factor X deficiency
XI (plasma thromboplastin antecedent)Activates IXHaemophilia C
XII (Hageman factor)Activates factor XI, VII and prekallikreinHereditary angioedema type III
XIII (fibrin-stabilizing factor)Crosslinks fibrinCongenital Factor XIIIa/b deficiency
von Willebrand factorBinds to VIII, mediates platelet adhesionvon Willebrand disease
prekallikrein (Fletcher factor)Activates XII and prekallikrein; cleaves HMWKPrekallikrein/Fletcher Factor deficiency
high-molecular-weight kininogen (HMWK) (Fitzgerald factor)Supports reciprocal activation of XII, XI, and prekallikreinKininogen deficiency
fibronectinMediates cell adhesionGlomerulopathy with fibronectin deposits
antithrombin IIIInhibits IIa, Xa, and other proteasesAntithrombin III deficiency
heparin cofactor IIInhibits IIa, cofactor for heparin and dermatan sulfate ("minor antithrombin")Heparin cofactor II deficiency
protein CInactivates Va and VIIIaProtein C deficiency
protein SCofactor for activated protein C (APC, inactive when bound to C4b-binding protein)Protein S deficiency
protein ZMediates thrombin adhesion to phospholipids and stimulates degradation of factor X by ZPIProtein Z deficiency
Protein Z-related protease inhibitor (ZPI)Degrades factors X (in presence of protein Z) and XI (independently)
plasminogenConverts to plasmin, lyses fibrin and other proteinsPlasminogen deficiency, type I (ligneous conjunctivitis)
alpha 2-antiplasminInhibits plasminAntiplasmin deficiency
tissue plasminogen activator (tPA)Activates plasminogenFamilial hyperfibrinolysis and thrombophilia
urokinaseActivates plasminogenQuebec platelet disorder
plasminogen activator inhibitor-1 (PAI1)Inactivates tPA & urokinase (endothelial PAI)Plasminogen activator inhibitor-1 deficiency
plasminogen activator inhibitor-2 (PAI2)Inactivates tPA & urokinase (placental PAI)
cancer procoagulantPathological factor X activator linked to thrombosis in cancer